Chapter 1
Introduction
1.1 Introduction
Vision is an asset to everything and even though visual impairment is not necessarily life threatening, it can cause some restriction in certain daily activities. Most of the time spectacle lenses are being used to correct visual impairment due to refractive error. Therefore, it is important to be well aware of how visual performance may be influence by any ophthalmic device. Apart from spectacles lenses, tinted spectacle lenses are the most common type of ophthalmic device. The purpose of tinted spectacle lenses is to increase contrast and do not obstruct the visual performance of the person (Shaik et al., 2013).
Optometrist prescribes tinted spectacles lenses due to many reason. In 2007, Mehta, Ramkissoon and Bhagwanjee, mentioned about the purpose of tints lenses such as provide protection from exposure to high levels of ultraviolet radiation and infrared radiation ,improve color perception in color deficient individuals, decrease glare from reflective surfaces such as snow, sand, and water, decrease illumination and thus decreases photophobia, decrease light scatter in conditions such as cataract, albinism and retinitis pigmentosa and improve cosmesis in disfigurements such as strabismus…show more content… Contrast sensitivity differs from visual acuity, which is a routine eye examination whereby measuring the ability to distinguish between smaller and smaller letters on a standard chart. Contrast sensitivity on the other measure the visual function, particularly in conditions of low light, fog or glare, when the contrast between objects and their background often is reduced. Driving at night is an example of an activity that requires good contrast sensitivity for safety. Even though a subject is having visual acuity of 6/6 due to some eye or health conditions the contrast sensitivity can