Abstract
Purpose:
The prevalence of myopia in premature infants is higher than in full term infants. However, the mechanisms and structural contributions to myopia in preterm infants are unclear. We conducted a case control study to test the hypothesis that the structural contribution to myopia in preterm and full term born children is different.
Methods:
This was a case control study. 114 children ranging from ages 2 to 17 who had myopia ≥ -3 diopters or hyperopia ≥3 diopters in at least one eye were examined with A-scans. The following data was collected and analyzed: history of birth, refractive error, visual acuity, cornea thickness, axial length of the eye, depth of anterior chamber (ACD) and thickness of lens.
Results:
Patients were tested and categorized into 3 major groups: group 1 consisting of premature infants with myopia (gestation age <32 wks., birth weight <1500g), group 2 consisting of full-term infants with myopia, and group 3 consisting of full-term infants without myopia. The refractive errors were -10.0±5.2 in group 1, -8.4±4.6 in group 2, and 2.3±2.4 in group 3. There was no difference found in corneal thickness among these groups. The axial length (AL) of myopic eyes in group 2 was longer than that of group 1 (mean AL = 24.9 ± 1.9 mm vs. 23.1 ±1.4mm), p=0.01. The ACD in premature children was more shallow than that of full term myopic eyes (2.5 ±0.5 vs. 3.2 ±0.3, p=0.01). Finally, lens thickness (LT) measurements in group 1 were thicker than those in group 2 (mean LT = 4.9 ± 1.0 vs 4.1 ± 0.3 mm, p=0.001, respectively).
Conclusions:
These results suggest that increased axial length plays an important role in myopia in full-term children, while lens thickness is a major contributor for myopia in preterm-born children.