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At least 757 records · Page 42Linked to original sources
PubMed2002

Influence of tyrosinase levels on pigment accumulation in the retinal pigment epithelium and on the uncrossed retinal projection.

To study the relationship among tyrosinase activity, melanin production, and the routing of retinal ganglion cell (RGC) axons at the optic chiasm, we analysed mice with varying doses of the tyrosinase gene. These include the dark-eyed albino (Tyrc44H), a radiation-induced hypomorphic allele of tyrosinase; and transgenic mice carrying 1 or 2 alleles of a tyrosinase minigene on both wild-type (Tyr+) and albino (Tyrc) backgrounds. Melanization of the retinal pigment epithelium (RPE) occurred gradually even at <2% wild-type tyrosinase activity and was sensitive to tyrosinase activity up to <35% of wild-type levels, beyond which melanin synthesis appeared to be saturated. Overexpression of tyrosinase led to tyrosinase activity above wild type level, but did not increase melanin production. Although a loss of melanin because of a mutation in tyrosinase is associated with a decrease in the number of uncrossed fibers, elevating tyrosinase levels does not appear to cause an increase in the size of the uncrossed retinal projection. Our results suggest that replacing less than 35% of wild-type tyrosinase activity is sufficient to restore normal pigmentation of the RPE, and potentially, to allay visual defects.

Albinism, Oculocutaneous↗
PubMed2002

Symptomatic abnormalities of dark adaptation in patients with EFEMP1 retinal dystrophy (Malattia Leventinese/Doyne honeycomb retinal dystrophy).

PURPOSE: To investigate the nature of symptomatic visual disturbance in patients with EFEMP1 retinal dystrophy in the absence of geographic atrophy or choroidal neovascularization. METHODS: Patients presenting to a tertiary referral centre underwent clinical evaluation, fluorescein angiography, colour contrast sensitivity, focal, pattern, and standard electroretinography, electrooculography, scotopic threshold perimetry and dark adaptometry. RESULTS: Clinical features included reduced central vision, difficulty passing from light to dark, and diffuse submacular and peripapillary deposits, which were hyperfluorescent by fluorescein angiography. Colour contrast thresholds were abnormal in all six patients studied and both pattern and focal electroretinograms were abnormal in five of six patients. The scotopic and mixed rod-cone single flash ERG was normal but two patients demonstrated reduced oscillatory potentials and one had borderline delayed 30 Hz responses. Scotopic thresholds were elevated and rod-mediated dark adaptation kinetics were markedly prolonged in all six patients when measured over the central visible confluent deposits. CONCLUSIONS: In patients with EFEMP1 retinal dystrophy with confluent macular deposits, scotopic sensitivity is reduced and dark adaptation kinetics are prolonged over the macular deposits but are normal elsewhere. These results emphasize the localised nature of functional deficits in some patients with EFEMP1 retinal dystrophy and correlate well with the patient's visual symptoms. Symptomatic visual dysfunction may precede the development of clinically evident geographic atrophy or choroidal neovascularization in this disorder.

Color Vision Defects↗
PubMed2003

Simian lentiviral vector-mediated retinal gene transfer of pigment epithelium-derived factor protects retinal degeneration and electrical defect in Royal College of Surgeons rats.

Retinitis pigmentosa (RP) is a heterogenous group of inherited retinal diseases resulting in adult blindness caused by mutations of various genes. Although it is difficult to cure the blindness that results from these diseases, delaying the disease progression may be of great benefit, since the majority of RP diseases are seen in middle age or later. To test a gene therapy strategy for RP using a neurotrophic factor gene, we assessed the effect of simian lentivirus (SIV)-mediated subretinal gene transfer of pigment epithelium-derived factor (PEDF), a potent neurotrophic factor, during the disease progression in Royal College of Surgeons (RCS) rats, a well-accepted animal model of RP. Regional gene transfer via SIV into the peripheral subretinal space at the nasal hemisphere was performed in all animals to monitor site-specific transgene expression as well as the therapeutic effect in each retina. Gene transfer of lacZ and PEDF was observed in the regional pigment epithelium corresponding to the regional gene transfer. Histologically, PEDF gene transfer significantly protected the loss of photoreceptor cells (PCs) corresponding to the regions of the gene transfer, compared to those of control groups during the course of the experiment. The antiapoptotic effect of PEDF on PCs is likely to be a related mechanism, because a significant reduction of terminal dUTP-nicked end labeling-positive PC numbers was found in PEDF-treated eyes compared to those of the control group (P<0.05). PEDF-treated eyes also retained a significant sensitivity to light flash during the experimental course. These findings clearly show that neuroprotective gene therapy using PEDF can protect retinal degeneration and functional defects in individuals with RP.

Animals↗
PubMed1981

[Retinal holes - cause and therapeutical key of retinal detachments. Iatrogenic holes (author's transl)].

The author reports on 20 hopeless cases of retinal detachment with no visible retinal hole after vitrectomy and membrane-peeling procedures. Nearly all these cases showed a funnel-shaped rigid retinal detachment. In order to perform an internal drainage and air tamponade from inside a iatrogenic hole was cut in the periphery of the retina. The hole was necessary for the internal drainage of the subretinal fluid. The air tamponade forced the retina to unfold. Astonishingly, in 12 out of these 20 cass the retina became reattached.

Drainage↗
PubMed2005

Isolation and characterization of a retinal pigment epithelial cell fluorophore: an all-trans-retinal dimer conjugate.

Several lines of investigation suggest that the nondegradable fluorophores that accumulate as lipofuscin in retinal pigment epithelium (RPE) cells contribute to the etiology of macular degeneration. Despite evidence that much of this fluorescent material may originate as inadvertent products of the retinoid cycle, the enzymatic pathway by which the 11-cis-retinal chromophore of rhodopsin is generated, the only fluorophores of the RPE to be characterized as yet have been A2E and its isomers. Here, we report the isolation and structural characterization of an additional RPE lipofuscin fluorophore that originates as a condensation product of two molecules of all-trans-retinal (ATR) dimer and forms a protonated Schiff base conjugate with phosphatidylethanolamine (PE), the latter conjugate (ATR dimer-PE) having UV-visible absorbance maxima at 285 and 506 nm. ATR dimer was found to form natively in bleached rod outer segments in vitro and when rod outer segments were incubated with ATR. HPLC analysis of eye-cups that included RPE and isolated neural retina from Abcr-/- mice and RPE isolated from human donor eyes revealed the presence of a pigment with the same UV-visible absorbance and retention time as synthetic ATR dimer-PE conjugate. Evidence that ATR dimer undergoes a photooxidation process involving the addition of oxygens at double bonds as well as an aromatic demethylation also may indicate a role for this molecule, or its derivatives, in the photoreactivity of RPE lipofuscin.

Animals↗
PubMed2005

Retinal degeneration associated with RDH12 mutations results from decreased 11-cis retinal synthesis due to disruption of the visual cycle.

Retinoid dehydrogenases/reductases catalyze key oxidation-reduction reactions in the visual cycle that converts vitamin A to 11-cis retinal, the chromophore of the rod and cone photoreceptors. It has recently been shown that mutations in RDH12, encoding a retinol dehydrogenase, result in severe and early-onset autosomal recessive retinal dystrophy (arRD). In a cohort of 1011 individuals diagnosed with arRD, we have now identified 20 different disease-associated RDH12 mutations, of which 16 are novel, in a total of 22 individuals (2.2%). Haplotype analysis suggested a founder mutation for each of the three common mutations: p.L99I, p.T155I and c.806_810delCCCTG. Patients typically presented with early disease that affected the function of both rods and cones and progressed to legal blindness in early adulthood. Eleven of the missense variants identified in our study exhibited profound loss of catalytic activity when expressed in transiently transfected COS-7 cells and assayed for ability to convert all-trans retinal to all-trans retinol. Loss-of-function appeared to result from decreased protein stability, as expression levels were significantly reduced. For the p.T49M variant, differing activity profiles were associated with each of the alleles of the common p.R161Q RDH12 polymorphism, suggesting that genetic background may act as a modifier of mutation effect. A locus (LCA3) for Leber congenital amaurosis, a severe, early-onset form of arRD, maps close to RDH12 on chromosome 14q24. Haplotype analysis in the family in which LCA3 was mapped excluded RDH12 as the LCA3 gene and thus suggests the presence of a novel arRD gene in this region.

Alcohol Oxidoreductases↗
PubMedDate not supplied

Preoperative laser photocoagulation to mark tiny retinal breaks in eyes with retinal detachment.

We used preoperative argon laser photocoagulation to create a white intraretinal color change to mark the location of a tiny retinal break in an aphakic eye with rhegmatogenous retinal detachment. The break was visible only by fundus biomicroscopy with a three-mirror contact lens and could not be seen by indirect ophthalmoscopy. Intraretinal uptake of laser energy is accomplished with a small spot size and moderate energy levels. This technique facilitates rapid intraoperative identification and localization of small retinal breaks that are otherwise difficult to visualize.

Humans↗
PubMed2003

Rhegmatogenous retinal detachment in the fellow phakic eyes of patients with pseudophakic rhegmatogenous retinal detachment.

PURPOSE: To determine the risk and clinical characteristics of rhegmatogenous retinal detachment (RD) in the fellow phakic eyes of patients with a pseudophakic retinal detachment (PPRD) in one eye. METHODS: The authors conducted a computer-generated chart review to find 64 consecutive patients with a PPRD in one eye and were phakic in the fellow eye. The clinical information was collected on all patients to investigate the risk and clinical characteristics of RD in the fellow eyes while still phakic. Information was also obtained on the fellow eyes that underwent cataract surgery and developed a PPRD. RESULTS: Sixty-four patients with a PPRD in one eye were phakic in the fellow eye. During an average follow-up of 57.4 months, five (7.8%) fellow eyes developed retinal detachment while still phakic. In addition to the five eyes with a phakic RD, 10 originally phakic fellow eyes underwent cataract surgery. Of these, one (10%) suffered an RD. CONCLUSION: Fellow eyes of patients with a PPRD have a significant risk of RD even if they do not undergo cataract surgery.

Aged↗
PubMed2003

Management of giant retinal tears with vitrectomy, internal tamponade, and peripheral 360 degrees retinal photocoagulation.

PURPOSE: To determine the effectiveness of vitrectomy, internal tamponade, and peripheral 360 degrees retinal photocoagulation in the management of giant retinal tears (GRTs). PARTICIPANTS: Eighteen eyes of 18 consecutive patients with GRTs were operated on at Jules Gonin Eye Hospital between 1992 and 1999. None of them had previous vitreoretinal surgery. METHODS: Eyes in the series underwent pars plana vitrectomy, perfluorocarbon liquid and silicone oil (17 eyes) or gas (one eye) exchange, and retinopexy. Retinopexy was applied to the edges of the tear using photocoagulation, and it was extended over 360 degrees to the peripheral attached retina. No scleral buckle was placed, even if proliferative vitreoretinopathy (PVR) was present. RESULTS: The GRT was 180 degrees or greater in seven eyes and 90 degrees to 180 degrees in 11 eyes. The lower edge of the GRT was located in an inferior quadrant in 15 eyes. PVR was grade A in seven eyes, grade B in eight eyes, and grade C in three eyes. In the last three eyes, PVR was anterior (C-A9, Patient 4) and posterior (C-P6 subretinal, Patient 11; C-P3, Patient 13). In 16 (88.8%) of the 18 eyes, the retina was successfully reattached after surgery, and silicone oil was removed after a mean period of 7.7 weeks. In the other two eyes, the retina remained detached or redetached despite the silicon oil tamponade. One of these two eyes underwent three further surgeries, but the retina did not reattach. The other eye was successfully reoperated on with an encircling and radial scleral buckle, and silicone oil was removed later. At the end of the follow-up, the retina was attached in 17 (94.4%) of the 18 eyes. The mean follow-up was 28.6 months (range, 4.5-73 months). CONCLUSIONS: The success rate of management of GRTs with vitrectomy, internal tamponade, and peripheral 360 degrees photocoagulation of the retina without scleral buckle is high. Photocoagulation of the peripheral retina over 360 degrees appears to decrease the risk of secondary peripheral retinal tears.

Adult↗
PubMed2004

Complications of ganciclovir implant surgery in patients with cytomegalovirus retinitis: the Ganciclovir Cidofovir Cytomegalovirus Retinitis Trial.

PURPOSE: To describe the complications of ganciclovir implant surgery in patients with cytomegalovirus retinitis. METHODS: Prospective data collection within the context of a randomized, controlled clinical trial, comparing a regimen of the ganciclovir implant plus oral ganciclovir to one of intravenous cidofovir for the treatment of cytomegalovirus retinitis in patients with AIDS. Adverse events were compared for patients undergoing implant surgery in the following groups: primary versus replacement implant surgery, inpatient versus outpatient surgery, and general versus local anesthesia. RESULTS: Fifty-six eyes of 42 patients underwent a total of 74 ganciclovir implant surgeries. Vitreous hemorrhage was the most common adverse event, occurring in 10% of eyes undergoing surgery with local anesthesia but in no eyes undergoing surgery with general anesthesia. All vitreous hemorrhages resolved within 60 days. Patients in the general anesthesia and inpatient surgery groups tended to have a lower risk of complications in the first 30 days than did patients in the local anesthesia and outpatient surgery groups, but no differences in the complication rate were found after 60 days. Visual acuity was similar among these different groups. There were no cases of endophthalmitis. CONCLUSION: Ganciclovir implant surgery in patients with AIDS and cytomegalovirus retinitis was associated with a low risk of serious complications in the first 60 days after surgery. Vitreous hemorrhage was the most commonly observed complication and resolved in all cases.

AIDS-Related Opportunistic Infections↗
PubMed2007

Retinal function after scleral buckling for recent onset rhegmatogenous retinal detachment: assessment with electroretinography and optical coherence tomography.

PURPOSE: To investigate central and peripheral retinal function after scleral buckling surgery for recent onset rhegmatogenous retinal detachment (RD). METHODS: Fifteen phakic patients with rhegmatogenous RD for <1 week underwent scleral buckling surgery. Clinical investigation, optical coherence tomography (OCT), full-field electroretinography (ERG), and multifocal ERG (mfERG) with fundus illumination were performed preoperatively and 6 months postoperatively. RESULTS: Anatomical success was achieved in 14 patients. mfERG amplitudes were reduced preoperatively in detached retina, with significant improvement at follow-up (P = 0.002). Foveal amplitudes improved significantly (P = 0.027). There was no significant difference in postoperative mfERG amplitudes between areas that had been preoperatively detached or attached (P = 0.739). In the subgroup of eight patients in whom the detachment engaged the fovea preoperatively, rod function improved significantly as assessed with full-field ERG (P = 0.008). In these patients, the extent of detachment ranged between 4 clock hours and 6 clock hours, as compared with 2 clock hours and 5 clock hours in the remaining patients. OCT showed subretinal foveal fluid in four patients at follow-up. CONCLUSIONS: In recent onset rhegmatogenous RD, total rod and localized central retinal dysfunction in detached retina can improve significantly after reattachment. mfERG and OCT are suitable tools for further studies of functional outcomes in RD.

Adult↗
PubMed1979

Retinal and choroidal contribution to retinal metabolism in vivo. A study in pigs.

The glucose metabolism of the retina was studied in vivo, by determining glucose, oxygen and lactate a-v differences for choroidal and retinal blood in pigs at different levels of intraocular pressure. At normal intraocular pressure the choroidal a-v differences were 0.07 and 0.11 mmol/l for glucose and oxygen respectively. The corresponding figures for the retina were 0.44 and 2.15. At increased levels of intraocular pressure the choroidal and retinal glucose and choroidal oxygen a-v differences increased, thus at least partly compensating for reduced blood flow. A major part of the oxygen and glucose consumed by the retina was delivered by the choroid. The total amount of oxygen extracted from choroidal and retinal blood could only account for complete oxidation of 37% of the extracted glucose. The results obtained in determinations of lactate a-v differences indicate that part of the remaining glucose is used for anaerobic glycolysis.

Animals↗
PubMed1991

Effect of protonation on the isomerization properties of n-butylamine Schiff base of isomeric retinal as revealed by direct HPLC analyses: selection of isomerization pathways by retinal proteins.

Alumina adsorption chromatography and ion-pair reversed-phase chromatography were developed to analyze the isomers of unprotonated and protonated n-butylamine Schiff base of retinal (RSB and PRSB), respectively. Photoisomerization starting from the all-trans, 11-cis and 13-cis isomers was traced for RSB in n-hexane, acetonitrile, methanol and 1-butanol, and for PRSB in methanol, acetonitrile and 1-butanol. The quantum yields of photoisomerization for the all-trans, 9-cis, 11-cis and 13-cis isomers were determined for RSB and PRSB in the above solvents except 1-butanol. On the other hand, photoisomerization of isomeric retinal bound (through Schiff base linkage) to bovine serum albumin (RBSA) in aqueous solution (pH 3, 7 and 12) as well as thermal isomerization of RSB (in n-hexane), PRSB (in methanol) and RBSA (in aqueous solution, pH 7) were traced starting from the all-trans, 11-cis, and 13-cis isomers. Protonation of RSB drastically changes the pathway of photoisomerization and increases the quantum yields of isomeric RSB. The solvent polarity increases the quantum yields of RSB differently depending on the configuration. Protonation enhances thermal isomerization also. The results of the above model systems are compared with those of retinal proteins to rationalize their selection of the particular isomerization pathways.

Butylamines↗
PubMed1981

Retinal vessels in the ora region. Possible role in the vitreo-retinal pathology in aphakia.

During intracapsular lens extraction the extreme retinal periphery is subjected to zonula-mediated traction and possible damage to the retinal vessels. The vascular pattern at the ora serrata was studied with special reference to the frequency and distribution of vessels positioned adjacent to the ora structures. The possible role of leakage from such vessels in vitreo-retinal pathology of the aphakic eye is discussed.

Aphakia, Postcataract↗
PubMed1993

Aqueous flare and cells in eyes with retinal vein occlusion--correlation with retinal fluorescein angiographic findings.

The laser flare cell meter (LFCM) was used to evaluate alterations of the blood-aqueous barrier in eyes with retinal vein occlusion (RVO). In 42 eyes of 42 patients with RVO (30 branch vein occlusions, 12 central vein occlusions) aqueous flare and aqueous cells were determined and retinal fluorescein angiography was performed. Flare and cell values were compared with 59 normal age and sex-matched control eyes and correlated with fluorescein angiographic findings. Both aqueous flare (12.321 (SD 6.717) photon counts/ms) and aqueous cells (mean 3.37 cells/0.075 x 10(6)/l) were significantly increased in eyes with RVO in comparison with the normal control group (flare 4.288 (SD 1.144) photon counts/ms, cells 0.54 cells/0.075 x 10(6)/l, p < 0.0001 and p < 0.005). Flare values in eyes with central RVO (19.517 (SD 7.762) photon counts/ms) were significantly higher than in eyes with branch RVO (9.443 (SD 3.307) photon counts/ms, p < 0.0001). Significant correlations were found between flare values and area of RVO (r = 0.70, p < 0.0001) and between flare values and area of retinal non-perfusion (r = 0.76, p < 0.0001). There were also significant correlations between flare values and number of cotton wool spots (r = 0.54, p < 0.0002) and between cell counts and degree of cystoid macular oedema (r = 0.46, p < 0.006). Our findings show that aqueous protein concentration, as indicated by flare, and aqueous cells are increased in RVO and that changes of aqueous flare correlate with fluorescein angiographic findings that reflect the severity of RVO. Measurements with LFCM may be useful non-invasively to quantify changes of the ocular barrier functions in RVO.

Adult↗
PubMed1994

Ocular manifestations in autosomal dominant retinitis pigmentosa with a Lys-296-Glu rhodopsin mutation at the retinal binding site.

A lysine to glutamic acid substitution at codon 296 in the rhodopsin gene has been reported in a family with autosomal dominant retinitis pigmentosa. This mutation is of particular functional interest as this lysine molecule is the binding site of 11-cis-retinal. The clinical features of a family with this mutation have not been reported previously. We examined 14 patients with autosomal dominant retinitis pigmentosa and a lysine-296-glutamic acid rhodopsin mutation. Four had detailed psychophysical and electrophysiological testing. Most affected subjects had severe disease with poor night vision from early life, and marked reduction of visual acuity and visual field by their early forties. Psychophysical testing showed no demonstrable rod function and severely reduced cone function in all patients tested.

Adolescent↗