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Frank A. Proudlock, Sarim Mohammad, Viral Sheth, Anil Kumar, Rebecca J. McLean, Mervyn G. Thomas, Christopher Degg, Irene Gottlob; Prediction Of Visual Acuity In Albinism Based On Objective Measurements Of Sensory And Motor Function. Invest. Ophthalmol. Vis. Sci. 2011;52(14):3019.
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© ARVO (1962-2015); The Authors (2016-present)
Attempts have been made to predict visual acuity in individuals with nystagmus based on motor function, i.e. from objective measures of nystagmus waveforms derived from eye movement recordings. Recently, we found that visual acuity is also correlated to objective anatomical measures of sensory function in patients with albinism, i.e. to retinal deficits measured using optical coherence tomography (OCT), in particular outer segment length (OSL) and outer nuclear layer (ONL) thicknesses. We have attempted to construct a model to predict visual acuity in albinism based on both motor and sensory measurements.
Thirty-six albinism patients were included in the study. Eye movement recordings (500Hz, n=36), posterior segment OCTs (3µm axial resolution, n=36) and five channel visual evoked potentials (VEP, n=22) were recorded. Nystagmus amplitude, frequency, intensity and foveation (eXtended Nystagmus Acuity Function, NAFX) were calculated from eye movement recordings. Photoreceptor layer, OSL and ONL thicknesses were measured from OCT. The degree of abnormal crossing at the chiasm was estimated from VEP asymmetry index (from Apkarian et al. 1983). Linear models were generated to predict visual acuity attempting to minimise the sum of squares of the residuals.
When considered in isolation the strongest predictor of visual acuity for motor function was nystagmus amplitude (p=0.001, r=0.52, n=36), and for sensory function the photoreceptor OSL (p=0.005, r=0.46, n=36). Including both sensory and motor measurements into the model improved the prediction of visual acuity compared to including single predictors alone (r=0.60, n=36). The model was further improved by including VEP asymmetry (r=0.72, n=21).
The use of eye movement recordings, OCT and multichannel VEP in patients with albinism now provides the possibility of predicting visual acuity based on objective measurements of motor and sensory function. These findings may also assist in estimating the level of improvement expected in individuals with albinism from treatments that reduce nystagmus intensity.
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