Disability Glare and Contrast on the Snellen Eye Chart in General Practice,

Seven male graduate students, that required no visual correction, were tested at six General Practitioners offices composed of three levels of disability glare technically-equivalent foot lamberts G1 below 0.18 G2 above 0.18 but below 0.45 and G3 above 0.45 and two levels of contrast fraction between background and character G1 below 0.940 and G2 above 0.940. The Snellen test scores were recorded by indicating the characters within a particular string of characters incorrectly identified by the test subject. Precise scores were determined by interpolating between the character strings based on the inverse of Sheards relative acuity of the individual characters. A randomized complete blocks design 2X3X7 with repeated measurements was selected for treatment by analysis of variance. The Newman-Keuls statistic was utilized for the interpretation of the interaction term. The results indicates a that there was a variance between treatments b that contrast was insignificant c that disability glare is significant d that disability glare and contrast have a significant interaction in the higher ranges of disability glare. Author