Effects of Strabismic Amblyopia and Strabismus without Amblyopia on Visuomotor Behavior, I: Saccadic Eye Movements

Abstract

Distinct patterns of saccade performance according to different levels of visual acuity and stereoscopic losses in strabismic amblyopia were found. These findings were in contrast to those in anisometropic amblyopia in which the altered saccade performance was independent of the extent of visual acuity or stereoscopic deficits. These results were most likely due to different long-term sensory suppression mechanisms in strabismic versus anisometropic amblyopia.

Saccadic latency in amblyopia

“…When the acuity difference is close to zero, so is the latency difference. The mean latency differences for the nonamblyopic strabismics, anisometropes, and strabismic-anisometropes (triangles), who have a negligible interocular difference in acuity, are nearly identical to that for the normal observers, as other studies have found (Ciuffreda et al, 1978a, 1978b; Niechwiej-Szwedo et al, 2010; Niechwiej-Szwedo et al, 2012). On average, the strabismic and strabismic anisometropic amblyopes (red and blue symbols) have a larger difference between their eyes in LogMAR acuity than the anisometropic amblyopes (green symbols), and consequently, a larger difference in saccadic latency.…”

“…They found a systematic increase with decreasing acuity—the worse the acuity, the larger the difference in reaction time. Saccadic latency is also longer in amblyopic eyes than in normal eyes (Ciuffreda, Kenyon, & Stark, 1978a, 1978b; Mackensen, 1958; Niechwiej-Szwedo, Chandrakumar, Goltz, & Wong, 2012; Niechwiej-Szwedo, Goltz, Chandrakumar, Hirji, & Wong, 2010;). Once initiated, the dynamics of amblyopic saccades are normal, indicating that their longer latency is due to sensory or cognitive factors rather than low-level motor problems (Ciuffreda et al, 1978a, 1978b; Ciuffreda, Levi, & Selenow, 1991; Niechwiej-Szwedo et al, 2010; Niechwiej-Szwedo et al, 2012; Perdziak, Witkowska, Gryncewicz, Przekoracka-Krawczyk, & Ober, 2014).…”

Horizontal Saccade Dynamics After Childhood Monocular Enucleation

“…Asterisk refers to statistically significant differences at P < 0.01. amplitude gain that depend on its degree and type. [42][43][44][45] These deficits are part of a number of visual and motor impairments absent in enucleated people who are not affected by the abnormal binocular interactions associated with amblyopia. 3,5 Our findings suggested that the true monocularity produced by early enucleation does not result in slower visual processing in the afferent (sensory) pathway, or in deficits in the efferent (motor) pathway of the saccadic system.…”

Pediatric ophthalmology and childhood reading difficulties

“…19–21 In a visuomotor task requiring a saccade to a target dot prior to reaching and touching that dot, amblyopic adults exhibit greater variability in saccade amplitude and a higher frequency of corrective saccades compared with visually normal adults. 22,23 In addition, amblyopic adults lack the binocular advantage for saccade initiation that is present in visually normal adults who initiate saccades about 10% faster when viewing binocularly compared to viewing monocularly. Taken together, slower saccade initiation, saccade amplitude variability, and increased frequency of secondary saccades can be expected to significantly slow reading speed in amblyopic children.…”

“…There is a solid evidence base demonstrating slower initiation of saccades and more variable saccade amplitudes in amblyopic individuals. 22,23 Even though it usually results in poor vision in just one eye, amblyopia can reduce reading speed in natural, binocular reading by 20%–50% and negatively affect academic performance. We have also found that amblyopic children are slower at transferring answers from a standardized test to a Scantron answer sheet compared with visually normal controls (Birch et al J AAPOS 2015;19:e10 Abstract 006).…”