Evaluation of the Accuracy of Intraocular Lens Formulae in the Different Ethnic Groups in Singapore

Abstract

The formation of cataract is a natural aging process of the crystalline lens where it is replaced by an artificial intraocular lens (IOL) during the cataract operation. New IOL formulae have been developed over the years with the purpose of meeting the patient’s expectation of a clear vision with minimal residual refractive error after the cataract operation. This retrospective database study sets out to evaluate the accuracy of the various IOL formulae in the different ethnic groups in Singapore, involving the Chinese, Malay and Indian ethnic groups over a period of 2 years with axial lengths of 22.00 to 25.99 mm (medium axial lengths). Different generation of IOL formulae were compared in this study with the 3rd generation IOL formulae comprising of SRK/T, Hoffer Q and Holladay 1. The 4th generation IOL formula comprised of Haigis and the 5th generation formulae comprised of both Barrett Universal II and Emmetropia Verifying Optical (EVO). In this study, the participants were divided into 2 groups, namely Chinese group and Non-Chinese group (Malay and Indian ethnic groups). It was found that SRK/T has the smallest mean absolute error (MAE) when compared to other IOL formulae, followed by Barrett Universal II and EVO in the Chinese group. In the Non-Chinese group, it was found that Barrett Universal II has the lowest MAE, followed by EVO and SRK/T. However, SRK/T, Barrett Universal II and EVO could be used interchangeably when generating the IOL powers in both the Chinese and Non-Chinese groups. In conclusion, this study showed that SRK/T, Barrett Universal II and EVO could be used interchangeably to generate IOL powers for medium axial lengths in the different ethnic groups in Singapore. Despite the emergence of newer generation IOL formulae, SRK/T formula is proven to be just as accurate as its newer counterparts.