Evaluation of relationship of ocular parameters and depth of anisometropic amblyopia with the degree of anisometropia

Purpose: (1) To find out the relationship of the depth of amblyopia with the degree of anisometropia, in untreated cases of anisometropic amblyopia without strabismus, for both myopic and hypermetropic individuals. (2) To find out the relationship between various ocular parameters, such as axial length and corneal curvature, with the degree of anisometropia between the two eyes. Materials and Methods: This prospective study was conducted between January 2001 and March 2003, in 85 cases of untreated anisometropic amblyopia, who attended the author's out patient department. All these patients were subjected to a meticulous ocular examination, with special emphasis on (1) refraction under cycloplegia (2) best corrected visual acuity (3) measurement of axial length by A Scan (4) keratometry. The depth of amblyopia was calculated in two ways: (1) By finding out decimal visual acuity for each eye and subsequently calculating their difference. (2) By converting the Snellen acuity into Log MAR units, which was calculated by finding the Logarithm of the reciprocal of the decimal visual acuity for the two eyes, followed by calculating the difference between the two. The difference in refraction between the two eyes as a measure of anisometropia, was determined by the difference in spherical equivalent between the refraction for each eye. Results: On comparing hypermetropic and myopic cases, a significant correlation was found between depth of amblyopia and the degree of anisometropia, in both myopic and hypermetropic patients. The correlation coefficients were however, found to be greater for hypermetropic than myopic individuals. It was observed that the difference between the axial length of the two eyes contributed to a major part of anisometropia, more so in myopic cases. Conclusions: The depth of amblyopia correlates with the degree of anisometropia in previously untreated anisometropic amblyopia patients.