Electron microscopic studies of human retinitis pigmentosa. I. Two cases of advanced retinitis pigmentosa

Persistent remodeling and neurodegeneration in late-stage retinal degeneration

Retinal remodeling is a progressive series of negative plasticity revisions that arise from retinal degeneration, and are seen in retinitis pigmentosa, age-related macular degeneration and other forms of retinal disease. These processes occur regardless of the precipitating event leading to degeneration. Retinal remodeling then culminates in a late-stage neurodegeneration that is indistinguishable from progressive central nervous system (CNS) proteinopathies. Following long-term deafferentation from photoreceptor cell death in humans, and long-lived animal models of retinal degeneration, most retinal neurons reprogram, then die. Glial cells reprogram into multiple anomalous metabolic phenotypes. At the same time, survivor neurons display degenerative inclusions that appear identical to progressive CNS neurodegenerative disease, and contain aberrant α-synuclein (α-syn) and phosphorylated α-syn. In addition, ultrastructural analysis indicates a novel potential mechanism for misfolded protein transfer that may explain how proteinopathies spread. While neurodegeneration poses a barrier to prospective retinal interventions that target primary photoreceptor loss, understanding the progression and time-course of retinal remodeling will be essential for the establishment of windows of therapeutic intervention and appropriate tuning and design of interventions. Finally, the development of protein aggregates and widespread neurodegeneration in numerous retinal degenerative diseases positions the retina as a ideal platform for the study of proteinopathies, and mechanisms of neurodegeneration that drive devastating CNS diseases.

Histopathological comparison of eyes from patients with autosomal recessive retinitis pigmentosa caused by novel EYS mutations

To evaluate the retinal histopathology in donor eyes from patients with autosomal recessive retinitis pigmentosa (arRP) caused by EYS mutations. Eyes from a 72-year-old female (donor 1, family 1), a 91-year-old female (donor 2, family 2), and her 97-year-old sister (donor 3, family 2) were evaluated with macroscopic, scanning laser ophthalmoscopy (SLO) and optical coherence tomography (OCT) imaging. Age-similar normal eyes and an eye donated by donor 1's asymptomatic mother (donor 4, family 1) were used as controls. The perifovea and peripheral retina were processed for microscopy and immunocytochemistry with markers for cone and rod photoreceptor cells. DNA analysis revealed EYS mutations c.2259 + 1G > A and c.2620C > T (p.Q874X) in family 1, and c.4350_4356del (p.I1451Pfs*3) and c.2739-?_3244 + ?del in family 2. Imaging studies revealed the presence of bone spicule pigment in arRP donor retinas. Histology of all three affected donor eyes showed very thin retinas with little evidence of stratified nuclear layers in the periphery. In contrast, the perifovea displayed a prominent inner nuclear layer. Immunocytochemistry analysis demonstrated advanced retinal degenerative changes in all eyes, with near-total absence of rod photoreceptors. In addition, we found that the perifoveal cones were more preserved in retinas from the donor with the midsize genomic rearrangement (c.4350_4356del (p.I1451Pfs*3) and c.2739-?_3244 + ?del) than in retinas from the donors with the truncating (c.2259 + 1G > A and c.2620C > T (p.Q874X) mutations. Advanced retinal degenerative changes with near-total absence of rods and preservation of some perifoveal cones are observed in arRP donor retinas with EYS mutations.

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Slowly progressive changes of the retina and retinal pigment epithelium in Briard dogs with hereditary retinal dystrophy. A morphological study

Seven eyes from 2 generations of Briard dogs (5 weeks--7 years old) with congenital night blindness and (in the second generation) impairment of day vision to varying degrees, were examined by light and electron microscopy. Specimens from 4 locations were studied: the central area, the midperiphery of the tapetal area, the upper periphery and the lower periphery. Disorientation of rod outer segment disc membranes was seen in the 5-week-old dog. Large electron-lucent inclusions were found in the RPE at 3.5 months of age. These inclusions occurred most frequently in the central and midperipheral-tapetal areas and seemed to increase in numbers and spread towards the periphery with increasing age. The content of these inclusions is not elucidated. Rod photoreceptor degeneration was apparent from 7 months of age and was most prominent in the peripheral areas. The cones were better preserved. The 7-year-old dog showed reduction of photoreceptors in the central and midperipheral-tapetal areas and almost complete photoreceptor degeneration in the periphery. This dog also showed severe changes of the inner retina in the peripheral fundus. It appears that these Briard dogs suffer from a very slowly progressive retinal degeneration, in which the photoreceptor degenerative changes do not correlate anatomically to the changes in the RPE cells. The disease seems to be different from the retinopathy described in the English Briards. It is not clear yet whether the lipid type of retinopathy found in American Briards is identical to the present disease.

Idiopathic retinal degeneration in the dog: differential patterns of [3H]uridine incorporation and HIOMT-like immunoreactivity in surviving photoreceptors

Photoreceptor cell pathology was investigated in an 8-yr-old mixed-breed dog which had displayed visual symptoms of 1 month duration. An electroretinogram detected no light-evoked responses. Light and electron microscopic features showed marked thinning and atrophy of the outer both the tapetal and non-tapetal retina appeared to be involved. In the non-tapetal region, a majority of the rod inner segments were missing, while scattered mitochondria-filled stubby inner segments of cones were readily identified. Inner segments of both rods and cones were observed in the tapetal region. Photoreceptor outer segments were completely absent from the affected retina, and no outer segment debris was observed between the photoreceptor layer and the retinal pigmented epithelium (RPE). Autoradiographic analysis of 3-mm retinal disks from the degenerate retina following incubation with [3H]uridine indicated that only 61% +/- 13 S.D. of the remaining nuclei of rod photoreceptors were undergoing RNA synthesis, whereas more than 99% of cone nuclei incorporated the label. Normal and degenerate retina were also analysed for localization of hydroxyindole-O-methyltransferase (HIOMT)-like immunoreactivity. While the normal retina showed immunoreactivity in both rod and cone photoreceptors with more intense immunoreactivity present in cones, the degenerate retina showed HIOMT-like immunoreactivity only in the remaining cone photoreceptors. The results of this study of idiopathic photoreceptor degeneration of the canine retina suggest that although both photoreceptor types are involved, rods are more severely affected than cones.

Retinitis pigmentosa and inner retina. Functional study by means of oscillatory potentials of the electroretinogram

The alterations of the inner retina in retinitis pigmentosa have been described in previous papers less often than the external retina alterations, both from the electrophysiological and morphological point of view. The oscillatory potentials (OPs) of the electroretinogram (ERG) are a good tool to investigate the inner part of the retina because of the deep anatomical location of their generators. We studied the photopic OPs in a group of 25 subjects affected with retinitis pigmentosa and compared them with other ERG components to obtain information about the functional damage of the inner retina. The OPs were recordable in 9 patients. No analogies were found with the inheritance modes. No relationship was found between OPs and 20 Hz ERG photopic response which was still present in a consistent number of eyes when OPs were no longer recordable. Such finding can be interpreted as an expression of inner retinal damage paralleling the photoreceptors and retinal pigment epithelium impairment.

Histopathologic study of autosomal dominant vitreoretinochoroidopathy. Peripheral annular pigmentary dystrophy of the retina

Autosomal dominant vitreoretinochoroidopathy (ADVIRC), a recently described disease, is clinically characterized by a slowly progressive or stationary circumferential peripheral pigmentary retinopathy with fibrillar condensation of the vitreous. Histopathologic study of an 88-year-old patient with this disease showed disorganization of the peripheral retina with focally atrophic retinal pigment epithelium (RPE). Altered pigment epithelial cells surrounded retinal blood vessels and lined the internal limiting membrane. At the equator, a remarkable and possibly unique multifocal loss of photoreceptor cells was seen. An extensive preretinal membrane, consisting of condensed vitreous with cellular debris and layers of Müller cells, was demonstrated by electron microscopic examination and immunohistochemistry. Histologically, this entity has some similarities to and some differences from retinitis pigmentosa. The clinical features are distinctive.

Retinitis pigmentosa

Retinitis pigmentosa is a clinically and genetically heterogeneous group of hereditary disorders in which there is progressive loss of photoreceptor and pigment epithelial function. The prevalence of retinitis pigmentosa is between 1/3000 and 1/5000 making it one of the most common causes of visual impairment in all age groups. The natural history, differential diagnosis, diagnostic clinical and electrophysiologic findings are reviewed. Generalization about the different genetic subtypes of retinitis pigmentosa are reviewed along with the uses of DNA probes for linkage studies. Syndromes in which retinitis pigmentosa is a manifestation are summarized.

Ganglioside administration in retinitis pigmentosa

The retinitis pigmentosa process typically causes variably progressive visual loss due to retinal photoreceptor and pigment epithelial cell deterioration. No effective agent either to retard or stop the deterioration has been known. Because gangliosides have been shown to have a variety of trophic effects on peripheral nervous tissue, we administered a daily 40 mg intramuscular dose in a prospective, double-blind, randomized, placebo-controlled trial in 30 persons with retinitis pigmentosa with or without congenital deafness. When we compared baseline performance on the two principal study outcomes, visual field area and electroretinographic response amplitudes, there was a marginally statistically significant increase in visual field area in the ganglioside-treated group. The subgroup of subjects who had recordable electroretinograms at baseline and who received the drug showed in three of five cases an increase in amplitude to all stimuli. These results appear encouraging; however, the data must be interpreted cautiously because the numbers of individuals are very small. Further study of the possible benefits of ganglioside administration to retinitis pigmentosa patients appears warranted.

Cone-rod dystrophy. A clinical and histopathologic report

Clinical, histopathologic, and electron microscopic findings in two postmortem eyes from a 29-year-old black man and the clinical and electrophysiologic findings of his 33-year-old sister, both of whom had bilateral atrophic macular lesions, confirmed the diagnosis of cone-rod dystrophy in these two patients. Light microscopy revealed a loss of photoreceptor cells primarily in the peripheral retina and macula, with relative preservation of both rod and cone cells in the equatorial area. Electron microscopy showed abundant lipofuscin-like granules aggregated in the basal portion of the retinal pigment epithelial cells. In the macular area, many retinal pigment epithelial cells were atrophic. The phagocytic capacity of the retinal pigment epithelium appeared to remain intact. The accumulation of lipofuscin-like granules in the retinal pigment epithelium may be one of the significant pathologic changes of this dystrophy.

Extensive subretinal pigment epithelial deposit in two brothers suffering from dominant retinitis pigmentosa. A histopathological study

The eyes of two brothers with retinitis pigmentosa were removed after death and examined by a variety of techniques, including conventional histology, fluorescence microscopy and both scanning and transmission electron microscopy. Their condition was considered to be of an autosomal dominant type but with some atypical clinical features. The outstanding histological feature in both pairs of eyes was a predominantly acellular deposit of amorphous material situated between the retinal pigment epithelium and Bruch's membrane. This material extended from the disc to beyond the ora serrata. In some regions of the retinae of both brothers, there was a cellular infiltrate into the deposit and this included multinucleate cells. In one brother the deposit was lined externally by a fibrovascular membrane in some few locations. All retinae were degenerate, but all showed preservation of abnormally short and sparse photoreceptor cells in both the peripheral and macular areas. There was only patchy loss of the choriocapillaris, which could have been age-dependent rather than disease-dependent, and the remaining choroidal vessels were patent in all cases. The widespread distribution of the deposit is unusual and suggests that it arises from disordered metabolism of the retinal pigment epithelium. We could not determine whether it was a primary disease process or if it arose as a secondary phenomenon.

Dominantly inherited retinitis pigmentosa. Ultrastructure and biochemical analysis

A 66-year-old white man had dominant retinitis pigmentosa. He developed progressive restriction of his visual field, night blindness, pallor of the optic discs, pigmentary retinopathy and posterior subcapsular cataracts. Postmortem examination of the eyes included electron microscopy and biochemical analysis of cyclic nucleotides and interphotoreceptor retinoid-binding protein (IRBP). Except for the fovea and periphery, the retina showed extensive gliosis and neuronal loss with loss of photoreceptor cells. The choriocapillaris was variably occluded in the regions of absent retinal pigment epithelium (RPE). In places, the pigment epithelium invaded the retina to the level of the internal limiting membrane. Biochemical analysis revealed that the interphotoreceptor retinoid-binding protein (IRBP), an important glycoprotein of the interphotoreceptor space, was virtually absent even in retinal areas where photoreceptor cells were still present. Cyclic nucleotide determinations indicated a decrease in the cyclic GMP concentration that reflected the general loss of photoreceptor elements. On the other hand the cyclic AMP levels in all retinal areas tested were abnormally elevated, indicating the possible involvement of this nucleotide in the pathogenesis of the disease.

Altered synthesis of Bruch's membrane proteoglycans associated with dominant retinitis pigmentosa

Proteoglycans, extracellular matrix molecules that have been shown to have filtration properties in some tissues, make up a significant proportion of the structural macromolecules of Bruch's membrane. Bruch's membrane may provide a selective filtration barrier between the choriocapillaris and the pigmented epithelium (PE) and outer retina. In this paper, we compare the proteoglycans extracted from metabolically-labeled normal and retinitis pigmentosa (RP) Bruch's membranes. Isolated RP Bruch's membrane proteoglycans were larger than those from normal donor eyes when chromatographed on a column of Sepharose CL-4B. In addition to the increased size, there was also a dramatic increase in the proportion of heparan sulfate proteoglycan being synthesized in RP. Considering the structural and filtration properties of proteoglycans, alterations such as these could affect the functioning of Bruch's membrane and, possibly, the PE and the outer retina.

Retinal histopathology of a carrier of X-chromosome-linked retinitis pigmentosa

Autopsy eyes were examined from a 79-year-old female carrier of X-chromosome-linked retinitis pigmentosa. At age 78 years, she had no visual symptoms but had intraretinal bone spicule pigmentation in the nasal and inferior periphery of both eyes. Rods, cones, and pigment epithelium in the central retina appeared normal. In the midperiphery, patches with advanced photoreceptor cell degeneration were observed overlying pigment epithelium containing melanolysosomes. Within these patches, rods and cones were reduced in number or absent, and pigment epithelial cells abutted the external limiting membrane. A precipitous decline in rod nuclei was observed in transitional zones between areas of apparently normal photoreceptors and areas of absent photoreceptors. In the far periphery, large areas lacked photoreceptors and pigment epithelium. Histopathologic findings in this elderly carrier are compared with those previously described in a 24-year-old man with X-chromosome-linked retinitis pigmentosa.

A dominantly inherited chorioretinal degeneration resembling sectoral retinitis pigmentosa

A light and electron microscopic study of an eye from a 79-year-old woman diagnosed as having sector retinitis pigmentosa is presented. Prominent bone spicule pigmentation was present bilaterally in the nasal quadrant. Retinal structure in the central fundus around the fovea and extending 2-3 mm peripherally was near normal with all photoreceptors and other retinal neurons present. Extensive degeneration of the retina occurred as one proceeded toward the peripheral regions from 3-5 mm from the fovea in all quadrants. Changes were evident within the entire choroid and were most severe in regions where retinal degeneration was most pronounced. It is likely that the extensive degenerative changes present in the retina were secondary effects that follow alterations in the choroidal blood supply in individuals affected with this disorder.

The atypical pigmentary retinopathy of Kearns-Sayre syndrome. A light and electron microscopic study

Two postmortem eyes from a 52-year-old man with Kearns-Sayre syndrome were examined by light, scanning, and transmission electron microscopy. Prior to death, pronounced ptosis, total external ophthalmoplegia, an episodic ventricular cardiac arrhythmia, and an atypical pigmentary retinopathy characterized by "choroidal sclerosis" and pigment clumping were documented. Histopathologic examination revealed atrophy of the retinal pigment epithelium and outer retina that was most marked posteriorly. The preservation of photoreceptors appeared to mirror the health of the underlying retinal pigment epithelium. Numerous healthy appearing rods were present in the relatively well-preserved temporal retina. The pattern of photoreceptor degeneration observed in this form of "atypical retinitis pigmentosa" suggests that the primary defect may reside in the retinal pigment epithelium.

Dominant retinitis pigmentosa. A clinicopathologic correlation

Autopsy and clinical studies were performed in a family with dominantly inherited retinitis pigmentosa. The eyes of two senior members of the family were obtained for histopathologic study, while three other family members were studied clinically. All family members studied had visual field loss, nyctalopia, and a spectrum of pigmentary disruption. There was variable expressivity of pigmentary migration, foveal atrophic changes, surface wrinkling retinopathy, choriocapillaris atrophy, drusen, vitreous synchysis, and optic pallor. Three specific zones of retinal and retinal pigment epithelial changes were identified histopathologically. A clinicopathologic correlation is presented.

Sensitivity losses in a long wavelength sensitive mechanism of patients with retinitis pigmentosa

the foveal vision of certain patients afflicted with retinitis pigmentosa may be mediated solely by a long wavelength sensitivity (lws) mechanism, because (1) increment threshold data could always be fitted to a single template curve with unity slope, (2) test and field sensitivities differ only by a proportionality constant over the visible spectrum, (3) intense background fields have additive (quantum catch) effects on thresholds, and (4) wavelength differences of bipartite foveal stimuli could not be distinguished. Both test and field sensitivities were appreciably lower than the lws sensitivity values for unaffected deuteranopes. The action spectrum was similar (but not identical) to estimates of the erythrolabe absorption spectrum. The results provide a better understanding of the photopic vision of patients with retinitis pigmentosa and further evidence that their effective optical density of residual cones is reduced.

Retinitis pigmentosa

The authors review the symptomatic and genetic aspects of the various entities of isolated retinitis pigmentosa (R.P), both in its typical form and in the forms associated with the affection of other ocular tissues. Syndromes in which R. P. is associated with the affection of other organs and systemic disorders are also cconsidered. Origin, diagnosis and the course of the disease are discussed with regard to electrophysiology, histopathology, fluorescein angiography and biochemistry. Animal research has provided new realizations about the ultrastructure and physiological mechanisms of retinal photoreceptors, and better understanding of abnormal changes. The possible pathogenesis of the human disease, based on research findings, is onsidered. Although R.P. is generally thought to be to be an "untreatable" disease, therapy may be effective in several pathological entities. Methods and results of therapy with vitamins, light deprivation and vision aids are discussed.