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City Research Online: http://openaccess.city.ac.uk/ [email protected] A study of pupil response components in human vision Sancho Moro Dissertation submitted for a Philosophical Doctorate degree at City University, London Department of Optometry and Visual Science July 2004 Table of Contents Acknowledgements ....................................................................................................................... 10 Abstract ......................................................................................................................................... 12 Thesis outline and summary of research .................................................................................... 13 Chapter 1: Anatomy and Physiology of the Visual System .......................................................15 1.1 Photo-transduction in the retina ........................................................................................15 1.2 The retina..........................................................................................................................16 1.3 Horizontal, amacrine and bipolar retinal cells ..................................................................18 1.4 Retino-geniculate pathway................................................................................................19 1.5 Retinal ganglion cells........................................................................................................20 1.6 The lateral geniculate nucleus (LGN) of the thalamus......................................................25 1.7 Functional organisation of the brain .................................................................................29 1.8 Visual striate cortex (V1)..................................................................................................29 1.9 Extra-striate areas V2, V3, V4 and V5 .............................................................................35 1.10 Non geniculo-striate pathways.....................................................................................37 1.11 Models for visual perception........................................................................................40 Chapter 2: The Role of the Pupil in Human Vision ...................................................................43 2.1 The iris and the pupil ........................................................................................................43 2.2 Effects on retinal image quality ........................................................................................43 2.3 Factors affecting pupil size ...............................................................................................43 2.4 Innervation of the iris sphincter and dilator muscles ........................................................46 2.5 The neural pathways of the pupil light reflex (PLR) ........................................................46 2.6 Sympathetic and parasympathetic neuro-transmitters.......................................................51 2.7 Asymmetry in constriction and dilation rates ...................................................................51 2.8 Drugs affecting pupil size .................................................................................................52 2.9 Disorders of the pupil........................................................................................................53 2.10 Summary ......................................................................................................................55 Chapter 3: Methods ......................................................................................................................57 3.1 Introduction.......................................................................................................................57 3.2 Basic Photometry and Colorimetry...................................................................................57 3.3 Computer displays: luminance and colour calibration......................................................61 3.4 Experimental set-up during psychophysics and pupillometry ..........................................63 3.5 Pupil measurements: the P_SCAN system .......................................................................64 3.6 Periodic modulation and Fourier signal analysis ..............................................................66 3.7 Use of isoluminant stimuli................................................................................................69 3.8 Doubly isoluminant coloured stimuli................................................................................69 3.9 Visual psychophysics........................................................................................................70 Chapter 4: Pupil responses to different visual stimulus attributes...........................................72 4.1 Pupil Light Reflex (PLR) response measurements ...........................................................72 4.2 Pupil responses to isoluminant stimuli..............................................................................75 4.3 Pupil Colour Response (PCR) measurements...................................................................76 4.4 Pupil Grating Response (PGR) measurements..................................................................77 4.5 Pupil Perimetry .................................................................................................................79 4.6 Spatial summation in the PLR ..........................................................................................82 2 4.7 Discussion.........................................................................................................................85 4.8 Summary...........................................................................................................................89 Chapter 5: Effect of cortical lesions on the pupil response........................................................91 1.1 Introduction: 'blindsight' ...................................................................................................91 5.1 Patients’ medical histories ................................................................................................92 5.2 Methods ............................................................................................................................92 5.3 Experiments and results ....................................................................................................93 5.4 Summary and discussion...................................................................................................98 Chapter 6: Effect of pretectal lesions on the pupil response .....................................................99 6.1 Introduction: Parinaud's syndrome ...................................................................................99 6.2 Patients’ medical histories ................................................................................................99 6.3 Methods ..........................................................................................................................100 6.4 Experiments and results ..................................................................................................102 6.5 Summary.........................................................................................................................107 6.6 Discussion.......................................................................................................................107 Chapter 7: Clinical applications of the pupil response ............................................................109 7.1 Optic neuritis (ON) and Multiple Sclerosis (MS) ...........................................................109 7.2 Methods and subject groups............................................................................................110 7.3 Data analysis and results: Group 1..................................................................................115 7.4 Data analysis and results: Group 2..................................................................................117 7.5 Discussion.......................................................................................................................123 Directions for further research ................................................................................................ 126 References .................................................................................................................................