Purchase this article with an account.
Kanmin Xue, Jasleen K Jolly, Thomas Edwards, Markus Groppe, Robert E MacLaren; Characterizing the natural history of visual function in choroideremia using microperimetry and multimodal retinal imaging. Invest. Ophthalmol. Vis. Sci. 2017;58(8):2480.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Centripetal retinal degeneration in choroideremia (CHM) leads to early visual field restriction and late central vision loss. The latter marks an acute decline in quality of life but visual prognostication remains challenging. We investigate the natural history of visual function in CHM by correlating best-corrected visual acuity (BCVA) with microperimetry and multimodal retinal imaging.
BCVA, 10-2 microperimetry (MAIA), OCT and fundus autofluorescence (AF) were performed in both eyes of 56 CHM patients. Microperimetry was repeated in 21 eyes, enabling Bland-Altman analysis of repeatability. BCVA and macular sensitivity were correlated with age and inter-eye symmetry was evaluated. Since loss of fixation stability from foveal degeneration could affect visual testing, the distance from the fovea (on OCT) to the nearest edge of AF (representing edge of degeneration) was assessed as a potential confounder on BCVA or macular sensitivity.
A Kaplan-Meier plot of the proportion of right or left eyes retaining 20/20 BCVA showed identical survival pattern (median survival 39yr). Macular sensitivity declined logarithmically with age (r=0.60, p<0.05) with a half-life of 14.72yr (95% CI 11.85 to 19.42). Zonal analysis showed faster decline nasal than temporal to the fovea. Inter-eye symmetry was more consistent for macular sensitivity (r=0.95, p<0.001) than BCVA (r=0.42, p=0.0006). The former had a coefficient of repeatability of 1.45dB (95% LOA +1.24 to -1.62). As the degeneration encroaches upon the fovea, linear reduction of both BCVA and macular sensitivity was seen such that near normal functions were measured when the fovea was +2500μm away from the edge of AF whereas minimal detectable levels were reached by -800μm.
In around half of CHM eyes, BCVA falls below 20/20 by age 39 accompanied by logarithmic decline in macular sensitivity. Both visual functions showed a high degree of inter-eye symmetry, particularly in early stages, indicating that the fellow eye can provide a suitable control for assessing interventions to one eye. A critical period of BCVA and macular sensitivity drop when the fovea is +2500 to -800μm from the edge of degeneration corresponds to patient perception of progression from ‘split’ to ‘eccentric’ fixation. The findings will help to tailor visual prognosis and interpret outcomes of novel treatments such as gene therapy.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
This PDF is available to Subscribers Only