Effect of intraocular lens implantation on visual acuity, contrast sensitivity, and depth of focus

PURPOSE: To determine the role of spherical and irregular aberrations in the optics of the natural eye and after intraocular lens (IOL) implantation in terms of visual acuity, contrast sensitivity, and depth of focus. SETTING: Laboratory of Experimental Ophthalmology, University of Groningen, Groningen, The Netherlands. METHODS: Visual acuity and defocus-specific contrast sensitivity in 11 pseudophakic patients (IOL group) and 27 age-matched phakic subjects were compared. The results were obtained psychophysically. Spherical and irregular aberrations were subsequently estimated by comparing the measured myopic shift (optimum focus of contrast sensitivity at 4 cycles per degree [cpd] compared to that at 16 cpd) and depth of focus with those of theoretical eye models with varying amounts of irregular and spherical aberrations. RESULTS: The best corrected visual acuity and best corrected contrast sensitivity in the IOL group did not significantly differ from that in the phakic group. The depth of focus was larger in the IOL group at a pupil diameter of 6.0 mm (P<.05). Comparison with theoretical eye models suggested a higher amount of spherical aberration in the IOL group; irregular aberration was almost the same in both groups. CONCLUSIONS: There was a higher amount of spherical aberration in the IOL group, related to a larger depth of focus, without loss of contrast sensitivity at optimum focus or loss of visual acuity. This might contribute to better quality of vision in pseudophakic subjects than in presbyopic phakic subjects.