Aspheric intraocular lenses: effect of residual spherical aberration on objective quality of vision

Abstract

Abstract Purpose To assess the impact of residual spherical aberration (SA) on objective quality of vision in pseudophakic patients. Methods 15 patients (25 eyes) were divided into 2 groups: 13 eyes received an aspherical AcriSmart36A® generating a negative SA, 12 eyes received a zero‐aberration AcriSmart46LC®. Postoperative evaluations were conducted 6 months after a 1.8mm micro incision cataract surgery. Aberrometric measurements were done for a standardized pupil size of 5 mm in mesopic conditions using Wavescan Aberrometer®. Modulation Transfer Function (MTF), Strehl ratio and depth of field were measured with Objective Quality Analysis System®. Results Best corrected 100% LogMar distance visual acuity (BCVA) was similar in both groups (p=0.89). 20% and 9% BCVA was increased in 36A® group (p=0.009 and 0.005). Mesopic contrast sensitivity was better and total spherical aberration were significantly less with 36A® IOL(SA=0.075±0.05 μm with 36A® and 0.20±0.05 μm with 46LC®,p=0,0002). Coma and trefoil were not different between the two groups (p>0,05). 36A® induced better image quality with an average MTF of 32.7±9.6 c/deg with 36A® and 23.8±8.1 c/deg with 46LC®, p=0.0002. The 36A® group had 1D less depth of focus than the 46LC® group at 6 months : respectively 1.3±0.59D and 2.27±0.63D. For the whole population, depth of focus appeared to be correlated with SA (r2=0.28, p=0.02) and with trefoil (r2=0.49, p=0.0009). Conclusion While reducing total ocular SA, aspheric IOLs improved mesopic contrast sensitivity, quality of vision with greater MTF values. Reduction of aberrations may be responsible for reduced depth of focus with 36A® IOLs. However, residual trefoil aberrations may be advantageous for depth of focus and reading ability.