Postgraduate Medicine
ISSN: 0032-5481 (Print) 1941-9260 (Online) Journal homepage: http://www.tandfonline.com/loi/ipgm20
A new Attitude Toward the Vitreous Patrick O'Malley To cite this article: Patrick O'Malley (1975) A new Attitude Toward the Vitreous, Postgraduate Medicine, 58:3, 233-238, DOI: 10.1080/00325481.1975.11714156 To link to this article: http://dx.doi.org/10.1080/00325481.1975.11714156
Published online: 07 Jul 2016.
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Date: 09 August 2017, At: 21:49
Downloaded by [University of Auckland Library] at 21:49 09 August 2017
Before the newer instrumentation for removal of abnormal vitreous was developed, the gelatinous body that makes up two thirds of the eye was regarded by most ophthalmologists as surgically off limits. Now, it is possible in many cases to remove abnormal vitreous without undue surgical trauma.
Until quite recently, most ophthalmologists looked on the vitreous as a substance not to be tampered with. Bitter experi~nce taught that surgical manipulation of the vitreous usually resulted in such serious complications as chronic inflammation, macular degeneration, corneal edema, retinal detachment, glaucoma, and infectious endophthalmitis. We now understand that many problems relating to the vitreous are traceable to its threedimensionallatticework of long collagen fibrils 1 (figure 1). These are so fine that 20 placed side by side are no wider than a wavelength of blue light. Yet they are quite tough, and a number of them, when aligned, can exert destructive traction on the retina and other ocular tissues. The fibrils also serve as a scaffold along which fibroblasts may lay clown dense scar tissue. Furthermore, it is difficult for phagocytes to remove from the vitreous any opaque material trapped far from the nearest capillary. This inaccessibility of the vitreous to the body's defense mechanism makes it ready prey to microorganisms, even those of low pathogenicity. The proximity of the vitreous to the retina and lens, together with the technical difficulty of grasping or of incising a gelatinous substance, served to reinforce the attitude of reluctance. The enthusiastic few ophthalmologic surgeons who held a different view and acted accordingly often regretted the encounter, and any success was viewed with skepticism. Shafer2 has noted that as recently as 19 years ago a prominent ophthalmologist, on hearing of Shafer's experience with aspiration of abnormal vitreous, asserted that to touch the vitreous was malpractice. Developments lnfluencing the New Attitude 3
Only when Kasner and associates insisted that an eye can function after removal of the
Vol. 58 • No. 3 • September 1975 • POSTGRADUATE MEDICINE
FAMILY PR.6CTICE AND
~
A NEW ATTITUDE TOWARD THE VITREOUS PATRICK O'MALLEY, MD Northwestern University Medical School Chicago
vitreous, as it does after removal of the lens, did the attitude begin to change. The surgical approach used by them, however, was traumatic, consisting of an extensive limbal incision with removal of vitreous much as the contents of a soft-boiled egg are removed. Therefore, little in the way of vitreous surgery was undertaken until Machemer and associates 4 in 1971 reported the development of an instrument that greatly reduces the surgical trauma. This instrument, called the vitreous infusion suction cutter (VISC), is inserted through the pars plana. It is no larger than a 17-gauge needle and consists of two concentric tubes that fit together tightly at the tip (figure 2). Near the tip, each tube has a small opening. Suction on the inner tube draws into these openings a minute "knuckle" of vitreous. Rotation of the inner tube (by a motor in the instrument's handle) cuts away the fragment of vitreous, which is theo withdrawn through this tube. Lost volume is restored by introduction of saline solution through the space between the tubes. One of a special series of articles on diagnosis and treatment of common eye problems. Coordinator of the series is Dr. Barton L. Hodes, associate in ophthalmology, Northwestern University Medical School, Chicago.
233
Figure 1. The vitreous is composed of water (about 99%) and a three-dimensional network of stra ight collagen fibrils in whose interstices are loosely wound molecules of hyaluronic acid.
Downloaded by [University of Auckland Library] at 21:49 09 August 2017
Adaptation (by John Lute) of a figure from Balazs. 1
With this instrument, it is possible to remove abnormal vitreous except when scarring is extreme. Other workers have been quick to enlarge on the concept represented, and numerous supporting instruments and techniques have been developed. Already sorne _patients heretofore doomed to a life of blindness because of vitreous opacities are benefiting, sorne even regaining 20/20 vision. Floaters, Flashing Lights, and Syneresis
Of particular importance to general physicians is an appreciation of symptoms referable to the vitreous. These may be due to vitreous opacities or to mechanical stimulation of the retina. Vitreous floaters are quite common. One or more dark forms are seen floating before the eyes, forms that resemble flies (muscae volitantes, flitting flies), spiderweb, haies, alphabetic letters, numbers, or other configurations. This
illusion occurs because the eye is a darkened chamber with a single small window, the pupil, and because an opacity in the vitreous prevents light entering the pupil from reaching the retina. The shadow cast on the retina is seen by the patient. It is more distinct if the opacity is close to the retina or if the pupil is small. An opacity sorne distance from the retina casts a less distinct shadow and is seen as an intermittent blur rather than a floater. Neural adaptive mechanisms are such that a stationary vitreous opacity is unnoticed as long as it does not interfere with the passage of light from pupil to macula. The normal vitteous in a child or young adult is a transparent firm gel with a superstructure of widely separated collagen fibrils, and an opacity in this firm substance will not move. Later in life, the vitreous is subject to a degenerative process, syneresis (figure 3), marked by breakdown of the gel and the formation of fluid clefts. The traction exerted on the firmly attached collagen fibrils at the anterior extremity of the retina by the almost incessant movement of the eye gradually distorts the vitreous, cornpressing the fibrils into lamellae (figure 3a) separated by fluid clefts. Later the fluid clefts interconnect along the anteroposterior axis of the globe, and continuing breakdown gradually enlarges the central cavity at the expense of the surrounding gel (figure 3b).5 In many persons, generally between 50 and 80 years of age, a hole develops in the posterior part of the shell of formed gel, allowing it to fall away from the retina. When this happens, the central liquid is transferred to the potential space that exists ~
Figure 2. The vitreous infusion suction cutter (VI SC), an instrument no larger than a 17-gauge needle, performs four functions. tt draws vitreous into the opening in the tip, cuts it, removes it from the eye, and infuses saline solution to replace tost volume. Adaptation (by John Lute) of a figure from Machemer and associates. •
234
POSTGRADUATE MEDICINE • 5eptember 1975 • Vol. 58 • No. 3
Downloaded by [University of Auckland Library] at 21:49 09 August 2017
Figure 3. Sequence of vitreous syneresis, including vitreous detachment (c) and retinal tears due to vitreous traction (d). Drawn by Patrick O'Malley, MD.
236
between the vitreous and retina (figure 3c). The condensed, membrane-like posterior surface of the detached vitreous, no longer taut and applied to the retina, becomes wrinkled. These wrinkles are seen as fine !ines which may be described as a spiderweb or a lacy curtain. The circular opacity corresponding to the rim of the optic nerve head appears as a ring or, if it is torn, as the letter S or C. These opacities move because the formed vitreous remains attached in the region of the ora serrata and moves in a whip-like manner with rotation of the eye. Fortunately, continuing liquefaction of the vitreous allows them slowly to disappear from view. Quite often a capillary ruptures at the rime of vitreous detachment. Blood escaping from the vesse! causes what may be described as a shower of black spots before the eyes. As a general rule, the blood is quickly absorbed. Occasionally a focal vitreoretinal adhesion impedes the separation of vitreous from retina. The jactitations of the vitreous adhering to this site may tear the delicate retina (figure 3d). If the fragment of retina is pulled free, usually there is no serious problem. But if the vitreous continues to tug in the vicinity of the hole, the liquid in the space behind the vitreous may be transferred behind the retina, resulting in retinal detachment. Even without retinal detachment, the bleeding from torn venules or arterioles may seriously compromise vision. When the vitreous pulls on the retina, the patient sees a flash of light. The combination of vitreous floaters and flashing lights usually signifies a fresh vitreous detachment. In this circumstance, examination for evidence of incipient retinal detachment is advised. It is consoling to know that in any year this dread condition affiicts only one person in about 10,000. Flashing lights usually indicate vitreous traction but may also be due to bleeding or edema in the macular area. Rarely they indicate an epileptic focus in the occipital pole. A careful history generally will distinguish these light flashes and the flashing arc-shaped, expanding scotoma of migraine. The latter is typically a battlement-like, scintillating figure that appears on one side of the visual field, persists for 15 to 20 minutes, may be associated with nausea, and usually is followed by headache. There is no ~
POSTGRADUATE MEDICINE •. September 1975 • Vol. 58 • No. 3
PATRICK O'MALLEY
Downloaded by [University of Auckland Library] at 21:49 09 August 2017
Dr. O'Malley is assistant professor of clinical ophthalmology, Northwestern University Medical School, Chicago, and attending physician, St. Joseph's Hospital, South Bend, Indiana.
known relationship of migrainous scotoma to ocular disease, and the attacks may recur for many years without apparent neurologie damage. Floaters are to be differentiated from the orderly motion of blood cells in macular capillaries, sometimes seen by children. Floaters are a feature of many ocular and systemic conditions in addition to breakdown of the vitreous gel. The systemic causes generally have in cornmon the rupture of retinal capillaries. Thus, B.oaters may be due to any disease that leads to retinal capillary bleeding. Direct ophth~lmoscopic examination of the fondus of the eye through an undilated pupil is of limited value in determining the causes of B.ashing lights and B.oaters. The examination may confirm the presence of diabetic or hypertensive retinopathy, retinal venous occlusion, or choked disk, or it may suggest vitreous detachment or a bleeding disease. It is necessary, however, to get a better view of the vitreous and retina to determine the pathogenesis and the seriousness of the symptoms. As an illustration, the mechanism of vitreous bleeding due to diabetic retinopathy may be rupture of fragile retinal capillaries, usually not a serious condition, or it may be rupture of new
blood vessels in the potential space between retina and vitreous, a devastating event. Although these new vessels arise from the retina or optic nerve, they spread out on and are firmly attached to the vitreous. The posterior layer of the vitreous eventually contracts, forming a taut drum over a greater or lesser part of the concave retinal surface. In the process, one of the new vessels is likely to break.6 The first such hemorrhage is generally resorbed with fair recovery of vision, but the vitreous usually continues to peel off the retina, causing further bleeding. Eventually the solid vitreous is permanently stained. In addition, the fibrovascular stalks associated with the new vessels pull on the retina, often with destructive force. Currently, surgical efforts to remove abnormal vitreous are directed primarily at benefiting these diabetic patients with blood-stained or scarred vitreous. The initial successes are heavily counterbalanced by failures, but ali observees agree that a significant avenue of therapy for ali vitreous opacities has been opened. Summary
Floaters in the field of vts1on and B.ashing lights are the only symptoms referable to the vitreous. Floaters are due to vitreous opacities which cast shadows on the retina. Flashing lights usually signify mechanical stimulation of the retina by vitreous traction. The combination of B.oaters and B.ashing lights usually means fresh vitreous detachment. Floaters are commonly related to degeneration of the vitreous gel that occurs with aging, but they may be due to any disease that leads to retinal capillary bleeding. With new instrumentation, it is now possible in many cases of disabling vitreous opacities to remove the abnormal vitreous. Address reprint requests to Patrick O'Malley, MD, 512 Sherland Bldg, South Bend, IN 46601.
REFERENCES 1. Balazs E: The molecular biology of the vitreous. In McPherson A (Editor) : New and Controversial Aspects of Retinal Detachment. New York, Paul B Hoeber Inc, 1967 2. Shafer DM: Evolution of vitreous surgery. In New and Controversial Aspects of Vitreoretinal Surgery. St. Louis, The CV Mosby Co (in press) 3. Kasner D, Miller GR, Taylor WH, et al: Surgical treatment of amyloidosis of the vitreous. Trans Am Acad Ophthalmol Otolaryngol 72:410-418, 1968
238
4. Machemer R, Buettner H, Norton EW, et al: Vitrectomy: A pars plana approach. Trans Am Acad Ophthalmol Otolaryngol 75:813-820, 1971 5. O'Malley P: The pattern of vitreous syneresis--a study of 800 autopsy eyes. In Irvine A, O'Malley C (Editors) : Advances in Vitreous Surgery. Springfield, Ill, Charles C Thomas, Publisher (in press) 6. Davis MD: Vitreous contraction in proliferative diabetic retinopathy. Arch Ophthalmol 74:741-751, 1965
POSTGRADUATE MEDICINE
o
September 1975
o
Vol. 58
o
No. 3
ISSN: 0032-5481 (Print) 1941-9260 (Online) Journal homepage: http://www.tandfonline.com/loi/ipgm20
A new Attitude Toward the Vitreous Patrick O'Malley To cite this article: Patrick O'Malley (1975) A new Attitude Toward the Vitreous, Postgraduate Medicine, 58:3, 233-238, DOI: 10.1080/00325481.1975.11714156 To link to this article: http://dx.doi.org/10.1080/00325481.1975.11714156
Published online: 07 Jul 2016.
Submit your article to this journal
View related articles
Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=ipgm20 Download by: [University of Auckland Library]
Date: 09 August 2017, At: 21:49
Downloaded by [University of Auckland Library] at 21:49 09 August 2017
Before the newer instrumentation for removal of abnormal vitreous was developed, the gelatinous body that makes up two thirds of the eye was regarded by most ophthalmologists as surgically off limits. Now, it is possible in many cases to remove abnormal vitreous without undue surgical trauma.
Until quite recently, most ophthalmologists looked on the vitreous as a substance not to be tampered with. Bitter experi~nce taught that surgical manipulation of the vitreous usually resulted in such serious complications as chronic inflammation, macular degeneration, corneal edema, retinal detachment, glaucoma, and infectious endophthalmitis. We now understand that many problems relating to the vitreous are traceable to its threedimensionallatticework of long collagen fibrils 1 (figure 1). These are so fine that 20 placed side by side are no wider than a wavelength of blue light. Yet they are quite tough, and a number of them, when aligned, can exert destructive traction on the retina and other ocular tissues. The fibrils also serve as a scaffold along which fibroblasts may lay clown dense scar tissue. Furthermore, it is difficult for phagocytes to remove from the vitreous any opaque material trapped far from the nearest capillary. This inaccessibility of the vitreous to the body's defense mechanism makes it ready prey to microorganisms, even those of low pathogenicity. The proximity of the vitreous to the retina and lens, together with the technical difficulty of grasping or of incising a gelatinous substance, served to reinforce the attitude of reluctance. The enthusiastic few ophthalmologic surgeons who held a different view and acted accordingly often regretted the encounter, and any success was viewed with skepticism. Shafer2 has noted that as recently as 19 years ago a prominent ophthalmologist, on hearing of Shafer's experience with aspiration of abnormal vitreous, asserted that to touch the vitreous was malpractice. Developments lnfluencing the New Attitude 3
Only when Kasner and associates insisted that an eye can function after removal of the
Vol. 58 • No. 3 • September 1975 • POSTGRADUATE MEDICINE
FAMILY PR.6CTICE AND
~
A NEW ATTITUDE TOWARD THE VITREOUS PATRICK O'MALLEY, MD Northwestern University Medical School Chicago
vitreous, as it does after removal of the lens, did the attitude begin to change. The surgical approach used by them, however, was traumatic, consisting of an extensive limbal incision with removal of vitreous much as the contents of a soft-boiled egg are removed. Therefore, little in the way of vitreous surgery was undertaken until Machemer and associates 4 in 1971 reported the development of an instrument that greatly reduces the surgical trauma. This instrument, called the vitreous infusion suction cutter (VISC), is inserted through the pars plana. It is no larger than a 17-gauge needle and consists of two concentric tubes that fit together tightly at the tip (figure 2). Near the tip, each tube has a small opening. Suction on the inner tube draws into these openings a minute "knuckle" of vitreous. Rotation of the inner tube (by a motor in the instrument's handle) cuts away the fragment of vitreous, which is theo withdrawn through this tube. Lost volume is restored by introduction of saline solution through the space between the tubes. One of a special series of articles on diagnosis and treatment of common eye problems. Coordinator of the series is Dr. Barton L. Hodes, associate in ophthalmology, Northwestern University Medical School, Chicago.
233
Figure 1. The vitreous is composed of water (about 99%) and a three-dimensional network of stra ight collagen fibrils in whose interstices are loosely wound molecules of hyaluronic acid.
Downloaded by [University of Auckland Library] at 21:49 09 August 2017
Adaptation (by John Lute) of a figure from Balazs. 1
With this instrument, it is possible to remove abnormal vitreous except when scarring is extreme. Other workers have been quick to enlarge on the concept represented, and numerous supporting instruments and techniques have been developed. Already sorne _patients heretofore doomed to a life of blindness because of vitreous opacities are benefiting, sorne even regaining 20/20 vision. Floaters, Flashing Lights, and Syneresis
Of particular importance to general physicians is an appreciation of symptoms referable to the vitreous. These may be due to vitreous opacities or to mechanical stimulation of the retina. Vitreous floaters are quite common. One or more dark forms are seen floating before the eyes, forms that resemble flies (muscae volitantes, flitting flies), spiderweb, haies, alphabetic letters, numbers, or other configurations. This
illusion occurs because the eye is a darkened chamber with a single small window, the pupil, and because an opacity in the vitreous prevents light entering the pupil from reaching the retina. The shadow cast on the retina is seen by the patient. It is more distinct if the opacity is close to the retina or if the pupil is small. An opacity sorne distance from the retina casts a less distinct shadow and is seen as an intermittent blur rather than a floater. Neural adaptive mechanisms are such that a stationary vitreous opacity is unnoticed as long as it does not interfere with the passage of light from pupil to macula. The normal vitteous in a child or young adult is a transparent firm gel with a superstructure of widely separated collagen fibrils, and an opacity in this firm substance will not move. Later in life, the vitreous is subject to a degenerative process, syneresis (figure 3), marked by breakdown of the gel and the formation of fluid clefts. The traction exerted on the firmly attached collagen fibrils at the anterior extremity of the retina by the almost incessant movement of the eye gradually distorts the vitreous, cornpressing the fibrils into lamellae (figure 3a) separated by fluid clefts. Later the fluid clefts interconnect along the anteroposterior axis of the globe, and continuing breakdown gradually enlarges the central cavity at the expense of the surrounding gel (figure 3b).5 In many persons, generally between 50 and 80 years of age, a hole develops in the posterior part of the shell of formed gel, allowing it to fall away from the retina. When this happens, the central liquid is transferred to the potential space that exists ~
Figure 2. The vitreous infusion suction cutter (VI SC), an instrument no larger than a 17-gauge needle, performs four functions. tt draws vitreous into the opening in the tip, cuts it, removes it from the eye, and infuses saline solution to replace tost volume. Adaptation (by John Lute) of a figure from Machemer and associates. •
234
POSTGRADUATE MEDICINE • 5eptember 1975 • Vol. 58 • No. 3
Downloaded by [University of Auckland Library] at 21:49 09 August 2017
Figure 3. Sequence of vitreous syneresis, including vitreous detachment (c) and retinal tears due to vitreous traction (d). Drawn by Patrick O'Malley, MD.
236
between the vitreous and retina (figure 3c). The condensed, membrane-like posterior surface of the detached vitreous, no longer taut and applied to the retina, becomes wrinkled. These wrinkles are seen as fine !ines which may be described as a spiderweb or a lacy curtain. The circular opacity corresponding to the rim of the optic nerve head appears as a ring or, if it is torn, as the letter S or C. These opacities move because the formed vitreous remains attached in the region of the ora serrata and moves in a whip-like manner with rotation of the eye. Fortunately, continuing liquefaction of the vitreous allows them slowly to disappear from view. Quite often a capillary ruptures at the rime of vitreous detachment. Blood escaping from the vesse! causes what may be described as a shower of black spots before the eyes. As a general rule, the blood is quickly absorbed. Occasionally a focal vitreoretinal adhesion impedes the separation of vitreous from retina. The jactitations of the vitreous adhering to this site may tear the delicate retina (figure 3d). If the fragment of retina is pulled free, usually there is no serious problem. But if the vitreous continues to tug in the vicinity of the hole, the liquid in the space behind the vitreous may be transferred behind the retina, resulting in retinal detachment. Even without retinal detachment, the bleeding from torn venules or arterioles may seriously compromise vision. When the vitreous pulls on the retina, the patient sees a flash of light. The combination of vitreous floaters and flashing lights usually signifies a fresh vitreous detachment. In this circumstance, examination for evidence of incipient retinal detachment is advised. It is consoling to know that in any year this dread condition affiicts only one person in about 10,000. Flashing lights usually indicate vitreous traction but may also be due to bleeding or edema in the macular area. Rarely they indicate an epileptic focus in the occipital pole. A careful history generally will distinguish these light flashes and the flashing arc-shaped, expanding scotoma of migraine. The latter is typically a battlement-like, scintillating figure that appears on one side of the visual field, persists for 15 to 20 minutes, may be associated with nausea, and usually is followed by headache. There is no ~
POSTGRADUATE MEDICINE •. September 1975 • Vol. 58 • No. 3
PATRICK O'MALLEY
Downloaded by [University of Auckland Library] at 21:49 09 August 2017
Dr. O'Malley is assistant professor of clinical ophthalmology, Northwestern University Medical School, Chicago, and attending physician, St. Joseph's Hospital, South Bend, Indiana.
known relationship of migrainous scotoma to ocular disease, and the attacks may recur for many years without apparent neurologie damage. Floaters are to be differentiated from the orderly motion of blood cells in macular capillaries, sometimes seen by children. Floaters are a feature of many ocular and systemic conditions in addition to breakdown of the vitreous gel. The systemic causes generally have in cornmon the rupture of retinal capillaries. Thus, B.oaters may be due to any disease that leads to retinal capillary bleeding. Direct ophth~lmoscopic examination of the fondus of the eye through an undilated pupil is of limited value in determining the causes of B.ashing lights and B.oaters. The examination may confirm the presence of diabetic or hypertensive retinopathy, retinal venous occlusion, or choked disk, or it may suggest vitreous detachment or a bleeding disease. It is necessary, however, to get a better view of the vitreous and retina to determine the pathogenesis and the seriousness of the symptoms. As an illustration, the mechanism of vitreous bleeding due to diabetic retinopathy may be rupture of fragile retinal capillaries, usually not a serious condition, or it may be rupture of new
blood vessels in the potential space between retina and vitreous, a devastating event. Although these new vessels arise from the retina or optic nerve, they spread out on and are firmly attached to the vitreous. The posterior layer of the vitreous eventually contracts, forming a taut drum over a greater or lesser part of the concave retinal surface. In the process, one of the new vessels is likely to break.6 The first such hemorrhage is generally resorbed with fair recovery of vision, but the vitreous usually continues to peel off the retina, causing further bleeding. Eventually the solid vitreous is permanently stained. In addition, the fibrovascular stalks associated with the new vessels pull on the retina, often with destructive force. Currently, surgical efforts to remove abnormal vitreous are directed primarily at benefiting these diabetic patients with blood-stained or scarred vitreous. The initial successes are heavily counterbalanced by failures, but ali observees agree that a significant avenue of therapy for ali vitreous opacities has been opened. Summary
Floaters in the field of vts1on and B.ashing lights are the only symptoms referable to the vitreous. Floaters are due to vitreous opacities which cast shadows on the retina. Flashing lights usually signify mechanical stimulation of the retina by vitreous traction. The combination of B.oaters and B.ashing lights usually means fresh vitreous detachment. Floaters are commonly related to degeneration of the vitreous gel that occurs with aging, but they may be due to any disease that leads to retinal capillary bleeding. With new instrumentation, it is now possible in many cases of disabling vitreous opacities to remove the abnormal vitreous. Address reprint requests to Patrick O'Malley, MD, 512 Sherland Bldg, South Bend, IN 46601.
REFERENCES 1. Balazs E: The molecular biology of the vitreous. In McPherson A (Editor) : New and Controversial Aspects of Retinal Detachment. New York, Paul B Hoeber Inc, 1967 2. Shafer DM: Evolution of vitreous surgery. In New and Controversial Aspects of Vitreoretinal Surgery. St. Louis, The CV Mosby Co (in press) 3. Kasner D, Miller GR, Taylor WH, et al: Surgical treatment of amyloidosis of the vitreous. Trans Am Acad Ophthalmol Otolaryngol 72:410-418, 1968
238
4. Machemer R, Buettner H, Norton EW, et al: Vitrectomy: A pars plana approach. Trans Am Acad Ophthalmol Otolaryngol 75:813-820, 1971 5. O'Malley P: The pattern of vitreous syneresis--a study of 800 autopsy eyes. In Irvine A, O'Malley C (Editors) : Advances in Vitreous Surgery. Springfield, Ill, Charles C Thomas, Publisher (in press) 6. Davis MD: Vitreous contraction in proliferative diabetic retinopathy. Arch Ophthalmol 74:741-751, 1965
POSTGRADUATE MEDICINE
o
September 1975
o
Vol. 58
o
No. 3
