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The purpose of this study is to ascertain whether inherent differences exist in the retinal function of two macaque species that are commonly used in experimental glaucoma investigations. We quantified and compared multifocal electroretinograms (mfERGs) from ocularly normal cynomolgus (n = 36) and rhesus (n = 18) monkeys. The stimulus array consisted of 103 equal-sized hexagonal elements, which subtended +/-44 degrees about the central visual axis. Mean luminance of the display was 100 cd/m2. The firstorder kernel (K1) and second-order (first slice) kernel (K2) of the mfERG were averaged into 4 rings radiating from the foveal element, and represented the central 56 degrees of visual field. Fifteen and 30-element segments were used for K1 and K2 quadrant and hemiretinal response determinations, respectively. Response measures for the rings, quadrants, and hemiretinae included K1 amplitude and implicit time, and K1 and K2 oscillatory potentials (OPs) and response amplitude root mean square (RMS). Species, gender, and retinotopic differences were assessed with repeated measures analysis of variance (split plot design). K1 amplitudes of the N1 waves, K1 and K2 OPs and K2 amplitude RMS for the ring, quadrant, and hemiretinal mfERG waveforms were larger in rhesus than in cynomolgus monkeys. Rhesus males (as compared to rhesus females) and cynomolgus females (as compared to cynomolgus males) exhibited larger amplitudes and less delayed implicit times in the central retina. These results demonstrate that species-specific differences in retinal function are evident in cynomolgus and rhesus monkeys. There also were gender-associated differences that varied across species. Thus, investigators should exercise caution when data from species or gender are combined.

Purpose: To determine the effects of panretinal photocoagulation (PRP) on the levels of cytochrome oxidase (CO), Zif268, synaptophysin, and growth-associated protein 43 (GAP-43) in the primary visual cortex of adult monkeys., Methods: Ten adult primates underwent unilateral argon laser PRP with instrument settings at 300 to 500 microns spot diameter, 200 to 500 mW power intensity, and 0.1 to 0.2 second duration, causing moderate to severe burns in the peripheral retina. At 20 hours, 12 days, 6 months, and 13 months after laser treatment, the visual cortex was assessed histologically for CO and immunohistochemically for Zif268, synaptophysin, and GAP-43., Results: PRP resulted in transneuronal changes in the relative distributions of CO, Zif268, synaptophysin, and GAP-43 in the primary visual cortex. CO activity was relatively decreased in the lasered eye's ocular dominance columns at 12 days post-PRP, with recovery by 13 months post-PRP. The level of Zif268 was dramatically decreased in the lasered eye's ocular dominance columns at 20 hours post-PRP, with gradual recovery by 13 months post-PRP. Levels of synaptophysin and GAP-43 immunoreactivity were increased in both the lasered and the nonlasered eyes' ocular dominance columns at 6 months post-PRP., Conclusion: PRP treatment results in metabolic activity changes in the visual cortex of the adult monkey. These changes are followed chronologically by spatial redistribution of synaptophysin and GAP-43, neurochemicals known to play a role in cortical plasticity. This study demonstrates, for the first time, that PRP as used in the treatment of diabetic retinopathy results in a redistribution of neurochemicals in the adult monkey visual cortex. Such changes may help explain the anomalous visual functional loss often reported by patients after PRP.

Objective: To determine whether selective cone loss could explain the acquired tritan-like color confusion found in diabetic retinopathy., Methods: Terminal deoxynucleotidyl transferase-mediated biotin-deoxyuridine triphosphate nick end labeling (TUNEL) was employed on paraffin sections of retinas from 5 donors with diabetic retinopathy. For quantitative analysis, postmortem retinas were obtained from 13 human donors; 7 from patients with various durations and stages of diabetic retinopathy (4 background, 3 proliferative) and 6 controls. Enzyme histochemical analysis for carbonic anhydrase (CA) was used to distinguish L/M-cones (positive for CA) from S-cones (negative for CA). Cone topography was determined by sampling 360 degrees from 0.1 to 1.5 mm of foveal eccentricity and along the horizontal meridians from 1.5 to 15.0 mm., Results: Rare cells in both the inner and outer nuclear layers of the diabetic eyes were positively labeled with the TUNEL method. The CA staining revealed incomplete and patchy losses of S-cones that were limited to the diabetic retinas. Statistically significant reduction in the density of S-cones was found at nearly all foveal eccentricities from 0.1 mm to 15.0 mm. This was not the case for the L/M-cones. On average, for all locations, the percentage of S-cones compared with L/M-cones was decreased by 21.0% +/- 3.4% with respect to the controls., Conclusion: The S-cones selectively die in diabetic retinopathy., Clinical Relevance: Selective loss of S-cones may contribute to the tritan-like color vision deficit seen in patients with diabetic retinopathy.

Objective: To test a hypothesis of photoreceptor involvement in retinal ganglion cell (RGC) death in chronic glaucoma., Methods: Laser spots were applied to 6 eyes of 3 rhesus monkeys, causing focal destruction of the outer retina, including the photoreceptors. After 3 to 4 weeks, experimental glaucoma was induced in the right eyes of each monkey using argon laser trabecular destruction (ALTD). The intraocular pressures in these eyes were elevated for 3 to 7 months. As a control, 1 additional monkey underwent retinal laser photocoagulation followed by optic nerve transection instead of ALTD. Following enucleation, the retinas were embedded and sectioned for histologic evaluation., Results: There was extensive loss of RGCs in the eyes with ALTD except over the large retinal laser spots, where there was an increased survival of RGCs. The RGC protection was not observed in the monkey that had undergone optic nerve transection., Conclusion: Photocoagulation of the outer retina that completely destroys the photoreceptors results in survival of the overlying RGCs in experimental glaucoma in monkey eyes., Clinical Relevance: Although this is an experimental model and not a therapeutic option, these results suggest that treatments other than lowering intraocular pressure may be potential therapies for preventing RGC death in glaucomatous eyes. Arch Ophthalmol. 2000;118:1242-1250

Objective: To determine whether outer retinal changes occur in chronic, presumed primary open-angle glaucoma (POAG)., Methods: The outer retinas from 128 human eyes with a diagnosis of chronic glaucoma (presumably POAG in most cases) and 90 control eyes were examined histologically by 3 masked observers for photoreceptor swelling and loss. Retinas from 9 rhesus monkeys with glaucoma induced experimentally by laser trabecular destruction were compared with 7 fellow (control) eyes. The mean pressure elevations in the eyes with laser trabecular destruction ranged from 26.6 to 53.6 mm Hg with durations varying from 7 to 33 weeks., Results: Swelling of the red- and green-sensitive cones was observed in a statistically significantly greater proportion of human eyes with presumed POAG compared with the control eyes. Patchy loss of red/green cones and rods was also found in some of the glaucomatous retinas. In a subset of the human eyes with end-stage disease, cone swelling was a variable finding. Although no photoreceptor loss was found in the 9 monkey eyes with experimental glaucoma, 8 had swelling of their red/green cones that was remarkably similar to that seen in the human eyes. Swelling was not present in any of the control monkey eyes., Conclusions: The photoreceptors are affected by chronically elevated intraocular pressure., Clinical Relevance: These findings may explain some of the abnormalities of color vision and the electrophysiological effects that have been observed in patients with POAG.

Purpose: First, to study the cellular mechanisms of acquired color vision loss in retinal detachment and diabetic retinopathy. Second, to learn why, in glaucoma, the type of color vision deficit that is observed is more characteristic of a retinal injury than it is of an optic neuropathy. Third, to test a hypothesis of photoreceptor-induced, ganglion cell death in glaucoma., Methods: Various histologic techniques were employed to distinguish the L/M-cones (long/medium wavelength-sensitive cones, or red/green sensitive cones) from the S-cones (short wavelength-sensitive cones, or blue sensitive cones) in humans and monkeys with retinal detachment, humans with diabetic retinopathy, and both humans and monkeys with glaucoma. To test if the photoreceptors were contributing to ganglion cell death, laser photocoagulation was used in a experimental model of glaucoma to focally eliminate the photoreceptors. As a control, optic nerve transection was done following retinal laser photocoagulation in one animal., Results: Selective and widespread loss of the S-cones was found in retinal detachment as well as diabetic retinopathy. By contrast, in human as well as experimental glaucoma, marked swelling of the L/M-cones was the predominant histopathologic feature. Retinal laser photocoagulation followed by experimental glaucoma resulted in selective protection of ganglion cells overlying the laser spots. This was not seen with retinal laser photocoagulation by optic nerve transection., Conclusions: In retinal detachment and diabetic retinopathy, acquired tritan-like color vision loss could be caused, or contributed to, by selective loss of the S-cones. Both L- and M-cones are affected in glaucoma, which is also consistent with a tritan-like deficit. Although not a therapeutic option, protection of ganglion cells by retinal laser in experimental glaucoma is consistent with an hypothesis of anterograde, photoreceptor-induced, ganglion cell death.

Objective: This study aimed to evaluate the treatment efficacy of a congenital vitreous cyst and to examine the cyst histopathologically to determine its cellular makeup and possible origin., Study Design: The study design was a case report, including a clinicopathologic correlation., Intervention: A 35-year-old woman with a known vitreous cyst since childhood became increasingly troubled by its symptoms. The cyst was treated initially with argon laser photocoagulation. Vitrectomy subsequently was performed because the deflated cyst remained near the visual axis. Histopathologic studies included light and electron microscopy; immunocytochemistry for actin and glial fibrillary acidic protein (GFAP); and enzyme histochemistry for carbonic anhydrase (CA)., Results: The cyst was composed of a single layer of heavily pigmented cells with a thick basement membrane along the internal borders of the cells. Ultrastructurally, the cells were connected with tight junctions, had microvillous processes at their apices, and contained numerous large melanosomes in various stages of maturity, including premelanosomes. Immunochemistry showed the cells were positive for actin but negative for GFAP. Enzyme histochemical staining for CA also was strongly positive., Conclusions: The confinement of this cyst to the region of Cloquet's canal, the presence of a Mittendorf's dot, the cyst's existence for many years, and the finding of pigment epithelial-type cells having immature melanosomes (a feature not seen after birth in normal pigment epithelium) lead the authors to believe that this cyst was a congenital remnant of the primary hyaloidal system. Because pigmented cells are not normally present in this part of the eye, the cyst was a choristoma of the primary hyaloidal system.

Background: Retinoblastoma is the most common childhood tumor of the eye, arising from cells that are defective in both copies of the retinoblastoma susceptibility gene (RB1). Most retinoblastoma tumor cells eventually undergo programmed cell death (i.e., apoptosis); however, some cells can acquire the ability to metastasize and become immortal. Transfection of immortal retinoblastoma cells with DNA sequences encoding wild-type p53 protein induces cell death, suggesting that the loss of both RB1 and p53 functions may be required for cell immortalization. We have examined this possibility by characterizing the p53 protein and messenger RNA in six independently isolated, immortalized retinoblastoma cell lines., Methods: Western blotting methods were used to assess p53 protein level in each cell line, and Cleavase Fragment-Length Polymorphism analysis of complementary DNAs was used to screen for mutations in p53 messenger RNA. Localization of p53 protein in cells of the immortalized lines and in specimens of retinoblastoma tumors was achieved by means of indirect immunofluorescence and immunocytochemistry, respectively., Results: All six immortalized cell lines expressed wild-type p53 messenger RNA and high levels of p53 protein. Although p53 is normally a nuclear protein, the p53 in four of the six cell lines was located predominately in the cytoplasm; in the remaining two cell lines, p53 was localized in both the nucleus and the cytoplasm. Cytoplasmic localization of p53 in retinoblastoma tumor specimens was rare and usually restricted to cells that had invaded adjacent ocular tissues, indicative of the early stages of metastasis., Conclusions: Some immortalized retinoblastoma cells may exhibit p53 dysfunction through nuclear exclusion of wild-type p53 protein.

Objective: To describe and classify a retinal tumor found in a dog that histologically resembles human retinoblastoma and to discuss the molecular mechanisms of retinal oncogenesis., Methods: A dog eye with a retinal tumor was examined histologically. Studies including immunocytochemical analysis for retinal S-antigen and glial fibrillary acidic protein, enzyme histochemical analysis for carbonic anhydrase, and nick-end DNA labeling were used to characterize the tumor. Normal retina from another dog and other tumors from dogs, including 2 ciliary body medulloepitheliomas and a brain medulloepithelioma, were examined as controls., Results: The retinal tumor disclosed characteristics typical of human retinoblastoma, including Flexner-Wintersteiner rosettes. It showed strong immunoreactivity with S-antigen and glial fibrillary acidic protein. Carbonic anhydrase activity also could be shown in the tumor. Apoptosis was found to be the predominant method of cell death as shown by nick-end DNA labeling. In contrast to the other tumors examined, this tumor contained areas with retinal photoreceptor and glial differentiation., Conclusions: The histopathologic findings and differential staining characteristics in this retinal tumor are compatible with retinoblastoma, making this, to our knowledge, the first documented case of spontaneous retinoblastoma in an animal.

Objectives: To determine whether apoptosis is a significant mode of cell death in human retinoblastoma (RB) and if it is regulated by the expression of p53., Methods: Apoptosis was analyzed using the criterion of internucleosomal DNA degradation as determined by agarose gel electrophoresis of DNA isolated from tumor specimens. Individual cells undergoing apoptosis were identified using terminal transferase-mediated biotin-dUTP nick end labeling (TUNEL) of fragmented DNA. The expression of p53 and WAF1 (a protein involved in p53-mediated cell cycle arrest) in human RB was determined by immunocytochemical analysis. The function of p53 in human RB cell lines was tested by transfecting them with a complementary DNA encoding a temperature-sensitive isoform of murine p53 under the control of a strong viral promoter., Results: DNA from RB tumor specimens showed a strong nucleosomal ladder of DNA fragments typical of apoptosis. The TUNEL staining indicated that poorly and moderately differentiated cells in tumors were undergoing DNA fragmentation. Immunoreactivity for p53 was variable. Cells expressing low levels of p53 seemed viable and expressed WAF1. Cells expressing high levels of p53 were found immediately adjacent to cells undergoing apoptosis. Human RB cells in culture that were expressing a murine temperature-sensitive isoform of p53 died at temperatures that allow this protein to assume a wild-type conformation., Conclusions: Apoptotic cell death is prevalent in RB. The close association of p53-immunoreactive cells and cells undergoing apoptosis in human tumors, and the ability of exogenous p53 to stimulate cell death in cultured human RB cells, suggests that p53 plays a role in regulating cell death in RB.

Objective: To describe the clinical course and immunocytochemical characteristics of an unusual intraocular tumor., Methods: Immunocytochemical analysis of the enucleated eye with an intraocular mass that markedly waxed and waned in size during 1 year of close observation of a 29-year-old woman., Results: Most of the tumor was composed of either dying or rapidly proliferating cells. One area located near the retina consisted mostly of well-differentiated cells in uniform sheets (bacillettes) with lacelike glial processes between the tumor cells. Almost all of the differentiated tumor cells were positive for S antigen. In particular, the dominant cell type stained positively for both antibodies known to be specific for those isoforms of S antigen found only in blue cones and rods but not in red or green cones. Only a few of these cells labeled positively with an anti-rhodopsin antibody., Conclusions: This is the first case of adult retinoblastoma to be confirmed immunocytochemically. The tumor was unusual because the differentiated regions contained bacillettes composed mostly of blue cones. It is possible that this and other adult retinoblastomas may arise from previously existing retinocytomas.

Background: Recent reports have indicated that acetazolamide alters human electroretinograms. We wished to determine the effects of administering acetazolamide on performance on the Nagel II anomaloscope., Methods: We tested 15 subjects matches of blue-green light to a mixture of blue and green lights (luminance match) on a Nagel type II anomaloscope 2.5 h after ingesting 500 mg of acetazolamide or a placebo., Results: The mean of the luminance settings for the subjects was 54.4 for the placebo condition and 58.5 for the acetazolamide condition. The mean difference of 4.1 was statistically significant, indicating that following ingestion of acetazolamide subjects were less sensitive to a blue-green light. In two supplementary experiments we tested (1) a second group of four normal subjects using the Nagel type II anomaloscope and (2) the previously untreated eyes of four patients with primary open-angle glaucoma before and after placing them on acetazolamide therapy. In both groups, more blue-green light was needed to make the match after ingestion of acetazolamide., Conclusions: Acetazolamide alters the sensitivity of one or more cone populations, probably the carbonic anhydrase-containing cones. The sensitivity loss is reversible and does not appear to be clinically significant. However, the results suggest that patients administered acetazolamide should be excluded from studies which compare the color vision of glaucomatous patients to that of normals.

Objective: To determine if there are histopathologic changes in the outer retina that could explain the blue-yellow color confusion previously described following rhegmatogenous retinal detachment in humans., Methods: Ten eyes with traumatic retinal detachments were studied. Eight of the eyes were removed from 2 1/2 to 11 days following trauma. In the remaining two eyes, the retinas were successfully reattached. Enzyme histochemical studies for carbonic anhydrase and immunochemical studies for S antigen were performed to distinguish blue cones from red/green cones., Results: With the 2 1/2- to 4-day-old detachments, nearly all of the carbonic anhydrase-negative (blue-sensitive) cones and many of the rods were seen to have signs of irreversible necrosis, including extreme swelling of the inner segments and mitochondria, loss of the outer segments, and pyknotic and displaced nuclei. In the 6- and 11-day-old detachments, almost all of the carbonic anhydrase-negative cones and many rods were missing. Blue cones were essentially absent from the reattached retinas, and there were only about half the normal number of rods., Conclusions: Rhegmatogenous retinal detachment results in rapid and almost total loss of the blue cones. Significant rod loss also occurs in this type of detachment but the red/green cones are comparatively resistant to damage. These findings could explain the observed blue-yellow color confusion in such patients. We discuss other clinical implications.

Objectives: To apply modern techniques of molecular cell biology and to revisit the old question of the cell of origin for retinoblastoma in hopes of gaining a better understanding of the retinoblastoma gene's antioncogenic mechanisms., Methods: Twenty-two consecutively accessed retinoblastomas were examined with immunocytochemical techniques for numerous retinal proteins. Both single and double labeling were used. Enzyme histochemistry for carbonic anhydrase was used as well., Results: Differentiated areas of the tumors contained abundant Müllerlike cells. Fleurettes stained mostly for red and green cone-specific antibodies while features of blue cones and rods predominated in areas with high cytoplasmic-to-nuclear ratios but no fleurettes. All of the differentiated neoplastic cells were either photoreceptors or Müller's cells. No other retinal cell types were found., Conclusions: The cells of retinoblastoma are capable only of bipotential differentiation, ie, Müller's cells and photoreceptors. Given this and recent findings concerning retinal embryogenesis, we argue for the rod photoreceptor as the cell of origin. A possible role for the retinoblastoma gene product is discussed.

Purpose: To determine whether, by employing recent advances in immunocytochemical technique, it is possible to identify reliably the product of the retinoblastoma (RB) susceptibility gene, p110RB1, in formalin-fixed, paraffin-embedded eyes with commercially available primary antibodies. If so, the authors sought to determine the distribution of p110RB1 in normal human eyes and retinoblastomas in hopes of better understanding its function., Methods: Four antibodies to p110RB1 were tested on normal human and monkey eyes, as well as on six human retinoblastomas. The human tissue was formalin-fixed and paraffin-embedded. Free antigen was used for an absorbed control. The monkey eye had been injected with tritiated (H3) thymidine 24 hours before enucleation., Results: Three of the four antibodies had acceptable reactivity (a polyclonal against the carboxyl-terminal epitope and two monoclonals against epitopes near the amino-terminus). Staining was confined to nucleated cells of the normal eyes and was strongest in the cycling cells of the lenticular and corneal epithelia. Somewhat weaker reactivity was seen in those corneal epithelial cells in S phase as determined by autoradiography for H3-thymidine. Of the six retinoblastomas, three had strong nuclear and cytoplasmic staining and one showed weaker staining in the tumor cells than in the adjacent vascular endothelial cells. Two of the tumors had positive cytoplasmic and negative nuclear staining with an amino-terminal antibody but were completely negative for carboxyl-terminal p110RB1 reactivity., Conclusions: Using appropriate immunocytochemical techniques, p110RB1 can be identified in paraffin-embedded tissues with commercially available antibodies. The observed staining pattern in retinoblastoma suggests that RB1 transcripts are commonly produced in the tumor cells and that they are sometimes, but not always, capable of nuclear binding. Thus, nuclear binding by the RB1 gene product per se is not sufficient to prevent tumor growth, nor does it indicate the presence of a normal transcript.

In three separate experiments albino rabbits, pigmented rabbits, and humans were tested following administration of acetazolamide and without acetazolamide. In all three experiments, we recorded electroretinograms (ERGs) under dark adapted and light adapted conditions and measured the b-wave amplitudes. Dark adapted ERG b-wave amplitudes were increased following administration of acetazolamide as compared to control conditions, in albino rabbits, pigmented rabbits and humans. Light adapted b-wave amplitudes showed no statistically significant changes as a function of acetazolamide administration although in all three experiments there was a trend toward light adapted b-wave amplitude reduction following administration of acetazolamide. In the human experiments, ERG a-wave amplitudes were also measured. Light adapted a-wave amplitudes were reduced following administration of acetazolamide. In the human experiments, several behavioral tests were performed, including L'Anthony desaturated D-15, Farnsworth-Munsell 100 hue, Cogan-Gunkel chromatograph, Nagel anomaloscope, Goldmann-Weekers dark adaptometry. There were no consistent changes in the human dark adaptation thresholds or color discrimination, although several measures approached significance.

Purpose: S-antigen (48 kDa protein or arrestin) is known to be present in rod photoreceptors. Its localization in cones is less clear with several conflicting reports among various species examined., Methods: This study employed three different anti-S-antigen antibodies (a48K, a polyclonal antiserum and two monoclonal antibodies, MAb A9-C6 and MAb 5c6.47) and examined their localization in rods and cones of human and cat retinas. To identify the respective cone types, an enzyme histochemical technique for carbonic anhydrase (CA) was employed to distinguish blue cones (CA-negative) from red or green cones (CA-positive). S-antigen localization was then examined by immunocytochemical staining of adjacent sections., Results: In human retinas, a similar labeling pattern was seen with both a48K and MAb A9-C6, i.e., the rods and blue-sensitive cones were strongly positive, whereas the red- or green-sensitive cones showed little immunoreactivity. All human photoreceptors showed reactivity to MAb 5c6.47. In the cat retina, only CA-positive cones could be found. As in the human retina, both rods and cones of the cat were positive for MAb 5c6.47. A difference from the labeling pattern in human retina was noted for the other S-antigen antibodies; a48K labeled rods and all of the cones, whereas MAb A9-C6 reacted strongly with the rods but showed no cone staining., Conclusions: These results suggest that both rods and cones contain S-antigen but that they are antigenically distinctive.

In one family with low-penetrance retinoblastoma, a germ-line deletion is shared by affected and unaffected, obligate carriers. The deletion encompasses exon 4 of the retinoblastoma gene and corresponds to a mutant protein without residues 127-166. In a second family, RFLP analysis shows that two distant relatives have independently derived mutations. These families, together with others reported elsewhere, indicate that attributes of alleles at the retinoblastoma locus specify penetrance.

The distribution of carbonic anhydrase (CA) among human photoreceptors has been a topic of dispute. In our experiments, by modifying an established enzyme histochemical technique, reproducible staining was observed. Of the cones in the peripheral retina, 91% were positive for CA. The CA-negative (CA-) cones were absent within approximately 8 arc min of the foveal center and their density peaked at 2 arc deg. No CA activity was found in the rods. Morphologic differences were noted between the CA-positive (CA+) and CA- cones. Compared to the CA+ cones, the CA- cones had longer and more nearly columnar inner segments, more nearly spherical nuclei, and more generous amounts of perikaryal cytoplasm. In the peripheral retina, the distance between CA+ to CA+ nearest neighbors were larger compared to CA- to CA+ nearest neighbors (P less than 0.0001). The frequency distribution and morphology of the CA- cones suggest that they are the blue-sensitive cones. As such, this study demonstrates a biochemical similarity between blue cones and rods that may provide insight into the function and phylogeny of the blue cones.

After an eye-wall resection for a choroidal melanoma, a 32-year-old woman had subsequent retinal detachment with proliferative vitreoretinopathy (PVR), and an unsuccessful attempt at repair with retinal tacks. Gross and light-microscopic examination of the globe revealed a total retinal detachment with extensive preretinal and subretinal membranes. The membranes surrounded the tack heads and extended in taut bands to form a tractional detachment of the pars plana. The membranes contained glial and nonglial cells. The glial cells immunolabeled for glial fibrillary acidic protein (GFAP), carbonic anhydrase-C (CA-C), vimentin, and glutamine synthetase (GS), thus suggesting that they were Müller's cells. While the tacks did not seem to cause PVR, in this case they may have provided an anchoring point from which membranes were able to exert traction on the retina and pars plana.

Two cases of Waardenburg's syndrome are presented. The first case is an example of Waardenburg's type II (without dystopia canthorum) with bilateral sectoral iris heterochromia and fundus bicolor, hyperpigmented skin patches, characteristic facies and deafness. The second case is an example of Waardenburg's type I (with dystopia canthorum) with complete iris heterochromia and characteristic facies. Bilateral glaucoma was also present in the second case. Previously unrecognized details of iris architecture in Waardenburg's syndrome are described. Pigmentation anomalies of the skin are also discussed. It is hypothesized that the ocular pigmentary disturbance in Waardenburg's syndrome is widespread and involves the hyperchromic as well as the hypochromic areas of the eyes. A possible association with glaucoma might be explained by such a hypothesis.

The frequency and extent of immunostaining for actin, fibronectin (FN), and glial fibrillary acidic protein (GFAP) were determined in 37 preretinal membranes (PRMs) obtained at vitrectomy from 35 patients with proliferative diabetic retinopathy (PDR) (n = 16), proliferative vitreoretinopathy (PVR) (n = 18), or idiopathic macular pucker (MP) (n = 3). All three proteins were detected in the vast majority of specimens (actin, 86%; FN, 95%; GFAP, 96%), although the extent of staining varied for each. Actin-FN co-localization was observed in all diagnostic groups on comparison of adjacent sections and in double-labeled sections. The extent of actin staining did not correlate with clinical grading of PRM contraction. In PDR membranes, FN staining was low overall, but proportional to the vascular content of the PRM. Fibronectin staining of PVR membranes was greater, and extensive even in avascular specimens. In MP membranes, most cells were GFAP-positive, whereas in PDR and PVR specimens, GFAP staining was variable. The lack of correlation of clinical contractility and membrane composition, as studied in this article by immunostaining, indicates that other factors must play significant roles in determining membrane behavior.

To test whether the Müller's cell, and not the fibrous astrocyte alone, is an active glial element in proliferative diabetic retinopathy, we developed a method using enzyme histochemical analysis for carbonic anhydrase and immunolabelling for glial fibrillary acidic protein on plastic-embedded sections to detect Müller's cells in degenerated retinas. Four postmortem eyes with proliferative diabetic retinopathy were studied. Four features of Müller's cell behavior were observed: (1) Müller's cell nuclei migrated within the retina. (2) They were the principal glial cells in preretinal membranes. (3) Müller's cells formed horizontal bands, in the outer retina, that gave the appearance of subretinal membranes. (4) They formed intraretinal bridges between cystic spaces. In conclusion, the Müller's cell (or its progeny) plays an active role in proliferative diabetic retinopathy.

Both Müller cells and astrocytes have been implicated in the dispute over the histogenesis of massive retinal gliosis. We studied three cases of massive retinal gliosis by light and electron microscopy and immunocytochemistry. Spindle fibrillary glial cells were joined by zonulae adherentes resembling those of the external limiting membrane of the retina. Furthermore, these cells produced a continuous basement membrane around an extracellular space filled with fine filaments, which was highly suggestive of vitreous cavity. In the proliferating cells, immunoperoxidase technique disclosed the presence of carbonic anhydrase isoenzyme C, characteristically found only in Müller cells. The glial cells in the preretinal membrane away from the gliotic nodule showed similar characteristics. We concluded that both the nodule of massive retinal gliosis and the associated preretinal glial membrane resulted from the proliferation and migration of Müller cells.

We developed an animal model that allows the early phases of iris neovascularization to be studied in detail. Three major retinal branch veins were occluded with the argon laser in five eyes of cynomolgus monkeys, after which the eyes were enucleated at various time intervals. We observed three phases of the neovascular process in the iris. The early phase was characterized by vessel dilation and intense uptake of tritiated thymidine in the vascular endothelial cells. In the intermediate phase, prominent new vessels, ectropion uveae, peripheral anterior synechiae, and elevated intraocular pressure developed. Also noted were a decrease in tritiated thymidine uptake of the endothelial cells, a remarkable increase in stromal cell tritiated thymidine activity, and the formation of a neovascular membrane in association with the anterior migration of stromal cells. The late phase was marked by a further reduction of tritiated thymidine uptake and regression of the neovascular membrane.

Electroretinography (ERG) has been utilized to claim that the various hereditary subtypes of retinitis pigmentosa (RP) could be distinguished according to the temporal characteristics of the b wave. This study compares two different ERG techniques, one utilizing constant amplitude response and the other balanced photopic and scotopic stimuli, for the early diagnosis of RP. Both methods were found to be reliable objective tests for diagnosing RP. Neither test could differentiate between dominant, autosomal recessive, or X-linked RP.

To determine the effect of timolol maleate on corneal epithelial wound closure, 6.4-mm (diameter) epithelial defects were created chemically in five experiments. In rabbits, wound closure was not significantly altered by the administration of 0.5% Timoptic (a commercially prepared timolol maleate solution) every eight hours, but it was inhibited during the first 15 hours of healing when a 4% solution was applied every two hours. Monkeys received a 5% solution every 12 hours and were divided into treated and control groups. Two phases of wound healing were apparent: a rapid initial phase and a slower final phase. Wound closure was inhibited in treated eyes during the initial rapid phase. This experiment repeated on the same monkeys, but with the control and treated animals switched, yielded the same result. Another experiment, with the fellow eye of the monkey used as a control, showed no significant difference in wound closure.