Aberration-free IOLs may perform best with low corneal spherical aberration

This study's authors used an adaptive optics visual simulator to demonstrate that aberration-free IOLs may do very well in virgin corneas and corneas with low degrees of myopic or hyperopic LASIK ablation (< -2.00 D and < +1.00 D), or when the spherical aberration (SA) is low, at between 0.027 to 0.277 µm. However, in simulations of eyes that have undergone LASIK for high myopia or high hyperopia, it appears that visual quality with an aspheric IOL can suffer without correcting for the induced spherical aberrations. 

They used the AO crx1 visual simulator (Imagine Eyes, Orsay, France) to simulate the aberration pattern of the aspheric Akreos Adapt AO IOL (Bausch & Lomb, Rochester, N.Y.) combined with five corneal profiles: virgin corneas and corneas with low and high myopic ablations and low and high hyperopic ablations. Ten eyes of 10 subjects were evaluated. Monocular distance visual acuity (VA) was measured at three contrast levels.

At 100 percent of contrast, there were no differences in VA values among virgin corneas, low and high myopic ablations and low hyperopic ablation groups (P = 0.06). All of these groups achieved better results than the high hyperopic ablation group (P < 0.001). At 50 percent and 10 percent of contrast, the best VA values were obtained for the virgin corneas and for the low myopic and low hyperopic ablation groups (P > 0.1, for both levels of contrast). There were significant differences between these three corneal profiles and the other two corneal profiles (P < 0.002 for high myopic and P <0.001 for high hyperopic, for both levels of contrasts).

Based on the results, the authors suggest that another IOL design should be chosen for patients with a higher corneal SA. They say an aberration-correcting IOL may be a good option for patients with a high myopic ablation because the negative SA value of these IOLs would better compensate for the increase in positive SA induced by myopic ablation. In patients with high hyperopic ablations, a spherical IOL may be the best option because these IOL designs have positive SA values that may compensate for the negative corneal SA caused by the high hyperopic ablation, improving the visual quality.

They recommend further studies that assess visual quality results with spherical and aberration-correcting designs combined with different corneal profiles in order to confirm these hypotheses.