Assessment of Variation in Keratometry with the Axial Length and Refractive Status of the Eye - A Cross Sectional Observational Study in South Asian Population

Abstract

BACKGROUND Refractive status of the eye depends on the balance between multiple factors such as corneal power, lens power, anterior chamber depth and axial length. Compensatory adjustments between the axial length and the keratometry of the cornea play an important role in emmetropisation. Capturing the biometric measurements of the eye is an important part of the preoperative work up of patients to calculate the intraocular lens (IOL) power, hence, the importance of better understanding of the interplay between the biometry parameters. Our aim was to assess the variation of keratometry with the refractive status and axial length of the eye. METHODS This is a cross sectional observational study of 299 eyes that were operated for cataract surgery from July 2018 to December 2018 at a tertiary care centre in South India. Axial length and central corneal curvature were measured and average was taken for analysis. Eyes with axial length ≤ 22 mm were grouped as hyperopic (Group 1), those with axial length between 22.0 mm and 24.0 mm were grouped as normal (Group 2) and eyes with axial length more than 24.0 mm were grouped as myopic (Group 3). The distribution of corneal curvature, AL / K ratio and IOL power across different ranges of axial length was assessed. RESULTS There was a statistically significant flattening of cornea with increase in axial length (P < 0.001). Distribution of axial length to corneal radius of curvature was also found to be statistically significant (P < 0.001) among the three groups. CONCLUSIONS With an increase in axial length there was a statistically significant progressive flattening of cornea. The AL / K ratio can be a better measure of the refractive status of an individual than axial length alone. KEYWORDS Axial Length, Keratometry, Myopia, Hyperopia, Axial Length to Corneal Radius of Curvature Ratio