Abstract
Purpose: :
To study the oculometric parameters of hyperopia in children with esotropic amblyopia, comparing amblyopic eyes with fellow eyes.
Methods: :
Forty patients (5 to 8 years old) with bilateral hyperopia and esotropic amblyopia underwent a comprehensive ophthalmological examination, including cycloplegic refraction, keratometry and A-scan ultrasonography. Anterior chamber depth, lens thickness, vitreous chamber depth and total axial length were recorded. The refractive power of the crystalline lens was calculated using Bennett`s formulas. Paired Student’s t-test was used to compare ocular biometric measurements between amblyopic eyes and their fellow eyes. The associations of biometric parameters with refractive errors were assessed using Pearson correlation coefficient and linear regression. Multivariable models including axial length, corneal power and lens power were also constructed.
Results: :
Amblyopic eyes were found to have statistically significant more hyperopic refraction, greater lens power, shorter vitreous chamber depth and shorter axial length, despite the similarity in corneal power, anterior chamber depth and lens thickness. In both amblyopic and fellow eyes there was a strong correlation (r=-0.68, p<0.001) between axial length and refractive error. Axial length represented the main factor associated with refractive error; it explained 45.8% (R2) of the refractive error variance in amblyopic eyes and 46,9% in fellow eyes. Lens power explained 24.1% in amblyopic eyes and 21.5% in fellow eyes, while corneal power explained only 6.0% in amblyopic eyes and 3.0% in fellow eyes. A statistically significant correlation was found between axial length and corneal power, indicating decreasing corneal power with increasing axial length, and they were similar for amblyopic eyes (r=-0.47, p=0.002) and fellow eyes (r=-0.48, p=0.002). A statistically significant correlation was also found between axial length and lens power, indicating decreasing lens power with increasing axial length (r=-0.80, p<0.001 for amblyopic eyes and r=-0.76, p<0.001 for fellow eyes).
Conclusions: :
We observed a predominant role for axial length in determining hyperopia both in amblyopic and fellow eyes. Given the similarities of the amblyopic and fellow eye, with regard to the correlations of ocular optical components, it appears that the reason why the amblyopic eye is more hyperopic is not simply a failure in the mechanisms of the inter-correlation among the ocular structures.
Keywords: amblyopia • refractive error development • hyperopia