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S. S. Choi, R. J. Zawadzki, J. S. Werner; A Close-Up Investigation of Cone Photoreceptors in Retinal and Optic Nerve Diseases as Revealed by Adaptive Optics - OCT Images. Invest. Ophthalmol. Vis. Sci. 2010;51(13):2326.
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© ARVO (1962-2015); The Authors (2016-present)
Adaptive optics - OCT (AO-OCT) provides a 5-fold increase in lateral resolution compared to Fourier-domain (Fd) OCT. This permits cellular level investigation of retinal changes in living eyes of patients. The goals of this study were (1) to evaluate inner and outer segments of cone photoreceptors in patients with retinal and optic nerve diseases and (2) to compare them with visual function at the corresponding retinal locations.
Twenty one patients with various types of retinal and optic nerve diseases including retinal dystrophy, maculopathy, optic neuropathy and glaucoma were imaged with ultrahigh resolution AO-OCT (3.5 µm in all three dimensions) and high resolution Fd-OCT (4.5 µm axial and ~15 µm lateral resolution) instruments developed in our laboratory. Retinal locations were chosen based on functional test results so that both affected and unaffected retinal areas could be imaged and compared. Functional tests included visual field maps and mfERG. Length of inner and outer segments of cone photoreceptors were measured from AO-OCT images and compared between retinal locations of different visual sensitivity.
Retinal and optic nerve disease patients showed significantly shorter cone outer segments at the retinal locations with reduced visual performance. Furthermore, there was great variation of outer segment length within the same patch of retina with reduced visual sensitivity. In retinal disease patients, the inner segment of cone photoreceptors was also shorter at the affected retinal locations, however, in optic nerve disease patients, there was no statistically significant difference in the inner segment length between the affected and unaffected areas. Unlike outer segments, the changes in inner segment length, when observed, was more stable within the same retinal location. This finding suggests that receptoral changes observed in retinal and optic nerve diseases are driven by different mechanisms.
This study demonstrated that outer segment length of cone photoreceptors provide a reliable measure correlated with visual function in both retinal and optic nerve disease patients.
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