A Comparative Study on Accuracy of SRK-T And Haigis Formulas in IOL Power Calculation in Axial Myopes Undergoing...

It has been a significant challenge since the advent of intraocular lens to give the best postoperative visual acuity and prevent refractive surprises due to biometry error. Among myopic eyes, it has been a debate among the various formulas introduced and their efficacy to prevent postoperative refractive surprises. Hence, the need for an accurate formula in high myopic eyes is obligatory.

To compare the accuracy of SRK-T and Haigis formulas in IOL power calculation in axial myopic eyes undergoing cataract surgery.

A total of 50 cases with axial length >24 mm were taken up for the study and were examined in detail and error between both formulas were assessed.

The mean age of the subjects in the study was 53.50 ± 16.12 years; 27 were males, and 23 were females. The majority of patients had PSC + NS II. Seven out of 50 cases had posterior staphyloma. Most of the patients had average K value in the 44-46-D range. AL of most of the patients (66%) was between 24 and 26 mm. The majority of patients had IOL power >15 D, and 82% (41 eyes) were found to have no post-op complications. Four eyes had severe iritis, and five eyes had striate keratopathy. At the follow-up at 6^th week postoperatively, 82% were found to have 6/6-6/9 vision on Snellen's chart. Four eyes had 6/12-6/24 post-op vision, mainly attributed to primary PCO. Five eyes (10%) had <6/24 post op vision at the end of 1 week due to the presence of posterior staphyloma. A higher percentage of eyes in the SRK/T group had a mean error >0.5 D. Upon comparing the mean error between the two groups, P was 0.005; hence, the results are statistically very significant, showing that Haigis formula is better than SRK/T formula in achieving target refraction (-1) in myopic eyes undergoing phacoemulsification.

Our study shows that Haigis formula was better than SRK/T formula for achieving the target postoperative refraction in high axial myopes.