Sector retinitis pigmentosa

Beyond Sector Retinitis Pigmentosa: Expanding the Phenotype and Natural History of the Rhodopsin Gene Codon 106 Mutation (Gly-to-Arg) in Autosomal Dominant Retinitis Pigmentosa

Sector and pericentral are two rare, regional forms of retinitis pigmentosa (RP). While usually defined as stable or only very slowly progressing, the available literature to support this claim is limited. Additionally, few studies have analyzed the spectrum of disease within a particular genotype. We identified all cases (9 patients) with an autosomal dominant Rhodopsin variant previously associated with sector RP (RHO c.316G > A, p.Gly106Arg) at our institution. Clinical histories were reviewed, and testing included visual fields, multimodal imaging, and electroretinography. Patients demonstrated a broad phenotypic spectrum that spanned regional phenotypes from sector-like to pericentral RP, as well as generalized disease. We also present evidence of significant intrafamilial variability in regional phenotypes. Finally, we present the longest-reported follow-up for a patient with RHO-associated sector-like RP, showing progression from sectoral to pericentral disease over three decades. In the absence of comorbid macular disease, the long-term prognosis for central visual acuity is good. However, we found that significant progression of RHO p.Gly106Arg disease can occur over protracted periods, with impact on peripheral vision. Longitudinal widefield imaging and periodic ERG reassessment are likely to aid in monitoring disease progression.

Minimizing axon bundle activation of retinal ganglion cells with oriented rectangular electrodes

OBJECTIVE

Retinal prostheses aim to restore vision in patients with retinal degenerative diseases, such as age-related macular degeneration and retinitis pigmentosa. By implanting an array of microelectrodes, such a device creates percepts in patients through electrical stimulation of surviving retinal neurons. A challenge for retinal prostheses when trying to return high quality vision is the unintended activation of retinal ganglion cells through the stimulation of passing axon bundles, which leads to patients reporting large, elongated patches of light instead of focal spots.

APPROACH

In this work, we used calcium imaging to record the responses of retinal ganglion cells to electrical stimulation in explanted retina using rectangular electrodes placed with different orientations relative to the axon bundles.

MAIN RESULTS

We showed that narrow, rectangular electrodes oriented parallel to the axon bundles can achieve focal stimulation. To further improve the strategy, we studied the impact of different stimulation waveforms and electrode configurations. We found the selectivity for focal stimulation to be higher when using short (33 μs), anodic-first biphasic pulses, with long electrode lengths and at least 50 μm electrode-to-retinal separation. Focal stimulation was, in fact, less selective when the electrodes made direct contact with the retinal surface due to unwanted preferential stimulation of the proximal axon bundles.

SIGNIFICANCE

When employed in retinal prostheses, the proposed stimulation strategy is expected to provide improved quality of vision to the blind.

Multifocal electroretinographic responses in sector retinitis pigmentosa

HEADINGS

Multifocal electroretinography (mfERG) may be useful in the management of sector retinitis pigmentosa (SRP).

AIM

To compare multifocal electroretinographic responses in SRP, generalised retinitis pigmentosa (GRP), and healthy controls.

METHODS

Eighteen patients with SRP, twelve with GRP, and fifteen controls were included in the study. All participants underwent: complete ophthalmological examination, Humphrey visual field testing, full-field ERG, and mfERG. The mean P1 amplitude, the implicit time (IT), and the mapping of the local responses were evaluated.

RESULTS

The mean P1 amplitude was higher in the SRPs than in GRPs (p < 0.001), while it did not differ between SRPs and controls (p = 0.913). In the SRPs, the P1 amplitude in pathologic areas was higher than in the GRPs (p < 0.001). In normal areas, this parameter did not differ from the controls (p = 0.499). Moreover, in the SRPs, no differences in the P1 amplitude and the IT between pigmented and non-pigmented areas were found.

CONCLUSION

In the present study, the mfERG examination displayed significant differences between sector and generalised RP, showing normal values in sector RP even in pigmented areas. Considering the patients included in this study, SRP seems to represent a favourable variant of the disease, characterised by a limited retinal involvement and apparently mild functional damage. It is still unclear how these results can be extended to other forms of SRP.

The molecular and cellular basis of rhodopsin retinitis pigmentosa reveals potential strategies for therapy

Inherited mutations in the rod visual pigment, rhodopsin, cause the degenerative blinding condition, retinitis pigmentosa (RP). Over 150 different mutations in rhodopsin have been identified and, collectively, they are the most common cause of autosomal dominant RP (adRP). Mutations in rhodopsin are also associated with dominant congenital stationary night blindness (adCSNB) and, less frequently, recessive RP (arRP). Recessive RP is usually associated with loss of rhodopsin function, whereas the dominant conditions are a consequence of gain of function and/or dominant negative activity. The in-depth characterisation of many rhodopsin mutations has revealed that there are distinct consequences on the protein structure and function associated with different mutations. Here we categorise rhodopsin mutations into seven discrete classes; with defects ranging from misfolding and disruption of proteostasis, through mislocalisation and disrupted intracellular traffic to instability and altered function. Rhodopsin adRP offers a unique paradigm to understand how disturbances in photoreceptor homeostasis can lead to neuronal cell death. Furthermore, a wide range of therapies have been tested in rhodopsin RP, from gene therapy and gene editing to pharmacological interventions. The understanding of the disease mechanisms associated with rhodopsin RP and the development of targeted therapies offer the potential of treatment for this currently untreatable neurodegeneration.

Mutational Analysis of the Rhodopsin Gene in Sector Retinitis Pigmentosa

BACKGROUND

To determine the role of rhodopsin (RHO) gene mutations in patients with sector retinitis pigmentosa (RP) from Northern Ireland.

DESIGN

A case series of sector RP in a tertiary ocular genetics clinic.

PARTICIPANTS

Four patients with sector RP were recruited from the Royal Victoria Hospital (Belfast, Northern Ireland) and Altnagelvin Hospital (Londonderry, Northern Ireland) following informed consent.

METHODS

The diagnosis of sector RP was based on clinical examination, International Society for Clinical Electrophysiology of Vision (ISCEV) standard electrophysiology, and visual field analysis. DNA was extracted from peripheral blood leucocytes and the coding regions and adjacent flanking intronic sequences of the RHO gene were polymerase chain reaction (PCR) amplified and cycle sequenced.

MAIN OUTCOME MEASURE

Rhodopsin mutational status.

RESULTS

A heterozygous missense mutation in RHO (c.173C > T) resulting in a non-conservative substitution of threonine to methionine (p. Thr58Met) was identified in one patient and was absent from 360 control individuals. This non-conservative substitution (p.Thr58Met) replaces a highly evolutionary conserved polar hydrophilic threonine residue with a non-polar hydrophobic methionine residue at position 58 near the cytoplasmic border of helix A of RHO.

CONCLUSIONS

The study identified a RHO gene mutation (p.Thr58Met) not previously reported in RP in a patient with sector RP. These findings outline the phenotypic variability associated with RHO mutations. It has been proposed that the regional effects of RHO mutations are likely to result from interplay between mutant alleles and other genetic, epigenetic and environmental factors.

RHO Mutations (p.W126L and p.A346P) in Two Japanese Families with Autosomal Dominant Retinitis Pigmentosa

Purpose. To investigate genetic and clinical features of patients with rhodopsin (RHO) mutations in two Japanese families with autosomal dominant retinitis pigmentosa (adRP). Methods. Whole-exome sequence analysis was performed in ten adRP families. Identified RHO mutations for the cosegregation analysis were confirmed by Sanger sequencing. Ophthalmic examinations were performed to evaluate the RP phenotypes. The impact of the RHO mutation on the rhodopsin conformation was examined by molecular modeling analysis. Results. In two adRP families, we identified two RHO mutations (c.377G>T (p.W126L) and c.1036G>C (p.A346P)), one of which was novel. Complete cosegregation was confirmed for each mutation exhibiting the RP phenotype in both families. Molecular modeling predicted that the novel mutation (p.W126L) might impair rhodopsin function by affecting its conformational transition in the light-adapted form. Clinical phenotypes showed that patients with p.W126L exhibited sector RP, whereas patients with p.A346P exhibited classic RP. Conclusions. Our findings demonstrated that the novel mutation (p.W126L) may be associated with the phenotype of sector RP. Identification of RHO mutations is a very useful tool for predicting disease severity and providing precise genetic counseling.

Rhodopsin p.N78I dominant mutation causing sectorial retinitis pigmentosa in a pedigree with intrafamilial clinical heterogeneity

OBJECTIVE

The purpose of this study was to determine the molecular basis of retinitis pigmentosa (RP) in a 4 affected sib-family segregating this retinal phenotype.

METHODS

Affected sibs underwent complete ophthalmologic examination including funduscopic inspection, electroretinogram, fluorescein angiography, visual field measurement, and optical coherence tomography. Both parents were deceased after their sixties and were reported with no visual handicap. Molecular analysis included direct nucleotide sequencing of the rhodopsin gene (RHO), at chromosome 3q21-q24, in DNA from a total of 4 affected sibs. A total of 200 ethnically matched alleles were included as mutation controls.

RESULTS

Sector RP was clinically documented in this family. Wide phenotypic variability was observed with visual acuities ranging from 20/20 to 20/200 and variable funduscopic appearance. Molecular analysis disclosed a c.233A>T mutation at RHO exon 1, predicting a missense p.N78I substitution.

CONCLUSIONS

Even though RP can be caused by mutations in a variety of genes, the RHO gene was chosen to be investigated in this RP family since it has been previously associated to sector disease. This case exemplifies the value of guiding RP molecular analysis based on funduscopic features.

Mutations in the USH1C gene associated with sector retinitis pigmentosa and hearing loss

PURPOSE

To determine the molecular cause of sector retinitis pigmentosa and hearing loss in two affected siblings.

METHODS

Direct DNA sequencing of the USH1C gene was performed in two affected siblings. Putative pathogenic sequence changes were assayed in their parent's chromosomes and in control chromosomes. Clinical examination included visual acuity measurement, visual field measurement, electrophysiologic assessment, and fine matrix mapping. Retinal imaging with fundus photography, scanning laser ophthalmoscope (fundus autofluorescence), and optical coherence tomography was performed. Hearing and vestibular function was also assessed.

RESULTS

The siblings were aged 42 years and 40 years, and both were compound heterozygotes for the p.R103H missense change and the novel splice site change c.2227-1G>A in the USH1C gene. Both alleles were found to be in trans. Neither allele was identified in a panel of 866 control chromosomes, and both were considered pathogenic. Both siblings had sector retinitis pigmentosa restricted to the inferior and nasal retina. Fundus autofluorescence imaging showed a clear demarcation between normal and abnormal areas of retina, which corresponded to areas of reduced sensitivity on fine matrix mapping and loss of visual field. Both siblings had severe hearing loss but were able to develop language.

CONCLUSION

We report a novel molecular cause of sector retinitis pigmentosa associated with hearing loss representing a new phenotype associated with mutations in the USH1C gene.

Atypical Retinitis Pigmentosa Masquerading as Primary Open Angle Glaucoma

PURPOSE

This study was conducted to describe a case of atypical retinitis pigmentosa initially diagnosed with primary open angle glaucoma.

METHODS

Complete ophthalmologic examination, visual field examination, electroretinogram, and Heidelberg Retinal Tomograph were performed.

RESULTS

Visual field examination showed arcuate defects extending to large temporal defects OU. Electroretinogram showed significant abnormalities with reduced b wave amplitudes and prolonged implicit times. Heidelberg Retinal Tomograph revealed a small central cup with no neuroretinal rim thinning or nerve fiber layer dropout OU.

CONCLUSIONS

The present report suggests that visual field defects atypical for glaucoma should be carefully scrutinized for other etiologies.

Sector retinitis pigmentosa

BACKGROUND

Retinitis pigmentosa (RP) is one of the most common hereditary retinal dystrophies and causes of visual impairment affecting all age groups. The reported incidence varies, but is considered to be between 1 in 3,000 to 1 in 7,000. Sector retinitis pigmentosa is an atypical form of RP that is characterized by regionalized areas of bone spicule pigmentation, usually in the inferior quadrants of the retina.

CASE REPORT

A 57-year-old Hispanic man with a history of previously diagnosed retinitis pigmentosa came to the clinic with a longstanding symptom of decreased vision at night. Bone spicule pigmentation was found in the nasal and inferior quadrants in each eye. He demonstrated superior and temporal visual-field loss corresponding to the areas of the affected retina. Clinical measurements of visual-field loss, best-corrected visual acuity, and ophthalmoscopic appearance have remained stable during the five years the patient has been followed.

DISCUSSION

Sector retinitis pigmentosa is an atypical form of RP that is characterized by bilateral pigmentary retinopathy, usually isolated to the inferior quadrants. The remainder of the retina appears clinically normal, although studies have found functional abnormalities in these areas as well. Sector RP is generally considered a stationary to slowly progressive disease, with subnormal electro-retinogram findings and visual-field defects corresponding to the involved retinal sectors.

CONCLUSION

Management of RP is very difficult because there are no proven methods of treatment. Studies have shown 15,000 IU of vitamin A palmitate per day may slow the progression, though this result is controversial. Low vision rehabilitation, long wavelength pass filters, and pedigree counseling remain the mainstay of management.

The assessment of L- and M-cone specific electroretinographical signals in the normal and abnormal human retina

Electroretinography (ERG) is a non-invasive method that can contribute to a description of the functional organization of the human retina under normal and pathological circumstances. The physiological and pathophysiological processes leading to an ERG signal can be better understood when the cellular origins of the ERG are identified. The ERG signal recorded at the cornea is initiated by light absorption in the photoreceptors which leads to activity in the photoreceptors and in their post-receptoral pathways. Light absorption in distinct photoreceptor types may lead to different ERG responses caused either by differences between the photoreceptors or between their post-receptoral pathways. The description of contributions of the different photoreceptor types to the ERG may therefore give more detailed insight in the origins of the ERG. Such a description can be obtained by isolating the responses of a single photoreceptor type. Nowadays, careful control of differently colored light sources together with the relatively well-known cone and rod fundamentals enables a precise description and control of photoreceptor excitation. Theoretically, any desired combination of photoreceptor excitation modulation can be achieved, including conditions in which the activity in only one photoreceptor type is modulated (silent substitution). In this manner the response of one photoreceptor type is isolated without changing the state of adaptation. This stimulus technique has been used to study the contribution of signals originating in the different photoreceptor types to the human ERG. Furthermore, by stimulating two or more photoreceptor types simultaneously, the interaction between the different signals can be studied. With these new techniques results of measurements in healthy subjects and patients with retinal diseases can be compared. This approach should ultimately help to develop better diagnostic tools and result in a fuller description of the changes and the pathophysiological mechanisms in retinal disorder. Finally, data obtained with cone and rod specific stimuli may lead to a reinterpretation of the standard ERG used in a clinical setting.

L- and M-cone driven large-field and multifocal electroretinograms in sector retinitis pigmentosa

The purpose was to study long- (L-) and middle-wavelength-sensitive (M-) cone-driven ERGs and multifocal ERGs (mfERGs) in sector retinitis pigmentosa (sector RP). Two eyes of two patients with sector RP were measured. ERG responses were measured to stimuli which modulated exclusively the L- or the M-cones or the two simultaneously (both in-phase and in counter-phase) with predefined cone contrast leaving the S-cones unmodulated. For comparison, mfERGs were recorded with the visual evoked response imaging system, using a resolution of 61 hexagonal elements within a 30-degree visual field. The two sector RP patients exhibited a general reduction of the L-/M-cone driven ERG sensitivity. Patient 1 exhibited a slight delay of the M-cone driven ERG. In patient 2, L-cone driven ERG was moderately delayed. In both patients, the phases of the L- and the M-cone driven ERGs were positively correlated with cone contrast. The data of the L/M-cone driven ERGs, the mfERGs and the standard photopic ERGs matched each other qualitatively. We conclude that the sector RP patients were clearly different from normal for both the L- and M-cone driven large-field and the multifocal ERGs. Previously, we investigated L- and M-cone driven ERGs in patients with generalized RP and found several features that differ from the sector RP patients. Our data are in agreement with our previous proposition that amplitudes and phases of the L- and M-cone driven ERGs can be differently affected by retinal disorders.

Preserved para-arteriolar retinal pigment epithelium retinitis pigmentosa

In two patients, we studied retinitis pigmentosa with preservation of the retinal pigment epithelium adjacent to and under the retinal arterioles (despite panretinal degeneration). Both patients with preserved para-arteriolar retinal pigment epithelium also exhibited a peculiarly strong hyperopia. In addition to previously reported features, these patients also had sheathing of the major vascular arcades, which suggested a vascular involvement in this uncommon form of retinitis pigmentosa.

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.

Clinical investigation of retinitis pigmentosa

The diagnostic features and future research directions of retinitis pigmentosa were documented in this update and review of the subject. An extensive and current bibliography is provided.

Rods are selectively altered by lead: II. Ultrastructure and quantitative histology

Electroretinographic and cyclic nucleotide metabolism studies have established that low-level lead exposure during early postnatal development results in long-term selective rod deficits. To determine whether there was a corresponding selective rod photoreceptor cell degeneration we examined retinas of adult rats exposed to low-level lead during development using light and electron microscopy. In all retinal regions, a rod but not cone cell degeneration was observed. Overall, 20% of the rod cells were lost. Moreover, two specific regional differences were found. Degeneration was much greater in the inferior (-25%) than superior (-15%) retina and greater in the posterior (-22%) than peripheral (-17%) retina. The latter pattern indicates a central-peripheral gradient of degeneration. Total retinal thickness decreased 15-20%, which reflects cell loss in the outer and inner nuclear layers. Ultrastructurally, the most obvious lead-induced alterations were swollen and disorganized rod outer segments and large accumulations of beta-glycogen particles in rod photoreceptor mitochondria. Glycogen accumulations were heaviest in rod inner segment mitochondria followed by rod axon and synaptic terminal mitochondria. Possible cellular mechanisms of action responsible for these lead-induced retinal alterations include an inhibition of retinal cyclic GMP phosphodiesterase and the resultant elevation of cyclic GMP, an inhibition of intermediary metabolism, and/or an alteration in calcium metabolism. In addition, the thinning of the inner nuclear layers could be due to transneuronal degeneration. As noted in our preceding paper, the first possibility has been demonstrated in rats similarly exposed to lead. These quantitative histological results, in combination with the ERG and biochemical results in the preceding paper, demonstrate that low-level lead exposure during early postnatal development produces long-term selective rod functional deficits and degeneration.

Atypical sector pigmentary dystrophy

The authors describe a family with atypical sector shaped pigmentary dystrophy in two generations with transmission from father to son. A review of the literature is given.

Sex-linked pigmentary retinopathy (P.R.)

The silently affected female relatives of a patient severely affected by pigmentary retinopathy may show on ophthalmoscopy a sector with pigmentary retinopathy and disturbed functional examinations; the risk factors to suggest X linked disease are described. In our case the mother appeared a heterozygote for sex linked P.R.

Retinal degeneration in the pcd cerebellar mutant mouse. I. Light microscopic and autoradiographic analysis

The Purkinje cell degeneration (pcd) mutant mouse rapidly loses cerebellar Purkinje cells between 3 and 5 weeks after birth and slowly loses retinal photoreceptor cells during the first year of life. In the present study, the retinal degeneration in the pcd mouse was analyzed by light microscopy and autoradiography throughout the first 15 months of age. By day 25 there is an abundance of pyknotic photoreceptor nuclei and many outer segments are clearly disorganized. Thereafter, as the photoreceptor cells are lost, their outer segments slowly become shorter and more variable in length; this slow change in length is explained by an almost proportional reduction in both rod outer segment renewal and disc shedding rates. At about 2 months of age, the rate of rod outer segment renewal is slightly less than half that in littermate controls, and the number of large phagosomes in pigment epithelial cells during the burst of disc shedding soon after light onset is one-half or less than that seen in littermate controls. Between 2 and 10.5 months of age, the retina in the inferior hemisphere of the eye shows substantially more-advanced photoreceptor degeneration than does the superior hemisphere, particularly in the far peripheral retina. A central-to-peripheral gradient of degeneration is conspicuous in the superior hemisphere; a similar but less obvious gradient of degeneration is also seen in the inferior hemisphere of the eye. Loss of photoreceptor cells and their synaptic terminals results in a predictable thinning of the outer synaptic layer. However, the inner nuclear layer shows no measurable thinning and the inner synaptic layer is reduced in thickness by only about 5-15%. Beginning at about 10 months of age, foci of thinned pigment epithelial cells are evident, and by 12 months there is some vascularization of the pigment epithelium by retinal capillaries.

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.

Investigation of retinitis pigmentosa

Retinitis pigmentosa is a solitary manifestation of separate genetically determined disorders in which there is progressive loss of vision and the appearance of characteristic fundus abnormalities. It is likely that each disease contained within this family of disorders has a different aetiology, a consideration which is important to the clinician, the researcher and the therapist. To the clinician it is essential to be able to identify the inheritance of the disorder in order to give educated genetic advice. It is the responsibility of the clinician to sub-divide retinitis pigmentosa into purer samples of disease since without such a sub-division research is unlikely to be fruitful. It is unreasonable to expect a biochemist to define systemic biochemical abnormalities if blood is analysed from a series of patients, each of which has a different disorder. If the cause of retinal degeneration in an animal homologue of human retinitis pigmentosa is identified the question is then raised as to whether the abnormality is relevant to human disease and, if so, to which one. Moreover, if a metabolic abnormality is identified in one disease it will not necessarily to be found in others and similarly, if therapy is effective in one form of the disease it may not be effective for all patients. A sub-division of retinitis pigmentosa may be made on the basis of inheritance of the disorder, on the basis of morphologic changes in the fundus, and on the qualitative functional changes identified. Such observations may also give some clues as to the pathogenesis of the different forms of RP or at least indicate in which cell system the primary disorders lie and will also show in what way the defect interferes with cell function. In this paper it is hoped to show that studies undertaken by the various disciplines within ophthalmology have now made limited achievements towards the goals of subdividing retinitis pigmentosa (RP) into purer samples of disease and typifying the functional and morphological attributes of the constituent disorders.

Preserved para-arteriole retinal pigment epithelium (PPRPE) in retinitis pigmentosa

Five patients with retinitis pigmentosa (RP) with probable autosomal recessive inheritance have been identified in whom there is relative preservation of retinal pigment epithelium adjacent to and under retinal arterioles despite a panretinal degenerative process. All the patients were hypermetropic, though patients with RP tend to be myopic. This implies that there is a factor associated with retinal arterioles which locally retards the RP process in these patients. It may be appropriate to look for the PPRPE pattern in hypermetropic RP patients.

Sector retinitis pigmentosa in juvenile nephronophthisis

In a patient with juvenile nephronophthisis, sector retinitis pigmentosa was found as an extrarenal manifestation, establishing a hitherto undescribed variety of retinal degeneration occurring in this disorder. The retinal function in this case was identical with that in the classic type of sector retinitis pigmentosa, namely, subnormal ERG amplitudes but normal cone and rod implicit times. The range of the retinal findings and their autosomal recessive transmission are discussed. Paucity of information makes it difficult to elucidate the basic genetic defect operating in this condition.

Retinal degeneration without pigment alterations in progressive external ophthalmoplegia

A 56-year-old black man had annular visual field defects and retinal electrophysiologic dysfunction with chronic progressive external ophthalmoplegia and no pigmentary abnormalities in the fundus. Because the association of retinal disease with neurodegenerative states has generally been based on the observation of pigmentary changes, the patient's fields were erroneously interpreted as the nerve fiber bundle defects of glaucoma.

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.

Sector retinitis pigmentosa. Electrophysiological and psychophysical study of the visual system

Combined clinical, psychophysical and electrophysiological examinations of the visual function were performed in two patients affected by sector retinitis pigmentosa. Psychophysical dark adaptation measurements, the electroretinogram (ERG) and the electro-oculogram (EOG) revealed that a larger area of the neural retina and pigment epithelium were pathologically involved than revealed by ophthalmoscopy and visual field. Five years of observation showed a stationary retinal defect in one patient, while in the other a slight clinical but a marked electroretinographical deterioration was found over a period of twelve years. However, visual acuity and the visually evoked potential (VEP) remained normal. In spite of subnormal ERG amplitudes, the photopic and scotopic peak latencies were normal in both cases. In the ophthalmoscopically normal relatives of one patient slight dark adaptation impairments, as well as EOG and ERG disturbances, were detected.

Atypical retinitis pigmentosa masquerading as a nerve fiber bundle lesion

"Sector" or "asymmetric" retinitis pigmentosa was mistaken as bilateral nerve fiber bundle defects in a 56-year-old man for six years, leading to an unnecessary work-up for anterior visual pathway disease and to an incorrect diagnosis of low-tension glaucoma. Confusion arises because this variant may present with bilateral, superior, half-ring visual field defects that intersect the blindspots. These defects may be misplotted as typical arcuate Bjerrum's scotomas. The ophthalmoscopic changes that correspond to these visual field defects may be so subtle as to be overlooked. Fluorescein angiography helps bring out the retinal lesions, and moderately subnormal electroretinographic and dark adaptation studies are definitive.