CONTINUOUS WAVE ARGON LASER IRIDECTOMY IN ANGLE-CLOSURE GLAUCOMA* BY Steven M. Podos, MD, Barry D. Kels, MD (BY INVITATION), Alan P. Moss, MD (BY INVITATION), Robert Ritch, MD (BY INVITATION), AND (BY INVITATION)
Malvin D. Anders, MD INTRODUCTION MEYER-SCHWICKERATH' FIRST EMPLOYED THE XENON ARC PHOTOCOAGULATOR IN
1956 to create patent openings in the human iris of patients with angleclosure glaucoma. However, because of technical difficulties inherent in achieving a patent iridectomy and complications of corneal and lenticular opacification, the xenon arc method of iris photocoagulation was abandoned. Subsequent investigators, including McDonald and Light,2 Hogan and Schwartz,3 and Burns,4 utilized modifications ofthe xenon and coppercovered carbon arc as sources of high intensity light for the penetration of mammalian irides. Once again, however, the unavoidable complications of corneal and lenticular opacification thwarted these efforts. As early as 1964, Flocks and Zweng5 recognized the capacity of laser radiation to produce retinal and iris bums with a shorter duration and lower amplitude of energy emission than comparable methods of photocoagulation. They attempted, albeit unsuccessfully, to produce a patent iridectomy with the ruby laser. Subsequently, Zweng and co-workers6 successfully created a patent iridectomy utilizing the pulsed ruby laser. Although the iridectomy subsequently required further treatment to maintain its patency, this marked the inception of the era of successful coherent laser iris surgery. In 1973, Beckman and Sugar7 reported the successful perforation of seven of nine human irides, utilizing the pulsed ruby laser adapted to the *From the Department of Ophthalmology, Mount Sinai School of Medicine of The City University of New York. This investigation was supported by a grant, EY-01867, from the National Eye Institute, Bethesda, Maryland, and an unrestricted grant from Research to Prevent Blindness, Inc., New York City. TR. AM. OPHTH. Soc. vol. LXXVII, 1979
Podos et al operating microscope. In the same year, Perkins and Brown8 utilized the pulsed ruby laser directed through the Gambs biomicroscope to achieve limited success in perforating the irides of several patients with angleclosure glaucoma. The pulsed ruby laser, operating at an optimal wavelength of 6,934A, permitted iris photocoagulation without creating the corneal and lenticular opacities so characteristic of xenon and carbon arc photocoagulation. It soon became apparent that the continuous wave argon laser (CWAL) is capable of producing more discrete photocoagulation burns than the ruby laser, and the peak wavelengths ofthe CWAL (4880 and 5145A) dictate that a significant portion of CWAL-emitted energy will be absorbed by circulating red blood cells, thereby obviating excessive heat buildup and permitting enhanced specificity for vascular structures where desired. Charles Khuri9 achieved the earliest successes with CWAL surgery of the iris and, in 1973, he reported the successful performance of ten iridectomies in as many Dutch pigmented rabbit eyes, utilizing the CWAL at an optimal wavelength of 5145A. Soon thereafter, Abrahaml0l" applied Khuri's methodology to the human irides of a selected series of patients; he utilized the CWAL in a two-burn technique to successfully perforate the irides of 37 of a total of 39 eyes with angle-closure glaucoma of either the acute or chronic variety. In Abraham's series, an initial, partial-thickness burn preceded a single perforating burn, which continued unabated until an iridectomy was achieved. In a comparable series of patients, Pollack and Patz'2 reported an 85% success rate in penetrating the human iris with a CWAL energy source employed in a two-phase, multiburn procedure. In the latter part of 1977, Schwartz and co-workers13 substantiated the applicability of a pulsed argon laser energy source to iris photocoagulation and iris surgery. In that series of 64 eyes with angle-closure glaucoma, pupillary block, or incomplete surgical iridectomy, patent iridectomies were achieved in 48 eyes utilizing the Britt 152 pulsed argon laser. The present paper examines the method and results of CWAL iris surgery in a series of 45 phakic eyes carrying the diagnosis ofeither acute or chronic angle-closure glaucoma. 52
MATERIALS AND METHODS
SUBJECTS
All phakic patients with angle-closure glaucoma presenting to the Glaucoma Service of The Mount Sinai Hospital from December 1, 1977, to November 30, 1978, who agreed to undergo laser iridectomy were in-
Laser Iridectomy
53
cluded in this study. This encompassed a series of45 eyes from 30 patients. No attempt was made to preselect or eliminate patients for factors such as iris color, head stability at the slit-lamp, pre-iridectomy intraocular pressure, or corneal condition; however, patients in the midst of an acute attack of angle-closure glaucoma necessarily had their intraocular pressures lowered and corneas cleared with appropriate medication prior to the performance of this procedure. A summary of the patient data is shown in Table I. Thirty-three of the eyes undergoing laser iridectomy carried the diagnosis ofchronic angle-closure glaucoma, while the remaining 12 eyes were diagnosed with acute angle-closuse glaucoma. Follow-up was from two to 14 months. Patients had the theory, practical application, and known potential complications of laser iridectomy explained to them before inclusion in the study group. It was explained to each patient consenting to this procedure that unknown and unforseen complications might one day develop as a consequence of this procedure. MATERIALS
The Coherent 900 continuous wave argon laser adapted to the Zeiss slitlamp was employed for all iridectomies performed in this series. The iridectomies reported herein were performed through clear cornea without the use of a contact lens. TABLE I SUMMARY OF PATIENT DATA
No of patients No of eyes Age range Sex: Male
Female
Race: Caucasian
Oriental
Hispanic Negro
30 45 40-91 years
23 eyes 22 eyes 43 1 1 0
eyes eye eye eyes
Iris Color: Brown Hazel Blue
40 eyes 4 eyes 1 eye
Diagnosis: Acute angle closure Attack eye Fellow eye Chronic angle closure
5 eyes 7 eyes 33 eyes
54
Podos et al TABLE II RESULTS OF LASER IRIDECTOMY IN 45 PATIENTS
Successful
37
One attempt Two attempts Three attempts
4 1
42
Total
Unsuccessful 1 2
Acute
Chronic
3_
Total METHODS
All the patients undergoing laser iridectomy were maintained on miotic therapy prior to the procedure. Each patient was instructed to take two tablets of aspirin upon awakening on the day of the laser surgery. In addition, all patients were requested to sign a standard surgical consent form just prior to the inception of the laser treatment. The only anesthesia employed for this procedure was a single drop of topical 0.5% proparacaine. Retrobulbar anesthesia was not utilized. The iridectomy was performed utilizing a two-phase multiburn technique described below. TECHNIQUE
Prior to the initiation of the procedure, the iris was carefully examined to select a suitable perforation site. Experience dictated that the perforation site was best selected in the horizontal meridian, approximately midway between the iris sphincter and the angle, and preferably in the area of an iris crypt. In other areas, increased comeal thickness, tenacity of the iris, and distortion of the pupil created problems. In the first, or centrifugal stretch phase, four to six large-diameter, short-duration, low-intensity burns were placed in a circumferential fashion around the eventual perforation site. The laser beam was directed TABLE III TREATMENT SESSIONS AND IRIS COLOR
Successful
One attempt Two attempts Three attempts
Unsuccessful One attempt Two attempts
BROWN
HAZEL
BLUE
33
3
1
4 1
1 1
1
Laser ItidectonW 55 perpendicular to the plane of the iris. The Coherent 900 CWAL settings utilized were 200 ,u spot size, 0.1-second duration, and 200 mW intensity. This phase was conceptualized to centrifugally place the iris on a stretch around the eventual perforation site and thereby facilitate phase two.
In the final penetration-perforation phase, a variable number of small diameter (50 ,), high intensity burns of slightly longer duration (0.1-0.2second) were directed into the center of the previously outlined circle. Careful focusing, with gradual increments in the depth of focus, was employed as the laser burns progressively penetrated the iris. The terminal perforating burns were directed away from the fovea. Subsequent to the production of the perforating laser burns, a mushroom cloud of dispersed pigment was frequently observed to rise from the iridectomy site, and a vapor bubble originating from the posterior chamber was often seen traversing the area of the iridectomy. The endpoint of the procedure was the direct visualization of anterior lens capsule through the newly created iridectomy site. Positive transillumination of the iridectomy site and unequivocal deepening of the anterior chamber were additional indications of presumed success. At the conclusion of the procedure the patient was instructed to utilize a mild topical corticosteroid preparation in the eye and to return for examination in 24 to 36 hours. RESULTS
Successful iridectomies were ultimately achieved in 42 of the 45 eyes subjected to CWAL iridectomy. Thirty-seven of the 42 successes were accomplished in a single sitting, while the remaining five successes required multiple sittings to finally perforate the iris (Table II). Thirty-three brown irides, as well as four ofthe lighter colored (hazel and blue) irides included in our series, were perforated after a single sitting at the laser. The irides requiring multiple sessions oflaser therapy to achieve patency were all brown in color, as were two of the three irides in which a ,patent laser iridectomy could not be produced (Table III). Considering only those irides perforated in a single sitting, the brown irides required fewer mean burns (60) than either the blue (66) or hazel (87) irides. The mean number of burns required to perforate those brown irides subjected to two sessions of argon laser therapy was 75. Four brown irides and one hazel iris in this series required a maximum power of 2000 mW to produce patent iridectomies. The remaining 34 brown irides subjected to successful CWAL iridectomies required no more than 1600 mW to achieve perforation. The remaining two successful CWAL iridectomies with hazel
56
Podos et al TABLE IV SETTINGS FOR PERFORATION IN SUCCESSFUL LASER IRIDECTOMIES
BROWN
One attempt Mean burns (range) Maximum mW
87
60
66
(45-128)
(26-158) 2000
Two attempts Mean burns (range) Maximum mW
BLUE
HAZEL
2000
1200
75 (40-128) 2000
irides required a maximum power of 1800 mW, while the single blue iris required no greater than 1200 mW to produce perforation (Table IV). Table V compares best corrected distance visual acuities before and after laser iridectomy with a follow-up period of from 2 to 14 months. Five eyes subjected to successful laser iridectomies demonstrated a decrement in Snellen visual acuity scores of from one to two lines. Only a single eye evinced greater than two lines of impairment of visual acuity after successful laser iridectomy. Significantly, three eyes actually had improvement in Snellen visual acuities of from one to two lines after successful CWAL iridectomy. In our series, the most frequently encountered complication was the subsequent occlusion of a previously patent iridectomy site with iris pigment epithelium. This occurred in ten eyes. The next most frequently encountered complication was the reduction in postoperative bestcorrected distance visual acuities discussed above. Additional complications encountered in two or more eyes included transient severe corneal burns, failure to perforate the iris, posterior synechiae, and isolated lens opacities at the iridectomy site (Table VI).
TABLE V SUCCESSFUL LASER IRIDECTOMY AND VISUAL ACUITY POST-LASER
20/20-20/30
20/40-20/50
20 3
3 5
20/60-20/80
Malvin D. Anders, MD INTRODUCTION MEYER-SCHWICKERATH' FIRST EMPLOYED THE XENON ARC PHOTOCOAGULATOR IN
1956 to create patent openings in the human iris of patients with angleclosure glaucoma. However, because of technical difficulties inherent in achieving a patent iridectomy and complications of corneal and lenticular opacification, the xenon arc method of iris photocoagulation was abandoned. Subsequent investigators, including McDonald and Light,2 Hogan and Schwartz,3 and Burns,4 utilized modifications ofthe xenon and coppercovered carbon arc as sources of high intensity light for the penetration of mammalian irides. Once again, however, the unavoidable complications of corneal and lenticular opacification thwarted these efforts. As early as 1964, Flocks and Zweng5 recognized the capacity of laser radiation to produce retinal and iris bums with a shorter duration and lower amplitude of energy emission than comparable methods of photocoagulation. They attempted, albeit unsuccessfully, to produce a patent iridectomy with the ruby laser. Subsequently, Zweng and co-workers6 successfully created a patent iridectomy utilizing the pulsed ruby laser. Although the iridectomy subsequently required further treatment to maintain its patency, this marked the inception of the era of successful coherent laser iris surgery. In 1973, Beckman and Sugar7 reported the successful perforation of seven of nine human irides, utilizing the pulsed ruby laser adapted to the *From the Department of Ophthalmology, Mount Sinai School of Medicine of The City University of New York. This investigation was supported by a grant, EY-01867, from the National Eye Institute, Bethesda, Maryland, and an unrestricted grant from Research to Prevent Blindness, Inc., New York City. TR. AM. OPHTH. Soc. vol. LXXVII, 1979
Podos et al operating microscope. In the same year, Perkins and Brown8 utilized the pulsed ruby laser directed through the Gambs biomicroscope to achieve limited success in perforating the irides of several patients with angleclosure glaucoma. The pulsed ruby laser, operating at an optimal wavelength of 6,934A, permitted iris photocoagulation without creating the corneal and lenticular opacities so characteristic of xenon and carbon arc photocoagulation. It soon became apparent that the continuous wave argon laser (CWAL) is capable of producing more discrete photocoagulation burns than the ruby laser, and the peak wavelengths ofthe CWAL (4880 and 5145A) dictate that a significant portion of CWAL-emitted energy will be absorbed by circulating red blood cells, thereby obviating excessive heat buildup and permitting enhanced specificity for vascular structures where desired. Charles Khuri9 achieved the earliest successes with CWAL surgery of the iris and, in 1973, he reported the successful performance of ten iridectomies in as many Dutch pigmented rabbit eyes, utilizing the CWAL at an optimal wavelength of 5145A. Soon thereafter, Abrahaml0l" applied Khuri's methodology to the human irides of a selected series of patients; he utilized the CWAL in a two-burn technique to successfully perforate the irides of 37 of a total of 39 eyes with angle-closure glaucoma of either the acute or chronic variety. In Abraham's series, an initial, partial-thickness burn preceded a single perforating burn, which continued unabated until an iridectomy was achieved. In a comparable series of patients, Pollack and Patz'2 reported an 85% success rate in penetrating the human iris with a CWAL energy source employed in a two-phase, multiburn procedure. In the latter part of 1977, Schwartz and co-workers13 substantiated the applicability of a pulsed argon laser energy source to iris photocoagulation and iris surgery. In that series of 64 eyes with angle-closure glaucoma, pupillary block, or incomplete surgical iridectomy, patent iridectomies were achieved in 48 eyes utilizing the Britt 152 pulsed argon laser. The present paper examines the method and results of CWAL iris surgery in a series of 45 phakic eyes carrying the diagnosis ofeither acute or chronic angle-closure glaucoma. 52
MATERIALS AND METHODS
SUBJECTS
All phakic patients with angle-closure glaucoma presenting to the Glaucoma Service of The Mount Sinai Hospital from December 1, 1977, to November 30, 1978, who agreed to undergo laser iridectomy were in-
Laser Iridectomy
53
cluded in this study. This encompassed a series of45 eyes from 30 patients. No attempt was made to preselect or eliminate patients for factors such as iris color, head stability at the slit-lamp, pre-iridectomy intraocular pressure, or corneal condition; however, patients in the midst of an acute attack of angle-closure glaucoma necessarily had their intraocular pressures lowered and corneas cleared with appropriate medication prior to the performance of this procedure. A summary of the patient data is shown in Table I. Thirty-three of the eyes undergoing laser iridectomy carried the diagnosis ofchronic angle-closure glaucoma, while the remaining 12 eyes were diagnosed with acute angle-closuse glaucoma. Follow-up was from two to 14 months. Patients had the theory, practical application, and known potential complications of laser iridectomy explained to them before inclusion in the study group. It was explained to each patient consenting to this procedure that unknown and unforseen complications might one day develop as a consequence of this procedure. MATERIALS
The Coherent 900 continuous wave argon laser adapted to the Zeiss slitlamp was employed for all iridectomies performed in this series. The iridectomies reported herein were performed through clear cornea without the use of a contact lens. TABLE I SUMMARY OF PATIENT DATA
No of patients No of eyes Age range Sex: Male
Female
Race: Caucasian
Oriental
Hispanic Negro
30 45 40-91 years
23 eyes 22 eyes 43 1 1 0
eyes eye eye eyes
Iris Color: Brown Hazel Blue
40 eyes 4 eyes 1 eye
Diagnosis: Acute angle closure Attack eye Fellow eye Chronic angle closure
5 eyes 7 eyes 33 eyes
54
Podos et al TABLE II RESULTS OF LASER IRIDECTOMY IN 45 PATIENTS
Successful
37
One attempt Two attempts Three attempts
4 1
42
Total
Unsuccessful 1 2
Acute
Chronic
3_
Total METHODS
All the patients undergoing laser iridectomy were maintained on miotic therapy prior to the procedure. Each patient was instructed to take two tablets of aspirin upon awakening on the day of the laser surgery. In addition, all patients were requested to sign a standard surgical consent form just prior to the inception of the laser treatment. The only anesthesia employed for this procedure was a single drop of topical 0.5% proparacaine. Retrobulbar anesthesia was not utilized. The iridectomy was performed utilizing a two-phase multiburn technique described below. TECHNIQUE
Prior to the initiation of the procedure, the iris was carefully examined to select a suitable perforation site. Experience dictated that the perforation site was best selected in the horizontal meridian, approximately midway between the iris sphincter and the angle, and preferably in the area of an iris crypt. In other areas, increased comeal thickness, tenacity of the iris, and distortion of the pupil created problems. In the first, or centrifugal stretch phase, four to six large-diameter, short-duration, low-intensity burns were placed in a circumferential fashion around the eventual perforation site. The laser beam was directed TABLE III TREATMENT SESSIONS AND IRIS COLOR
Successful
One attempt Two attempts Three attempts
Unsuccessful One attempt Two attempts
BROWN
HAZEL
BLUE
33
3
1
4 1
1 1
1
Laser ItidectonW 55 perpendicular to the plane of the iris. The Coherent 900 CWAL settings utilized were 200 ,u spot size, 0.1-second duration, and 200 mW intensity. This phase was conceptualized to centrifugally place the iris on a stretch around the eventual perforation site and thereby facilitate phase two.
In the final penetration-perforation phase, a variable number of small diameter (50 ,), high intensity burns of slightly longer duration (0.1-0.2second) were directed into the center of the previously outlined circle. Careful focusing, with gradual increments in the depth of focus, was employed as the laser burns progressively penetrated the iris. The terminal perforating burns were directed away from the fovea. Subsequent to the production of the perforating laser burns, a mushroom cloud of dispersed pigment was frequently observed to rise from the iridectomy site, and a vapor bubble originating from the posterior chamber was often seen traversing the area of the iridectomy. The endpoint of the procedure was the direct visualization of anterior lens capsule through the newly created iridectomy site. Positive transillumination of the iridectomy site and unequivocal deepening of the anterior chamber were additional indications of presumed success. At the conclusion of the procedure the patient was instructed to utilize a mild topical corticosteroid preparation in the eye and to return for examination in 24 to 36 hours. RESULTS
Successful iridectomies were ultimately achieved in 42 of the 45 eyes subjected to CWAL iridectomy. Thirty-seven of the 42 successes were accomplished in a single sitting, while the remaining five successes required multiple sittings to finally perforate the iris (Table II). Thirty-three brown irides, as well as four ofthe lighter colored (hazel and blue) irides included in our series, were perforated after a single sitting at the laser. The irides requiring multiple sessions oflaser therapy to achieve patency were all brown in color, as were two of the three irides in which a ,patent laser iridectomy could not be produced (Table III). Considering only those irides perforated in a single sitting, the brown irides required fewer mean burns (60) than either the blue (66) or hazel (87) irides. The mean number of burns required to perforate those brown irides subjected to two sessions of argon laser therapy was 75. Four brown irides and one hazel iris in this series required a maximum power of 2000 mW to produce patent iridectomies. The remaining 34 brown irides subjected to successful CWAL iridectomies required no more than 1600 mW to achieve perforation. The remaining two successful CWAL iridectomies with hazel
56
Podos et al TABLE IV SETTINGS FOR PERFORATION IN SUCCESSFUL LASER IRIDECTOMIES
BROWN
One attempt Mean burns (range) Maximum mW
87
60
66
(45-128)
(26-158) 2000
Two attempts Mean burns (range) Maximum mW
BLUE
HAZEL
2000
1200
75 (40-128) 2000
irides required a maximum power of 1800 mW, while the single blue iris required no greater than 1200 mW to produce perforation (Table IV). Table V compares best corrected distance visual acuities before and after laser iridectomy with a follow-up period of from 2 to 14 months. Five eyes subjected to successful laser iridectomies demonstrated a decrement in Snellen visual acuity scores of from one to two lines. Only a single eye evinced greater than two lines of impairment of visual acuity after successful laser iridectomy. Significantly, three eyes actually had improvement in Snellen visual acuities of from one to two lines after successful CWAL iridectomy. In our series, the most frequently encountered complication was the subsequent occlusion of a previously patent iridectomy site with iris pigment epithelium. This occurred in ten eyes. The next most frequently encountered complication was the reduction in postoperative bestcorrected distance visual acuities discussed above. Additional complications encountered in two or more eyes included transient severe corneal burns, failure to perforate the iris, posterior synechiae, and isolated lens opacities at the iridectomy site (Table VI).
TABLE V SUCCESSFUL LASER IRIDECTOMY AND VISUAL ACUITY POST-LASER
20/20-20/30
20/40-20/50
20 3
3 5
20/60-20/80
