A COMPARATIVE STUDY OF INTRAOCULAR LENS POWER CALCULATION FORMULAE (SRK/T, HOFFER Q, SRK II AND HAIGIS) IN EYES OF PATIENTS WITH VARIOUS AXIAL LENGTHS

Neebha Anand*, A. K. Khurana, Ketan Bhardwaj, Jyoti Deswal and Sunil Verma

ABSTRACT

Title: A Comparative Study of Intraocular Lens Power Calculation Formulae (SRK/T, Hoffer Q, SRK II and Haigis) in Eyes of Patients with Various Axial Lengths. Aim: To compare intraocular lens power calculation formulae (SRK/T, Hoffer Q, SRK II and Haigis) in eyes of patients with various axial lengths. Material and Methods: The study was a prospective study conducted in a tertiary care hospital in North India. 90 patients were enrolled and divided into groups of 30 with axial length <22mm; 22-24.5mm and >24.5mm. At the end of 6 weeks the post-operative residual / consecutive spherical equivalent (SE), was calculated. The predictive accuracy of each formula was analysed by comparing the difference between the actual and predicted post-operative spherical error, mean estimation error (ME) and mean absolute error (MAE). Result: The mean post-operative unaided vision at the end of 6 weeks was 0.16±0.06, 0.17±0.07 and 0.16±0.06 log MAR units in Groups 1, 2 and 3 respectively with no statistically significant difference among the three groups (p value = 0.924). The mean values of post-operative spherical equivalents of the three groups at the end of 6 weeks were -0.25±0.78 D, -0.23±0.61 D, -0.19±0.73 D, with difference being statistically significant (p value=0.049). SRK II formula had the least MAE and ME in group 1 and 2 whereas in group 3, SRK/T had the least MAE and ME. Conclusion: SRK II has better predictive accuracy for calculations of IOL power in eyes with axial length (AL) 24.5mm.

Keywords: Intraocular lens power, SRK/T, Hoffer Q, SRK II, Haigis formula.