Spherical aberration and coma with an aspherical and a spherical intraocular lens in normal age-matched eyes

Purpose

To study optical aberrations in eyes having uneventful cataract surgery and in-the-bag implantation of an aspherical Tecnis Z9000 intraocular lens (IOL) (AMO) or a spherical CeeOn Edge 911 IOL (Pharmacia) and compare the results with those in a group of phakic age-matched eyes.

Setting

Ophthalmic Unit, Hospital and University of Verona, Verona, Italy.

Materials

Three groups, each with 30 patients (30 eyes), were examined with the Topcon KR-9000PW topographer/aberrometer. Spherical aberration and coma were analyzed in detail for 4.0 mm optical zone. Internal values were obtained by subtracting corneal aberrations from ocular aberrations. Point spread function and modulation transfer function (MTF) were considered for optical quality.

Results

The mean internal spherical aberration Z₄⁰ was −0.048 μm ± 0.017 (SD) in the Tecnis group, +0.033 ± 0.026 μm in the 911 Edge group (P<.001), and −0.013 ± 0.056 μm in the phakic group (P = .149). The mean internal vertical coma Z₃⁻¹ was 0.087 ± 0.056 μm, 0.054 ± 0.043 μm (P = .005), and 0.044 ± 0.044 μm (P<.001), respectively. The internal horizontal coma Z₃⁺¹ showed a similar pattern; however, total resulting coma was similar in the 3 groups. The mean Strehl ratio was 0.284 ± 0.166 in the Tecnis group, 0.145 ± 0.077 in the 911 Edge group (P<.01), and 0.164 ± 0.097 in the phakic group (P<.01). The MTF curve was better in the Tecnis group (P<.001).

Conclusions

After uneventful implantation, the aspherical IOL yielded better ocular aberration and optical quality results than the spherical IOL. Induced coma was somewhat higher in the Tecnis group; however, the overall results were not affected. Physiologic IOL decentration after correct in-the-bag implantation did not negate the advantages of asphericity.