Ординатура / Офтальмология / Английские материалы / Training‐induced Visual Field Recovery in Chronic Stroke Patients_Bergsma_2011

Promotoren:

Prof. dr. G. Fernandez

Prof. dr. L. Fasotti

Copromotoren:

Dr. G.J. van der Wildt

Prof. dr. A.V. van den Berg

Manuscriptcommissie:

Prof. dr. C. Hoyng

Prof. dr. H. De Leeuw

Prof. dr. B. Steenbergen

Paranimfen:

Stefan van der Stigchel

Roel Bergsma

ISBN 978 90 8891 303 7

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Training induced Visual Field Recovery

in Chronic Stroke Patients

Printed by: Proefschriftmaken.nl || Printyourthesis.com

Published by: Uitgeverij BOXPress, Oisterwijk

© Douwe Bergsma 2011

The research presented in this thesis was financially supported by:

A financial contribution for printing the thesis was made by:

Stichting Wetenschappelijk Fonds De Hoogstraat, Utrecht

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Voor Daniëlle

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PROLOGUE

Seeing comes natural. You don’t have to think about it, you just open your eyes and there it is: the outer world. Whether our visual perception is a true representation of it or not can be argued, but intact vision is the prime survival tool for everyone. Vision helps us to quickly orient in unfamiliar surroundings, it guides our eye movements during reading and it helps us to handle objects appropriately. Much of this is done automatically and naïve owners of intact vision rarely appreciate the tremendous complexity that lies behind even the simplest of visual tasks like looking at a familiar face. This becomes clear in case of visual defects, which immediately interfere with all kinds of behaviour and force the patient to act consciously where an automated response was normal. Among the many possible visual disturbances, losing sight in a part of the visual field intuitively qualifies as one of the most profound visual disturbances, next to loosing all visual capabilities. Patients with visual field defects (VFDs), a part of the visual field in which there is no or disturbed visual input, can experience problems in activities that are usually easy to perform with normal vision: reading can be disturbed, driving a car may be prohibited, but even easy tasks such as finding an object on a shelf, avoiding an obstacle while walking and recognizing landmarks can be severely hampered.

Based on stroke incidence, prevalence and prognosis, it is estimated that there were more than 50.000 persons with VFDs in the Netherlands in 2007. Because the overall life span of humans increases, stroke incidence will also increase. Added to the improving stroke care, the number of persons with a VFD will increase even further in the years to come. This warrants the need for treatment of VFDs.

In this thesis, I describe experiments that were done in order to assess whether treatment of hemianopia by Restorative Function Training (RFT) can lead to visual field recovery in patients with acquired brain damage (damage that is not hereditary or congenital) and if it does, to what degree. This description includes the quality of the regained visual field after training; the transition of the visual field from the pre training to post training state; the question whether perimetry results are contaminated by eye movements during perimetry; the generalization effects to other visual tasks that have not been the subject of training (colour and shape perception) and to activities of daily life (reading and driving). I also describe the results of a pilot experiment using functional Magnetic Resonance Imaging (fMRI), conducted in a group of 8 patients, which includes the possibility of an fMRI Retinotopic Mapping procedure in conjunction with traditional, subjective perimetry to serve as a predictor for expected training effect.

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Abbreviations in alphabetical order

ABS = Absolute Border Shift

ADL = Activities of Daily Life

CNS = Central Nervous System

CST = Compensatory Saccade Training

ECSG = Estimated Cortical Surface Gain

EEG = Electroencephalography

fMRI = functional Magnetic Resonance Imaging

GLM = General Linear Model

HRP = High Resolution Perimetry

HVFD = Homonymous Visual Field Defect (VFD is congruent in both eyes)

ISI = Inter Stimulus Interval

ITC = Inferior Temporal Cortex

LGN = Lateral Geniculate Nucleus

MEG = Magneto Encephalography

PET = Positron Emission Tomography

RFT = Restorative Function Training

RTR = Risk Taking Ride

SLO = Scanning Laser Ophthalmoscope

TAP =Tübingen Automated Perimetry

VEP = Visual Evoked Potential

VFD = Visual Field Defect

VFE = Visual Field Enlargement

VRT = Vision Restoration Therapy

The picture that is repeatedly shown at the beginning of each chapter is an adaptation of an artist’s impression of the human brain.

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Chapter 1

General Introduction