Retinitis Pigmentosa and Allied Disorders

Weleber, Richard G.; Gregory-Evans, Kevin

doi:10.1016/b978-0-323-02598-0.50023-9

Cited by 59 publications

(64 citation statements)

References 838 publications

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“…However, decreasing pixel size two or four times for higher resolution arrays will require proximity between electrodes and cells on the order of 20 or even 10 µm, which is very challenging (if at all possible) in the epiretinal approach. Similarly, in degenerated retina the inner nuclear layer is typically separated from the retinal pigment epithelium by no less than 20-50 µm of debris [38], so placing an electrode array in subretinal space will face similar proximity challenges.…”

Section: Three-dimensional Implants For Higher Resolutionmentioning

confidence: 99%

Optoelectronic retinal prosthesis: system design and performance

et al. 2007

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The design of high-resolution retinal prostheses presents many unique engineering and biological challenges. Ever smaller electrodes must inject enough charge to stimulate nerve cells, within electrochemically safe voltage limits. Stimulation sites should be placed within an electrode diameter from the target cells to prevent 'blurring' and minimize current. Signals must be delivered wirelessly from an external source to a large number of electrodes, and visual information should, ideally, maintain its natural link to eye movements. Finally, a good system must have a wide range of stimulation currents, external control of image processing and the option of either anodic-first or cathodic-first pulses. This paper discusses these challenges and presents solutions to them for a system based on a photodiode array implant. Video frames are processed and imaged onto the retinal implant by a head-mounted near-to-eye projection system operating at near-infrared wavelengths. Photodiodes convert light into pulsed electric current, with charge injection maximized by applying a common biphasic bias waveform. The resulting prosthesis will provide stimulation with a frame rate of up to 50 Hz in a central 10• visual field, with a full 30• field accessible via eye movements. Pixel sizes are scalable from 100 to 25 µm, corresponding to 640-10 000 pixels on an implant 3 mm in diameter.

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Section: Three-dimensional Implants For Higher Resolutionmentioning

confidence: 99%

Optoelectronic retinal prosthesis: system design and performance

et al. 2007

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“…RP exhibits extensive genetic heterogeneity and can show autosomal recessive, autosomal dominant, or X-linked patterns of inheritance (Heckenlively, Yoser et al 1988). Clinical features in RP patients often include early night blindness, followed later by visual field loss (Heckenlively, Yoser et al 1988;Weleber and Gregory 2006), suggesting that in these patients rod photoreceptors degenerate first followed later by the degeneration of cone photoreceptors.…”

Section: Introductionmentioning

confidence: 99%

Xenopus laevis P23H rhodopsin transgene causes rod photoreceptor degeneration that is more severe in the ventral retina and is modulated by light

Zhang

Oglesby

Marsh-Armstrong

2008

Experimental Eye Research

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Rhodopsin transgenes carrying mutations that cause autosomal dominant retinitis pigmentosa in humans have been used to study rod photoreceptor degeneration in various model organisms including Xenopus laevis. To date, the only transgenes shown to cause rod photoreceptor degeneration in Xenopus laevis have been either mammalian rhodopsins or chimeric versions of rhodopsin based mainly on Xenopus laevis rhodopsin sequences but with a mammalian Cterminus. Since the C-terminal sequence of rhodopsin is highly conserved in mammals and divergent in Xenopus laevis, and mammalian and epitope-tagged rhodopsins may have unexpected properties as transgenes, we decided to test whether a Xenopus laevis rhodopsin transgence carrying only the P23H mutation could also cause rod photoreceptor degeneration. Xenopus laevis tadpoles expressing these transgenes indeed had shortened outer segments and, in severely affected animals, the loss of rod photoreceptors but not the loss of cone photoreceptors. RT-PCR analyses showed that less than 10% of mutant transgenic rhodopsin relative to wild-type endogenous rhodopsin mRNA was sufficient to produce severe rod photoreceptor degeneration. As observed in other animal models as well as humans carrying this particular rhodopsin mutation, the rod photoreceptor degeneration was most severe in the ventral retina and was modified by light. Thus, the rod photoreceptor degeneration produced in Xenopus laevis by the P23H mutation in an otherwise untagged Xenopus laevis rhodopsin is generally similar to that seen with mammalian rhodopsins and epitope-tagged versions of Xenopus laevis rhodopsin, though some differences remain to be explained.

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“…4,5 Stargardt's disease usually inherited autosomal recessively causes visual loss beginning in the first two decades of life often with a normal fundus and later associated with macular atrophy and yellowish deep retinal flecks. Gass subdivided this disease into four subgroups according to clinical presentations: group 1 with vermillion fundi and hidden choroidal fluorescence; group 2Fatrophic maculopathy with or without flecks; group 3Fatrophic maculopathy with late signs of retinitis pigmentosa; group 4Fflecks not associated with macular atrophy.…”

Section: Commentmentioning

confidence: 99%

“…ERG can show markedly decreased or absent photopic responses and mildly decreased scotopic responses. 4,5 Inverse RP is characterized by the presence of pigmentary disturbances similar to those occurring in classical RP, which occur solely in the pericentral retina sparing the peripheral retina. Both scotopic and photopic ERG responses are often subnormal consistent with region disease.…”

Section: Commentmentioning

confidence: 99%