VISUAL PREDICTORS FOR POOR MOBILITY PERFORMANCE IN PEOPLE WITH AGE RELATED MACULAR DEGENERATION Remy Sheena Mathew, B.Sc A thesis submitted in partial fulfilment of the requirements for admission to the degree of Doctor of Philosophy School of Optometry and Vision Science, University of New South Wales, Sydney, Australia September 2009 Visual predictors for poor mobility performance in people with AMD Originality statement ‘I hereby declare that this submission is my own work and to the best of my knowledge it contains no materials previously published or written by another person, or substantial proportions of material which have been accepted for the award of any other degree or diploma at UNSW or any other educational institution, except where due acknowledgement is made in the thesis. Any contribution made to the research by others, with whom I have worked at UNSW or elsewhere, is explicitly acknowledged in the thesis. I also declare that the intellectual content of this thesis is the product of my own work, except to the extent that assistance from others in the project's design and conception or in style, presentation and linguistic expression is acknowledged.’ Signed …………………………...................... Remy Sheena Mathew. ii Visual predictors for poor mobility performance in people with AMD Copyright and Authenticity Statements COPYRIGHT STATEMENT ‘I hereby grant the University of New South Wales or its agents the right to archive and to make available my thesis or dissertation in whole or part in the University libraries in all forms of media, now or here after known, subject to the provisions of the Copyright Act 1968. I retain all proprietary rights, such as patent rights. I also retain the right to use in future works (such as articles or books) all or part of this thesis or dissertation. I also authorise University Microfilms to use the 350 word abstract of my thesis in Dissertation Abstract International (this is applicable to doctoral theses only). I have either used no substantial portions of copyright material in my thesis or I have obtained permission to use copyright material; where permission has not been granted I have applied/will apply for a partial restriction of the digital copy of my thesis or dissertation.' Signed ……………………………………………........................ Date ……………………………………………........................... AUTHENTICITY STATEMENT ‘I certify that the Library deposit digital copy is a direct equivalent of the final officially approved version of my thesis. No emendation of content has occurred and if there are any minor variations in formatting, they are the result of the conversion to digital format.’ Signed ……………………………………………...................... Date …………………………………………….......................... iii Visual predictors for poor mobility performance in people with AMD Abstract 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 iv Visual predictors for poor mobility performance in people with AMD 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. v Visual predictors for poor mobility performance in people with AMD Acknowledgements I am grateful to Dr Michele Madigan for her expert guidance through the most difficult times of my candidature. Her positive outlook and constant support kept me going to the point of completion of this thesis. Although she became involved in my supervision towards the end of my candidature, her guidance and inputs have been invaluable- without which this thesis would not be completed. I am extremely grateful to Dr Vaegan for all the thought provoking discussions we had and for inspiring me to ask the why’s and how’s of research during the time of his supervision, before his passing away late last year. He is much missed. I am extremely grateful to Dr Paul Beaumont, you were always there for me. Your support and guidance was of great help. Prof. Stephen Lord, your valuable feedback, constant support and understanding has helped me complete this journey; you were always there for me besides your hectic schedule. Dr Peter Herse, thank you for helping me through the initial phase of my candiature and helping me to embark on this intellectual journey. I am grateful to the friendly staff at the School of Optometry and Vision Science, UNSW. You made my stay in Australia very pleasant. My special thanks go to Professor Stephen Dain for loaning photometric instruments from ORLAB, and to Dr. Alexander for helpful discussions related to psychophysics and vision. I am grateful to Thomas John for the discussions on statistics during my candidature. I gratefully acknowledge the University of New South Wales for providing financial assistance, through the PhD Student Completion Scholarships. Thanks are due to my friends and colleagues at Retina and Vitreous Centre for their patience and kindness that made this study possible. Special thanks to Netty for sorting out the subject folders and Nikki for proof reading the references for me. Jane, Netty, Nikki, Jen, Christine and Sapna you all were simply great- Thank you. vi Visual predictors for poor mobility performance in people with AMD My family has always been the source of inspiration to my studies all my life. A prayer of grattitude to the almighty for giving me a father who inspired me to make my life worthwhile to the community I live in, my mother for her silent constant encouragement, my elder sister who is my strength, my jijaji (brother-in-law) for his encouragement and my younger sister who is the pillar of my support. Special thanks is also due for my better half, Ginu for understanding my dream and for battling the hardship of financial burden due to the tuition fees with a smile, never complaining. You have been very patient and a real motivating factor. Your love and support have inspired my continued efforts to complete this project. My family’s unconditional love through some very difficult phases has made completion of this thesis possible. vii Visual predictors for poor mobility performance in people with AMD Table of contents Originality statement ...................................................................................... ii Copyright and Authenticity Statements ...................................................... iii COPYRIGHT STATEMENT ....................................................................... iii AUTHENTICITY STATEMENT ................................................................ iii Abstract ........................................................................................................... iv Table of contents .......................................................................................... viii List of Figures ...............................................................................................