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Cover:

A patient demonstrating eccentric viewing and the use of the eccentric viewing spectacles. We kindly acknowledge this patient for her written permission to use the pictures for this purpose.

Lay out by In Zicht Grafisch Ontwerp, Arnhem

Printed and bound by PrintPartners Ipskamp, Enschede

Eccentric Viewing Spectacles

Including

An Introduction in Low Vision Rehabilitation

Een wetenschappelijke proeve

op het gebied van de Medische Wetenschappen

Proefschrift

ter verkrijging van de graad van doctor aan de Radboud Universiteit Nijmegen

op gezag van de rector magnificus prof. mr. S.C.J.J. Kortmann, volgens besluit van het College van Decanen

in het openbaar te verdedigen op woensdag 28 januari 2009 om 15:30 uur precies

door

Cornelis Anthonius Verezen geboren op 29 april 1958

te Rotterdam

Promotor:

Prof.dr. J.E.E. Keunen

Copromotores:

Dr. B.J. Klevering

Dr. C.B. Hoyng

Manuscriptcommissie:

Prof. dr. Th. Thien (voorzitter) Prof. dr. A.C. Kooijman

Prof. dr. G.P.M. Luyten Prof. dr. G.H.M.B. van Rens Dr. K. Ingels

List of abbreviations	11
Chapter 1 Perspectives on low vision	13

1.1Low vision

1.1.1Definitions

1.1.2Prevalence and causes of low vision

1.2Low vision aids

1.2.1General considerations in prescribing low vision aids

1.2.2Non-magnifying low vision aids

1.2.2.1Illumination

1.2.2.2Reduction of glare

1.2.2.3Night vision devices

1.2.3Magnifying low vision aids

1.2.3.1High add spectacle lenses

1.2.3.2Magnifiers

1.2.3.3Telescopic magnification

1.2.3.4Electronic vision enhancement systems

1.2.4The prescription of low vision aids

1.2.4.1Referral and basic examination

1.2.4.2The type of low vision aid

1.2.4.3The amount of magnification

1.2.4.4Training and follow-up

Chapter 2 The principle of eccentric viewing spectacles

2.1Prisms

2.1.1Basic optics

2.1.2Fresnel prisms

2.1.3Prismatic aberrations

2.1.4The effect of prisms on eye movements

2.2Eccentric viewing spectacles

2.2.1The fovea

2.2.2Eccentric fixation

2.2.3The prescription of eccentric viewing spectacles

2.2.4Adapting to eccentric viewing spectacles

2.2.5Review of the literature

2.3Other indications for prism spectacles

Chapter 3 Eccentric viewing spectacles in patients with		129
	age-related macular degeneration
Chapter 4	Effect of eccentric viewing spectacles on the	145
	visual search time
Chapter 5	Long-term evaluation of eccentric viewing spectacles	159
	in patients with bilateral central scotomas
Chapter 6	Eccentric viewing gaze directions in patients with	179
	central field loss
Chapter 7	General discussion	203