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K. Oomachi, K. Oogata, T. Sugawara, A. Hata, S. Yamamoto; Evaluation of Contrast Visual Acuity in Patients With Retinitis Pigmentosa. Invest. Ophthalmol. Vis. Sci. 2009;50(13):988.
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The conventional visual acuity (VA) is measured with optotypes of almost 100% contrast. For patients with retinitis pigmentosa (RP), however, other assessments with lower contrasts might be more representative of the visual stimuli encountered in daily living. The purpose of this study was to determine the usefulness of contrast VA in RP patients.
Thirty-eight eyes of 21 control individuals, 154 eyes of 93 RP patients without other ophthalmological disorders (RP-1 group), and 55 eyes of 33 RP patients with moderate cataract (RP-2 group) were studied. The contrast VA was measured with 100% and 10% contrast under daylight and mesopic conditions with the CAT-CP (NEITZ CO). The VA was also measured with a conventional Landolt ring chart (conventional VA). The VAs were converted to logMAR units, and the mean values were used for the analyses. Differences between the conventional VA and the 100% contrast VA under daylight condition, between the conventional VA and 100% contrast VA at mesopic levels, between VA with 100% and 10% contrast both at daylight and mesopic conditions were compared by Mann-Whitney U test in the three groups.
No significant differences were observed among the three groups in the difference between 100% contrast VA and 10% contrast VA under daylight conditions. On the other hand, the values for both the RP-1 and RP-2 groups were significantly higher than the controls for differences between conventional VA and 100% contrast VA under daylight conditions (P<0.001), between conventional VA and 100% at mesopic conditions (P<0.05), between 100% and 10% contrasts (P<0.05).
The contrast VA in RP patient depended on the surround light levels, and the variation was larger than that of the conventional VA. These findings indicate the possible clinical usefulness of contrast VA to assess the daily visual challenges of RP patients.
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