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Carina Kelbsch, Fumiatsu Maeda, Torsten Strasser, Tobias Peters, Helmut Wilhelm, Barbara Wilhelm; Color pupillography in Glaucoma and Ocular Hypertension - the role of the intrinsically photosensitive retinal ganglion cells. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):580.
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Intrinsically photosensitive retinal ganglion cells (ipRGCs) mediate the sustained post-illumination pupil response (PIPR) following a visual stimulation with bright blue light. The purpose of this study was to quantify this PIPR by means of color pupillography in manifest glaucoma and ocular hypertension to find out how ipRGCs are involved respectively and whether color pupillography could be a useful tool for glaucoma diagnostics.
25 patients with manifest glaucoma, 16 patients with ocular hypertension and 16 healthy control subjects were examined by stimulating one eye with either red (605nm) or blue (420nm) colored light of 28 lx intensity and a stimulus duration of either 1s or 4s. The consensual pupil light reaction was recorded by means of infrared pupillometry over a period of 16 seconds. As primary variable the post-illumination pupil response, PIPRblue-red, was calculated and compared using t-test (Tukey-Kramer) for statistical analysis.
Using the 1s stimulus conditions we found significant differences of the PIPRblue-red between glaucoma and normals (p<0,001) and between glaucoma and ocular hypertension (p<0,007) whereas there was no significant difference between ocular hypertension and normals (p=0,9). However, when applying the 4s stimulus conditions we could only identify significant differences between glaucoma and normals if the PIPR was calculated starting 2s after stimulus offset. This may be explained by strong differences in the dynamics (slope of the fitted line) of the pupillary responses during the 4s red stimulus between the groups (p<0,001).
We demonstrated a significantly reduced PIPR in manifest glaucoma that was consistent with the hypothesis of an early impairment of the ipRGCs in glaucoma. Furthermore we observed a pupillary escape during the 4s red stimulus in the glaucoma group that cannot be fully explained so far but indicates an interaction of ipRGCs and outer photoreceptors.
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