Abstract
IntroductionChoroideremia and RPGR-associated retinitis pigmentosa (RP) are two distinct inherited rod-cone degenerations, where good visual acuity (VA) is maintained until late disease stages, limiting its usefulness as a disease marker. Low luminance VA and low luminance deficit (standard VA minus low luminance VA) may be more sensitive visual function measures.MethodsStandard VA was obtained using Early Treatment Diabetic Retinopathy Study letter charts (Precision Vision, Bloomington, IL, USA). Low luminance VA was assessed using a 2.0-log unit neutral density filter, with the same chart setup, without formal dark adaptation. Mean central retinal sensitivity was assessed using MAIA microperimetry (Centervue SpA, Padova, Italy). Optical coherence tomography imaging was attained with Heidelberg Eye Explorer software (Heidelberg Engineering, Heidelberg, Germany).ResultsTwenty-four male participants with confirmed pathogenic RPGR mutations, 44 male participants with confirmed pathogenic CHM mutations, and 62 age-matched controls underwent clinical assessment prior to clinical trial recruitment. Low luminance VA was significantly reduced in both disease groups compared to controls. The low luminance deficit correlated with microperimetry retinal sensitivity and ellipsoid zone width. Eleven participants with moderate VA had poor low luminance VA (subsequently a large low luminance deficit), no detectable microperimetry sensitivity, and severely constricted ellipsoid zone widths.ConclusionsLow luminance VA and subsequently low luminance deficit are useful markers of central macular visual function in both choroideremia and RPGR-associated RP, when standard VA is preserved.Translational RelevanceLow luminance visual acuity and low luminance deficit are useful vision measures in two distinct rod-cone degenerations and may be useful in other retinal degenerations.
Highlights
Choroideremia and retinitis pigmentosa GTPase regulator gene (RPGR)-associated retinitis pigmentosa (RP) are two distinct inherited rod-cone degenerations, where good visual acuity (VA) is maintained until late disease stages, limiting its usefulness as a disease marker
Patients with choroideremia and RPGR-associated RP were assessed as part of the screening process, prior to recruitment into gene therapy trials (NCT02407678 and NCT03116113), at Oxford Eye Hospital, in accordance with the tenets of the Declaration of Helsinki
All three groups were age-matched (Kruskal-Wallis test, P = 0.413). The results show both standard VA and Low luminance VA (LLVA) (Table 1) are significantly reduced in both RPGR-associated RP and choroideremia compared to controls (Kruskal-Wallis test with post hoc analyses, P ≤ 0.01)
Summary
Choroideremia and RPGR-associated retinitis pigmentosa (RP) are two distinct inherited rod-cone degenerations, where good visual acuity (VA) is maintained until late disease stages, limiting its usefulness as a disease marker. Inherited retinal degenerations are the leading cause of visual impairment in the working population.[1] For many of these conditions, there are no treatments available, this is changing with recent advancements in gene therapy. Therapies for conditions such as RPE65 Leber congenital amaurosis, choroideremia, and RPGR-associated retinitis pigmentosa (RP) have shown promising results.[2,3,4]. Patients present typically during the second decade of life with nyctalopia and progressive visual field loss, gradually progressing until severe visual impairment, often by the third or fourth decade.[6]
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