Abstract
Purpose: :
To determine the association between the thickness of various retinal layers and visual sensitivity in patients with retinitis pigmentosa (RP).
Methods: :
Retinal thickness in six patients with RP was evaluated by optical coherence tomography (OCT) and subsequently compared to dark–adapted and light–adapted thresholds obtained by psychophysical testing using Tübinger and Humphrey (HVF) perimeters.
Results: :
Based upon the findings on these six patients with different levels of RP severity, four patterns of association between retinal thickness and visual sensitivity by psychophysical testing were observed. (1) A reduced thickness of all retinal layers was present only when both rod and cone thresholds were elevated by psychophysical testing. (2) Retinal thickness was normal when both rod and cone psychophysical thresholds were normal. (3) Of interest, the retina retained normal thickness when cone thresholds were normal, or only slightly elevated, even in the presence of elevated rod thresholds. (4) Normal retinal thickness and normal Humphrey field thresholds were observed in the presence of elevated rod and cone thresholds by Tübinger perimetry.
Conclusions: :
Retinal thinning was observed only when both rod and cone thresholds were elevated. However, normal retinal thickness was not necessarily accompanied by normal visual sensitivity. Our findings suggest that a comparison of psychophysical thresholds and the thickness of various retinal layers obtained from OCT imaging could prove useful for identifying those patients who could be most suitable for inclusion in future therapeutic trials.
Keywords: retinal degenerations: hereditary • imaging/image analysis: clinical • photoreceptors: visual performance