Assessment of Everyday Visual Tasks in Carriers of X-Linked Retinitis Pigmentosa: Use of the Visual Activities and Low Luminance Questionnaires

Abstract

Purpose: : Female carriers of X-linked Retinitis Pigmentosa (XLRP) with a family history of retinitis pigmentosa GTPase Regulator (RPGR) mutations display a spectrum of phenotypes from asymptomatic to severely affected. Initial assessment of a subject's level of severity can be difficult since carriers of genetic X-linked diseases are thought to be asymptomatic. The purpose of this study is to assess the usefulness of a modified Visual Activities Questionnaire (VAQ) in classifying severity of symptoms in females with a family history of XLRP.

Methods: : An 8-subscale Visual Activities Questionnaire (VAQ; Sloane et al., Tech Digest 1992), used to measure a subject's difficulty with daily visual tasks, was given along with the general dim lighting subscale of the Low Luminance Questionnaire (LLQ; Owsley et al., IOVS 2006). The LLQ in its entirety was initially designed to assess self-reported visual problems under dim lighting. The 39-item composite survey was scored on a 5-to-7 point Likert scale; all scores were converted to a 100 point scale for comparison. The survey was given to 15 obligate and at-risk carriers before visual function assessment which included ISCEV standard electroretinography. Based on visual function findings, subjects were classified as minimally affected (n=9) or moderate to severely affected (n=6) (e.g., delayed timing --> non-detectable responses).

Results: : All carriers scored lowest on questions dealing with glare (48.1±26.6) and light/dark adaptation (56.3±28.1). For the 8 VAQ subscales, all carriers scored highest on color discrimination (89.5±21.5) and depth perception (86.7±21.5). Moderate to severely affected carriers scored significantly lower (LLQ=52.1±23.8; VAQ=59.6±27.3; p=0.03) on the LLQ subscale and slightly lower on the VAQ than minimally affected carriers (LLQ=81.9±11.6; VAQ=80.6±12.3; p=0.05).

Conclusions: : In general, carriers who responded with fewer difficulties in daily tasks and fewer difficulties with tasks in dim lighting were found to be less severely affected than carriers whose responses indicated more difficulties in everyday visual tasks. The findings from this study will be used to develop a refined questionnaire sensitive to phenotypic characteristics of XLRP carriers.

Keywords: retinal degenerations: hereditary • quality of life • genetics