Refractive State in Childhood with Normal Visual Acuity

ABSTRACT

To manifest visual acuity of 20/20 or better, the requirements are good optical imagery, foveal fixation, intact receptor structure and function, and full integrity of the involved neural pathways. Person with hyperopia of 1-10 diopter or astigmatism of 1 diopter may be able to read the line marked 20/20 of Snellen's chart. Non-cycloplegic and cycloplegic subjective manifest refractions were done on 380 normal eyes with visual acuity of 20/20 or more to observe the prevalence, type and degree of the refractive errors. The results were as follows; 1. In non-cycloplegic subjective manifest refraction, 147 eyes(38.7%) had refractive error such as simple hyperopic astigmatism(50.3%), hyperopia(37.4%), simple myopic astigmatism(6.8%) and compound hyperopic astigmatism(5.4%). In cycloplegic subjective manifest refraction, 183 eyes(48.2%) were ametropia such as simple hyperopic astigmatism (49.7%), hyperopia(38.3%), compound hyperopic astigmatism(8.7%) and simple myopic astigmatism(3.2%). 2. As to the type of astigmatisms, "with the rule" astigmatism was 2.5 times more than "against the rule". 3. Average degree of refractive errors were 0.12 diopter in non-cycloplegic refraction and 0.22 diopter in cycloplegic refraction. 4. The degree of hyperopia was less than 1.00 diopter in all cases of noncycloplegic refractions and in most cases(93%) of cycloplegic refractions. 5. Degree of astigmatism were less than 1.00 diopter in the majority(98%).