The participants will undergo comprehensive eye examination which would include refraction, slit lamp bio - microscopy, intraocular pressure measurement.  The participants, then be undergoing visual function tests including visual acuity, reverse polarity, contrast sensitivity, colour vision, cone flicker and microperimetry. Apart from these, the patients would also be undergoing OCT, Fundus photographs.Colour vision, contrast sensitivity function, photoreceptor (cone flicker) sensitivity will be measured using simple psychophysical procedures, where participants will be required to identify the location of the coloured patch of light or flicker in the computer screen using a numeric key pad. There will be a total of five tests, which will be administered monocularly for each individual. The length of time for participation is approximately 60 minutes for each eye. The total testing time, excluding the comprehensive eye examination would be approximately 2 hrs.  The results of the tests are not provided to the participants, however if patient prefers, it would be provided after the study has been concluded.All these test procedures are done routinely in research. Instruments used will be Advanced Vision and Optometric Testing (AVOT) systems. This instrument has been previously used safely in human participants over large number of studies over the past decade.