Visual predictors for poor mobility performance in people with age-related macular degeneration

Age-related macular degeneration is the leading cause of visual impairement in older people in developed countries. Although, several studies have considered aspects of quality of life and depression in people with AMD, case control studies and investigations of visual function and its impact on mobility have not been extensively explored; these studies form the focus for this study. This thesis aimed to analyze the quality of life in people with moderate to moderately severe AMD compared to age-and-gender matched controls. Further, the study examined different aspects of visual function, sensorimotor function and mobility performance in AMD and controls. Analysis of these findings was conducted to determine whether poor mobility performance in people with AMD could be predicted using particular measures of visual function. A quality of life profile was mapped for AMD (n=145) and Control (n=136) subjects using the Short Form general health (SF-36), Low Luminance Questionnaire (LLQ), Goldberg Anxiety and Depression Scale (GADS), Incidental and Planned Activity questionnaire (IPAQ) and Assistance for daily living activities. Visual function (high contrast visual acuity, contrast sensitivity, photostress test, visual fields and dark adaptation), sensorimotor function (proprioception, contrast sensitivity, muscle strength, reaction time and balance) and mobility performance (under five levels of illumination) were assessed for a subset of 68 subjects (AMD: 33; Control: 35). The differences between the two groups were assessed using independent t-tests and multi-variate analysis. Visual predictors for poor mobility performance were modelled using stepwise linear regression.This study showed that people with AMD have reduced quality of life on both functional and emotional domains, with more anxiety and depressive symptoms when compared to age-and-gender-matched controls. People with AMD also required more assistance for daily living activities. Significant functional impairments for visual acuity, contrast sensitivity, photostress test, visual field indices and dark adaptation indices (cone threshold, rod threshold and rod-cone break up time) were also seen in people with AMD compared to controls. Multivariate analysis showed similar performances for the sensorimotor functions in both groups after correcting for age, gender and visual input (factored in terms of visual acuity). Mobility performance for people with AMD was significantly reduced for all the obstacle courses when compared with controls. Poor mobility performance in people with AMD, particularly with changes in surrounding illumination could be best predicted from the presence of focal defects in the central visual field, delayed recovery of macular function and delayed dark adaptation. Taken together, this study indicates the need for assessment and improved intervention to maintain independence and quality of life in people with AMD