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PubMed1997

Electrophysiology in some animal and human hereditary diseases involving the retinal pigment epithelium.

The present paper surveys slow electrophysiological responses recorded by a d.c. technique in some hereditary eye diseases involving the retinal pigment epithelium (RPE) in animals (English setter dogs and Polish Owczarec Nizinny (PON) dogs with ceroid lipofuscinosis and Briard dogs with a slowly progressive rod-cone dystrophy associated with RPE inclusions) and in humans (Best's disease). The electroretinogram c-wave was typically either decreased in amplitude, lacking or replaced by a negative wave. These c-wave changes could be seen at fairly early stages of disease, when the a- and b-waves of the electroretinogram were still within normal limits.

Adolescent↗

PubMed1999

[From the symptom to electroretinography diagnosis].

Retinal function can be documented noninvasively and objectively by electroretinography, complementing clinical examinations. Symptoms of nightblindness and of dayblindness with photoaversion, nystagmus, poor vision in infants or unclear visual field defects are meaningful indications for ERG testing. We use standardized (ISCEV) full-field single flash ERGs to evaluate the function of the rod- and of the cone-system. In infants, general anesthesia is useful to combine an abbreviated ERG protocol with ophthalmoscopy and fundus photography. ERG testing facilitates to distinguish between functional deficits in the rod- and cone-system, between congenital-stationary retinal dysfunction and progressive retinal heredo-degenerations. Frequently a functional deficit of the retina without ophthalmoscopic changes can be assessed. These entities include achromatopsia, congenital stationary night blindness, early stages of retinitis pigmentosa (RP) or progressive cone dystrophy, as well as toxic retinal changes. Congenital amaurosis Leber (LCA), infantile RP, Usher's syndrome and retinal involvement in other neuropediatric or metabolic syndromes can be diagnosed or excluded by ERG recording early-on. Synoptic evaluation of the full-field ERG, pattern-ERG and VEP completes neuro-ophthalmological screening.

Adult↗

PubMed1999

Conformational changes in guanylyl cyclase-activating protein 1 (GCAP1) and its tryptophan mutants as a function of calcium concentration.

Guanylyl cyclase-activating proteins (GCAPs are 23-kDa Ca2+-binding proteins belonging to the calmodulin superfamily. Ca2+-free GCAPs are responsible for activation of photoreceptor guanylyl cyclase during light adaptation. In this study, we characterized GCAP1 mutants in which three endogenous nonessential Trp residues were replaced by Phe residues, eliminating intrinsic fluorescence. Subsequently, hydrophobic amino acids adjacent to each of the three functional Ca2+-binding loops were replaced by reporter Trp residues. Using fluorescence spectroscopy and biochemical assays, we found that binding of Ca2+ to GCAP1 causes a major conformational change especially in the region around the EF3-hand motif. This transition of GCAP1 from an activator to an inhibitor of GC requires an activation energy Ea = 9.3 kcal/mol. When Tyr99 adjacent to the EF3-hand motif was replaced by Cys, a mutation linked to autosomal dominant cone dystrophy in humans, Cys99 is unable to stabilize the inactive GCAP1-Ca2+ complex. Stopped-flow kinetic measurements indicated that GCAP1 rapidly loses its bound Ca2+ (k-1 = 72 s-1 at 37 degrees C) and was estimated to associate with Ca2+ at a rate (k1 > 2 x 10(8) M-1 s-1) close to the diffusion limit. Thus, GCAP1 displays thermodynamic and kinetic properties that are compatible with its involvement early in the phototransduction response.

Animals↗

PubMed2001

Biochemical defects in 11-cis-retinol dehydrogenase mutants associated with fundus albipunctatus.

Mutations in the gene encoding 11-cis-retinol dehydrogenase (RDH5; EC ) are associated with fundus albipunctatus, an autosomal recessive eye disease characterized by stationary night blindness and accumulation of white spots in the retina. In addition, some mutated alleles are associated with development of cone dystrophy, especially in elderly patients. The numbers of identified RDH5 mutations linked to fundus albipunctatus have increased considerably during recent years. In this work, we have characterized the biochemical and cell biological properties of 11 mutants of RDH5 to understand the molecular pathology of the disease. All RDH5 mutants showed decreased protein stability and subcellular mislocalization and, in most cases, loss of enzymatic activity in vitro and in vivo. Surprisingly, mutant A294P displays significant enzymatic activity. Cross-linking studies and molecular modeling showed that RDH5 is dimeric, and co-expression analyses of wild-type and mutated alleles showed that the mutated enzymes, in a trans-dominant-negative manner, influenced the in vivo enzymatic properties of functional variants of the enzyme, particularly the A294P mutant. Thus, under certain conditions, nonfunctional alleles act in a dominant-negative way on functional but relatively unstable mutated alleles. However, in heterozygous individuals carrying one wild-type allele, the disease is recessive, probably due to the stability of the wild-type enzyme.

Alcohol Oxidoreductases↗

PubMed2004

Mutant carbonic anhydrase 4 impairs pH regulation and causes retinal photoreceptor degeneration.

Retina and retinal pigment epithelium (RPE) belong to the metabolically most active tissues in the human body. Efficient removal of acid load from retina and RPE is a critical function mediated by the choriocapillaris. However, the mechanism by which pH homeostasis is maintained is largely unknown. Here, we show that a functional complex of carbonic anhydrase 4 (CA4) and Na+/bicarbonate co-transporter 1 (NBC1) is specifically expressed in the choriocapillaris and that missense mutations in CA4 linked to autosomal dominant rod-cone dystrophy disrupt NBC1-mediated HCO3- transport. Our results identify a novel pathogenic pathway in which a defect in a functional complex involved in maintaining pH balances, but not expressed in retina or RPE, leads to photoreceptor degeneration. The importance of a functional CA4 for survival of photoreceptors implies that CA inhibitors, which are widely used as medications, particularly in the treatment of glaucoma, may have long-term adverse effects on vision.

Carbonic Anhydrase IV↗

PubMed1994

Genetic diseases of vision.

Among the genetic diseases of vision, retinitis pigmentosa (alone or in combination with systemic afflictions like Usher syndrome, Kearns-Sayre syndrome) deserves special interest because it can be autosomal dominant, autosomal recessive, and X-linked. Leber's hereditary optic neuropathy, the first mitochondrial disease to be defined at the molecular level, manifests at mitochondrial DNA position 11778, but 10 other mutations have recently been found, all residing within mitochondrial DNA-encoded respiratory chain polypeptides. The analysis of Leber's optic neuropathy mutations has provided new important insight into the phenotypic expression of mitochondrial DNA mutations. Some rarer hereditary diseases of vision such as Cone dystrophy, dominant optic atrophy, Leber's congenital amaurosis, Stargardt maculopathy, and choroideremia are discussed.

Genes, Dominant↗

PubMed2006

Visual loss and idiopathic intracranial hypertension in children with Alagille syndrome.

BACKGROUND: Alagille syndrome (AGS) is an autosomal dominant, multisystem disorder defined by developmental abnormalities of the liver, heart, eye and skeleton. Although visual problems are recognised, the severity of visual loss and its link with idiopathic intracranial hypertension (IIH) has not been reported. AIM: To review the incidence of visual loss and IIH in children with AGS managed at a National Paediatric Liver Unit between 1989 and 2004. SUBJECTS AND METHODS: Retrospective case note review of children who fulfilled criteria for diagnosis of AGS and had an ophthalmic examination by a paediatric ophthalmologist. RESULTS: Fifty-five children with AGS were evaluated. Of these, 41 children fulfilled diagnostic criteria and had a documented ophthalmic examination. Six children had undergone liver transplantation. Three children had a definite diagnosis of IIH, 2 of whom developed postliver transplant. All 3 were treated medically, but 1 child with IIH required lumboperitoneal shunting. All 3 children with definite IIH have normal vision after treatment. Another child with probable undiagnosed IIH has bilateral optic atrophy and is registered blind. Two children with AGS are registered partially sighted, one with rod cone dystrophy and the other with pigmentary retinopathy and right disc atrophy. SUMMARY: Although visual abnormalities are well described in children with AGS, a minority of children have significant progressive visual loss. Idiopathic intracranial hypertension has been identified as a potentially treatable precipitating factor. CONCLUSIONS: We recommend annual fundoscopy in the follow-up of children with AGS to facilitate early detection and appropriate management of IIH to prevent visual loss.

Alagille Syndrome↗

PubMed1987

Visual thresholds measured with red test object on backgrounds of high and low luminance.

Visual thresholds measured at the central and midperipheral visual field have been tested in the eyes of a series of 10 healthy normal persons using a monochromatic red test light object (Goldmann area III, 25' of arc in the visual field) of 632 nm wavelength presented on white backgrounds of 150 cd/m2 (5000 K) and 1 cd/m2 (2800 K) luminance, as well as with no background illumination following a 45 min period of dark-adaptation. Another series of 10 normal subjects were tested with an equally large white (2800 K) test object shown on a white background of 1 cd/m2 (2800 K) luminance. Results obtained in congenital and acquired achromatopsia as well as in three relatively mild cases of rod-cone dystrophy have been related to the normal thresholds.

Adult↗

PubMed1990

Evaluation of patients with obvious or suspected degenerative and dystrophic disorders of the retina, pigment epithelium and choroid. Experience from a Swedish referral center.

Between August 1, 1982, and December 31, 1988, 487 patients with clinically established or suspected diagnosis of a hereditary degenerative or dystrophic disorder of the ocular fundus or of a disorder of the optic pathways were evaluated with an extensive set of clinical and electrophysiological tests, 67% of the patients were referred from other eye departments. In order of magnitude the most frequently encountered diagnoses were: 1) 'functional' disturbances (18%), 2) disorders of the optic nerve (9%), 3) retinitis pigmentosa (8%), 4), 5) and 6) progressive cone dystrophy, disorders of the central optic pathways, and fundus flavimaculatus/Stargardt's disease (5% each), and 7) choriocapillaris atrophy (4%). Choriocapillaris atrophy affected older patients than retinitis pigmentosa (P less than 0.001). A male preponderance was observed for juvenile retinoschisis (P less than 0.005) and congenital stationary night blindness (P less than 0.05), and a female dominance in the groups of patients with 'functional' symptoms (P less than 0.01). A specific diagnosis was established in 469 patients. After exclusion of 16 patients referred because of a known hereditary disposition, 196 (43%) of the remaining 453 patients were referred under the same diagnosis as our final diagnosis, 153 (34%) under a different diagnosis and 104 (23%) without any clear diagnosis. Obviously, there is a need for regional centers specialized in these disorders.

Adolescent↗

PubMed2006

Functional characterisation and serial imaging of abnormal fundus autofluorescence in patients with retinitis pigmentosa and normal visual acuity.

AIM: To characterise and monitor abnormal fundus autofluorescence (AF) in patients with retinitis pigmentosa (RP) who have good visual acuity. METHODS: 21 patients with a clinical diagnosis of RP were examined. All had rod-cone dystrophy (ISCEV standard electroretinograms (ERGs)), visual acuity of 6/9 or better, and manifested a parafoveal ring of high density fundus AF. Repeat AF imaging was performed after periods of between 2 years and 5 years in 12 patients. Pattern ERG (PERG) and multifocal ERG (mfERG) were performed in 20 cases. Visual fields (VF), photopic and scotopic fine matrix mapping and small field PERGs were performed in representative cases. RESULTS: The rings of high density AF varied in size between patients (from 4 degrees -16 degrees diameter). MfERGs showed relative preservation over the central macular area, correlating with the size of AF ring and with PERG and psychophysical data. Progressive constriction of the AF ring was demonstrated at follow up in three patients. Serial PERG, mfERG, and VFs, performed in one of these cases, showed evidence of deterioration concordant with ring constriction. CONCLUSIONS: High density rings of AF, seen in some patients with RP with good visual acuity, demarcate areas of preserved central photopic function. MfERGs correlate with the area encircled by high density AF and the PERG data. The size of the ring of AF can show progressive constriction accompanied by increasing macular dysfunction.

Adolescent↗

PubMed1982

The inverse electro-oculogram.

An electro-oculogram ratio of less than one was found to be caused by limited ocular excursions under photopic conditions in a patient with a rod-cone dystrophy. Because this inverse electro-oculogram ratio was not caused by a decrease in standing potential under photopic conditions, it should be considered an artefact.

Adult↗

PubMed1998

Visual function in retinitis pigmentosa related to a codon 15 rhodopsin gene mutation.

To determine the phenotype of a Japanese family in which retinitis pigmentosa cosegregates with a rhodopsin gene mutation, i.e. an asparagine-to-serine change at codon 15 (Asn-15-Ser), 5 affected and 5 unaffected members of one pedigree underwent several ophthalmic examinations as well as Ganzfeld electroretinography (ERG) and multifocal ERG. Genomic DNA samples were analyzed by PCR amplification, sequencing and restriction enzyme digestion. A codon 15 rhodopsin gene mutation (Asn-15-Ser) was found in all affected members. The region of pigmentary degeneration was localized in the lower hemiretina, and visual field defects corresponded to the retinal pigmentary changes. Scotopic ERG amplitudes, rather than photopic ERG amplitudes, were reduced. Multifocal ERG revealed a low magnitude of response density, even for the upper hemiretina, which showed no bony corpuscle pigmentation. Visual function in sectorial retinitis pigmentosa associated with rhodopsin gene codon 15 mutation is on the basis of the rod-cone dystrophy, regardless of differences in phenotypic expression.

Adult↗

PubMed2003

Pattern ERG correlates of abnormal fundus autofluorescence in patients with retinitis pigmentosa and normal visual acuity.

PURPOSE: To examine the functional significance of central abnormalities present in fundus autofluorescence (AF) images in patients with rod-cone dystrophy and good visual acuity. METHODS: Thirty patients were selected according to three criteria: a clinical diagnosis of retinitis pigmentosa (RP) confirmed with International Society for Clinical Electrophysiology of Vision (ISCEV) standard ERGs, a parafoveal ring of increased high density on fundus AF imaging, and a visual acuity of 20/30 or better. Macular function was assessed with pattern electroretinography (PERG) to checkerboard stimuli of different field sizes. Fundus AF imaging was performed with a confocal scanning laser ophthalmoscope. RESULTS: The radius of the parafoveal ring of high density varied between 1.5 degrees and 9 degrees. The PERG P50 amplitude correlated highly with the radius of the ring of increased autofluorescence (r = 0.80, P < 0.0005, n = 30). PERGs to smaller circular field sizes were present, but increasing field size to beyond that of the high-density autofluorescence ring did not produce further increases in P50 amplitude. There was a high correlation between the minimum stimulus size required to elicit a maximum-amplitude PERG and the radius of the ring (r = 0.87). CONCLUSIONS: The high correlation between AF imaging and PERG, an established technique in the assessment of central retinal function, demonstrates the likelihood that autofluorescence abnormalities have functional significance and may therefore be a valuable additional parameter in the monitoring of these patients.

Adolescent↗

PubMed2004

Comparison of fundus autofluorescence with photopic and scotopic fine-matrix mapping in patients with retinitis pigmentosa and normal visual acuity.

PURPOSE: To compare psychophysically determined spatial variations in photopic and scotopic sensitivity across the macula in patients with retinitis pigmentosa (RP) and normal visual acuity who manifest an abnormal high-density ring of fundus autofluorescence (AF). METHODS: Eleven patients with a clinical diagnosis of RP were examined. All had rod-cone dystrophy (International Society for Clinical Electrophysiology of Vision [ISCEV]-standard ERGs), visual acuity of 6/9 or better, and an abnormal parafoveal annulus of high density AF. Fine-matrix mapping (FMM) was performed over macular areas of abnormal high-density AF under photopic and dark-adapted conditions. Pattern ERGs (PERGs) were performed in 9 of 11 patients, by using different sizes of circular checkerboards. RESULTS: Rings of high-density AF varied between patients (approximately 3 degrees -18 degrees in diameter). Photopic sensitivity was preserved over central macular areas, but there was a gradient of sensitivity loss over high-density segments of the ring and severe threshold elevation outside the arc of the ring. Scotopic sensitivity losses were more severe, and they encroached on areas within the ring. The radius of the high-density ring correlated with the lateral extent of preserved photopic sensitivity (r=0.86) and PERG data. CONCLUSIONS: High-density rings of AF, which are present in some patients with RP with normal visual acuity, demarcate areas of preserved central photopic sensitivity. Scotopic sensitivity losses encroach on areas within the ring of high density and may reflect dysfunction before accumulation of lipofuscin.

Adult↗

PubMed1994

Autosomal dominant cerebellar ataxia with retinal degeneration: clinical, neuropathologic, and genetic analysis of a large kindred.

The autosomal dominant cerebellar ataxias (ADCA) comprise a heterogeneous group of neurologic disorders characterized by degeneration of the cerebellum, spinal cord, and brainstem. Genetic analysis has revealed two loci, SCA1 on chromosome 6p, and SCA2 on chromosome 12q, responsible for some ADCA. We present a four-generation kindred of 42 individuals, 12 of whom were clinically affected with ADCA and an associated cone dystrophy. Early loss of color discrimination with retinal and macular signs is followed by gradual progression of cerebellar dysfunction and development of pyramidal signs. Pathology shows degeneration of cerebellum, basis pontis, inferior olive, and retinal ganglion cells. For genetic analysis, we used polymorphic markers D6S89 and D12S79; linkage analysis gave negative results, excluding linkage to both SCA1 and SCA2. The data strongly support genetic heterogeneity consistent with the unique clinicopathologic features of the form of ADCA displayed in this large family.

Adolescent↗

PubMed2004

Bardet-Biedl syndrome with syndrome X: a patient report.

Bardet-Biedl syndrome (BBS) is an autosomal recessive condition with a wide spectrum of clinical features. The principal manifestations are rod-cone dystrophy (sometimes called atypical retinitis pigmentosa), postaxial polydactyly, central obesity, mental retardation, hypogonadism, and renal dysfunction. The clinical diagnosis of syndrome X defines a patient with abnormal glucose metabolism, hypertension, hyperlipidemia and obesity. We report here a 15 year-old girl with BBS presenting with syndrome X.

Adolescent↗

PubMedDate not supplied

Electrophysiological and eye-movement abnormalities in children with the Bardet-Biedl syndrome.

We investigated 17 patients with clinical features of Bardet-Biedl syndrome by electroretinogram (ERG), visual-evoked potentials (VEP), and electro-oculographic (EOG) eye movement assessment. The ERGs were grossly abnormal in 16 cases. Pattern VEPs were generally well preserved, but showed a tendency to increase in latency and decrease in amplitude with age. These results confirm other reports that the retinopathy appears to be a progressive rod-cone dystrophy initially affecting mainly extramacular areas but involving the macula at later stages. Seven of 11 patients showed abnormalities of either optokinetic nystagmus, vestibulo-ocular reflex, or both. These eye-movement abnormalities have not been reported previously, and are further evidence of central nervous system involvement in this syndrome.

Adolescent↗

PubMed1999

Repeated injections of a ciliary neurotrophic factor analogue leading to long-term photoreceptor survival in hereditary retinal degeneration.

PURPOSE: To determine whether ciliary neurotrophic factor (CNTF) or brain-derived neurotrophic factor (BDNF) treatment leads to long-term photoreceptor survival in hereditary retinal degeneration. METHODS: An autosomal dominant feline model of rod-cone dystrophy was used throughout the study with two normal animals. In the first experiment, intravitreal injections of a human CNTF analogue (Axokine; Regeneron Pharmaceuticals, Tarrytown, NY) were administered to one eye of each animal (n = 10) beginning on postnatal day 10 and were repeated every 4 weeks. Clinical and histopathologic examinations were performed at 5.5, 9.5, and 13.5 weeks. In the second experiment, animals (n = 17) were randomly assigned to receive intravitreal injections of either Axokine (at half the initial dose), human BDNF, or the vehicle for Axokine to one eye at 5.5 weeks. The same therapy was repeated every 4 weeks in each group. Clinical and histopathologic examinations were performed at 9.5, 13.5, and 17.5 weeks. Photoreceptor survival was assessed by cell counting. Apoptotic cells were identified by morphology and a modified TdT-dUTP terminal nick-end labeling (TUNEL) technique. In the third experiment, two normal animals were treated with Axokine as in the first experiment. Glial fibrillary acidic protein ((GFAP) immunohistochemistry was performed to assess glial cell reaction. RESULTS: In the first two experiments, Axokine significantly prolonged photoreceptor survival (P < 0.01) and reduced the presence of apoptotic cells (P < 0.05) and TUNEL-positive cells (P < 0.05). In the second experiment, results in the the BDNF- and sham-injected eyes were not significantly different from those in the untreated eyes. Minimal posterior subcapsular cataract and mild retinal folds were found in all Axokine-treated eyes in both dystrophic and normal animals. These complications were milder in the second experiment when injections were started later and at a reduced dose. GFAP immunolabeling was also increased in all Axokine-treated eyes. CONCLUSIONS: Axokine, but not BDNF, delays photoreceptor loss in this hereditary retinal degeneration. Repeated injections maintain the protective effect.

Animals↗