Background: From the investigations of Wiesel and Hubel an influence of early spectacle correction of refractive errors on visual development is to be expected. Nevertheless the benefit of early spectacle correction in young children is being discussed controversially.
Patients and methods: In a retrospective study the records of 103 strabismic children were analyzed. Myopic children and those with hypermetropia less than 2.0 diopters without astigmatism were excluded from this study. Visual acuity of the dominant eye only was compared between the following subgroups: early spectacle correction (A) not later than at the age of 30 months; "early" spectacle correction (B) between 30 months and 4 years; late spectacle correction (S) after the age of 8 years. In further subgroups we analyzed hypermetropia of more than 3.0 diopters and the combination of hypermetropia and astigmatism of 1.0 diopter or more. Visual acuity was determined using commercially available target projectors 2 times with an interval of at least 3 months. For analysis, the mean of these two examinations was calculated. In all children visual acuity after the age of 8 years was analyzed, the children of group S wore their glasses at least 6 months before the first determination of visual acuity included in this study. The dominant eye was analyzed only.
Results: Early corrected eyes developed better visual acuity than late corrected ones: 45% of the early corrected children (A + B) had a visual acuity exceeding 1.0 (20/20) versus 22% in the late corrected (S) subgroup (p = 0.046). 53% of the children corrected within the first 30 months (A) developed a visual acuity exceeding 1.0 (20/20) compared with 22% in the late corrected subgroup (p = 0.019). In hypermetropia exceeding 3.0 diopters (without astigmatism) the difference of early correction (A + B) compared with late correction (S) was even more significant: 72% of early corrected children developed a visual acuity of better than 1.0 (20/20), but no child corrected late did so (p = 0.0015). On the other hand, no child in these 2 subgroups developed a visual acuity of below 1.0 (20/20). Astigmatic eyes had a worse visual acuity: 13% of the early corrected subgroup (A) developed a visual acuity below 1.0 (20/20) versus 55% in the late corrected (S) subgroup (p = 0.024).
Conclusion: Early correction of hypermetropia (3.0 diopters or more) and of hypermetropic astigmatism (1.0 diopter or more) results in better development of visual acuity as measured at the age of 8 years or later. Since visual acuity of better than 1.0 (20/20) is "normal", late corrected children often did not develop "normal", visual acuity. By early correction of relevant hypermetropia and hypermetropic astigmatism this "refractive amblyopia" at least in part could be avoided.