Sensitivity of random dot stereoacuity and Snellen acuity to optical blur

The purpose of this study is to investigate the usefulness of a random dot stereogram for the detection of refractive blur by determining the relative sensitivity of random dot stereoacuity (RDS) and Snellen visual acuity to the effects of optically induced blur. Measurements of Snellen and stereoacuity were compLeted on four young adult subjects under cycloplegia and through artificial pupils. Optical blur was varied binocularly and monocularly in 0.50 D steps up to +/- 6.00 D while the subjects viewed targets composed of stimuli arranged in 0.1 log unit size increments. The results show the relation between RDS and Snellen acuity to be SA = 1.341 (VA) + 0.281 for equal amounts of binocularly induced optical blur. Moreover, the RDS appeared more highly sensitive when the blur in the 2 eyes was unequal [SA = 3.774 (VA) - 1.180], a condition approximating refractive anisometropic amblyopia. These results provide a rationale for the use of random element stereograms for the detection of refractive amblyopia and ametropia in the vision screening of children.