Characterization of membranes removed during open-sky vitrectomy.

Membranes removed during open-sky vitrectomy have been characterized by electron microscopy, reaction with anti-human fibrinogen, susceptibility to enzymatic digestion, amino acid analysis, and electrophoresis in sodium dodecyl sulfate. There were significant differences between longstanding and newly formed membranes. Longstanding membranes contained substantial amounts of hydroxyproline, glycine, and hydroxylysine, were capable of digestion by collagenase but not by plasmin, yielded faint positive results with anti-human fibrinogen, and showed fibrils characteristic of collagen by electron microscopy. After digestion with pepsin, electrophoresis revealed bands that migrated the same distance as vitreous collagen chains. This type of membrane is evidently collagenous in nature. A second type of membrane, which developed in the course of vitrectomy, contained no hydroxyproline, only traces of hydroxylysine, and relatively small amounts of glycine, was digested by plasmin, yielded strong positive results with anti-human fibrinogen, and showed fibers that were not characteristic of collagen by electron microscopy. Electrophoresis demonstrated bands similar to authentic fibrin in these newly formed membranes. These data suggest that this second type of membrane is composed largely of fibrin. Prevention of the formation of this second type of membrane during vitrectomy may require the addition of agents that inhibit fibrin formation.

Variation of energy density in argon laser photocoagulation.

The power density at the retina provided by presently available laser photocoagulators is subject to variation. Three factors contribute to making the retinal image of the laser beam substantially different from the spot size indicated on the selector of the photocoagulator. These are the operator's variable accommodation, the astigmatism introduced by the contact lens, and the depth of focus of the observation system. The assumption that the same setting on the instrument regularly produces the same power density at the retina will lead to errors in comparing lesions. The safest procedure is to start from the threshold in every location.

Closed vitreous surgery: XV. Fibrovascular ingrowth from the pars plana sclerotomy.

Ten eyes developed fibrovascular ingrowth from the sclerotomy following closed vitreous surgery. The complication was detected by examining all patients postoperatively by indirect ophthalmoscopy and biomicroscopy with a three-mirror lens. The average follow-up was 13.2 months. Nine patients had proliferative retinal disease prior to surgery and related systemic disease. In six eyes, useful vision was lost due to the ingrowth. In three eyes, a stabilization occurred. In one eye, that of a 12-year-old girl with an undefined syndrome of cochlear and retinal neovascularization, the ingrowth involuted. Rubeosis iridis was observed in 6 eyes that developed vascular ingrowth as opposed to 11 eyes in a control group of 78 eyes. Eyes with rubeosis iridis should not have vitreous surgery, and careful dissection of the Tenon capsule should be done over the sclerotomy.

Self-retaining iris speculum for open-sky vitrectomy.

We have designed a self-retaining iris speculum for use in open-sky vitrectomy. This speculum retracts the iris away from the central field and thus allows the surgeon better visibility and less reliance on an assistant's help for retraction. The possibility of iris laceration and dialysis with excessive bleeding, as sometimes seen with other forms of iris retraction, can be prevented.

Four-port bimanual vitrectomy.

A further subdivision of functions during vitrectomy surgery has been enabled. By means of a separate, suture-secured fiberoptic endoilluminator and a modified infusion cannula located in the inferior quadrants, two superior sclerotomies are kept free for the use of a variety of simple and complex instruments, alone or in combination. Included among these are vitreous scissors, forceps, picks, spatulas, diathermy probes, and endophotocoagulators.

An insulated diathermy electrode.

A thin, conical diathermy electrode with a smooth-surfaced bent, insulated tip was designed for use in narrow incisions, corners, and angles of dissected scleral flaps. It permits precise delivery of focal diathermy and avoids undesirable parafocal tissue damage. This electrode is especially valuable for preventing uveal bleeding from a sclerochoroidal incision over the pars plana ciliaris and for treating small posterior retinal breaks.

Biomicroscopic evaluation and photography of posterior vitreous detachment.

This is a preliminary effort to demonstrate conditions of the posterior vitreous more objectively by slit-lamp photography. For this purpose, a + 58.6-diopter, aspherical, preset lens (El Bayadi-Kajiura lens [Nikon]) and a photoslit (Zeiss Jena) were used. The most fundamental aspect in our technique of observation and photography of the posterior vitreous is that of catching the appropriate moment during the vitreous movement that follows horizontal and/or vertical displacement of the patient's eye. Posterior vitreous photographs by this method in normal eyes, retinitis pigmentosa, Wagner's disease, and preretinal macular fibrosis associated with macular edema in phakic eyes are presented, and biomicroscopic characteristics in each of these diseases are discussed. Our observations clearly demonstrate a new technique for detailed examination and photography of the posterior vitreous.

Retinal detachment following congenital cataract surgery. I. Preoperative findings in 114 eyes.

One hundred fourteen eyes of patients with retinal detachment occurring after congenital cataract surgery were studied. Retinal detachment was typified by high incidences of men, myopia, preference for the second and fourth decades of life, and a fairly long interval after cataract surgery. Frequently found were the following: (1) undetected retinal breaks, (2) high incidences of small oval or round holes in the upper nasal quadrant near the ora serrata, (3) retinal detachment in more than one quadrant, and (4) extensive vitreous and preretinal traction. Preoperative examination was often hampered by a small, bound-down pupil, nystagmus, extreme photophobia, and an inability to move the eye in desired directions. The major factor in the pathogenesis of retinal detachment after congenital cataract surgery appears to be chronic vitreoretinal traction in the anterior vitreous caused by cataract removal.

Vision in stage 5 retinopathy of prematurity after retinal reattachment by open-sky vitrectomy.

Performing vitrectomy in stage 5 retinopathy of prematurity is controversial, partially due to limited anatomical and poor reported visual results. Fifty-five eyes of 50 patients whose retinas were reattached by open-sky vitrectomy in stage 5 retinopathy of prematurity and who were followed up for more than 12 months were analyzed retrospectively to ascertain clinical factors that may influence visual outcome. Vision was evaluated by preferential looking. Visual ability to discriminate stationary objects was obtained in 32 (58.2%) eyes, 18 (32.7%) had motion perception, and five (9.1%) had light stimulus perception. Although visual acuities were relatively low, they were useful to these patients. Age at the time of vitrectomy and the shape of the retinal detachment were found to be important factors in predicting visual prognosis.

Intravitreous silicone injection. Histopathologic findings in a human eye after 12 years.

Histopathologic changes occurred in a human eyeball enucleated 12 years after intravitreous silicone injection for the treatment of complicated retinal detachment with massive preretinal membrane. Silicone "bubbles" (droplets) were found in the chamber angle, iris, ciliary body, retina, and preretinal and subretinal membrane, as well as in the optic nerve. Clinically, glaucoma developed in the eye. A review of the literature indicates that the common late complications of intravitreous silicone injection are cataract, glaucoma, and retinal changes.

Hyaluronic acid vitreous substitute. A six-year clinical evaluation.

Hyaluronic acid vitreous substitute (HYVISC) was used during 347 operations performed on 294 eyes of 286 patients. It was injected intraocularly in 266 operations (73 scleral bucklings, 175 open-sky vitrectomies, among others) on eyes with complex retinal detachments that were considered inoperable by ordinary surgical techniques. During 81 closed vitrectomies, it was applied extraocularly between the surgical contact lens and the cornea. Hyaluronic acid was found to be well tolerated by human eyes. In eyes that had been given a poor prognosis, scleral buckling with hyaluronic acid tamponade produced reattachment in 16% of the eyes; open-sky vitrectomy, scleral buckling, and hyaluronic acid salvaged 18%. It also appeared helpful in the preservation of corneal epithelial integrity and clarity during closed vitrectomy.

Gelatin implants in scleral buckling procedures.

In 375 scleral buckling procedures, an absorbable gelatin implant (Retina Gelfilm) was used. This series included 192 trapdoor and scleral pouch procedures, and 183 operations in which a gelatin implant was used beneath a silicone rubber implant. Two thicknesses of gelatin implants were used, 0.5 mm and 0.75 mm. Absorption time varied from 2 to 24 months, depending on the thickness of the implant and whether it was used alone or beneath a silicone rubber implant. Gelatin is an excellent absorbable implant when used alone or under a silicone rubber implant in selected patients with retinal detachment to produce a temporary elevation or posterior extension of the buckle, or both.

Vitreous surgery. XIV. Complications from sclerotomy in 89 consecutive cases.

All patients were examined preoperatively and postoperatively by indirect ophthalmoscopy and biomicroscopy with a three-mirror lens. The average follow-up was eight months. Our technique of sclerotomy consisted of an incision parallel to the limbus, measuring 1.5 times the diameter of the surgical instrument. The pars plana location was always verified with transillumination. A mattress suture over the lips of the sclerotomy was used to prevent any leakage during the procedure. The intraoperative complications included ciliary body laceration (1%), retinal tears (8%), and vitreous base incarceration in the wound. The postoperative complications consisted of retina dragged into the wound (4%), vitreous tract left by the instrument (6%), neovascular ingrowth (6%), and external symptoms from the Dacron (32%) or polyglycolic acid (5%) suture. The rate of complications is considered low for such high-risk surgery.

A new solid-state, frequency-doubled neodymium-YAG photocoagulation system.

We have developed a solid-state laser system that produces a continuous green monochromatic laser beam of 532 nm by doubling the frequency of a neodymium-YAG laser wavelength of 1064 nm with a potassium-titamyl-phosphate crystal. Photocoagulation burns of equal size and intensity were placed in two rabbit eyes with the solid-state laser system and the regular green argon laser system, respectively, using the same slit-lamp mode of delivery. Histologic findings of lesion sections revealed no important differences between the two systems. In theory, the longer wavelength of the solid-state laser offers the advantages of less scattering in ocular media, higher absorption by oxyhemoglobin, and less absorption by macular xanthophyll than the 514-nm wavelength of the regular green argon laser. The solid-state laser has impressive technical advantages: it contains no argon-ion gas tube that wears out and is expensive to replace; it is much more power efficient, and thus considerably smaller and compact; it is sturdier and easily movable; it does not require external cooling; it uses a 220-V monophasic alternating current; and it requires little maintenance.

Long-term complications of the MAI hydrogel intrascleral buckling implant.

Seven cases in which long-term complications developed from swelling of the MAI hydrogel intrascleral buckling implant are reported herein. Micro-Fourier transform infrared spectroscopic analysis of two recovered implants demonstrated the occurrence of chemical changes leading to increased swelling. Clinical problems with the implants appeared 7 to 11 years after surgery, suggesting the need for periodic, long-term follow-up. It is possible that the present-day MIRAgel implant, which has the same chemical composition as the MAI implant, may require similar precautions.

Vitreous surgery. XII. New instrumentation for vitrectomy.

An improved instrument for removing vitreous tissue consists of a replaceable cutting tip and a micromotor that powers the cutting tip. The cutting tip consists of a helical cutter and a metallic tube housing the cutter. An automated power-control unit is also available to control evacuation, infusion, and speed of rotation of the instrument. Several devices for monitoring the outflow of evacuation material and pressure in the eye and in the evacuation line are included. The cutting tip is illuminated by a fiber-optic system, which provides an additional factor of safety. The instrument contains a cleaning mechanism that eliminates the need for disassembling the cutting tip. When an automated control unit is not available, the vitreous nibbler may be used with manual suction, gravity-controlled infusion, and a simplified control unit.

Experimental vitreous surgery. XIII. Open-sky partial vitrectomy through pars plana incision.

The effects of an incision through the pars plana ciliaris for open-sky subtotal vitrectomy were evaluated in four groups of monkeys, with incisions ranging from 170 degrees to 240 degrees. The nasal long ciliary artery and nerve and the anterior ciliary arteries from the inferior and medial recti were left intact in all cases. Follow-up observation ranging from three to 24 months indicates that the 170 degrees incision and the longer incisions in which the temporal ciliary artery and nerve were sacrificed do not cause severe anterior segment necrosis. The advantages of the incision through the pars plana ciliaris are (1) easier approach to the vitreous cavity, (2) preservation of the crystalline lens and an intact iris, and (3) circumvention of the corneal and chamber angle complications sometimes associated with the transcorneal approach.

Immersion A- and B-scan ultrasonography. Its use in preoperative evaluation of diabetic vitreous hemorrhage.

Immersion A- and B-scan ultrasonography was performed before vitreous surgery in 256 eyes with diabetic vitreous hemorrhage. Of 32 eyes with vitreous hemorrhage without vitreous traction (group 1), 28 (88%) showed useful postoperative vision. Of 87 eyes with vitreous traction without tractional retinal detachment (group 2), 69 (79%) had useful postoperative vision. Eyes with tractional retinal detachments were classified as follows: X-shaped detachment with narrow vitreoretinal adhesions (group 3, 75 eyes), and H-shaped detachment with broad vitreoretinal adhesions (group 4, 62 eyes). Useful postoperative vision returned in 43 eyes in group 3 (57%) and in only 14 eyes in group 4 (23%), a statistically significant difference. Visual improvement was greater in groups 1 and 2 than in groups 3 and 4. Postoperative functional results were worse when the macular area was the site of vitreoretinal adhesion and traction.

Manifestations of Whipple's disease in the posterior segment of the eye.

Ocular manifestations of Whipple's disease result from CNS involvement, direct intraocular involvement, or both. Ocular signs caused by CNS involvement occurred in 30 of the 34 patients with ocular manifestations described in the literature. In only four of the 34 cases were ocular manifestations due solely to intraocular involvement. Two cases reported herein had unique intraocular involvement, manifested as diffuse chorioretinal inflammation. Fluorescein angiography showed diffuse vasculitis, with hemorrhages, exudates, retinal capillary occlusion in the perifoveal and midperipheral areas, capillary dilation at the optic disc, and choroidal folds. Proper antibiotic treatment resulted in ocular and systemic recovery. Follow-up is mandatory because of possible recurrences, which may start with intraocular signs, followed by systemic manifestations. Some cases progress to fetal CNS involvement. Therefore, when intraocular signs recur in treated patients, antibiotic therapy should be restarted or dose should be increased.

Choroidal neovascularization in fellow eyes of patients with advanced senile macular degeneration. Role of laser photocoagulation.

Choroidal neovascularization in fellow eyes of patients with advanced disciform macular scars usually has an unfavorable prognosis. Fifty-two such fellow eyes were treated, using the monochromatic green argon laser. The neovascular membranes were foveal in 24 eyes, juxtafoveal in ten eyes, and perifoveal in 18 eyes. Complete closure of the choroidal new vessels after treatment was seen in 46 eyes. Only one eye in the foveal group and five eyes in the juxtafoveal group had residual new vessels. After an average follow-up period of 16 months, improvement or stabilization of vision was seen in 36 eyes--18 eyes in the foveal group, four in the juxtafoveal group, and 14 in the perifoveal group. In view of the rewarding anatomical and functional results, photocoagulation, using the monochromatic green argon laser, should be considered in these high-risk eyes. Treatment of foveal neovascular membranes seems to be indicated if the visual acuity is 20/70 or worse.