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Zhanhan Tu, Christopher Degg, Irene Gottlob, Frank Proudlock; Comparison of electroretinographical responses in albinism, idiopathic infantile nystagmus and healthy controls. Invest. Ophthalmol. Vis. Sci. 2013;54(15):5984.
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Previous studies described children with albinism showing significantly larger a-wave amplitudes and shorter a- and b-wave latencies for scotopic standard flash (S.F.), compared to controls (Russell-Eggitt et al., 1990), while children with idiopathic infantile nystagmus (IIN) have been shown to have normal ERG (Brecelj and Strin-Kranjc, 2003; Beharié et al., 2012). ERG studies into albinism and IIN prove technically difficult to perform due to possible artefacts resulting from nystagmus. The aim of this study is to systematically compare ERG results between a large sample of adults with albinism, IIN (with a clinically normal fundus) and controls.
Fifty-seven albinism participants, 39 IIN participants and 24 controls were recruited to the study. Dilated Ganzfeld flash ERG testing was performed using DTL™ corneal surface contact electrodes. A photopic stimulus of 1.885 cdsm-2 was used. Scotopic stimuli ranged from a standard intensity flash (1.885 cdsm-2) through to a dim scotopic stimuli attenuated by 2.5 log units, applied in 12 steps of increasing intensity.
The IIN group demonstrated significantly smaller photopic a- and b-wave amplitudes compared to controls (P < 0.01). The IIN group also showed significantly longer photopic b-wave latencies compared to the albinism group (P < 0.05). We did not, however, observe any of the scotopic S.F. latency effects previously reported between albinism and controls. There were also no significant differences between any of the three groups for responses ranging from scotopic dim flash through to the scotopic S.F.
Our findings of reduced photopic a- and b-wave amplitudes and longer b-wave latencies in IIN may indicate a subclinical reduction of retinal function in IIN which has not been previously detected. Differences in ages of our patients or methodology might explain different results in the literature. Interestingly, participants with albinism did not show the same changes despite having nystagmus possibly because hypopigmented retinae can cause increased ERG responses. It is also possible that reduction of ERG is caused by artefacts due to eye movements in nystagmus, however this did not occur in scotopic ERGs in our study.
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