A Modified Protocol for the Assessment of Visual Function in Patients with Retinitis Pigmentosa

Abstract

1.1Background

The assessment of visual function for retinitis pigmentosa routinely includes: electroretinography, visual acuity and visual field-testing. Patients with retinitis pigmentosa sometimes complain of changes in visual function, which are not paralleled by routine eye tests.

1.2. Aims and Objectives

To determine which visual function test or group of tests can predict reliably perceived visual function in patients with retinitis pigmentosa

1.3. Methods

Subjects with progressive retinitis pigmentosa are recruited from the Ocular genetics program of The Hospital for Sick Children and Mount Sinai Hospital, Toronto. Subjects will be tested four times over the over the period of one year. On each visit they undergo following tests- 1) Central visual acuity (VA) using the crowded IogMAR acuity chart, 2) Contrast Sensitivity (CS) using Pelli-Robson contrast sensitivity chart, 3) Visual field test (VF) using Humphrey (10-2), 4) Color vision using Mollon-Reffin `minimalist’ test and 5) Subjective visual function questionnaire testing near and global perceived visual function respectively.

The phase I results shows that correlation of measured visual function to patient’s subjective visual perception improves significantly by adding contrast sensitivity assessment. Contrast sensitivity correlated very significantly with visual fields. The variability in the contrast sensitivity in relation with visual field observed may reflect the variability in field constriction included in the study. This includes the presence or absence of central or paracentral scotomata.

High repeatability of the tests between visits of phase proves the reliability of the tests used in the-study.

The addition of Contrast Sensitivity and Humphrey Visual Field testing (10-2) to the routine visual assessment should improve the quality of the longitudinal data of visual function obtained from these patients. This is especially true for patients with visual fields measuring less then ten degrees, where a Goldman visual field does not give as much information about field changes.

All the patients will be seen again at six month (phase II) and one year (phase III). Twenty-seven have returned for six-month visit (phase II).