The Ability to Perceive a Minor Change in Luminosity Lab Report

The Ability to Perceive a Minor Change in Luminosity - Lab Report Example To perform the CS test (CST), the basic requirements for all four tests were: 1) to have an adequate luminance level required for each test; 2) to have precise test distance; and 3) to perform each test approximately at the same eye sight level as that of test charts. The CST luminance requirement for Pelli-Robson charts was 60–120 cd/m2, while for Vistech6000 and Cambridge plates the adequate luminance levels were 103–240 cd/m2 and 100 cd/m2 respectively. The Lux value required for Cardiff cards CST was equal to that of the gray background cards. For each test the required Lux level was verified by using a Lux meter. The value of precise test distance varies from test to test. For Pelli-Robson CST the required separation was 1 m. For Vistech and Cambridge plates CSTs, the required separation was 3.048 m and 6 m respectively, and within the acuity limit for Cardiff cards CST (Wood and Wood 1995). After having all basic requirements for each test, the test charts/cards w ere hung vertically on a wall one after the other. To determine CS values, corresponding observations were made: first with the right eye (without any correction), starting horizontally on each line of charts/cards and moving from the left hand side to the right hand side, and then from top to bottom for each letter/symbol on the chart /card. The tests were repeated for a plastic in front of an eye pretended to be a cataract. The tests were concluded when two or three letters/symbols were named incorrectly. The corresponding observations for CS were recorded. The CS function (CSF) value obtained for monocular right eye (RE) testing without cataract through Pelli-Robson CST is 1.95 while with cataract it is 1.65 – a quite lower value (fig. 4 and 5) . From Cardiff CST the evaluated contrast (%) values for monocular.