Prediction of effective lens position (ELP) and its changes in different monofocal intraocular lens (IOL’s)

Abstract

Objectives: To evaluate effective lens position (ELP) is more accurately predicted by anterior chamber depth (ACD) alone or by ACD + ½ lens thickness (LT) and to compare the ELP and refractive outcome of different monofocal intraocular lens (IOLs) in patients undergoing phacoemulsification. Materials and Methods: A total of 122 eyes with senile cataract underwent phacoemulsification with three different types of IOL implantation. Biometry data were obtained by IOL master 700 (SS-OCT) and IOL power was calculated using Barrett Universal II formula. Two prediction formulae for ELP were compared, one with ACD + ½ LT and other with ACD alone; furthermore, comparison was done among three types of IOL. Mean prediction error was calculated for both methods and among three IOL groups. Results: In the study, predicted ELP according to ACD + ½ LT was 5.27 ± 0.27 and Mean pre-op ACD was 3.069 ± 0.349 mm, achieved ELP (post-op ACD) was 4.98 ± 0.47 mm and between the two; ACD + ½ LT is closer to achieved ELP. The difference between mean ACD + ½ LT (5.22) and achieved ELP (4.71) was 0.50 in ALCON ACRYSOF IQ (SN60WF) and difference of ACD + ½ LT (5.33) and achieved ELP (5.07) was 0.25 in J and J TECNIS 1 (ZCB00), while the difference of ACD + ½ LT (5.28) and achieved ELP (5.16) was 0.114 in ZEISS CT LUCIA (611P). Residual refraction predicted by IOL master 700 and achieved residual refraction at post-op 1 month was −0.15 ± 0.19 and −0.10 ± 0.30 in ACRYSOF IQ, was −0.11 ± 0.18 and −0.01 ± 0.20 in TECNIS 1 and was −0.10 ± 0.20 and + 0.396 ± 0.22 in ZEISS CT LUCIA, respectively. Conclusion: ELP may be better predicted by formulae ACD + ½ LT than ACD alone with mean differences of 0.29 and 1.92 in two prediction groups, respectively. ALCON ACRYSOF IQ (SN60WF) and J and J TECNIS 1 (ZCB00) group had myopic shifts of 0.10 and 0.11, respectively, while ZEISS CT LUCIA (611P) group had hyperopic shifts of 0.5002 which was statistically significant, as ALCON ACRYSOF IQ (SN60WF) and J and J TECNIS 1 (ZCB00) ELP is positioned more anterior and ZEISS CT LUCIA (611P) relatively posterior.