Abinaya Priya Venkataraman
Vision Beyond the Fovea: Evaluation and Stimuli Properties
Time: Fri 2016-09-23 13.00 - 16.00
Lecturer: Abinaya Priya Venkataraman
Title: Vision Beyond the Fovea: Evaluation and Stimuli Properties
Candidate: Abinaya Priya Venkataraman
Time: Friday September 23, 2016, at 13:00
Location: Room FB42, Albanova, Roslagstullsbacken 21, KTH, Stockholm
Opponent: PhD Hema Radhakrishnan, Senior Lecture in Optometry, Deputy Associate Dean for Social Responsibility, Faculty of Life Sciences, Univeristy of Manchester, Manchester, England.
Supervisor: Assistant professor Linda Lundström
Abstract: This research is about evaluating vision in the periphery. Peripheral vision is of fundamental importance in the performance of our everyday activities. The aim of this thesis is to develop methods suitable for the evaluation of peripheral vision and to assess how different visual functions vary across the visual field. The results have application both within the field of visual rehabilitation of people with central visual field loss (CFL) and as well as in myopia research.
All methods for assessing peripheral vision were implemented with adaptive psychophysical algorithms based on Bayesian statistics. A routine for time efficient evaluation of peripheral contrast sensitivity was implemented and verified for measurements out to 30° in the visual field. Peripheral vision was evaluated for different properties of the stimuli: sharpness, motion, orientation, and extent. Optical quality was controlled using adaptive optics and/or corrective spectacles specially adapted for the peripheral viewing angle. We found that many peripheral visual functions improved with correction, especially in people with CFL. We also found improvements in peripheral contrast sensitivity for low spatial frequencies when stimuli drifted at 5 to 10 Hz; this applies both for people with normal vision and those with CFL. In the periphery, it is easier to see lines that are oriented parallel with respect to the visual field meridian. We have shown that this directional bias is present for both resolution and detection tasks in the periphery, even when the asymmetric optical errors are minimized. For accurate evaluation or peripheral vision, we therefore recommend using gratings that are oriented oblique to the visual field meridian. The directional bias may have implications in how peripheral image quality affects myopia progression. Another proof that peripheral vision can influence central visual function is the fact that, when the stimulus extent was increased beyond the fovea, the blur in the stimulus was less noticeable.