Abstract
Purpose :
The study aims to evaluate the inter-ocular differences in Fixational Eye Movements (FEM) metrics obtained in subjects with amblyopia and strabismus without amblyopia, and examine the correlation between inter-ocular FEM abnormalities and visual acuity and stereoacuity deficits.
Methods :
High-resolution video-oculography was used to record FEMs from 172 subjects (controls=46, amblyopia=104, strabismus without amblyopia=22) under fellow eye viewing(FEV), amblyopic eye viewing(AEV) and both eye viewing(BEV). FEMs were evaluated and subjects were categorized as those without nystagmus(none), fusion maldevelopment nystagmus(FMN) and those with nystagmus that do not meet the criteria of FMN or congenital motor nystagmus. Bivariate Contour Ellipse Area(BCEA) and median composite of amplitude of fast FEM and eye position variance of slow FEM of fellow eye(FE) and amblyopic eye(AE) were quantified. We computed an inter-ocular ratio (AE/FE) for each subject using the FEM metrics obtained under BEV[BEV ratio] and of the viewing eye obtained under AEV and FEV [MEV ratio][Figure1]. Multiple linear regression analysis was done to evaluate the effects of age, visual acuity of FE and AE, stereo-acuity deficit, strabismus angle and FEM waveform on inter-ocular FEM metrics.
Results :
None of the subjects with anisometropic amblyopia had FMN. Subjects with strabismic amblyopia were more likely to have FMN, whereas subjects with mixed amblyopia were more likely to have nystagmus without FMN(chi-square,p < 0.001). Figure 2 plots the relationship between stereoacuity, visual acuity deficit and strabismus as a function of FEM waveforms. Subjects with nystagmus, with or without FMN, were more likely to have absent stereopsis. On the other hand, for subjects without nystagmus, absent stereopsis was seen only in those with severe amblyopia. The BEV and MEV interocular BCEA ratios and BEV fast and slow FEM ratios increased as the amblyopic eye (AE) VA deficit (p<0.01) and strabismus angle (p<0.05) increased. The MEV ratios of fast FEM amplitude and eye position variance of slow FEMs only increased as the AE-VA deficit (p<0.01).
Conclusions :
This is the first study to evaluate FEMs abnormalities in a large cohort of amblyopia and strabismus subjects. We have described FEM characteristics that can be useful for early detection of amblyopia and strabismus and reflect the severity of visual impairments.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.