Abstract
Purpose: :
Albinism is associated with profound structural deficits in the retina that we have recently quantified using optical coherence tomography (OCT). Mechanisms underlining infantile nystagmus (IN) in albinism are poorly understood but both sensory and motor causes have been implied. We have compared nystagmus characteristics of the null-region, with retinal abnormalities which we have measured using OCT.
Methods: :
Eye-movement recordings (EyeLink II, 500Hz) and retinal OCT scans (SOCT Copernicus) were acquired in 49 volunteers diagnosed with albinism. Retinal layers were measured using ImageJ(National Institutes of Health, MD, USA).Null-region location and definition along the horizontal plane were used to assign volunteers into following five categories: left null (n=10), central null (n=12), right null (n=11), no null (n=8), small nystagmus (n=8). Thickness of the nerve fibre, ganglion cell, outer nuclear, outer segment layers as well the total foveal thickness were compared amongst the groups using a one-way ANOVA.In addition nystagmus amplitude, frequency, intensity and foveation characteristics in the null region were compared to a foveal development index (fdi) which was calculated using the following formula:fdi=(processing layer thickness/photoreceptor layer thickness)
Results: :
We found a significant correlation between the foveal development index and nystagmus amplitude (p<0.005, r=0.542), intensity (p<0.005, r=-0.460) and NAFX (p<0.005, r=-0.407) in the null region. However there was no significant difference in the thickness of retinal layers between the different null groups (p>0.05).
Conclusions: :
Our results indicate a significant association between the degree of foveal development and nystagmus characteristics especially amplitude. However the relationship between retinal abnormalities in albinism and null region location remains unclear.