Prediction Of Effective Lens Position (Elp) And Changes In Different Monofocal Intraocular Lens

To evaluate effective lens position (ELP) is more accurately predicted by ACD (anterior chamber depth) alone or by ACD+1/2LT (lens thickness) and to compare the ELP and refractive outcome of different monofocal IOLs in patients undergoing phacoemulsification.

Nethradhama superspecialty eye hospital, Bangalore ,India 

A total of 122 eyes with senile cataract underwent phacoemulsification with three different type of IOL implantation. Biometry data was 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+ ½LTand 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.

 In the study Predicted ELP according to ACD+ ½LT 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+1/2LT is closer to achieved ELP. The difference of mean ACD + ½ LT (5.22) and achieved ELP (4.71) was 0.50 in ACRYSOF IQ, and difference of ACD + ½ LT (5.33) and achieved ELP (5.07) was 0.25 in TECNIS 1, while the difference of ACD + ½ LT (5.28) and achieved ELP (5.16) was 0.114 in ZEISS CT LUCIA. Residual refraction predicted by IOL master 700 and achieved residual refraction at post-op 1month was -0.15+/- 0.19 and -0.10+/-0.30 in ACRYSOF, was -0.11+/-0.18and -0.01+/-0.20 in TECNIS, was -0.10+/-0.20 and +0.396+/-0.22 in ZEISS respectively.

ELP may be better predicted by formulae ACD + ½ LT than ACD alone with mean difference of 0.29 and 1.92 in two prediction group respectively. ACRYSOFIQ and TECNIS 1 group had myopic shift of 0.10 and 0.11 respectively while Zeiss CT Lucia group had hyperopic shift of 0.5002 which was statistically significant, as ACRYSOFIQ and TECNIS 1 ELP is positioned more anterior and Zeiss CT Lucia relatively posterior.