Materials and Method: Başkent University Medical Faculty Phase II students, with no known systemic and ocular disease and whose visual acuities corrected or non-corrected were 10/10 in Snellen chart were included in the study. Visual acuity determination was done under relatively at the same illumination levels and at 6 meters from the chart for all participants. The color discrimination screening test was made by commercially available Ishihara test plates under standard illumination for all participants. To avoid any cheating and habituation to the test plates, the order of presentation was changed every time the test applied and some plates were shown repetitively.

Statistical method: ?One sample test of a proportion? was used in the study. Frequency (n) and percentage (%) values were given for determinant statistics. While N is known (N=137, a=0.05, d=0.1 ve p=0.50) to calculate the necessary sample prediction of the population, minimum sample number can be deducted from the:

formula. Accordingly minimum sample number to be included in the study was 97 students.

Results: Of the tested 100 subjects, 63 were females and 37 were males. None of the females had color vision defects but one male had redgreen color vision defect (2.7%). Protan defect was medium but green defect was severe.

Discussion: In our study the rate of color blindness, compared to other percentages in the literature was low. This is due to the fact that our population included smaller numbers of participant males. Regarding the fact that the study was carried out in only phase II students of medical faculty, it was quite hard to bring the participants into the testing room because of the study time was limited. In order to obtain comparable results with the literature, determination of color blindness needs larger numbers of samples. Keywords : Color vision defects, congenital, protanopia, deuterenopia