Abstract
Purpose: :
Retinal image quality and therefore visual experience during the critical period depend on accommodative accuracy. There is currently a paucity of quantitative accommodative performance data from clinically abnormal children. Ingram et. al. (1994) have proposed that patients with refractive strabismus have poor sensitivity to blur. The goal of this study was to measure accommodative performance in a group of optically corrected refractive esotropes.
Methods: :
Subjects were developmentally normal, non-strabismic children and refractive esotropes of less than 13 years of age. The subjects, wearing habitual optical correction, were presented with a high contrast animated movie binocularly at four viewing distances: 1m(1D), 50cm(2D), 33cm(3D) and 25cm(4D). Accommodative performance was measured using Nott dynamic retinoscopy for the two principal meridia of each eye at each of the viewing distances. Each child also underwent a full examination including assessment of acuity, eye alignment and refraction.
Results: :
The non-strabismic subjects had a mean spherical equivalent refractive error of -0.3D (range: -3.25D to +1.25D). The mean in the strabismic group was +4.80 (range: +2.50D to +9.50D). The subjects without strabismus demonstrated mean accommodative lags of less than 1.1D across stimulus positions. The strabismic subjects demonstrated mean accommodative lags of less than 0.5D more than the non-strabismic subjects across this range of viewing distances.
Conclusions: :
While uncorrected hyperopes may demonstrate large lags of accommodation, most optically corrected refractive esotropes demonstrate accommodative performance that is close to that of typically developing children. Thus, the strabismic visual system can be capable of near normal accommodative performance.
Keywords: accomodation • strabismus: etiology • development