Hereditary degenerations of the human retina are genetically heterogeneous, with well over 100 genes implicated so far. This Seminar focuses on the subset of diseases called retinitis pigmentosa, in which patients typically lose night vision in adolescence, side vision in young adulthood, and central vision in later life because of progressive loss of rod and cone photoreceptor cells. Measures of retinal function, such as the electroretinogram, show that photoreceptor function is diminished generally many years before symptomic night blindness, visual-field scotomas, or decreased visual acuity arise. More than 45 genes for retinitis pigmentosa have been identified. These genes account for only about 60% of all patients; the remainder have defects in as yet unidentified genes. Findings of controlled trials indicate that nutritional interventions, including vitamin A palmitate and omega-3-rich fish, slow progression of disease in many patients. Imminent treatments for retinitis pigmentosa are greatly anticipated, especially for genetically defined subsets of patients, because of newly identified genes, growing knowledge of affected biochemical pathways, and development of animal models.
"Knowledge of cell types and corresponding functions in the retina provide insight into treatments for neurodegenerative diseases of the retina (Lagali et al., 2008; Bramall et al., 2010; Wright et al., 2010; Doroudchi et al., 2011). Many retinal diseases, such as age-related macular degeneration and retinitis pigmentosa, cause irreversible and progressive damage to the photoreceptors in the retina (Hartong et al., 2006); this group of cells initiates the sequence of events required for vision (Schmidt et al., 2008; Lorach et al., 2013). The photoreceptors convert visual stimuli into analog, graded-potential electrical signals that cascade through several layers of signal-processing cells to the retinal ganglion cell layer, which ultimately sends the visual signals to the brain through the optic nerve (Dowling, 2012). "
[Show abstract][Hide abstract] ABSTRACT: Knowledge of neuronal cell types in the mammalian retina is important for the understanding of human retinal disease and the advancement of sight-restoring technology, such as retinal prosthetic devices. A somewhat less utilized animal model for retinal research is the hamster, which has a visual system that is characterized by an area centralis and a wide visual field with a broad binocular component. The hamster retina is optimally suited for recording on the microelectrode array (MEA), because it intrinsically lies flat on the MEA surface and yields robust, large-amplitude signals. However, information in the literature about hamster retinal ganglion cell functional types is scarce. The goal of our work is to develop a method featuring a high-density (HD) complementary metal-oxide-semiconductor (CMOS) MEA technology along with a sequence of standardized visual stimuli in order to categorize ganglion cells in isolated Syrian Hamster (Mesocricetus auratus) retina. Since the HD-MEA is capable of recording at a higher spatial resolution than most MEA systems (17.5 μm electrode pitch), we were able to record from a large proportion of RGCs within a selected region. Secondly, we chose our stimuli so that they could be run during the experiment without intervention or computation steps. The visual stimulus set was designed to activate the receptive fields of most ganglion cells in parallel and to incorporate various visual features to which different cell types respond uniquely. Based on the ganglion cell responses, basic cell properties were determined: direction selectivity, speed tuning, width tuning, transience, and latency. These properties were clustered to identify ganglion cell types in the hamster retina. Ultimately, we recorded up to a cell density of 2780 cells/mm(2) at 2 mm (42°) from the optic nerve head. Using five parameters extracted from the responses to visual stimuli, we obtained seven ganglion cell types.
Frontiers in Neuroscience 10/2015; 9. DOI:10.3389/fnins.2015.00360 · 3.66 Impact Factor
"Retinitis pigmentosa (RP) is a genetically heterogeneous disease characterised by progressive retinal photoreceptor degeneration  . The worldwide population affected has been estimated to be over one million individuals, whereas the frequency is approximately 1/4000  . Although RP has several mutations and genetical patterns , the symptoms and histopathological findings are similar . "
[Show abstract][Hide abstract] ABSTRACT: Aim. To evaluate the peripapillary retinal nerve fiber layer (RNFL) changes in retinitis pigmentosa (RP) patients using spectral domain optic coherence tomography (Sd-OCT). Methods. We retrospectively examined medical records of forty-four eyes of twenty-two RP patients. The results were also compared with those of previously reported forty-four eyes of twenty-two normal subjects (controls). Records of average and four quadrants peripapillary RNFL thickness measurements using Sd-OCT were assessed. Results. In RP patients the mean RNFL thickness was 97.57 ± 3.21 μm. The RNFL in the superior, temporal, nasal, and inferior quadrants was 119.18 ± 4.47 μm, 84.68 ± 2.31 μm, 75.09 ± 3.34 μm, and 113.88 ± 4.25 μm, respectively. While the thinning of RNFL was predominantly observed in the inferior quadrant, the thickening was mostly noted in temporal quadrant. The differences between mean, superior, and nasal quadrant RNFL thicknesses were not statistically significant when compared with control group. The RP patients had thinner inferior quadrant and thicker temporal quadrant than control group (p < 0.05). Conclusion. Sd-OCT is highly sensitive and effective instrument to detect RNFL changes in RP patients. RNFL measurements can provide information about the progression of retinitis pigmentosa and may provide prognostic indices for future treatment modalities.
Journal of Ophthalmology 09/2015; 2015(2):157365. DOI:10.1155/2015/157365 · 1.43 Impact Factor
"Several medical treatments have been proposed to slow down disease progression. Specifically, the trophic and antioxidant effects of vitamins have been evaluated in RP patients in order to demonstrate a protective action on photoreceptors   . Other nutritional supplementations, including docosahexaenoic acid (DHA), an omega 3 fatty acid found in high concentration in oil fish, lutein, and gangliosides are cited as a potential therapeutic modality that can help in preserving the visual function of patients with RP. "
[Show abstract][Hide abstract] ABSTRACT: Aims.
Several treatments have been proposed to slow down progression of Retinitis pigmentosa (RP), a hereditary retinal degenerative condition leading to severe visual impairment. The aim of this study is to systematically review data from randomized clinical trials (RCTs) evaluating safety and efficacy of medical interventions for the treatment of RP.
Randomized clinical trials on medical treatments for syndromic and nonsyndromic RP published up to December 2014 were included in the review. Visual acuity, visual field, electroretinogram, and adverse events were used as outcome measures.
The 19 RCTs included in this systematic review included trials on hyperbaric oxygen delivery, topical brimonidine tartrate, vitamins, docosahexaenoic acid, gangliosides, lutein, oral nilvadipine, ciliary neurotrophic factor, and valproic acid. All treatments proved safe but did not show significant benefit on visual function. Long term supplementation with vitamin A showed a significantly slower decline rate in electroretinogram amplitude.
Although all medical treatments for RP appear safe, evidence emerging from RCTs is limited since they do not present comparable results suitable for quantitative statistical analysis. The limited number of RCTs, the poor clinical results, and the heterogeneity among studies negatively influence the strength of recommendations for the long term management of RP patients.
Journal of Ophthalmology 09/2015; 2015(5):737053. DOI:10.1155/2015/737053 · 1.43 Impact Factor
Kristof Van Schil, B Jeroen Klevering, Bart P Leroy, Jan Willem R Pott, Dikla Bandah-Rozenfeld, Marijke N Zonneveld-Vrieling, Dror Sharon, Anneke I den Hollander, Frans P M Cremers, Elfride De Baere, Rob W J Collin, L Ingeborgh van den Born,
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