The Visual Perception Lab focuses on understanding how the visual system perceives the things around through the information that comes through one’s eye. The visual information could be as simple as a single alphabet or as complicated as a picture of Kumbh Mela (a mass Hindu pilgrimage). Most of the people, whom we consider visually normal, process such information without any difficulty. A certain percentage of people due to a variety of reasons such as uncorrected refractive errors, or lazy eye or eye diseases, have difficulty with some or most of these visual tasks. The lab studies how the visually normal individuals process simple to complicated images, and how this process is altered in people with different eye diseases.
Details of the projects carried out in the Visual Perception Lab are:-
(a) Visual Acuity: The lab currently is working on designing the most sensitive visual acuity test. Visual acuity refers to the ability of seeing fine details in a scene. The higher the visual acuity, the finer one can see these details. In the clinics, visual acuity is usually measured using letter charts with black letter printed on white charts. While these charts are very useful, they also have certain limitations. We are currently exploring ways of removing these limitations by exploring ways such as, altering the brightness of the chart, giving a different contrast color to the letters, replacing the letters with images of the natural environment around us.
(b) Models of Amblyopia: Amblyopia, more popularly known as lazy eye, is a developmental dysfunction of the visual system. In individuals with amblyopia usually (though not always), information from one eye (called the fellow eye) is used by the brain to understand the scene in front of them while the information from the other eye (called the amblyopic eye) is discarded or only minimally used by the brain. It is estimated that about 1.1% of the children in India have amblyopia. There are different types of amblyopia associated with squint (crossed eye), difference in the eye sizes, cataract from birth, etc. Amblyopia in many children goes undiagnosed or untreated (due to the false belief that crossed-eyes is a sign of good luck) resulting in these individuals growing with effectively one eye only. Hence it is important that all children undergo an eye examination before they start going to school.
The amblyopic eye is not able to process different types of visual information affectively. Many visual functions, starting from reduced visual acuity to processing certain types of motion stimulus are affected.
The team in the lab focuses on understanding the differences between the normal eye and the amblyopic eye in combining information from various regions of the scene. This is studied by using gratings of different sizes and movements of randomly moving dots. Results from these studies could be used to design novel treatment modalities for amblyopia.
Books: Lakshminarayanan V, Varadharajan S. Special Functions for Optical Science and Engineer ing. SPIE Press, Bellingham, WA, USA. 2015.
Book Chapters: Varadharajan S. Spatial Vision and Pattern Perception. In Chen J, Cranton W, Fihn M, Hand book of Visual Display Technology. Springer-Verlag Berlin Heildelberg, 2012, p109 – 119. (Second edition: 2015).
Raja M, Ramamurthy D, Srinivasan K, Varadharajan L S. Development of pocket vision screener and its effectiveness at screening visual acuity deficits. Ind J Ophthalmol 62: 1152–1155; 2014.
Vemuri K, Bisla K, Mulpuru S, Varadharajan S. Do normal pupil diameter differences in the population underlie the color selection of #thedress? J Opt Soc Am A 33(3): 137–142; 2016.
Lakshminarayanan V, Ghalila H, Ammar A, Vasradharajan S. Role of simulations in Optics Education. Proc. of SPIE 9946, Optics Education and Outreach IV; 99460N; 2016.