The relationship of axial length to cycloplegic refraction and keratometry in amblyopic eyes of hyperopic children.

BACKGROUND

In nonamblyopic eyes of hyperopic children, axial length has a consistent mathematical relationship to cycloplegic refraction and keratometry such that estimated axial length = ([-0.04 × refraction] + 2.98) × (corneal radius)]. The purpose of this study is to determine whether the pathophysiology of amblyopia affects this relationship.

METHODS

This a prospective case series of children 5 to 16 years of age diagnosed with esotropia related to uncorrected hyperopia who underwent keratometry and optical biometry by the IOLMaster in addition to cycloplegic refraction. The equation was assessed in affected eyes of consecutive children with unilateral amblyopia (at least 2 lines interocular difference with refractive correction).

RESULTS

Of the 23 identified children (16 males, 7 females, 5-14 years of age), all had a cycloplegic spherical equivalent of ≥+2.75 D in at least one eye, 14 were anisometropic (by >1.00 D), and none had myopia. Estimated and measured axial lengths of amblyopic eyes were strongly correlated (Pearson coefficient 0.9; 95% confidence interval, 0.79-0.96) and did not differ significantly by the 2-sided paired t test (P = 0.3; difference between means, 0.1). The two values differed by ≤ 0.5 mm for most eyes (20/23) and were within 0.9 mm for all eyes, similar to what has been described for nonamblyopic eyes.

CONCLUSIONS

The intraocular relationship of axial length to cycloplegic refraction and keratometry in hyperopic nonamblyopic eyes is maintained in hyperopic amblyopic eyes. Thus, the pathophysiology of amblyopia in this setting does not involve a mismatch among these biometric variables.