February, 1978
Intraocular Lens Implantation
Intraocular Lens Implantation: A Review Roger H. S. Langston ABSTRACT
I t causes magnification which averages about 25% and results in a n astonishing increase in t h e size of familiar objects and consequent false spatial localization. Consequently, hand-eye coordination must be relearned. If only one eye is to be operated on, binocular vision is impossible. The 25% difference in image size between the two eyes and the differences in spatial localization lead t o intolerable double vision. Visual information transmitted through t h e center of th e spectacles after cataract surgery is relatively undistorted except for th e magnification. However, that seen through th e rest of the lens is considerably distorted by the spherical aberration of even the best-made lenses; all straight lines are transformed into curves and the world becomes parabolic. Movement of the eyes or of the person or environment leads t o startling changes. As a doorway is approached, its sides seem to cave in on the wearer of these lenses. Moreover, some of the information from the peripheral visual field is lost because of a ring scotoma inherent i n th e lenses. All of these things make spectacle correction of the patient following cataract surgery less than completely satisfactory. T h e spectacles may be good enough for viewing television and reading or other stationary purposes, b u t they are distinctly deficient for an active life.1-3And, as one patient said, “They make m e look llke a frog!” T h e conventional answer to these problems is the use of contact lenses. Because a contact lens is placed on th e eye rather than in front of it, the magnification averages a tolerable 8’36, and double vision and problems with spatial localization rarely occur. There is also no appreciable spherical aberration with its attendant distortions. Moreover, the lens is cosmetically satisfactory. However, contact lenses are not easily worn by persons in the age group in which cataracts occur. A s a result, studies show t h a t several years after surgery more t h a n half t h e p a tie n ts wearing c o n ta c t lenses have stopped using them a n d rely on either the unoperated eye or on spectacle^.^,^ These observations demonstrate the problem for which th e intraocular lens (Fig. 1)is a n answer. With the intraocular lens implant, a plastic lens is inserted in the place of the removed cataractous lens and the quality of resulting vision is essentially normal. Magnification averages 2%, and spherical aberrations are avoided without the need for patient compliance with optical devices other th a n the ordinary glasses such a s are worn by noncataract patients.
Intraocular lens implantation has been developing over the past 15 years in Europe and is now becoming popular in the United States. Lens materials and designs as well as surgical techniques are still being evaluated. T h e overall results are excellent, with a small increase in complications being th e price paid for a dramatic increase in visual rehabilitation. intraocular lens implant, anterior chamber lens, iris clip lens, iridocapsular lens, extracapsular cataract extraction, intracapsular cataract extraction
INTRODUCTION Modern cataract surgery is highly successful when measured by t he ability of a postoperative patient to sit in the ophthalmologist’s examining chair and read th e 20/20 line on the wall chart. This, however, does not fully measure his visual rehabilitation in the real world. A brief examination of this problem will clarify why intraocular lens implantation has generated such interest among ophthalmologists, the government, the press and in patients who are seriously considering cataract surgery. A cataract is a n opacification of th e crystalline lens of the eye, usually resulting from normal aging changes. There is no prophylaxis against it and no medical treatment for it. Surgical removal of the cataractous lens becomes appropriate when th e patient suffers sufficient visual disability to compromise his life-style. This will vary from patient to patient, depending on his needs, a s he faces such problems as difficulties with depth perception, loss of night vision, or inability to drive, read, or ultimately even t o get around the house. Removal of the cataractous crystalline lens in the operating room only partially solves these problems for in removing the cataractous lens, the surgeon is also removing one of the major focusing elements from the patient’s visual system. Th is must be replaced. T h e conventional way of managing this is to replace the cataractous lens with a spectacle lens. Such lenses are safe, simple and relatively inexpensive. However, the quality of vision which they give often is poor. Because the corrective spectacle lens is a strong convex lens and lies 10 to 15m m in front of the eye, rather than 5 mm within the eye, it leads t o several distortions. ~-
From the Depcirtment of Ophtl~ul~riolog~, The Cleveland Clinic Foundntion. Clevelund, Ohm 44106
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Vol. 2, No. 1
Artificial Organs
.I
\
/
I
I I I
\ \
\ \ \ ‘ 4
FIG. 1. Intraocular lens implant one week post-op. FIG.2. Position of aphakic corrections: spectacles, contact lenses, and intraocular lenses.
HISTORY The idea of intraocular lens implantation is not new. In the l a t e 18th century, a glass intraocular lens was implanted unsuccessfully in Dresden.6 Modern intraocular lens implantation, however, had its start with Harold Ridley7 a t St. Thomas’s Hospital in London. A student asked Dr. Ridley why he did not replace the cataractous lens with a new one. As it happened, Ridley had observed during the Second World War that when fragments of P e r s p e F canopies of airplanes became lodged in pilots’ eyes, almost no inflammatory reaction resulted. In 1949, Ridley implanted the first PerspexB (polymethyl methacrylate; I.C.I., Plastics Division, Welwyn Garden City, Herts., England) intraocular lens. The original lenses were implanted behind the iris and were known as posterior chamber lenses. A so-called extracapsular cataract extraction was performed in which the posterior capsule of the lens was left intact while the anterior capsule and cataractous substance of the lens were removed. The disc-shaped lens implant (Figs. 2 & 3) was then placed in the space previously occupied by the lens substance. More than 1,000 of these operations were performed by various surgeons, but the procedure was eventually given up because of the following problems: inflammation, mainly because of residual lens material in the eye and partially because of inadequate lens implant sterilization; secondary glaucoma because of inflammation or displacement of the iris blocking the normal filtration angle; dislocation of the lenses; and damage to the cornea by the lens a t or following the ~peration.~-lO It was apparent that the problems with this lens were due t o its size and heaviness, t o the need for an extracapsular cataract extraction with its use and to the lack of stable support. Exceptional surgical ability was necessary to perform the cataract extraction without damaging the delicate zonular fibers t o the lens capsule which were needed to support the lens implant.
FIG.3. The original Ridley lens was a large, heavy posterior chamber lens, occupying the space between the irisand the posterior lens capsule.
The complications and technical difficulties with this lens led to the development of the so-called anterior chamber lenses in which the lens was placed in front of the iris. With these lenses, the cataract could be removed by the extracapsular technique or by the intracapsular method in which the entire cataract lens is removed en bloc in its capsule. The anterior chamber lenses (Fig. 4 ) were fixed in a variety of ways but were, in essence, wedged into the anterior chamber close in front of the iris. Danheim,ll BarraqueP and others developed and implanted a number of these lenses in the 50’s and 60’s. A
56
February, 1978
Intl-aocular Lens Implantation
-_ c
FIG.5. T h e iris-plane lenses take the form of a maltese cross and are fixed by placing two of the flanges anterior t o and two posterior to the iris.
FIG.4. T h e anterior chamber lenses lie anterior to the iris and are fixed by wedging into the scleral spur.
large number had to be removed because of complications, chief of which were damage to the cornea because of unstable lens fixation, especially by the edges of the lens which impinged on the cornea, the inner surface of which is extremely delicate and is the site of the metabolic pump which keeps the cornea clear; disintegration of the lens parts; and irritation of the iris and drainage angle by loosely fixated lenses, leading to inflammation and glaucoma.l* One of the anterior chamber lenses has been modified repeatedly over the past two decades and is still in current use: the Choyce Mark VIII lens.13It is made in various sizes and a lens must be selected that can be carefully wedged into the anterior chamber and be absolutely immobile. The current generation of lenses began with Epstein in 1953.l4 These lenses are small and lightweight and are supported by the iris. They include iris plane lenses
FIG. 6. The Binkhorst type, four-loop lens, is one of the most successful intraocular lenses. Most surgeons suture the superior loops together through a n iridectomy.
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Artificial Orga.ns
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FIG. 7. The Worst “medallion” lens is the most popular lens now available. It requires suturing to the iris.
FIG. 8. The Fyodorov “Sputnik” lens has had relatively little use outside the USSR.
(Fig. 5))iris clip lenses (Figs. 6-8) and iridocapsular lenses (Fig. 9). All these lenses are in current use and will be considered later. They have been used in some European centers for 15 years and their use is spreading to the United States to the extent that an estimated 20,000 lenses will be implanted this year.
intraocular lenses are supplied in several powers. To assure t h a t the correct lens is selected, so t h a t the postoperative refractive state of t h e eye is close t o normal, several observations must be made. Measurement of the length of the eye, position of the iris (and, therefore, of the lens implant), and the power of the other major refracting surface of the eye, the cornea, allows precise calculation of the power of the lens implant which should be used.15These observations can be made with ordinary ophthalmic equipment plus the use of A-Scan ultrasonography. However, the relationship of these measurements is usually fairly regular in eyes suited for lens implantation. Consequently, the lens power can be chosen with use of nomograms or even from observations of the strength of spectacle lenses required by the patient prior to development of the cataract. The
LENS POWER The intraocular lens gives the postoperative cataract patient the quality of vision he had with his own lens prior to surgery. The difference in image size averages 2%. The visual field approach is normal, as opposed to that with spectacles following cataract surgery. Quantitative correction of vision for distance and reading, the fine tuning so to speak, is ordinarily achieved with regular bifocal spectacles in addition to the implant. However,
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February, 1978
Intraocular Lens Implantation having a specific gravity of 1.19, little more than that of aqueous fluid of the eye (1.004). PMMA does have some disadvantages as a lens implant material. Since it is easily scratched, it must be carefully handled in manufacturing and implantation; this does not. lead to serious difficulties. PMMA is inert and nontoxic when fully polymerized. However, monomer is extremely toxic. In addition, some polymerizing agents are also toxic. This means that an extra potential hazard is possible if the lens material is improperly manufactured. This has not yet been a recognized problem with Perspex CQ.@ Although nontoxic, PMMA is extremely damaging to the corneal endothelium if the two make inadvertent contact during implantation surgery.17 This means that considerably more surgical skill is needed to implant lenses than is necessary in conventional cataract surgery and, consequently, considerably greater liability for damage is suffered by the patient. Problems with manufacturers' quality control have occurred. These have been in a form of imperfect manufacture of lenses or inaccurate labeling especially with the Choyce Mark VIII lenses which require exact fit.18 These problems have occurred particularly with lenses from new manufacturers. The most serious problem with quality control to date has been with regard to sterilization. PMMA cannot be boiled without risking optical distortion. It is affected by a variety of alcohols, solvents and amides which are conventionally used for sterilization. A technique was developed by Ridleylg in which the lens is sterilized in 10%NaOH for one hour a t 30°C. The lens is then stored in 1%NaOH and is neutralized with 0.5% NaHCO, just before use. Finally, it is rinsed with saline or a similar irrigating solution. This method was used safely for almost 20 years before two epidemics of endophthalmitis (devastating intraocular infection) occurred. These proved to be due to contamination of the NaHCO, solution supplied by the (recent) manufacturers. Paecilomyces lilacinus fungus was the cause of one epidemic and the other was caused by Pseudomonas aerugenosa.20.21The NaHCO, cannot be heat-sterilized and is usually sterilized by passage through Millipore& filters. An error in the technique presumably occurred. In intraocular lens design, various materials have been used for the loops or plates which support and fixate the central optical portion of the lens. Initially these were PMMA. Other materials have been utilized recently, chiefly because of greater strength and ease of manufacturing. In 1975 and 1976 many lenses with platinumiridium loops and clips were used. These again led to the observation that a heavy lens leads to problems. Platinum-iridium alloy has a specific gravity of about 9 and its use for lens loops increases the weight of a lens from
FIG.9. The Binkhorst iridocapsular lenses are fured by adhesion to the cataract remnants left posterior to the ills in extracapsular surgery.
optimum strength lens implant gives no significant magnification and, fortuitously, also results in a slight nearsightedness, which allows the patient to function at arms-length without glasses.16
LENS DESIGN The design goals for an intraocular lens include the following: The lens must be optically satisfactory, inert, nontoxic, sterile, structurally sound, lightweight, easily implanted and securely fixated. It is preferable that it can be secondarily implanted-that is, implanted at some date remote from the cataract extraction. It is also preferable that it should be relatively inexpensive. The optical portion of all intraocular lenses is currently made of polymethyl methacrylate (PMMA).This material transmits more than 90% of incident light, is inert and optically stable. It can be machined, polished and molded. It is nontoxic. I t is strong. I t is lightweight,
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about 1.4 mg to approximately 8 mg. Such lenses were unstable when utilized with intracapsular cataract extraction leadmg to a high incidence of dislocation, iritis, cystoid macular edema of the retina, corneal damage and even laceration of They have been discontinued except for special purposes. The conventional loop material is now Nylon 66. Some lenses are now being manufactured with Prolene loops. This material has a specific gravity of 0.91 and suggests the possibility of a “weightless” lens. With respect to structure, lens implant design has now evolved into three basic types: the anterior chamber implant (Fig. 4), the iris clip lens (Figs. 6-8) and the iridocapsular lens (Fig. 9). Optically these lenses are similar. Their structural difference is derived from the method of fixation used. Anterior chamber lenses modeled after the Choyce Mark VIII lens are firmly fixed in place by wedging them into a lip of the white scleral coat of the eye a t either side of the anterior chamber. The chief advantage of these lenses is that their insertion does not involve manipulation of the face of the vitreous body. This is a gel which occupies the space between the lens-iris diaphragm anteriorly and the retina posteriorly. The rupture of the delicate face of this vitreous body is often associated with decreased vision and occasionally with significant inflammation. Its rupture is generally considered a contraindication to lens implantation. Because vitreous manipulation is not involved, secondary lens implantation is also possible with the anterior chamber lenses after intra or extracapsular surgery, whereas with other lens types, it is possible only after extracapsular surgery. The lens has been used much less than those of other designs because of the inherent difficulties a t surgery in finding exactly the right size lens for use,18and because inadvertent use of a lens which does not have precisely the correct dimensions almost invariably leads to serious damage.23 Iris clip lenses, as developed by Binkhorst, Worst and Fyodorov, are suspended in the pupillary aperture using a paper-clip-llke arrangement in which loops or projections fit on either side of the iris. If light in weight, these lenses are very successful and have the advantage of being suitable for use with standard intracapsular cataract surgery. Their precise dimensions are not critical to the success of the surgical procedure. Their design is a compromise between long loops, which do not dislocate easily but tend to traumatize the corneal endothelium, and short loops which may easily lead to lens dislocation if the pupil dilates. The problem of dislocation occurs in 4 to 6% of cases with most such lens designs. 24.25 The other major difficulty with this type of lens is the need for it to be sutured to the iris, so that if it dislocates partially, it cannot fall into the vitreous or anterior chamber. This suturing requires considerable dexterity and is one of the
factors causing the surgeon to be the other major complication of the Iridocapsular lenses are used with extracapsular cataract extraction. In an extracapsular cataract extraction, the anterior surface of the lens capsule is broken and most of the cataractous lens material is removed. The clear posterior capsule and some remnants of cataractous cortical material behind the iris in the periphery remain. The loops of the lens rest in the residual cortical remnants where scarring leads to fixation. The chief advantage of this lens design is that it results in firm fixation of the implant. The dislocation rate is about 2%?’ There are also no loops near the corneal endothelium. No suture is required. The major disadvantage of the technique is that further surgery to cut the posterior capsule, which has become opaque, is necessary in about one-half the cases.27In addition, extracapsular surgery is not the standard method for most surgeons. Consequently, there is an obvious disadvantage in combining the new technique of lens implantation with an unfamiliar method of cataract extraction. In summary, the current generation of intraocular lenses are optically satisfactory, inert, structurally sound and reasonably light in weight. They are not expensive, each costing about $150.00. There are potential problems with sterilization, largely due to manufacturers’ problems with quality control. PMMA, while nontoxic, causes considerable damage when it contacts the corneal endothelium. This and difficulties with fixation systems for the lens make a high degree of surgical skill necessary for lens implantation. There is a need for a lens which makes this less of a hazard for the patient.
INDICATIONS AND CONTRAINDICATIONS TO LENS IMPLANTATION There are no firm indications for the use of intraocular lenses. Because of their advantages, they are suited to almost all patients. The reason that they are not universally used is that there is a small, but definite, increase in complications with their use. Intraocular lens implantation is definitely indicated in patients who cannot tolerate cataract glasses or contact lenses; for example, the very elderly or persons with limited manual dexterity due to arthritis, injury, etc. The elderly are also considered good candidates for lens implantation because their limited life expectancy reduces the hazard of late or long-term complications. Lens implantation is also definitely indicated in patients with macular degeneration plus dense cataracts which prevent them from ambulating satisfactorily. These patients do very poorly with standard cataract spectacles or contact lenses. Children may also be considered candidates for intraocular lens implantation because of their problems in managing contact lenses.28There are
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February, 1978
Intraocular Lens Implantation macular edema. There is potential for more irritation of t h e iris l a t e r with t h e use of iris suspended lenses. Experienced surgeons, however, have not found this t o be a problem on t h e whole (Table 2). Certain complications of cataract surgery are directly related t o lens implantation. Lens dislocation is t h e major complication of lens implantation (Table 3). I t can be managed medically b u t leads t o reoperation in 0.5% of usually t o reposition t h e lens. Lens removal, for various reasons, becomes necessary in 1%to 2% of cases.33 Most of these patients suffer some visual loss. Overall, t h e incidence of secondary surgery in intracapsular cataract extraction with lens implantation is about I t is very rare without implantation. T h e incidence of secondary surgery with extracapsular cataract extraction and lens implantation is about 50%.27It is also common in extracapsular surgery without lens implantation. Most patients who are candidates for cataract surgery can be operated on equally successfully b y intracapsular or extracapsular techniques. Great concern has been expressed t h a t lens implant surgery will result in damage to t h e corneal endothelium with subsequent corneal edema and need for corneal transplantation. Contact between the implant lens and t h e cornea isknown t o be damaging, with permanent loss of endothelial cells (since these cells do not replicate). Examination of t h e corneal endothelium postoperatively with the specular microscope shows that, in t h e hands of competent surgeons, about 35%of the endothelial cells are lost with intraocular lens implantation, a s opposed t o about 7% with t h e conventional cataract surgery.17 Not all the endothelial cells are necessary t o maintain a clear cornea, however, a s is evident from studies showing a decrease in endothelial cell population with patient’s age.34T h e r e is, t h o u g h , a limit t o how many endothelial cells can be lost before t h e cornea decompensates. Hence, there is concern t h a t corneas damaged by lens implantation will decompensate in future years, as age results in further loss of endothelial cells. This is one of t h e major reasons t h a t lens implantation is usually reserved for those with a limited life span. Endophthalmitis is a rare complication of cataract surgery, with or without lens implantation. As has been pointed o u t earlier in this article, contamination of the implant lens materials has occurred and has changed endophthalmitis from a sporadic t o an epidemic disease.20.21 T h e results of the average surgeon with intraocular lens implants are not well documented. However, acting by congressional mandate, the Food and Drug Administration has established a Bureau of Medical Devices which, over t h e next year, will monitor the results of all surgeons who implant lenses. All lenses will be utilized through a n investigational device exemption. Investigat-
also occupational indications for lens implantation such a s ranching, mining, diving a n d others. Contraindications t o implantation include inability of the patient t o participate in a n informed consent or inability t o receive adequate postoperative care. There are also a wide variety of pre-existing eye conditions which would make the surgery hazardous or which are likely t o advance t o t h e point where t h e lens implant might become a problem in t h e future. These include corneal endothelial dystrophies, uveitis, glaucoma, iris atrophy or abnormalities and retinal degenerations associated with increased incidence of detachment. In essence, a lens implant is usually not indicated unless t h e patient has two good eyes with no problem other than a cataract. Once the decision t o operate has been made, the surgeon can only state t h a t he plans a lens implantation. He cannot, or should not, guarantee implantation because t h e final decision must be made a t surgery. Vitreous bulging or loss, hemorrhage, iris laceration or paralysis, corneal trauma and other conditions are relative contraindications. T h e other major contraindication, pointed out by one of the masters in t h e field, is lack of appropriate training and skill on t h e part of the surgeon and his operating room This is a major problem; although a number of seminars and courses about lens i m p l a n t a t i o n a r e available, t h e r e is n o good animal model on which t o practice. I n addition, lens implantation generally requires the use of the operating microscope, the use of which is not familiar t o most ophthalmologists who trained more t h a n 10 years ago.
RESULTS I n the hands of experienced lens implant surgeons, the results are excellent a s indicated in t h e accompanying tables. T h e visual results (Table 1) only speak t o t h e ability of the patient t o read the Snellen chart. Because of the improved quality of vision, the visual results are even better t h a n indicated. This is universally reported by implant surgeons, though not well documented. T h e incidence of most serious complications of cataract surgery is not apparently increased or decreased with lens implantation (Table 2). Retinal detachment is substantially more difficult t o manage after lens implantation. The rate of reattachment, however, is not diminished in the hands of the best s~rgeons.~~-,’~ Initially, there was concern t h a t the incidence of cystoid macular edema of the retina might be significantly elevated. This was based on t h e observation t h a t lens implant surgery involves considerable manipulation of t h e iris with increased iritis in t h e immediate postoperative period, and t h a t iritis is often associated with cystoid
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A rtificial Organs TABLE 1 RESULTS Intraocular Lens Implantation
Conventional Surgery ~
Vision
Straw35
~~
Ma~menee~~
Binkhorst40
Worstz4
Choyce4'
29%
24%
-
43%
20/20 20/40+
She~ard~~
38%
45%
85%
36%
ao/100
18%
22%
12%
20/200
4%
-
-
20/4000
10%
-
-
5%
62%
79%
1%
TABLE2 COMPLICATIONS Conventional Surgery Straw35
Loss of eye Serious Infection
Ma~menee~~
Intraocular Lens Implantation BinkhorsP
Not reported 0.2%
Removal of Implant
W or@
C h ~ y c e ~ ~ . ~S ~ he~ard~~.~~
0.07%
0.2%
0.27%
0.2%
0.7%
0.4%
0.125%
0.8%
1.O%
1.O%
2.0%
1.2%
1.4%
0.2%
not reported
-0-
Chronic Inflammation
0.8%
Retinal Detachment
1.8%
4%
1.3%
1.6%
0.4%
1.4%
Cystoid Macular Edema
0.9%
3.0%
3.31%
3.1%
3.2%
not reported
-0-
ing surgeons will be sponsored by the lens manufacturers who will collect the data from the investigators and supply it t o the FDA, following the model of a new drug application. The type and amount of data accumulated will be the same for all sponsors. Approval of the investigational protocol is left to institutional review committees.
TABLE 3 INTRAOCULAR LENS DISLOCATION Series Worst24 Binkhorstz7 BinkhorstzT She~ard~~ Fy0dorov3~ SnideP Choy~e~~
CONCLUSION Cat,aract surgery has been for centuries and is today the most frequently performed major eye operation. The conventional method is well thought out and technically refined. Why, then, all this interest in intraocular lens implantation? Perhaps there are several answers to the question. Various people have various reasons for becoming acquainted with the new technique. The overwhelming reason, however, is that modern technology, as it relates to the implants themselves, to microsurgery, to suturing technique and materials, has opened the door to a new awareness of what can be done to meet the needs of the cataract patient and fully rehabilitate him. Lens implantation is still in its childhood. Materials,
No. of Patients 2,000
500 ECCE 500 ICCE 500
Incidence 4.3% 1.8% 6.9% 7.6%
2,000
4.0%
500
4.4%
1,000
1.0%
designs and surgical techniques are still being worked out. But already it has stimulated in surgeons a greater awareness of what is possible and has given them reason to upgrade their skills. It has stimulated interest in other methods of aphakic correction, such as full-time soft contact lens wear. It has also stimulated greater government interest in and regulation of the ophthalmic community. The end result of all this must be better care for the cataract patient.
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February, 1978
Intraocular Lens Implantation
References 1. WOODS,A. C. T h e adiustment to aphakia. Am J Ophthalmol, 35:118, 1952. 2. MCLEMONE. C. S.Cadillacs. Volkswaaens and auhakic corrections. Arch Ophthalmol, 70:734, 1963. 3. MCLEMONE, C. S.Aphakic correction from an aphake’s point of view (correspondence). Arch Ophthalmol, 74 :443, 1965. S. P. and MASSIN,M. Les verres de contact. 4. BONNET,R., GERHARD, Bull SOCOphthalmol Fr, Special issue, 1966. LEWIS,E . M. Scleral contact lens wear in 5. MILLS,R. 1‘.and TERRY unilateral aphakia, Br J Ophthalmol, 55:116, 1971. 6. TAIEB,A. Des memoires de Casanova a l’operation de Ridley. Arch Ophthalmol (Park), 15:501, 1955. 7. RIDLEY,€4. Further observations o n intraocular acrylic lenses in cataract surgery. Trans Am Acad Ophthalmol Otolaryngol, 57:98, 1953. 8. RIDLEY,H. Further experiences of intraocular acrylic lens surgery. Br J Ophthalmol, 38:156, 1956. 9. RIDLEYH. Cataract surgery with particular reference t o intraocular lenticular implants of various types. Trans Ophthalmol SOC UK, 78:585, 1958. 10. RIDLEY,H. Intraocular acrylic lenses. Ten years’development.Br J Ophthalmol, 44: 705, 1960. 11. DANNHEIM. H. Types of anterior chamber lenses with elastic loops. Ann Inst Barraquer 111, 4:570, 1962. J. and BAILBE,N. Complicaciones de la inclusion 12. BARRAQUEK, segun 10s divesostipos de centes. Ann Inst Barraquer 111, 4:588, 1962. 13. TENNANT, J. L. Results of primary and secondary implants using Choyce Mzrk VIII lenses. Ophthalmol Surg, 8:54, 1977. 14. EPSTEIN,E. Experiences with modified Ridley Lenses and others. .4nn Inst Rarraquer 111, 4:555, 1962. 15. BINKHORST, C. D. and LOONES,L. H. Intraocular lens power. i’rans Am Acad Ophthalmol Otolaryngol, 81:70, 1976. 16. BINKHORST, C. D. Power of the prepupillary pseudophakos. Br J Ophthalmcl, 56:332, 1972. H. E. Endothelial damage associat17. BOURNE,W. M. and KAUFMAN, ed with intraocular lenses. Am J Ophthalmol, 81:482, 1976. 18. ELLINGSOK, F. I. The importance of inspecting Choyce Mark VIII lenses. Am Intraocular Implant SOCJ, 3:118, 1977. 19. RIDLEY,H. Anterior chamber lenticularimplant. Br J Ophthalmol, 41:355, 1957. 20. Morbidity & Mortality Weekly Report. 24:437, 1975. 21. Morbidity & Mortality Weekly Report. 25:369, 1976. 22. SHEPARD,D. D. The dangers of metal-loop intraocular lenses. Ophthalmol Surg, 8:93, 1977. 23. PEARSE, J. L. Long-term results of Choyce anterior chamber lens implants Marks, V, VII a n d VIII. Br J Ophthalmol, 59:99, 1975.
-
24. WORST,J. G. F., MOSSELMAN, C. D. and LUDWIG,H. H. H. T h e artificial lens-experience with 2,000 lens implantations. Am In traocular Implant Soc J, 3:14, 1977. M. E . The Intraocular Zinplant Lens. Williams and 25. NORDLOHNE, Wilkins Co., Baltimore, p. 93, 1975. 26. WORST,J. G. F. Complications, complication factors and adverse conditions in lens implantation surgery. Trans Am Acad Ophthalmol Otolaryngol, 81: 105, 1976. 27. BINKHORST, C. D. Five hundred planned extracapsular extract,ions with indo-capsular and iris clip lens implantation in senile cataract. Ophthalmol Surg, Special issue. 8:37, 1977. 28. HILES, D. A. T h e need forintraocular lens implanta tion in children. Ophthalmol Surg, Special issue. 8:162, 1977. 29. NORTON,E. W. D. Management of retinal detachment, in patients with intraocular lens. T r a n s Am Acad Ophthalmol Otolaryngol, 81:135, 1976. 30. BINKHORST, C. D., KATS,A,, TJAN,T. T. and LOONES,L. H. Retinal accidents in pseudophakia-intracapsular vs. extracapsular surgery. Trans Am Acad Ophthalmol Otolaiyngol, 81:120, 1976. 31. JUNGSCHAFFER, 0. H. Retinal detachments after intraocular lens implants. Arch Ophthalmol, 95:1203, 1977. 32. SHEPARD,D. D. Intraocular lens implantation-analysis of 500 consecutive cases. Ophthalmol Surg, 8:57, 1977. D. D. Indications for intraocular lens removal. Ophthal33. SHEPARD, mol Surg, 8:144, 1977. W. M. and KAUFMAN, H. E. Specular microscopy of human 34. BORNE, corneal endothelium in vzuo. Am J. Ophthalmol, 81:319, 1975. 35. STRAW, W. F. Review of 10 years of cataract surgery. Emory, J., ed. Current Coizcepts of Caturact Surgery C. V. Mosby, St. Louis, 1972. 36. MAUMENEE,A. E. Survey of 500 cases of cataract extraction. Emory, J., ed. Current Concepts of Cataract Surgery. C . V. Mosby, St.Louis, 1972. S. N. Long-term results of 2,000 operations of implanta37. FYODOROV, tion of Fyodorov intraocular lenses performed in the Soviet Union. Am Intraocular Implant SOCJ, 3:101, 1977. 38. SNIDER, N. L. and MCREYNOLDS, W. V. Results and complications of our first 500 implantations. Am Intraocular Implant Soc J, 3:10, 1977. 39. CHOYCE,D. P. The long-term results of ocular implants. Proc R. SOCMed, 63:3, 1970. 40. NORDLOHNE, M. E. T h e intraocular implant lens. Williams and Wilkins Co., Baltimore, p. 79, 1975. D. P. The Choyce Mark VIII anterior chamber implant: 41. CHOYCE, primary and secondary implantation compared. Ophthalmol Surg, 8:39, 1977.
63
Intraocular Lens Implantation
Intraocular Lens Implantation: A Review Roger H. S. Langston ABSTRACT
I t causes magnification which averages about 25% and results in a n astonishing increase in t h e size of familiar objects and consequent false spatial localization. Consequently, hand-eye coordination must be relearned. If only one eye is to be operated on, binocular vision is impossible. The 25% difference in image size between the two eyes and the differences in spatial localization lead t o intolerable double vision. Visual information transmitted through t h e center of th e spectacles after cataract surgery is relatively undistorted except for th e magnification. However, that seen through th e rest of the lens is considerably distorted by the spherical aberration of even the best-made lenses; all straight lines are transformed into curves and the world becomes parabolic. Movement of the eyes or of the person or environment leads t o startling changes. As a doorway is approached, its sides seem to cave in on the wearer of these lenses. Moreover, some of the information from the peripheral visual field is lost because of a ring scotoma inherent i n th e lenses. All of these things make spectacle correction of the patient following cataract surgery less than completely satisfactory. T h e spectacles may be good enough for viewing television and reading or other stationary purposes, b u t they are distinctly deficient for an active life.1-3And, as one patient said, “They make m e look llke a frog!” T h e conventional answer to these problems is the use of contact lenses. Because a contact lens is placed on th e eye rather than in front of it, the magnification averages a tolerable 8’36, and double vision and problems with spatial localization rarely occur. There is also no appreciable spherical aberration with its attendant distortions. Moreover, the lens is cosmetically satisfactory. However, contact lenses are not easily worn by persons in the age group in which cataracts occur. A s a result, studies show t h a t several years after surgery more t h a n half t h e p a tie n ts wearing c o n ta c t lenses have stopped using them a n d rely on either the unoperated eye or on spectacle^.^,^ These observations demonstrate the problem for which th e intraocular lens (Fig. 1)is a n answer. With the intraocular lens implant, a plastic lens is inserted in the place of the removed cataractous lens and the quality of resulting vision is essentially normal. Magnification averages 2%, and spherical aberrations are avoided without the need for patient compliance with optical devices other th a n the ordinary glasses such a s are worn by noncataract patients.
Intraocular lens implantation has been developing over the past 15 years in Europe and is now becoming popular in the United States. Lens materials and designs as well as surgical techniques are still being evaluated. T h e overall results are excellent, with a small increase in complications being th e price paid for a dramatic increase in visual rehabilitation. intraocular lens implant, anterior chamber lens, iris clip lens, iridocapsular lens, extracapsular cataract extraction, intracapsular cataract extraction
INTRODUCTION Modern cataract surgery is highly successful when measured by t he ability of a postoperative patient to sit in the ophthalmologist’s examining chair and read th e 20/20 line on the wall chart. This, however, does not fully measure his visual rehabilitation in the real world. A brief examination of this problem will clarify why intraocular lens implantation has generated such interest among ophthalmologists, the government, the press and in patients who are seriously considering cataract surgery. A cataract is a n opacification of th e crystalline lens of the eye, usually resulting from normal aging changes. There is no prophylaxis against it and no medical treatment for it. Surgical removal of the cataractous lens becomes appropriate when th e patient suffers sufficient visual disability to compromise his life-style. This will vary from patient to patient, depending on his needs, a s he faces such problems as difficulties with depth perception, loss of night vision, or inability to drive, read, or ultimately even t o get around the house. Removal of the cataractous crystalline lens in the operating room only partially solves these problems for in removing the cataractous lens, the surgeon is also removing one of the major focusing elements from the patient’s visual system. Th is must be replaced. T h e conventional way of managing this is to replace the cataractous lens with a spectacle lens. Such lenses are safe, simple and relatively inexpensive. However, the quality of vision which they give often is poor. Because the corrective spectacle lens is a strong convex lens and lies 10 to 15m m in front of the eye, rather than 5 mm within the eye, it leads t o several distortions. ~-
From the Depcirtment of Ophtl~ul~riolog~, The Cleveland Clinic Foundntion. Clevelund, Ohm 44106
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Artificial Organs
.I
\
/
I
I I I
\ \
\ \ \ ‘ 4
FIG. 1. Intraocular lens implant one week post-op. FIG.2. Position of aphakic corrections: spectacles, contact lenses, and intraocular lenses.
HISTORY The idea of intraocular lens implantation is not new. In the l a t e 18th century, a glass intraocular lens was implanted unsuccessfully in Dresden.6 Modern intraocular lens implantation, however, had its start with Harold Ridley7 a t St. Thomas’s Hospital in London. A student asked Dr. Ridley why he did not replace the cataractous lens with a new one. As it happened, Ridley had observed during the Second World War that when fragments of P e r s p e F canopies of airplanes became lodged in pilots’ eyes, almost no inflammatory reaction resulted. In 1949, Ridley implanted the first PerspexB (polymethyl methacrylate; I.C.I., Plastics Division, Welwyn Garden City, Herts., England) intraocular lens. The original lenses were implanted behind the iris and were known as posterior chamber lenses. A so-called extracapsular cataract extraction was performed in which the posterior capsule of the lens was left intact while the anterior capsule and cataractous substance of the lens were removed. The disc-shaped lens implant (Figs. 2 & 3) was then placed in the space previously occupied by the lens substance. More than 1,000 of these operations were performed by various surgeons, but the procedure was eventually given up because of the following problems: inflammation, mainly because of residual lens material in the eye and partially because of inadequate lens implant sterilization; secondary glaucoma because of inflammation or displacement of the iris blocking the normal filtration angle; dislocation of the lenses; and damage to the cornea by the lens a t or following the ~peration.~-lO It was apparent that the problems with this lens were due t o its size and heaviness, t o the need for an extracapsular cataract extraction with its use and to the lack of stable support. Exceptional surgical ability was necessary to perform the cataract extraction without damaging the delicate zonular fibers t o the lens capsule which were needed to support the lens implant.
FIG.3. The original Ridley lens was a large, heavy posterior chamber lens, occupying the space between the irisand the posterior lens capsule.
The complications and technical difficulties with this lens led to the development of the so-called anterior chamber lenses in which the lens was placed in front of the iris. With these lenses, the cataract could be removed by the extracapsular technique or by the intracapsular method in which the entire cataract lens is removed en bloc in its capsule. The anterior chamber lenses (Fig. 4 ) were fixed in a variety of ways but were, in essence, wedged into the anterior chamber close in front of the iris. Danheim,ll BarraqueP and others developed and implanted a number of these lenses in the 50’s and 60’s. A
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Intl-aocular Lens Implantation
-_ c
FIG.5. T h e iris-plane lenses take the form of a maltese cross and are fixed by placing two of the flanges anterior t o and two posterior to the iris.
FIG.4. T h e anterior chamber lenses lie anterior to the iris and are fixed by wedging into the scleral spur.
large number had to be removed because of complications, chief of which were damage to the cornea because of unstable lens fixation, especially by the edges of the lens which impinged on the cornea, the inner surface of which is extremely delicate and is the site of the metabolic pump which keeps the cornea clear; disintegration of the lens parts; and irritation of the iris and drainage angle by loosely fixated lenses, leading to inflammation and glaucoma.l* One of the anterior chamber lenses has been modified repeatedly over the past two decades and is still in current use: the Choyce Mark VIII lens.13It is made in various sizes and a lens must be selected that can be carefully wedged into the anterior chamber and be absolutely immobile. The current generation of lenses began with Epstein in 1953.l4 These lenses are small and lightweight and are supported by the iris. They include iris plane lenses
FIG. 6. The Binkhorst type, four-loop lens, is one of the most successful intraocular lenses. Most surgeons suture the superior loops together through a n iridectomy.
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FIG. 7. The Worst “medallion” lens is the most popular lens now available. It requires suturing to the iris.
FIG. 8. The Fyodorov “Sputnik” lens has had relatively little use outside the USSR.
(Fig. 5))iris clip lenses (Figs. 6-8) and iridocapsular lenses (Fig. 9). All these lenses are in current use and will be considered later. They have been used in some European centers for 15 years and their use is spreading to the United States to the extent that an estimated 20,000 lenses will be implanted this year.
intraocular lenses are supplied in several powers. To assure t h a t the correct lens is selected, so t h a t the postoperative refractive state of t h e eye is close t o normal, several observations must be made. Measurement of the length of the eye, position of the iris (and, therefore, of the lens implant), and the power of the other major refracting surface of the eye, the cornea, allows precise calculation of the power of the lens implant which should be used.15These observations can be made with ordinary ophthalmic equipment plus the use of A-Scan ultrasonography. However, the relationship of these measurements is usually fairly regular in eyes suited for lens implantation. Consequently, the lens power can be chosen with use of nomograms or even from observations of the strength of spectacle lenses required by the patient prior to development of the cataract. The
LENS POWER The intraocular lens gives the postoperative cataract patient the quality of vision he had with his own lens prior to surgery. The difference in image size averages 2%. The visual field approach is normal, as opposed to that with spectacles following cataract surgery. Quantitative correction of vision for distance and reading, the fine tuning so to speak, is ordinarily achieved with regular bifocal spectacles in addition to the implant. However,
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Intraocular Lens Implantation having a specific gravity of 1.19, little more than that of aqueous fluid of the eye (1.004). PMMA does have some disadvantages as a lens implant material. Since it is easily scratched, it must be carefully handled in manufacturing and implantation; this does not. lead to serious difficulties. PMMA is inert and nontoxic when fully polymerized. However, monomer is extremely toxic. In addition, some polymerizing agents are also toxic. This means that an extra potential hazard is possible if the lens material is improperly manufactured. This has not yet been a recognized problem with Perspex CQ.@ Although nontoxic, PMMA is extremely damaging to the corneal endothelium if the two make inadvertent contact during implantation surgery.17 This means that considerably more surgical skill is needed to implant lenses than is necessary in conventional cataract surgery and, consequently, considerably greater liability for damage is suffered by the patient. Problems with manufacturers' quality control have occurred. These have been in a form of imperfect manufacture of lenses or inaccurate labeling especially with the Choyce Mark VIII lenses which require exact fit.18 These problems have occurred particularly with lenses from new manufacturers. The most serious problem with quality control to date has been with regard to sterilization. PMMA cannot be boiled without risking optical distortion. It is affected by a variety of alcohols, solvents and amides which are conventionally used for sterilization. A technique was developed by Ridleylg in which the lens is sterilized in 10%NaOH for one hour a t 30°C. The lens is then stored in 1%NaOH and is neutralized with 0.5% NaHCO, just before use. Finally, it is rinsed with saline or a similar irrigating solution. This method was used safely for almost 20 years before two epidemics of endophthalmitis (devastating intraocular infection) occurred. These proved to be due to contamination of the NaHCO, solution supplied by the (recent) manufacturers. Paecilomyces lilacinus fungus was the cause of one epidemic and the other was caused by Pseudomonas aerugenosa.20.21The NaHCO, cannot be heat-sterilized and is usually sterilized by passage through Millipore& filters. An error in the technique presumably occurred. In intraocular lens design, various materials have been used for the loops or plates which support and fixate the central optical portion of the lens. Initially these were PMMA. Other materials have been utilized recently, chiefly because of greater strength and ease of manufacturing. In 1975 and 1976 many lenses with platinumiridium loops and clips were used. These again led to the observation that a heavy lens leads to problems. Platinum-iridium alloy has a specific gravity of about 9 and its use for lens loops increases the weight of a lens from
FIG.9. The Binkhorst iridocapsular lenses are fured by adhesion to the cataract remnants left posterior to the ills in extracapsular surgery.
optimum strength lens implant gives no significant magnification and, fortuitously, also results in a slight nearsightedness, which allows the patient to function at arms-length without glasses.16
LENS DESIGN The design goals for an intraocular lens include the following: The lens must be optically satisfactory, inert, nontoxic, sterile, structurally sound, lightweight, easily implanted and securely fixated. It is preferable that it can be secondarily implanted-that is, implanted at some date remote from the cataract extraction. It is also preferable that it should be relatively inexpensive. The optical portion of all intraocular lenses is currently made of polymethyl methacrylate (PMMA).This material transmits more than 90% of incident light, is inert and optically stable. It can be machined, polished and molded. It is nontoxic. I t is strong. I t is lightweight,
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about 1.4 mg to approximately 8 mg. Such lenses were unstable when utilized with intracapsular cataract extraction leadmg to a high incidence of dislocation, iritis, cystoid macular edema of the retina, corneal damage and even laceration of They have been discontinued except for special purposes. The conventional loop material is now Nylon 66. Some lenses are now being manufactured with Prolene loops. This material has a specific gravity of 0.91 and suggests the possibility of a “weightless” lens. With respect to structure, lens implant design has now evolved into three basic types: the anterior chamber implant (Fig. 4), the iris clip lens (Figs. 6-8) and the iridocapsular lens (Fig. 9). Optically these lenses are similar. Their structural difference is derived from the method of fixation used. Anterior chamber lenses modeled after the Choyce Mark VIII lens are firmly fixed in place by wedging them into a lip of the white scleral coat of the eye a t either side of the anterior chamber. The chief advantage of these lenses is that their insertion does not involve manipulation of the face of the vitreous body. This is a gel which occupies the space between the lens-iris diaphragm anteriorly and the retina posteriorly. The rupture of the delicate face of this vitreous body is often associated with decreased vision and occasionally with significant inflammation. Its rupture is generally considered a contraindication to lens implantation. Because vitreous manipulation is not involved, secondary lens implantation is also possible with the anterior chamber lenses after intra or extracapsular surgery, whereas with other lens types, it is possible only after extracapsular surgery. The lens has been used much less than those of other designs because of the inherent difficulties a t surgery in finding exactly the right size lens for use,18and because inadvertent use of a lens which does not have precisely the correct dimensions almost invariably leads to serious damage.23 Iris clip lenses, as developed by Binkhorst, Worst and Fyodorov, are suspended in the pupillary aperture using a paper-clip-llke arrangement in which loops or projections fit on either side of the iris. If light in weight, these lenses are very successful and have the advantage of being suitable for use with standard intracapsular cataract surgery. Their precise dimensions are not critical to the success of the surgical procedure. Their design is a compromise between long loops, which do not dislocate easily but tend to traumatize the corneal endothelium, and short loops which may easily lead to lens dislocation if the pupil dilates. The problem of dislocation occurs in 4 to 6% of cases with most such lens designs. 24.25 The other major difficulty with this type of lens is the need for it to be sutured to the iris, so that if it dislocates partially, it cannot fall into the vitreous or anterior chamber. This suturing requires considerable dexterity and is one of the
factors causing the surgeon to be the other major complication of the Iridocapsular lenses are used with extracapsular cataract extraction. In an extracapsular cataract extraction, the anterior surface of the lens capsule is broken and most of the cataractous lens material is removed. The clear posterior capsule and some remnants of cataractous cortical material behind the iris in the periphery remain. The loops of the lens rest in the residual cortical remnants where scarring leads to fixation. The chief advantage of this lens design is that it results in firm fixation of the implant. The dislocation rate is about 2%?’ There are also no loops near the corneal endothelium. No suture is required. The major disadvantage of the technique is that further surgery to cut the posterior capsule, which has become opaque, is necessary in about one-half the cases.27In addition, extracapsular surgery is not the standard method for most surgeons. Consequently, there is an obvious disadvantage in combining the new technique of lens implantation with an unfamiliar method of cataract extraction. In summary, the current generation of intraocular lenses are optically satisfactory, inert, structurally sound and reasonably light in weight. They are not expensive, each costing about $150.00. There are potential problems with sterilization, largely due to manufacturers’ problems with quality control. PMMA, while nontoxic, causes considerable damage when it contacts the corneal endothelium. This and difficulties with fixation systems for the lens make a high degree of surgical skill necessary for lens implantation. There is a need for a lens which makes this less of a hazard for the patient.
INDICATIONS AND CONTRAINDICATIONS TO LENS IMPLANTATION There are no firm indications for the use of intraocular lenses. Because of their advantages, they are suited to almost all patients. The reason that they are not universally used is that there is a small, but definite, increase in complications with their use. Intraocular lens implantation is definitely indicated in patients who cannot tolerate cataract glasses or contact lenses; for example, the very elderly or persons with limited manual dexterity due to arthritis, injury, etc. The elderly are also considered good candidates for lens implantation because their limited life expectancy reduces the hazard of late or long-term complications. Lens implantation is also definitely indicated in patients with macular degeneration plus dense cataracts which prevent them from ambulating satisfactorily. These patients do very poorly with standard cataract spectacles or contact lenses. Children may also be considered candidates for intraocular lens implantation because of their problems in managing contact lenses.28There are
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Intraocular Lens Implantation macular edema. There is potential for more irritation of t h e iris l a t e r with t h e use of iris suspended lenses. Experienced surgeons, however, have not found this t o be a problem on t h e whole (Table 2). Certain complications of cataract surgery are directly related t o lens implantation. Lens dislocation is t h e major complication of lens implantation (Table 3). I t can be managed medically b u t leads t o reoperation in 0.5% of usually t o reposition t h e lens. Lens removal, for various reasons, becomes necessary in 1%to 2% of cases.33 Most of these patients suffer some visual loss. Overall, t h e incidence of secondary surgery in intracapsular cataract extraction with lens implantation is about I t is very rare without implantation. T h e incidence of secondary surgery with extracapsular cataract extraction and lens implantation is about 50%.27It is also common in extracapsular surgery without lens implantation. Most patients who are candidates for cataract surgery can be operated on equally successfully b y intracapsular or extracapsular techniques. Great concern has been expressed t h a t lens implant surgery will result in damage to t h e corneal endothelium with subsequent corneal edema and need for corneal transplantation. Contact between the implant lens and t h e cornea isknown t o be damaging, with permanent loss of endothelial cells (since these cells do not replicate). Examination of t h e corneal endothelium postoperatively with the specular microscope shows that, in t h e hands of competent surgeons, about 35%of the endothelial cells are lost with intraocular lens implantation, a s opposed t o about 7% with t h e conventional cataract surgery.17 Not all the endothelial cells are necessary t o maintain a clear cornea, however, a s is evident from studies showing a decrease in endothelial cell population with patient’s age.34T h e r e is, t h o u g h , a limit t o how many endothelial cells can be lost before t h e cornea decompensates. Hence, there is concern t h a t corneas damaged by lens implantation will decompensate in future years, as age results in further loss of endothelial cells. This is one of t h e major reasons t h a t lens implantation is usually reserved for those with a limited life span. Endophthalmitis is a rare complication of cataract surgery, with or without lens implantation. As has been pointed o u t earlier in this article, contamination of the implant lens materials has occurred and has changed endophthalmitis from a sporadic t o an epidemic disease.20.21 T h e results of the average surgeon with intraocular lens implants are not well documented. However, acting by congressional mandate, the Food and Drug Administration has established a Bureau of Medical Devices which, over t h e next year, will monitor the results of all surgeons who implant lenses. All lenses will be utilized through a n investigational device exemption. Investigat-
also occupational indications for lens implantation such a s ranching, mining, diving a n d others. Contraindications t o implantation include inability of the patient t o participate in a n informed consent or inability t o receive adequate postoperative care. There are also a wide variety of pre-existing eye conditions which would make the surgery hazardous or which are likely t o advance t o t h e point where t h e lens implant might become a problem in t h e future. These include corneal endothelial dystrophies, uveitis, glaucoma, iris atrophy or abnormalities and retinal degenerations associated with increased incidence of detachment. In essence, a lens implant is usually not indicated unless t h e patient has two good eyes with no problem other than a cataract. Once the decision t o operate has been made, the surgeon can only state t h a t he plans a lens implantation. He cannot, or should not, guarantee implantation because t h e final decision must be made a t surgery. Vitreous bulging or loss, hemorrhage, iris laceration or paralysis, corneal trauma and other conditions are relative contraindications. T h e other major contraindication, pointed out by one of the masters in t h e field, is lack of appropriate training and skill on t h e part of the surgeon and his operating room This is a major problem; although a number of seminars and courses about lens i m p l a n t a t i o n a r e available, t h e r e is n o good animal model on which t o practice. I n addition, lens implantation generally requires the use of the operating microscope, the use of which is not familiar t o most ophthalmologists who trained more t h a n 10 years ago.
RESULTS I n the hands of experienced lens implant surgeons, the results are excellent a s indicated in t h e accompanying tables. T h e visual results (Table 1) only speak t o t h e ability of the patient t o read the Snellen chart. Because of the improved quality of vision, the visual results are even better t h a n indicated. This is universally reported by implant surgeons, though not well documented. T h e incidence of most serious complications of cataract surgery is not apparently increased or decreased with lens implantation (Table 2). Retinal detachment is substantially more difficult t o manage after lens implantation. The rate of reattachment, however, is not diminished in the hands of the best s~rgeons.~~-,’~ Initially, there was concern t h a t the incidence of cystoid macular edema of the retina might be significantly elevated. This was based on t h e observation t h a t lens implant surgery involves considerable manipulation of t h e iris with increased iritis in t h e immediate postoperative period, and t h a t iritis is often associated with cystoid
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A rtificial Organs TABLE 1 RESULTS Intraocular Lens Implantation
Conventional Surgery ~
Vision
Straw35
~~
Ma~menee~~
Binkhorst40
Worstz4
Choyce4'
29%
24%
-
43%
20/20 20/40+
She~ard~~
38%
45%
85%
36%
ao/100
18%
22%
12%
20/200
4%
-
-
20/4000
10%
-
-
5%
62%
79%
1%
TABLE2 COMPLICATIONS Conventional Surgery Straw35
Loss of eye Serious Infection
Ma~menee~~
Intraocular Lens Implantation BinkhorsP
Not reported 0.2%
Removal of Implant
W or@
C h ~ y c e ~ ~ . ~S ~ he~ard~~.~~
0.07%
0.2%
0.27%
0.2%
0.7%
0.4%
0.125%
0.8%
1.O%
1.O%
2.0%
1.2%
1.4%
0.2%
not reported
-0-
Chronic Inflammation
0.8%
Retinal Detachment
1.8%
4%
1.3%
1.6%
0.4%
1.4%
Cystoid Macular Edema
0.9%
3.0%
3.31%
3.1%
3.2%
not reported
-0-
ing surgeons will be sponsored by the lens manufacturers who will collect the data from the investigators and supply it t o the FDA, following the model of a new drug application. The type and amount of data accumulated will be the same for all sponsors. Approval of the investigational protocol is left to institutional review committees.
TABLE 3 INTRAOCULAR LENS DISLOCATION Series Worst24 Binkhorstz7 BinkhorstzT She~ard~~ Fy0dorov3~ SnideP Choy~e~~
CONCLUSION Cat,aract surgery has been for centuries and is today the most frequently performed major eye operation. The conventional method is well thought out and technically refined. Why, then, all this interest in intraocular lens implantation? Perhaps there are several answers to the question. Various people have various reasons for becoming acquainted with the new technique. The overwhelming reason, however, is that modern technology, as it relates to the implants themselves, to microsurgery, to suturing technique and materials, has opened the door to a new awareness of what can be done to meet the needs of the cataract patient and fully rehabilitate him. Lens implantation is still in its childhood. Materials,
No. of Patients 2,000
500 ECCE 500 ICCE 500
Incidence 4.3% 1.8% 6.9% 7.6%
2,000
4.0%
500
4.4%
1,000
1.0%
designs and surgical techniques are still being worked out. But already it has stimulated in surgeons a greater awareness of what is possible and has given them reason to upgrade their skills. It has stimulated interest in other methods of aphakic correction, such as full-time soft contact lens wear. It has also stimulated greater government interest in and regulation of the ophthalmic community. The end result of all this must be better care for the cataract patient.
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Intraocular Lens Implantation
References 1. WOODS,A. C. T h e adiustment to aphakia. Am J Ophthalmol, 35:118, 1952. 2. MCLEMONE. C. S.Cadillacs. Volkswaaens and auhakic corrections. Arch Ophthalmol, 70:734, 1963. 3. MCLEMONE, C. S.Aphakic correction from an aphake’s point of view (correspondence). Arch Ophthalmol, 74 :443, 1965. S. P. and MASSIN,M. Les verres de contact. 4. BONNET,R., GERHARD, Bull SOCOphthalmol Fr, Special issue, 1966. LEWIS,E . M. Scleral contact lens wear in 5. MILLS,R. 1‘.and TERRY unilateral aphakia, Br J Ophthalmol, 55:116, 1971. 6. TAIEB,A. Des memoires de Casanova a l’operation de Ridley. Arch Ophthalmol (Park), 15:501, 1955. 7. RIDLEY,€4. Further observations o n intraocular acrylic lenses in cataract surgery. Trans Am Acad Ophthalmol Otolaryngol, 57:98, 1953. 8. RIDLEY,H. Further experiences of intraocular acrylic lens surgery. Br J Ophthalmol, 38:156, 1956. 9. RIDLEYH. Cataract surgery with particular reference t o intraocular lenticular implants of various types. Trans Ophthalmol SOC UK, 78:585, 1958. 10. RIDLEY,H. Intraocular acrylic lenses. Ten years’development.Br J Ophthalmol, 44: 705, 1960. 11. DANNHEIM. H. Types of anterior chamber lenses with elastic loops. Ann Inst Barraquer 111, 4:570, 1962. J. and BAILBE,N. Complicaciones de la inclusion 12. BARRAQUEK, segun 10s divesostipos de centes. Ann Inst Barraquer 111, 4:588, 1962. 13. TENNANT, J. L. Results of primary and secondary implants using Choyce Mzrk VIII lenses. Ophthalmol Surg, 8:54, 1977. 14. EPSTEIN,E. Experiences with modified Ridley Lenses and others. .4nn Inst Rarraquer 111, 4:555, 1962. 15. BINKHORST, C. D. and LOONES,L. H. Intraocular lens power. i’rans Am Acad Ophthalmol Otolaryngol, 81:70, 1976. 16. BINKHORST, C. D. Power of the prepupillary pseudophakos. Br J Ophthalmcl, 56:332, 1972. H. E. Endothelial damage associat17. BOURNE,W. M. and KAUFMAN, ed with intraocular lenses. Am J Ophthalmol, 81:482, 1976. 18. ELLINGSOK, F. I. The importance of inspecting Choyce Mark VIII lenses. Am Intraocular Implant SOCJ, 3:118, 1977. 19. RIDLEY,H. Anterior chamber lenticularimplant. Br J Ophthalmol, 41:355, 1957. 20. Morbidity & Mortality Weekly Report. 24:437, 1975. 21. Morbidity & Mortality Weekly Report. 25:369, 1976. 22. SHEPARD,D. D. The dangers of metal-loop intraocular lenses. Ophthalmol Surg, 8:93, 1977. 23. PEARSE, J. L. Long-term results of Choyce anterior chamber lens implants Marks, V, VII a n d VIII. Br J Ophthalmol, 59:99, 1975.
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24. WORST,J. G. F., MOSSELMAN, C. D. and LUDWIG,H. H. H. T h e artificial lens-experience with 2,000 lens implantations. Am In traocular Implant Soc J, 3:14, 1977. M. E . The Intraocular Zinplant Lens. Williams and 25. NORDLOHNE, Wilkins Co., Baltimore, p. 93, 1975. 26. WORST,J. G. F. Complications, complication factors and adverse conditions in lens implantation surgery. Trans Am Acad Ophthalmol Otolaryngol, 81: 105, 1976. 27. BINKHORST, C. D. Five hundred planned extracapsular extract,ions with indo-capsular and iris clip lens implantation in senile cataract. Ophthalmol Surg, Special issue. 8:37, 1977. 28. HILES, D. A. T h e need forintraocular lens implanta tion in children. Ophthalmol Surg, Special issue. 8:162, 1977. 29. NORTON,E. W. D. Management of retinal detachment, in patients with intraocular lens. T r a n s Am Acad Ophthalmol Otolaryngol, 81:135, 1976. 30. BINKHORST, C. D., KATS,A,, TJAN,T. T. and LOONES,L. H. Retinal accidents in pseudophakia-intracapsular vs. extracapsular surgery. Trans Am Acad Ophthalmol Otolaiyngol, 81:120, 1976. 31. JUNGSCHAFFER, 0. H. Retinal detachments after intraocular lens implants. Arch Ophthalmol, 95:1203, 1977. 32. SHEPARD,D. D. Intraocular lens implantation-analysis of 500 consecutive cases. Ophthalmol Surg, 8:57, 1977. D. D. Indications for intraocular lens removal. Ophthal33. SHEPARD, mol Surg, 8:144, 1977. W. M. and KAUFMAN, H. E. Specular microscopy of human 34. BORNE, corneal endothelium in vzuo. Am J. Ophthalmol, 81:319, 1975. 35. STRAW, W. F. Review of 10 years of cataract surgery. Emory, J., ed. Current Coizcepts of Caturact Surgery C. V. Mosby, St. Louis, 1972. 36. MAUMENEE,A. E. Survey of 500 cases of cataract extraction. Emory, J., ed. Current Concepts of Cataract Surgery. C . V. Mosby, St.Louis, 1972. S. N. Long-term results of 2,000 operations of implanta37. FYODOROV, tion of Fyodorov intraocular lenses performed in the Soviet Union. Am Intraocular Implant SOCJ, 3:101, 1977. 38. SNIDER, N. L. and MCREYNOLDS, W. V. Results and complications of our first 500 implantations. Am Intraocular Implant Soc J, 3:10, 1977. 39. CHOYCE,D. P. The long-term results of ocular implants. Proc R. SOCMed, 63:3, 1970. 40. NORDLOHNE, M. E. T h e intraocular implant lens. Williams and Wilkins Co., Baltimore, p. 79, 1975. D. P. The Choyce Mark VIII anterior chamber implant: 41. CHOYCE, primary and secondary implantation compared. Ophthalmol Surg, 8:39, 1977.
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