Abstract
P 065
Temporal contrast sensitivity after LED full-field flicker adaptation in normal subjects
Christopher Rössler, Folkert Horn, Jan Kremers, Anselm Jünemann
Universitäts-Augenklinik Erlangen
Objective
New functional tests for early detection of glaucoma with determination of temporal contrast sensitivity (TCS) have been developed in the recent past. Background is the theory of a selective ganglion cell loss in a numerically small and low redundant group of retinal ganglion cells. Determination of TCS with flicker stimuli can test selectively the function of the magnocellular system. Through an additional neuronal feedback, e.g. with flickerlight as stress stimulus the sensitivity and specificity of this tests might get improved. The aim of this study was to determine the influence of flicker adaptation in a LED full-field on TCS in healthy normal control subjects to identify suitable adaptation and test conditions for further measurements in glaucoma patients.
Methods
TCS was determined in 7 normal subjects after flicker adaptation in a LED full-field with constant average illumination of 159 Troland. Flicker adaptation was done with 9 different frequencies (9, 15, 20, 25, 31, 37, 44, 51 and 100Hz). For each of these adaptation frequencies the TCS was determined for the same frequencies except 100Hz. After the adaptation frequency was shown for 20s with 100% contrast, a 5s test period and a 5s re-adaptation period (again 100% contrast) alternated continuously. In the test period, the contrast was increased gradually until recognition as flicker by the subject. The mean of 3 threshold determinations entered the evaluation. The TCS after adaptation with 100Hz represents the unadapted TCS. For characterization of the influence of flicker adaptation on the TCS a “curve shifting factor” was calculated.
Results
Flicker adaptation resulted in a consistent reduction of TCS in the entire test frequency spectrum. Notches at certain adaptation frequencies were not noticed. There was a significant reduction of the TCS in all adaptation conditions in comparison with the 100Hz curve (= unadapted TCS) (ANOVA, p≤0,001). The “curve shifting factor” was largest at 25Hz adaptation frequency (4,6±1,87).
Conclusions
Flicker adaptation with a frequency of 25Hz has the biggest impact on TCS in the LED full-field. The relevance of flicker adaptation for early glaucoma detection is currently under evaluation.
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