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E. Wegscheider, B. Wabbels, R. Schillinger, M. Preising, C. Hamel, B. Lorenz; Rod or Cone Vision in Young Patients With Early Onset Retinal Degeneration Associated With the RPE65 Genotype? . Invest. Ophthalmol. Vis. Sci. 2003;44(13):525.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To investigate the photoreceptor system mediating vision in young patients with early onset retinal degeneration associated with mutation in the RPE65 gene. Background: RPE65 is an essential protein in the recycling of retinol. Absence of RPE65 is associated with virtual absence of active rhodopsin in the rods of RPE65-/- mice. Despite this, ERG studies with high intensity flashes indicated rod mediated answers. If so, gene therapy could be expected to only restore rod vision. As patients with the RPE65 genotype have some color vision, cone mediated vision appears possible. Methods: A total of 6 patients aged 10-27 years suffering from an early onset retinal degeneration associated with compound heterozygous or homozygous mutations in the RPE65 gene underwent spectral sensitivity testing under dark adapted conditions and two patients also under light adapted conditions using a HFA modified for automated scotopic and spectrally resolved perimetry (16 monochromatic filters 400 - 700 nm, mean bandwidth 9.6 nm). In dependence on the photopic visual field two to three different loci were tested in the central 10°. Results: In the group 15 years and younger (4 patients) V.A. ranged from 0.1- 0.3. No photophobia was present, and bright light was necessary for optimal visual performance. The two older patients (19 and 27 years) had only residual visual function and were photophobic. Only the patients under 15 were able to distinguish colors. Spectral sensitivity testing under dark and light adapted conditions revealed similar curves. The general sensitivity ranged around 20 dB. The whole tested color range was seen with the maximum around 580 nm corresponding well with the cone system. Blue cone related responses were diminished. The two older patients had a residual sensitivity around 10 dB. The wave lengths seen ranged from 500 - 640 nm. Conclusions: Vision is cone mediated in young patients with early onset retinal degeneration associated with the RPE65 genotype. Successful gene therapy could therefore have the potential to restore cone vision. Because of the progressive nature of the disease with increasing RPE cell death gene therapy would have to be performed at early stages of the disease.
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