Distribution of cones in human and monkey retina: individual variability and radial asymmetry.

The distribution of photoreceptors is known for only one complete human retina and for the cardinal meridians only in the macaque monkey retina. Cones can be mapped in computer-reconstructed whole mounts of human and monkey retina. A 2.9-fold range in maximum cone density in the foveas of young adult human eyes may contribute to individual differences in acuity. Cone distribution is radially asymmetrical about the fovea in both species, as previously described for the distribution of retinal ganglion cells and for lines of visual isosensitivity. Cone density was greater in the nasal than in the temporal peripheral retina, and this nasotemporal asymmetry was more pronounced in monkey than in human retina.

Human photoreceptor topography.

We have measured the spatial density of cones and rods in eight whole-mounted human retinas, obtained from seven individuals between 27 and 44 years of age, and constructed maps of photoreceptor density and between-individual variability. The average human retina contains 4.6 million cones (4.08-5.29 million). Peak foveal cone density averages 199,000 cones/mm2 and is highly variable between individuals (100,000-324,000 cones/mm2). The point of highest density may be found in an area as large as 0.032 deg2. Cone density falls steeply with increasing eccentricity and is an order of magnitude lower 1 mm away from the foveal center. Superimposed on this gradient is a streak of high cone density along the horizontal meridian. At equivalent eccentricities, cone density is 40-45% higher in nasal compared to temporal retina and slightly higher in midperipheral inferior compared to superior retina. Cone density also increases slightly in far nasal retina. The average human retina contains 92 million rods (77.9-107.3 million). In the fovea, the average horizontal diameter of the rod-free zone is 0.350 mm (1.25 degrees). Foveal rod density increases most rapidly superiorly and least rapidly nasally. The highest rod densities are located along an elliptical ring at the eccentricity of the optic disk and extending into nasal retina with the point of highest density typically in superior retina (5/6 eyes). Rod densities decrease by 15-25% where the ring crosses the horizontal meridian. Rod density declines slowly from the rod ring to the far periphery and is highest in nasal and superior retina. Individual variability in photoreceptor density differs with retinal region and is similar for both cones and rods. Variability is highest near the fovea, reaches a minimum in the midperiphery, and then increases with eccentricity to the ora serrata. The total number of foveal cones is similar for eyes with widely varying peak cone density, consistent with the idea that the variability reflects differences in the lateral migration of photoreceptors during development. Two fellow eyes had cone and rod numbers within 8% and similar but not identical photoreceptor topography.

Retrolental fibroplasia and factors influencing oxygen transport.

The hospital records of 58 premature infants in whom proliferative retrolental fibroplasia (RLF) developed were matched with the records of 58 infants without RLF for birth weight, gestational age, and duration oxygen therapy. The two groups were compared for factors likely to influence tissue delivery of oxygen by blood. No significant difference was found in incidence of blood transfusions or exchange transfusions, use of phototherapy, or occurrence of acidosis.

Increased survival of low birth weight infants: impact on the incidence of retinopathy of prematurity.

Retinopathy of prematurity is a retinal vascular disease that occurs only in premature infants. Because of concern that the occurrence of this potentially blinding disease is increasing, a retrospective chart review was undertaken to compare the incidence of retinopathy of prematurity at the University of Washington during the years 1981 to 1984 with previously published data collected at the same institution during the years 1968 to 1980. During 1981 to 1984, there was an increase in the annual numbers of admissions and survivors weighing 1750 g at birth; the survival rate increased significantly (P less than .000001). A trend toward an increased risk for proliferative retinopathy of prematurity (P = .057) during 1981 to 1984 period was noted, but the number of "excess cases" was calculated to be only 6 per year. The remainder of the additional cases, 19 annually, were due to increased survival of infants at risk. Thus, the "second epidemic" of retinopathy of prematurity is largely due to improved survival of low birth weight infants rather than to new iatrogenic factors. In infants with proliferative retinopathy of prematurity, there was a previously unreported association between increased severity of disease and lower birth weight (P = .015). There were four children with severe bilateral visual loss due to retinopathy of prematurity identified during the 1981 to 1984 period, whereas only one bilaterally blind infant was noted during the preceding 12.7 years.

PaO2 levels and retrolental fibroplasia: a report of the cooperative study.

The relation between PaO2 and retrolental fibroplasia (RLF) was studied prospectively in 719 premature infants born in or treated in the intensive care units of a group of university hospitals. Blood gas studies were performed on 589 of these infants, 66 of whom had a diagnosis of RLF; in 27 of these 66, some grade of mostly nonblinding cicatricial disease developed. The frequency of RLF was highest among infants of lowest birth weight. A multivariate statistical method was used to analyze simultaneously the effect of possible etiologic factors associated with RLF. The occurrence of RLF was found to be unrelated to PaO2, as determined by the limited information available from intermittent sampling. RLF is associated with concentration of oxygen administered in the lightest birth weight group, but the strongest association, aside from birth weight, was with time in oxygen. None of the other variables involving blood chemical values appeared to be associated with RLF. The severity of cicatricial RLF is clearly greater in infants weighing less than 1,200 g at birth. Conservative administration of oxygen may have been responsible for failure to demonstrate quantitative association between PaO2 levels and disease. Agreement between the observed and predicted numbers of infants with RLF demonstrate the strength of the multivariate technique employed in making the statistical analyses.

Dexamethasone inhibition of experimental endothelial cell proliferation in retinal venules.

The observation that endothelial cell proliferation in retinal blood vessels is induced by ocular trauma in rats has been extended to mice. Indomethacin, 10 mg/kg/day, failed to block incorporation of tritiated thymidine into nuclei of venular endothelial cells in rat retinas observed 40 hr after puncturing the lens, but dexamethasone effectively suppressed tritiated thymidine incorporation, with 50% inhibition obtained with 0.2 mg/kg/day. The prostaglandin pathway does not appear essential to the activation of endothelial cell proliferation in this system.

Clinical-ultrastructural study of a retinal dystrophy.

An ultrastructural and cytochemical study was performed on the retina and retinal pigment epithelium of an eye surgically enucleated for choroidal melanoma from an otherwise healthy 31-year-old man. The patient and his identical twin show a retinal dystrophy that, based on clinical appearance, visual fields, amd electrophysiology, is most likely autosomal recessive retinitis pigmentosa. Rod and cone photoreceptors were reduced in numbers and outer segments were virtually absent in the region corresponding to the patient's poorest vision. In the region from approximately 20 degrees to 60 degrees (best field of vision), the outer segments of rods and cones were shortened and disorganized. The retinal pigment epithelium showed reactive changes in areas of most severe photoreceptor pathology, including re-duplication, loss of melanin, increased melanolysosomes, and migration of individual cells into the retina. The acid phosphatase reactivity of both the retinal pigment epithelium and photoreceptor cells appeared normal, as were the photoreceptor cilia and inner layers of the retina. This study thus provides improved ultrastructural documentation of a relatively early case of retinitis pigmentosa that may provide a foundation for further functional studies aimed at elucidation of this enigmatic retinal dystrophy.

Aging of the human photoreceptor mosaic: evidence for selective vulnerability of rods in central retina.

PURPOSE: Because previous studies suggested degeneration and loss of photoreceptors in aged human retina, the spatial density of cones and rods subserving the central 43 degrees of vision as a function of age was determined. METHODS: Cones and rods were counted in 27 whole mounted retinas from donors aged 27 to 90 years with macroscopically normal fundi. Photoreceptor topography was analyzed with new graphic and statistical techniques. RESULTS: Changes in cone density throughout this age span showed no consistent relationship to age or retinal location, and the total number of foveal cones was remarkably stable. In contrast, rod density decreased by 30%, beginning inferior to the fovea in midlife and culminating in an annulus of deepest loss at 0.5 to 3 mm eccentricity by the ninth decade. Space vacated by dying rods was filled in by larger rod inner segments, resulting in a similar rod coverage at all ages. At the temporal equator, cone density declined by 23%, but rods were stable throughout adulthood. CONCLUSIONS: The stability of both rod coverage and rhodopsin content despite decreasing cell number suggests plasticity of the adult rod system and that age-related declines in scotopic sensitivity may be due to postreceptoral factors. There is no evidence for the massive loss of foveal cones required to explain even modest decrements in acuity, consistent with evidence that visual deficits at high photopic levels may be largely due to optical factors. Why the rods of central retina, which share a common support system and light exposure with the neighboring cones, are preferentially vulnerable to aging remains to be determined.

Facio-oculo-acoustico-renal (FOAR) syndrome: case report and review.

We report on an 11-year-old boy with distinct facial anomalies, iris coloboma, iris hypoplasia, cataract, high myopia, retinal detachment, moderate sensorineural hearing loss, and proteinuria. He appears to have the facio-oculo-acoustico-renal (FOAR) syndrome, a rare familial disorder reported only 4 times previously. In contrast to the other patients, he has normal intellect.

Possible autosomal-recessive ocular coloboma.

Ocular coloboma as an isolated anomaly often is inherited as an autosomal dominant trait. Possible autosomal recessive inheritance is suggested by the presence of colobomatous malformations in a brother and sister whose parents have apparently normal eyes. Possible genetic heterogeneity of isolated ocular coloboma makes genetic counseling in sporadic cases difficult since cases may be due to autosomal dominant and autosomal recessive mutations and nongenetic causes.

Proliferative retinopathy after treatment of carotid-cavernous fistulas.

The carotid-cavernous fistulas of two young patients were treated by multiple carotid artery ligations. The fistulas persisted, supplied by retrograde flow through the ophthalmic artery. In one patient, neovascularization of the optic disc occurred and, in spite of suspected later spontaneous closure of the fistula, progressed to cause nearly total loss of vision. Spontaneous closure of the fistula also occurred in the other patient, but vitreous hemorrhage due to neovascularization of the retina developed four years later.

Choroidal involvement in systemic necrotizing vasculitis.

Wegener's granulomatosis and lymphomatosis are systemic necrotizing vasculitides of unknown cause. We report similar involvement of the choriocapillaris in these two diseases. A presumed choriocapillaritis caused ischemia and infarction of the choriocapillaris-retinal pigment epithelium-outer neurosensory retina complex. Systemic corticosteroid and immunosuppressive agents were successful in controlling systemic disease and preserving useful vision. At the time of this study, one patient had not had a recurrence for 12 years, and the other patient had been asymptomatic for seven years.

Multifocal choroidal melanoma in ocular melanocytosis.

A 29-year-old white women had ocular melanocytosis with scleral pigmentation and a diffuse choroidal nevus. The eye was enucleated because of two choroidal tumors. Light and electron microscopy showed two separate choroidal melanomas with differential cytologic characteristics. The extreme rarity of multicentric choroidal melanomas support the belief that ocular melanocytosis predisposes to malignancy.

An evaluation of saline irrigation and comparison of povidone-iodine and antibiotic in the surface decontamination of donor eyes.

We evaluated the effect of saline irrigation on 38 pairs of donor eyes and determined the relative efficacy of antibiotic rinse/storage (neomycin-polymyxin B-gramicidin) and povidone-iodine immersion. Microbial growth was found in 49 (64.5%) of 76 eyes from which cultures were taken before irrigation, and only four (8.2%) became culture negative after irrigation. Of 27 eyes culture negative before irrigation, 15 (55.6%) became positive after irrigation. One eye of each pair was then assigned randomly to antibiotic rinse/storage and the other eye to 3-minute immersion in 1% povidone-iodine. Both antimicrobial treatments decreased the numbers of positive cultures, with povidone-iodine showing an advantage that did not reach significance. These results demonstrate that saline irrigation of donor eyes in situ does not reduce surface contamination and that povidone-iodine immersion should be considered as an alternative for donor eye decontamination.

Retinal oxalosis. A clinicopathologic report.

A 55-year-old woman with chronic renal failure treated with hemodialysis had severe bilateral visual loss develop due to retinal ischemia. Ophthalmoscopy showed crystals in the distribution of the retinal arteries, but not veins, and this led to a diagnosis of systemic oxalosis. Factors contributing to systemic oxalosis in addition to renal failure were ascorbic acid dietary supplementation, pyridoxine deficiency, and ileal resection. Histopathologic findings showed ocular calcium oxalate deposition limited nearly entirely to the walls of retinal blood vessels.

Radiation retinopathy after orbital irradiation for Graves' ophthalmopathy.

Recent reports indicate that orbital irradiation for Graves' ophthalmopathy is sometimes beneficial, particularly for dysthyroid optic neuropathy, and is not associated with serious complications. We are aware, however, of four patients who were found to have radiation retinopathy after orbital irradiation for Grave's ophthalmopathy. All four patients have decreased central acuity, and three of the four are legally blind in one or both eyes. Computer reconstruction of the dosimetry, based on computed tomography and beam profiles, shows that errors in dosage calculations and radiotherapy technique probably account for the radiation retinopathy in three of the four patients. Radiotherapy for Graves' ophthalmopathy should be administered only by competent radiotherapists who are experienced in the treatment of this disease. Similar errors in dosage calculations and treatment techniques may account for other reports of radiation retinopathy after reportedly safe dosages.

Cone dysfunction in a subgroup of patients with autosomal dominant cerebellar ataxia.

Four patients with autosomal dominant cerebellar ataxia and retinal degeneration underwent neurologic and ophthalmologic examinations and computer-assessed corneal electroretinography. Previous reports described progressive panretinal degeneration initially involving the cones and subsequently spreading to the rods. By contrast, all our patients displayed evidence of selective dysfunction of the cone system in one or two successive electroretinograms, irrespective of their age or duration of visual symptoms. Color vision testing, funduscopy, and fluorescein angiography suggested a cone dystrophy. Within the period of observation only one patient showed progression of cone dysfunction. In patients with hereditary ataxias, quantitative electroretinography provides an objective and sometimes early indication of retinal degeneration and helps to characterize it.

Contamination of corneal tissue from infected donors.

Thirty-two corneas with scleral rims were cultured from the eyes of 17 cadavers that harbored systemic infection at the time of death. Twelve (71%) of 17 cadavers demonstrated corneal contamination from one or both corneas. Eleven (92%) of 12 donors with positive postmortem blood cultures had positive corneal cultures from at least one eye. Six of these 12 had the same organism isolated from both the blood and corneal tissue. Bacterial corneal cultures were negative in the five donors with negative postmortem blood cultures. Control cultures were obtained from 19 eyes of ten donors without evidence of infection at death. Four (21%) of 19 control eyes yielded Staphylococcus epidermidis. There was a significantly higher incidence of corneal contamination in donors who died with systemic infections. Eye banks should continue to screen donors carefully for documented or suspected sepsis in an effort to reduce the incidence of postkeratoplasty infections.

Ocular complications of arteriovenous communications of the retina.

Primary arteriovenous communications of the retina (AVCR) are usually considered to be stable retinal lesions. Complications were documented in seven cases of AVCR, including intraretinal macular hemorrhage, central and peripheral retinal vein occlusions, neovascular glaucoma, and vitreous hemorrhage. To explain these developments, a hypothesis is presented that AVCR are associated with localized decreased retinal arterial pressure, increased retinal venous pressure, increased turbulence of blood flow, and decreased perfusion of adjacent retinal tissues.

Ocular effects following the volcanic eruptions of Mount St Helens.

Three hundred thirty-two ophthalmologists examined 1,523 patients with immediate ocular complaints following the 1980 eruptions of Mount St Helens. Loggers working up to 18 months in environments with high concentrations of volcanic ash were compared with a control group of loggers without volcanic ash contact. Although the ash particles acted as ocular foreign bodies, the small particles were apparently well tolerated for the most part, except for acute irritation. Patients with contact lenses or sicca syndrome had the most frequent ocular complaints. To date, no long-term ocular effects have been noted secondary to volcanic ash exposure.