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M. Makridaki, R. L. P. van der Veen, T. T. J. M. Berendschot, D. Carden, N. R. A. Parry, I. J. Murray; Dark Adaptation in Arm Patients and Its Link to Fundus Grading; A Pilot Study. Invest. Ophthalmol. Vis. Sci. 2009;50(13):3317.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the link between the kinetics of rod and cone photoreceptors in early stage ARM and the severity of drusen.
Fundus photographs were taken with a retinal camera (Topcon TRC-NW6S Non-Mydriatic Retinal Camera) and graded according to an international classification system in 33 patients. Of these, 30 were classified as ARM (stage 3 and below) and 3 were stage 4. Age of participants varied from 50 to 86 years and their VA was better than 6/12. Dark Adaptation data were recorded using a VSG 2/5 (Cambridge Research Systems Ltd, Rochester, UK). Stimuli (1 degrees diameter) presented at 11 degrees and modulated at 1Hz were displayed on a Sony GDM-f500 high resolution graphics display. ND filters were used to increase the luminance range of the monitor. Rod - cone recovery, based on thresholds, was recorded after bleaching of photopigments at the test location using a well calibrated electronic Flash Gun (Autofocus Speedlight Nikon SB-800). Dark adaptation curves were highly repeatable. Data were compared with age-matched normals. The following parameters were extracted from the rod-cone recovery curves: initial cone sensitivity, cone threshold, absolute threshold, cone recovery rate, rod recovery rate and rod-cone break ( point).
All patients had either abnormal rod - or abnormal cone - recovery rates. The mean (SD) point for the normal observers was 7.35 minutes (± 2.5) whilst that for the patients was 13.43 minutes (±7.06), this effect was highly significant (p<0.001). There was a wide variety of sensitivity recovery functions amongst the patients. Some required more than 1 hour to reach maximum sensitivity as has been reported previously, but others with extensive drusen had close to normal dark adaptation curves. Of the 19 patients in ARM category 1 and 2, 11 had abnormal points. In this limited data set, we find no characteristic rod-cone recovery function to predict the different ARM groups based on severity of drusen.
We find no evidence for a link between any particular parameter of the dark adaptation curve and the severity of drusen. This may be due to the high inter-individual variation in the dark adaptation curves. Monitoring photoreceptor kinetics can provide valuable additional information about the functional deficit in early stage macular disease.
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