title: Decreased fixation stability of the preferred retinal location in juvenile macular degeneration.
abstract: Macular degeneration is the main cause for diminished visual acuity in the elderly. The juvenile form of macular degeneration has equally detrimental consequences on foveal vision. To compensate for loss of foveal vision most patients with macular degeneration adopt an eccentric preferred retinal location that takes over tasks normally performed by the healthy fovea. It is unclear however, whether the preferred retinal locus also develops properties typical for foveal vision. Here, we investigated whether the fixation characteristics of the preferred retinal locus resemble those of the healthy fovea. For this purpose, we used the fixation-offset paradigm and tracked eye-position using a high spatial and temporal resolution infrared eye-tracker. The fixation-offset paradigm measures release from fixation under different fixation conditions and has been shown useful to distinguish between foveal and non-foveal fixation. We measured eye-movements in nine healthy age-matched controls and five patients with juvenile macular degeneration. In addition, we performed a simulation with the same task in a group of five healthy controls. Our results show that the preferred retinal locus does not adopt a foveal type of fixation but instead drifts further away from its original fixation and has overall increased fixation instability. Furthermore, the fixation instability is most pronounced in low frequency eye-movements representing a slow drift from fixation. We argue that the increased fixation instability cannot be attributed to fixation under an unnatural angle. Instead, diminished visual acuity in the periphery causes reduced oculomotor control and results in increased fixation instability.
authors.affiliation: Experimental Psychology, Helmholtz Institute, Utrecht University, Utrecht, The Netherlands; Autism Research Centre, Department of Psychiatry, University of Cambridge, Cambridge, United Kingdom.
authors.forename: Richard A I
authors.initials: RA
authors.lastname: Bethlehem
authors.affiliation: Experimental Psychology, Helmholtz Institute, Utrecht University, Utrecht, The Netherlands.
authors.forename: Serge O
authors.initials: SO
authors.lastname: Dumoulin
authors.affiliation: Experimental Psychology, Helmholtz Institute, Utrecht University, Utrecht, The Netherlands.
authors.forename: Edwin S
authors.initials: ES
authors.lastname: Dalmaijer
authors.affiliation: Experimental Psychology, Helmholtz Institute, Utrecht University, Utrecht, The Netherlands; Rudolf Magnus Institute of Neuroscience and Centre of Excellence for Rehabilitation Medicine, University Medical Centre Utrecht and Rehabilitation Centre De Hoogstraat, Utrecht, The Netherlands.
authors.forename: Miranda
authors.initials: M
authors.lastname: Smit
authors.affiliation: University Eye Clinic Maastricht, Maastricht, The Netherlands.
authors.forename: Tos T J M
authors.initials: TT
authors.lastname: Berendschot
authors.affiliation: Experimental Psychology, Helmholtz Institute, Utrecht University, Utrecht, The Netherlands; Rudolf Magnus Institute of Neuroscience and Centre of Excellence for Rehabilitation Medicine, University Medical Centre Utrecht and Rehabilitation Centre De Hoogstraat, Utrecht, The Netherlands.
authors.forename: Tanja C W
authors.initials: TC
authors.lastname: Nijboer
authors.affiliation: Experimental Psychology, Helmholtz Institute, Utrecht University, Utrecht, The Netherlands.
authors.forename: Stefan
authors.initials: S
authors.lastname: Van der Stigchel
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D005133:Eye Movements; D005260:Female; D005403:Fixation, Ocular; D005500:Follow-Up Studies; D006801:Humans; D008268:Macular Degeneration / Q000151:congenital* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D000080362:Stargardt Disease; D014792:Visual Acuity; D058609:Visual Field Tests; D055815:Young Adult