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Photoreceptor orientation and alignment in nasal fundus ectasia
V Lakshminarayanan1, J E Bailey, J M Enoch
1School of Optometry and Department of Physics and Astronomy, University of Missouri-St. Louis 63121-4499, USA.
Background:
We investigated whether Stiles-Crawford (SCE) functions, a measure of photoreceptor orientation and alignment, are disturbed in patients with nasal fundus ectasia (tilted disc; Fuch's coloboma without apparent pupillary involvement).
Methods:
SCE functions were obtained in three observers with nasal fundus ectasia, using psychophysical methods.
Results:
In all cases, disruption of photoreceptor alignment can be inferred. Results include location of the SCE peaks outside the pupil in the direction of the lesion, differential alignment, and reduction of the magnitude of SCE at various retinal loci (reduced curvature or p factor). Additional results obtained with the selective adaptation technique imply that receptor disarray (splaying) may be responsible for loss of retinal directional sensitivity.
Conclusions:
From these results, it may be surmised that mechanical tractional forces can play a major role in defining photoreceptor orientation in the retina. Inferred anomalous photoreceptor alignment has heretofore not been specifically linked with Fuch's coloboma/tilted disc syndrome.