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Brett G Jeffrey, Laryssa Huryn, Paul A Sieving, Catherine A Cukras; Spatial Variation of Rod-Mediated Function in Late-Onset Retinal Degeneration (L-ORD). Invest. Ophthalmol. Vis. Sci. 2019;60(9):4495.
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© ARVO (1962-2015); The Authors (2016-present)
Delayed dark adaptation (DA) is an early phenotypic marker in L-ORD and may precede symptoms and retinal changes. Here we measure rod-mediated function within, and around retinal areas with structural changes in L-ORD.
In 7 patients from 2 families with S163R missense mutations in CTRP5, rod-mediated thresholds were measured with 2-color perimetry following >1 hour in the dark, along the horizontal (144o) and vertical (60o) meridians. After a 30% bleach, DA was measured at 8-15 loci, located 8-30 o along the horizontal and/or vertical meridians. DA was characterized by rod intercept time (RIT: min), the time to reach a criterion threshold of -3.1 log cd/m2 and the time constant (sec) of the 2nd component.
A 25 yo asymptomatic patient had normal rod function. Six patients, aged 57-63 yrs, 5 with acuity of 20/25 or better and 1 with 20/50, had typical clinical findings of L-ORD including nyctalopia. In these 6 patients, scotopic thresholds were elevated by 2-4 log units at loci tested horizontally from the optic disc to 20-30o temporal to the fovea. One patient was dark-adapted overnight and demonstrated improvement of rod-mediated thresholds by >2 log units across the macula in all but a few temporal loci. In 2 patients, scotopic thresholds were normal/near normal at loci nasal to the optic disc, and in the far temporal retina (≥48o). DA was markedly slowed at all loci; RITs were delayed (median=55 min; range 16-112 min) and time constants longer (median=542 sec; 135-934 sec) relative to healthy volunteers (RIT <10 min, time constant <145 sec). DA progressively slowed from peripheral to central loci. The pattern of DA delays varied between patients; DA was considerably slower in the superior retina relative to the nasal retina in 1 patient and was the most delayed in the nasal retina of the sibling.
Rod function was most severely affected in the temporal retina where structural changes have been first observed. Rod function was best preserved in the nasal and far temporal retina, but functional rods may still be present in the macula as demonstrated with overnight dark adaptation. The spatial gradient in DA abnormality suggests abnormal retinal function precedes degeneration. The combined results suggest rods may be preserved after onset of symptoms, and retinal changes follow perhaps because of abnormal retinal/RPE function.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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