In the absence of strabismus what constitutes a visual deficit in children?

To examine the range of monocular crowded logMAR acuity and cycloplegic refraction of children aged 3 years and 4 years without strabismus.

Data were collected prospectively. All children had full orthoptic and ophthalmic examination. Inclusion principally required the absence of strabismus, symptoms, and ocular pathology. Criteria were used to categorise the refraction findings as normal, borderline, or abnormal.

118 children aged 3 years (mean 3 years 6 months (SD 2 months) and 67 children aged 4 years (mean 4 years 4 months (SD 3 months) fulfilled the inclusion criteria. For the children with normal refraction, the mean monocular logMAR acuity was 0.200 (SD 0.09) for 3 year olds (n = 84) and 0.140 (SD 0.08) for 4 year olds (n = 45); the mean interocular acuity difference (IAD) was 0.03 (SD 0.06) for 3 year olds and 0.03 (SD 0.04) for 4 year olds. The 95% confidence limits were calculated for monocular acuity and IAD and compared to the acuity scores of the children with borderline (n = 17) and abnormal refractive error (n = 38). 15 borderline and 16 abnormal cases had a visual acuity within these limits.

A wide range of refraction may be associated with a good level of visual acuity in children aged 3 years and 4 years.