Characterization of corneal proteoglycans under vitamin A deficiency.

Comparison of in vivo radiolabeled corneal proteoglycans from vitamin A deficient, pair-fed control and normal rabbits by chromatographic and enzymatic methods, reveals subtle but reproducible changes in the proteoglycans present in the vitamin A deficient corneas relative to those of pair-fed and normal control corneas. Although the total amounts of [3H]leucine and [35S]sulfate incorporated in vivo into the proteoglycans per cornea are similar in the three types of cornea, the proteoglycan affinity for DEAE-Sepharose is different, with more of the vitamin A deficient proteoglycans requiring a higher NaCl concentration for elution. Analysis of in vivo labeled rabbit corneal proteoglycans reveals that in vitamin A deficient animals, relative to pair-fed controls, there is (1) an increase in the proteoglycans digested by chondroitinase AC indicative of decreased epimerization of glucuronic acid to iduronic acid; (2) an increase in the amount of keratan sulfate proteoglycan with high affinity for an anion exchange resin, consistent with a greater negative charge; (3) differences in proteoglycan affinities for octyl-Sepharose, reflecting differences in hydrophobicity; (4) increased susceptibility to proteolysis by trypsin; (5) no significant difference in sulfation.

Aminoguanidine inhibits reactive oxygen species formation, lipid peroxidation, and oxidant-induced apoptosis.

Aminoguanidine (AG) treatment, like nerve growth factor (NGF) treatment, prevents diabetes-induced apoptosis of retinal Müller cells in the rat eye, but the mechanism involved is unknown. In this study, the effects of preincubation with AG on oxidant-induced apoptosis, oxidant-induced intracellular reactive oxygen species (ROS) production, and lipid peroxidation were determined in rat retinal Müller cells and compared with the effects of NGF, a protein that protects neuronal cells from oxidative stress. The effect of AG on rabbit vitreous lipid peroxide levels was also determined. After exposure to increasing concentrations of H2O2, there was a corresponding increase in the percentage of apoptotic Müller cells. Preincubation with AG for 48 h completely inhibited oxidant-induced apoptosis in response to 10 micromol/l H2O2 (+AG 0 vs. 10 micromol/l, NS), and reduced the percentage of apoptotic cells in response to 50 micromol/l H2O2 by 50% (+AG vs. -AG, P < 0.01). Longer preincubation did not increase the antiapoptotic effect of AG. The effect of AG was dose-dependent. Similar results were obtained after preincubation with NGF. Both AG and NGF preincubation prevented the twofold increase in oxidant-induced lipid peroxides. The fivefold increase in oxidant-induced ROS production was decreased 100% by NGF, but only 61% by AG preincubation. The twofold increase in vitreous lipid peroxide level in diabetic rabbits was completely prevented by AG treatment. AG reduced H2O2-induced benzoate hydroxylation in a dose-dependent manner. Intracellular glutathione content was unchanged. These data demonstrate that AG can act as an antioxidant in vivo, quenching hydroxyl radicals and lipid peroxidation in cells and tissues and preventing oxidant-induced apoptosis.

Measurement of retinal blood vessel width using computerized image analysis.

We report a new method for quantitating retinal blood vessel width from fluorescein angiogram negatives using a computerized image analyser. Interuser and intrauser variability were 3 to 4 times lower than reported with older methods. In addition, model blood vessels were used to test the accuracy of our method under four clinically relevant conditions: variations in vessel width, fluorescein concentration, flash intensity and background fluorescence. Although computed measurements were affected by vessel width, fluorescein concentration and flash intensity, the linearity of the actual versus computed width was maintained during wide variations in all four conditions (r = 0.95, P less than 0.0001). Accuracy was best achieved at a flash intensity of 150 W/sec and a fluorescein concentration of 45 micrograms/ml. The results of this study provide a better understanding of factors affecting the apparent width of retinal blood vessels in fluorescein angiograms. This technique should be useful in rapidly obtaining accurate measurements of blood vessel width from fluorescein angiograms.

Photodynamic retinal vascular thrombosis. Rate and duration of vascular occlusion.

Dye-sensitized photochemical thrombosis is a new method of producing vascular occlusion in the eye for experimental purposes. The rate and duration of photodynamic occlusions of branch retinal vessels was measured in pigmented and albino rat eyes after intravenous injection of the photosensitizing dye, rose bengal. Selected vessels were exposed to focused, white light until vascular occlusion was observed biomicroscopically. A slit lamp was used for a light source in this procedure, allowing adjustment of spot size, shape, and orientation. Arterioles occluded more rapidly than venules, and the time required to produce vascular occlusion decreased when animals breathed pure oxygen administered by face mask. Rose bengal doses of 40 and 80 mg/kg were effective, 20 mg/kg was partially effective, and 1 and 10 mg/kg were ineffective in producing branch arteriole occlusion at a light intensity of 73.5 mW/cm2. The total light energy required to produce occlusion increased from an average of 0.06 J using 80 mg/kg to 0.50 J using 20 mg/kg of rose bengal. Lower light intensities produced vessel occlusion less rapidly (46 mW/cm2) or not at all (17.5 mW/cm2). The rate of retinal arteriolar occlusion was not affected by ocular pigmentation. The duration of branch vessel occlusion depended on length of vessel treated and did not exceed 3 days in arterioles and 4 days in venules. Histologic sections showed discrete areas of retinal and choroidal vascular thrombosis confined to the area of direct light exposure. Choroidal vascular thrombosis and outer retinal damage predominated in eyes treated at low light intensity. Thrombosis usually extended into the deep choroidal vessels in albino but not pigmented eyes.(ABSTRACT TRUNCATED AT 250 WORDS)

Retinal blood flow in normal and diabetic dogs.

We have found retinal blood flow to be decreased in diabetic dogs 5 months after the onset of diabetes, which is long before they can be expected to develop morphological changes of diabetic retinopathy. Retinal blood flow was determined using radionuclide labelled microspheres. In eight alloxan diabetic dogs without retinopathy, the retinal blood flow was 0.53 +/- 0.08 (mean +/- SE) ml/min/gm dry tissue weight. This compares with 0.91 +/- 0.17 (mean +/- SE) ml/min/gm dry tissue weight in seven normal dogs. The decreased blood flow in diabetic retinas is statistically significant (P = 0.05). Blood glucose levels did not significantly affect retinal blood flow. This data suggest that changes in retinal blood flow and oxidative metabolism may precede the morphological signs of diabetic retinopathy.

Vitrectomy prevents retinal hypoxia in branch retinal vein occlusion.

Vitrectomy has been shown to halt diabetic retinal neovascularization, but the mechanism of this process is unknown. We propose that vitrectomy improves the oxygen supply to ischemic inner retina by way of fluid currents in the vitreous cavity. In order to test this hypothesis, we induced branch retinal vein occlusion in cats and measured preretinal oxygen tension before and after branch retinal vein occlusion in ten nonvitrectomized and five vitrectomized eyes. Branch retinal vein occlusion caused a significant decrease in preretinal oxygen tension in nonvitrectomized eyes, in which the oxygen tension fell from 20 +/- 7 to 6 +/- 5 mmHg (P = 0.001). Conversely, in vitrectomized eyes the oxygen tension was not significantly reduced after branch retinal vein occlusion. The data demonstrate that branch retinal vein occlusion causes retinal hypoxia in nonvitrectomized eyes, whereas after vitrectomy the hypoxic effect of branch retinal vein occlusion is reduced. The relief of retinal hypoxia that follows vitrectomy may be responsible for halting retinal neovascularization after vitrectomy in diabetic patients.

Treatment of experimental preretinal neovascularization using photodynamic thrombosis.

Retinal or preretinal neovascularization (NV) is the result of many ischemic conditions of the retina and is an important factor leading to severe visual loss in diabetic retinopathy. Panretinal photocoagulation does not always control its growth or bleeding sequelae. A potential new treatment modality, photodynamic therapy (PDT), was evaluated for limiting the progression of experimental NV in the rabbit eye. The NV was produced by injecting cultured dermal fibroblasts into the preretinal vitreous space after combined enzymatic and mechanical vitreolysis. This method results in traction retinal detachment with a rapid and consistent growth of NV. After administration of the photosensitizing dye rose bengal (20 mg/kg intravenously), PDT was done using a slit-lamp light source focused through a fundus contact lens (45 J/cm2). The NV was treated on two separate occasions during the active phase of growth (on days 13 and 21 after fibroblast injection). Control animals were exposed to light before injection of rose bengal. Eight randomly assigned animals in each group were followed between treatments and for 28 days after the second treatment. The appearance of NV was documented by frequent photography and fluorescein angiography. The PDT resulted in thrombosis of NV for at least 3 days. Reperfusion, however, was consistently noted at 7 days. Thrombosis was associated with a delay in the growth and maturation of NV fronds, which resumed after reperfusion. Twenty-eight days after the second treatment, NV in both experimental and control eyes had undergone atrophy. At that time (the conclusion of follow-up), however, the size of treated NV fronds (estimated from computerized image analysis of fluorescein angiograms) was significantly less than that of controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Histopathology of experimental preretinal neovascularization.

Despite the morbidity resulting from abnormal retinal neovascularization, morphological events associated with its development have not been fully described. We therefore studied sequential morphologic events during preretinal neovascularization in an experimental model induced by injection of 250,000 homologous fibroblasts into the vitreous cavity of rabbits. Within 2 days following fibroblast injection, thickening of many venular and capillary endothelial cells resulted in partial obliteration of their lumina. 3H-thymidine incorporation occurred first in the nonvascular cells of the superficial medullary ray and thereafter in the preretinal vessels and extraretinal fibroblasts. Capillary budding was obvious within 3 days, with endothelial cells extending cytoplasmic processes into fragmented extracellular matrix (ECM). Endothelial cells, at the tips of budding vessels, and at more proximal sites in the parent vessel, incorporated 3H-thymidine and did not lose cell contact or migrate individually into the ECM. Lumina were present throughout the entire length of the buds and endothelial cells remained polarized. Neovascular events observed in this experimental model parallel those previously described in diabetic retinopathy and retinopathy of prematurity in humans.

Secondary aqueous humor stimulates the proliferation of cultured bovine corneal endothelial cells.

Secondary aqueous humor (2 degrees AH) is known to contain elevated levels of serum macromolecules and has been shown to stimulate the proliferation of lens epithelial cells both in vivo and in vitro as well as corneal endothelial cells in vitro. The purpose of this study was to characterize the response of bovine corneal endothelial cells to 2 degrees AH from rabbits and to compare the effect when the cells were grown on plastic dishes covered with an extracellular matrix or on plastic alone. The addition of varying amounts of 2 degrees AH protein (0.1 to 10 mg/ml) to bovine corneal endothelial cells (cultured in MEM plus 1% serum) resulted in a dose dependent proliferative response as measured by the incorporation of 3H-thymidine into DNA. Except for a 2-hr lag phase, the proliferative response increased with increasing time of exposure (6-18 hrs) of the cells to 2 degrees AH containing a constant amount (2.0 mg/ml) of protein. The generation time and final density of the cells, but not the plating efficiency, was significantly greater when the cells were grown in the presence of 2 degrees AH protein on an extracellular matrix rather than plastic alone. Selective adsorption of prostaglandins and aromatic compounds from 2 degrees AH reduced its ability to produce a proliferative response to control levels. These results indicate that 2 degrees AH can alter or regulate events in the cell cycle of corneal endothelial cells. The responsible factor(s) could be involved in control of cellular regeneration in the eye following injury.

The safety of intravitreal hyaluronidase. A clinical and histologic study.

The authors previously developed a new model of preretinal neovascularization in the rabbit eye using hyaluronidase for enzymatic vitreolysis. The purpose of this study was to evaluate the safety of intravitreal injections of hyaluronidase. Concentrations of 1, 15, 30, 50, and 150 IU of hyaluronidase in 0.1 ml of 0.9% saline were injected intravitreally and aspirated repetitively until the vitreous was partially liquified. The animals were examined with indirect ophthalmoscopy, fundus photography, and fluorescein angiography before injection and on days 1 and 7 after injection. Light and electron microscopic retinal sections were prepared from enucleated eyes at days 1 and 7. All concentrations of hyaluronidase were effective in producing partial vitreolysis. Eyes treated with 1 IU showed no abnormalities on days 1 or 7. Eyes treated with 15 IU showed no retinal abnormalities on day 1, but on day 7 histologic abnormalities were present in two of four eyes. At higher concentrations, clinical and histologic changes were seen in proportion to the concentration and included focal whitening, edema, vitreous haze, vascular abnormalities, and retinal necrosis at the highest doses. Histologic evaluation of the retina revealed marked destruction in all layers at the higher concentrations. The authors conclude that 1 IU of intravitreal hyaluronidase is sufficient for partial vitreolysis and nontoxic to the rabbit retina.

Oxygen kinetics in the vitreous substitute perfluorotributylamine: a 19F NMR study in vivo.

Perfluorocarbon (PFC) vitreous substitutes yielded promising results in the surgical management of retinal detachments. This success is due primarily to their physical properties. However, oxygen kinetics in PFC in vivo have not been investigated. The oxygen flux in the vitreous substitute perfluorotributylamine (FTBA) was assessed in the rabbit eye by monitoring the partial oxygen pressure (PO2) in real-time using Fluorine-19 nuclear magnetic resonance spectroscopy (19F NMR) The spin-lattice relaxation rate (T1)-1 of the CF3 resonance of FTBA is a rapid and sensitive index of PO2. T1-derived PO2 from the FTBA-filled rabbit eye was followed at regular time intervals under different oxygenation protocols. In the first series of experiments, FTBA in the vitreous space was oxygenated by ventilating the rabbit with a mixture of 95% O2 and 5% CO2. The oxygen uptake profile could be approximated by a simple exponential function with a time constant of 159 +/- 110 min (mean +/- SD, n = 3). A more reproducible correlate was obtained by performing an initial rate analysis on the first hour of ventilation with high oxygen levels. This analysis showed that the rate of increase in FTBA PO2 was 2.34 +/- 0.67 mm Hg/min (mean +/- SD, r2 = 0.99, n = 7). After the animal was removed from the 95% O2/5% CO2 gas and was ventilated with room air, the oxygen clearance profile could be approximated in all cases by a single exponential with a time constant of 59.8 +/- 9.6 min (mean +/- SD, n = 4).(ABSTRACT TRUNCATED AT 250 WORDS)

Herpetic keratitis in experimental vitamin A deficiency.

Herpes simplex virus type I (KOS) was instilled onto the eyes of rabbits with experimentally induced xerophthalmia (vitamin A deficient) and control animals fed a vitamin A supplemented diet. The severity of the herpes virus-induced corneal disease, assessed by biomicroscopic examination and by counting the number of corneal lesions as well as by determining the virus titers, was significantly less in vitamin A deficient animals than in controls. Infection of the corneas of the vitamin A deficient rabbits with herpes simplex virus did not precipitate keratomalacia. The few lesions present on the corneas of the vitamin A deficient animals were in the corneal periphery, which was less keratinized than the central cornea. Electron microscopy suggested that virus was capable of replicating in the basal and wing cells in the peripheral corneal lesions in the vitamin A deficient animals. These studies indicate that vitamin A deficiency alone may not predispose the host to more severe ocular herpesvirus infections.

Acid proteases and histologic correlations in experimental ulceration in vitamin A deficient rabbit corneas.

Although xerophthalmia due to severe vitamin A deficiency is the leading cause of childhood blindness in the underdeveloped countries, little is known about the proteases (other than collagenase) that are involved in the degradative mechanism. The degree of cellular autolysis and stromal degradation observed histologically in early stages of xerophthalmia and in ulcerating corneas in vitamin A deficient rabbits in this study were, in general, proportional to the levels of the proteases studied. The only major histologic and ultrastructural alteration observed in early xerophthalmic corneas was autolysis of superficial epithelial and stromal cells. In contrast, in the ulcerating corneas the stroma was infiltrated heavily with inflammatory cells and extensive stromal degradation was observed in the central necrotic region of the lesions. Maximal proteolytic activity toward hemoglobin was observed at pH 3.3 for corneal extracts from normal (N) and pair-fed control (C) rabbits and rabbits with early xerophthalmia (X) and ulcerating xerophthalmia (U) corneas. This activity was a cathepsin D-like enzyme per cornea that had a ratio of 1:1:3:16 in the N, C, X, and U corneas. The ratio of cathepsin B-like activity per cornea for N, C, X, and U corneas was 1:2:2:10.

The effect of combined daunorubicin and triamcinolone acetonide treatment on a refined experimental model of proliferative vitreoretinopathy.

Prior studies have shown that intravitreal daunorubicin (9-15 nmol) and triamcinolone acetonide (2 mg) are effective individually in preventing retinal detachment in experimental proliferative vitreoretinopathy. This report compares the efficacy of the combination of daunorubicin (15 nmol) and triamcinolone acetonide (2 mg) with that of daunorubicin alone in a refined experimental model of proliferative vitreoretinopathy. The degree of retinal detachment in each treatment group was graded, with the unequivocal absence or presence of retinal detachment used as an indicator of treatment success or failure. Both treatments (daunorubicin alone and in combination with triamcinolone acetonide) effectively prevented retinal detachment. However, there was no significant difference in the rate of retinal detachment between the two treatment groups. These results indicate that combination therapy with daunorubicin/triamcinolone is no more effective at preventing retinal detachment than daunorubicin alone.

Inhibition of human subconjunctival fibroblast proliferation by immunotoxin.

The ability to target proliferating cells is important for agents used to modulate wound healing by decreasing the growth of fibroblasts. Proliferating cells are known to express increased numbers of transferrin receptors and have increased receptor turnover. 454A12 Mab-rRA, an immunotoxin containing anti-human transferrin receptor monoclonal antibody conjugated to recombinant ricin A chain, was shown to inhibit the proliferation of human subconjunctival fibroblasts in vitro. A dose-related reduction of cell counts was observed in proliferating cells. More than 90% inhibition was achieved with an immunotoxin concentration of 10 ng/ml per 20,000 cells plated. In contrast, confluent fibroblasts were markedly less sensitive to the immunotoxin at equivalent concentrations. Comparative experiments demonstrated that 5-fluorouracil has less specificity for proliferating cells, with significant death of confluent fibroblasts at high drug concentrations.

Reduction of basement membrane thickening in diabetic cat retina by sulindac.

Capillary basement membrane thickening is one of the earliest histologic lesions in diabetic retinopathy. Its pathogenesis is not understood; however, recent evidence suggests that aldose reductase may play a role. In this study, a new animal model, the diabetic cat, was used to determine whether retinal capillary basement membrane thickening occurred early in the course of hyperglycemia, and if so, whether it could be inhibited by sulindac, an aldose reductase inhibitor. Retinal capillary basement membrane thickness was significantly increased in diabetic cats compared to normal cats (114 +/- 15 vs 72 +/- 12 nm, mean +/- SD) [corrected]. Basement membrane thickness was significantly less in sulindac-treated diabetic cats (93 +/- 9 nm) compared to the untreated diabetic cats (114 +/- 15 nm). In addition, quantitation of endothelial cells, pericytes, and contacts between endothelial cells and pericytes in electron micrographs revealed that they were not reduced in number in untreated diabetic cats compared to normal or sulindac-treated diabetic animals.

An experimental model of preretinal neovascularization in the rabbit.

Although progressive retinal neovascularization is a potentially blinding complication of several diseases, there are no good animal models. The authors developed a consistent model of preretinal neovascularization in the rabbit by partially digesting the posterior vitreous with repeated injection and aspiration of 1 IU of hyaluronidase before injection of 250,000 homologous dermal fibroblasts. The evolution of the new preretinal vessels was monitored by indirect ophthalmoscopy, fundus photography, and fluorescein angiography. A grading system was devised using fundus photographs and fluorescein angiograms to describe the progression of new vessel growth and the extent of fluorescein leakage. Ninety-five percent of the eyes had vascular enlargement and hyperemia but no fluorescein leakage by day 1. Fifteen percent of the eyes had clinically evident new preretinal vessels, and 32% had severe fluorescein leakage by day 7. Ninety-five percent of the eyes had definite neovascularization by day 14. Severe fluorescein leakage peaked at day 14 (55% of the eyes) and decreased thereafter. Involution or atrophy of the vessels occurred in all eyes by day 42. This model will be useful for studying the pathogenesis of preretinal neovascularization and evaluating potential treatments for its prevention.

Ultrastructure of fiber cells and multilamellar inclusions in experimental diabetes.

PURPOSE: The goal of this ultrastructural study was to examine fiber cell shape and intercellular junctions during the early stages of fiber cell breakdown and edema in diabetic rabbit lenses. METHODS: Lens abnormalities were recorded with a slit lamp. Between 6-10 mo after drug treatment, diabetic lenses and untreated control lenses were freshly enucleated and sectioned with a vibrating knife microtome. The thick tissue sections were chemically fixed and processed for thin-section electron microscopy. RESULTS: Alloxan-induced diabetes in albino rabbits produced clinically apparent cataracts as soon as 1 mo after the animals became hyperglycemic. The cataracts displayed cortical fluid-filled vacuoles in the equatorial region and at the cortex-nucleus interface, white specks scattered throughout the cortex, and posterior subcapsular cataracts. Fiber cells just deeper than the large cortical vacuoles had oval or spindle-shaped cross sections. Multilamellar inclusions, not reported previously for diabetic lenses, were observed at or near the fiber cell interfaces and were composed of concentric or spiral rings of plasma membrane-bound cytoplasmic processes. Undulating membranes were present throughout most of the multilamellar inclusions. Transparent lenses from untreated controls did not have such multilamellar bodies or extensive membrane undulations in cells at the same distance from the lens surface. CONCLUSIONS: Fiber cells respond to the diabetic insult differently depending on their stage of differentiation and age. The observed changes are consistent with the hypothesis that hyperglycemia accelerates the formation of age-related changes in fiber cells.

Retinal hypoxia in long-term diabetic cats.

PURPOSE: To determine whether the retina is hypoxic in early stages of diabetic retinopathy in cats and to correlate intraretinal PO2 with fluorescein angiographic and histologic alterations. METHODS: Intraretinal PO2 was measured with microelectrodes in three cats with long-standing diabetes (>6 years) that had been followed with fluorescein angiographs every 6 months. Average PO2 in the inner vascularized half of the retina was compared with similar measurements in 21 control animals. Photoreceptor oxygen consumption was also compared. The retinal vascular endothelium of the diabetic animals was stained for ADPase activity in flatmounts, and transverse sections were used to visualize microscopic alterations in vascular structure. RESULTS: PO2 in the inner half of the retina was abnormally low in the diabetic cats, 7.7+/-5.2 mm Hg (35 penetrations in 3 cats) versus 16.4+/-9.3 mm Hg in normal cats (85 penetrations in 21 cats) (P << 0.001). Oxygenation was almost normal in some regions of the diabetic retinas, but little evidence of oxygen supply from the retinal circulation was observed in other regions. Inner retinal hypoxia was present in areas with no detectable capillary dropout in fluorescein angiograms or flatmounts. The worst changes histologically were microaneurysms, leukocyte and platelet plugging of aneurysms and venules, and degenerating endothelial cells in capillary walls. These histologic abnormalities were confined to small regions, some of which could be positively correlated with markedly abnormal PO2 profiles. Photoreceptor oxygen utilization was not affected in two diabetic cats, but was below normal in one animal in which choroidal PO2 was low. CONCLUSIONS: This is the first direct demonstration of retinal hypoxia in early diabetic retinopathy, before capillary dropout was evident clinically. Hypoxia was correlated with endothelial cell death, leukocyte plugging of vessels, and microaneurysms.

Aclacinomycin A in the treatment of experimental proliferative vitreoretinopathy. Efficacy and toxicity in the rabbit eye.

PURPOSE: Aclacinomycin A is an oligosaccharide anthracycline that, by contrast with daunomycin, lacks carcinogenicity. The authors evaluated the efficacy of aclacinomycin A in prevention of experimental proliferative vitreoretinopathy (PVR) and its toxicity on the rabbit retina. METHODS: Dutch-belted rabbit were used to create a model for traction retinal detachment. Seven to 10 days after vitreous gas compression, 25,000 homologous fibroblasts were injected into the vitreous cavity. Subsequently, the eyes received either sham injections or doses of 6, 30, or 60 nmol of aclacinomycin A, respectively. The fundus findings were documented on days 7, 14, and 28 after the fibroblast injection. The toxicity studies were conducted according to the same protocol as was used for the efficacy evaluation but without the fibroblast injection. Simultaneous electroretinograms were recorded on days 0, 3, 7, and 14 from the right eyes that were injected with 30 or 60 nmol of aclacinomycin A and the left eyes that were sham injected. Morphologic studies were conducted on the eyes enucleated on days 3, 7, and 14 after drug exposure. RESULTS: Intraocular administration of 30 nmol of aclacinomycin A on day 2 after fibroblast injection resulted in a detachment rate of 37.5% (controls, 100%; P < 0.01, by Fisher's exact test). Administration of 60 nmol of aclacinomycin A 3 days after fibroblast injection resulted in a detachment rate of 26.7% (controls, 100%; P < 0.0001). Six nanomoles of aclacinomycin A 3 days after fibroblast injection had no effect. No electroretinogram changes were present in eyes treated with 30 nmol of aclacinomycin A. Such recordings from eyes exposed to 60 nmol of aclacinomycin A demonstrated decreased a- and b-waves on day 3; these completely recovered by day 7. Morphologic studies of these eyes revealed no damage to the retina. CONCLUSIONS: These results suggest that aclacinomycin A should be considered an alternative to daunomycin for treatment of human PVR because, in addition to its lack of carcinogenicity, it shows good efficacy and causes less retinal toxicity.