Accuracy of biometry using automated and manual keratometry for intraocular lens power calculation

A comparison of precision of intraocular implant power calculation by computing keratometry values by two different methods, namely, the automated and manual keratometry (MK), was done. For checking this accuracy, the parameter taken into consideration was the absolute refractive error which was ascertained postoperatively.

This study was conducted in the Department of Ophthalmology, Sri Aurobindo Institute of Medical Sciences and PG Institute, Indore. At a tertiary eye care centre in Central India (Sri Aurobindo Institute of Medical Sciences, Indore). Duration of the study was 18 months. Sample size was 66 individuals who were with cataract (nuclear sclerosis I to III). Although keratometry was done by both methods and implant power derived separately by computing both readings, decision of which power to be implanted in an eye would depend on the group, in which patient would fall. Group A were prospective candidates who would be implanted intraocular lens (IOL) of that power as assessed by computing MK value, whereas Group B were participants who would be implanted IOL of that power as assessed by computing value obtained by automated keratometry (AK). First patient fell in Group A and second in Group B, third again in Group A till 33 patients had been operated in each group.

Bland-Altman plot thus obtained showed that the two keratometers are comparable. The postoperative refractive errors for the two Groups (A and B), showed that if an error of ±0.50 D or less is considered, then in Group A 81% of patients achieved this and 87% of patients required this as spectacle aid in Group B.

In this study, we compared the accuracy of AK with that of MK for calculation of implant power. It was concluded from this study that AK is a simple keratometric technique that appeared to be more accurate than MK.