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Jasleen Kaur Jolly, Markus Groppe, Robert E MacLaren; Functional Defects In Colour Vision In Patients With Choroideremia. Invest. Ophthalmol. Vis. Sci. 2014;55(13):6242.
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In an ongoing clinical trial to assess gene therapy in choroideremia (NCT01461213), some patients commented that their colour vision appeared more vivid in the injected eye after surgery compared to their unoperated eye. Since the operated eyes would ordinarily be expected to have reduced colour discrimination due to foveal detachment, we hypothesised that choroideremia might be associated with subtle defects in colour vision, which might in part be reversed following gene therapy. We therefore sought to determine the baseline colour vision in these patients.
Twenty-one eyes of 13 male patients with an established diagnosis of choroideremia and a residual surviving fovea underwent colour vision testing with the Farnsworth Munsell 100 hue colour vision test, Snellen or ETDRS visual acuity testing, optical coherence tomography (OCT) and autofluorescence imaging. In order to differentiate colour vision loss due to degeneration from colour vision loss due to a stationary impairment of the visual cycle, eyes were divided into two groups: 6/6 or better (n=11), or worse than 6/6 (n=10). A third group of age-matched male controls with no known colour vision defects was also included (n=11) Statistical analysis was performed using ANOVA and correlation analysis.
Colour vision scores were significantly reduced in patients with choroideremia compared with age-matched controls (p < 0.01). Colour vision was significantly impaired in the subgroup of patients with vision 6/6 or better and a normal fovea (P < 0.05). Degeneration appeared to reduce this further as a correlation was noted between colour vision loss and proximity of the degeneration to the fovea (r = 0.45, p = 0.06).
Patients with choroideremia have an underlying functional defect in colour vision compared with age-matched controls. The colour vision deteriorates further as the degeneration encroaches on the fovea. This might be explained by a key role of the choroideremia protein (REP1) in retinal pigment epithelium homeostasis, which is indirectly involved in cone photoreceptor function.
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