Abstract
Purpose: :
Motion discrimination is a complex visual task which is mainly processed by the magnocellular pathway. We hypothesised that high myopes may have functional losses on motion perception due to axial elongation induced retinal stretching.
Methods: :
Ninety young adults aged 18-26 years participated: emmetropes (n=30), low myopes (myopia 1 to 5 D, n=30) and high myopes (myopia > 5 D, n=30). Random dot patterns were used to measure motion perception for three tasks: minimum displacement of dots (Dmin), maximum displacement of dots (Dmax) and motion coherence. Each task was performed centrally and at four peripheral visual fields (superior temporal, superior nasal, inferior temporal and inferior nasal) at 3.65, 12 or 10.75 degrees for the Dmin, Dmax and motion coherence tasks, respectively. A blind spot monitoring system was used. Macular retinal thickness was measured using optical coherence tomography.
Results: :
For the Dmin central task, a significant effect of refractive group was observed (F2, 87=5.27; p<0.01). This was due to differences between the highly myopic and emmetropic groups; high myopes had elevated Dmin values (worse performance than emmetropes). A similar, though not quite statistically significant (p=0.054) effect of refractive group on Dmin was observed for stimuli presented to the inferior nasal retina. For both Dmax and coherence tasks there were no significant effects of refractive group on performance. Thinner retinas were observed in high myopes compared to emmetropes at the parafovea (p<0.05).
Conclusions: :
Central motion perception, as assessed using minimum displacement detection, is reduced in highly myopic eyes. Peripheral performance may also be influenced by myopia, particularly in the inferior nasal retina. Retina stretching due to axial elongation, that may lead to changes in retinal neurons (e.g. magnocellular ganglion cell death), may be a cause of this reduced performance in high myopes.
Keywords: myopia • perception • refractive error development