Effect of spherical aberration on visual acuity and depth of focus in pseudophakic eyes

Abstract

Purpose: Assess the performances of four intraocular lenses (IOLs) in various spherical aberration (SA) conditions, using the VAO adaptive optics simulator (Voptica S.L.). Setting: Cullen Eye Institute, Baylor College of Medicine, Houston, TX. Design: Prospective case series. Methods: Distance-corrected visual acuities at distance (CDVA), intermediate (DCIVA), and near (DCNVA) were measured in 42 dilated pseudophakic eyes at baseline and with ocular SA ranging from –0.4 to +0.4 μm in increments of 0.2 μm (6.0-mm pupil). Four IOL types were assessed: monofocal IOLs with zero-SA, enhanced-monofocal, extended depth-of-focus (EDoF), and continuous-range-of-vision. Results: Compared to SA = 0μm, significant changes (all P<.05) were: 1) zero-SA monofocal IOLs’ DCNVA at high contrast improved by 0.13 logMAR with SA = – 0.4 μm and worsened by 0.09 and 0.10 logMAR with SA = +0.2 and +0.4 μm, respectively. DCNVA at low contrast worsened by 0.09 logMAR with SA = +0.4 μm; and 2) with SA = –0.4 μm, the enhanced monofocal IOL lost 0.06 logMAR of CDVA at high contrast and gained 0.09 logMAR of DCNVA at low contrast. There were no significant changes from SA = 0 μm for EDoF and continuous-range-of-vision IOLs. Conclusions: Zero-SA and EDoF IOLs were the most and least sensitive to SA modulation, respectively. In perfect optical systems where all the optical elements are aligned, induction of targeted amounts of negative SA improved the depth of focus of some IOL types. We found no benefit with positive SA.

Impact of spherical aberration on visual quality and depth of focus

“…For emmetropia, negative ocular SA will have the clearest image at intermediate and near distances but sacrifice 1 line of best corrected distance acuity because of the enlarged blur circle. 1,5 There is no benefit at intermediate or near for positive ocular SA, and there is the same reduction in distance acuity as with negative ocular SA. An additional important factor that favors negative ocular SA when measuring near vision performance is the pupil miosis from the synkinetic reflex.…”

“…clarifying the impact of spherical aberration (SA) on visual acuity and depth of focus in pseudophakia. 1 We have provided a figure that graphically illustrates their findings and demonstrates why there was no "expansion of the depth of field" with positive SA and why "they did not see a near benefit" (Figure 1).…”

“…The zero SA would therefore have the clearest image for a target at distance and clinically has been shown to be approximately 1 logMAR visual acuity line better than an ocular SA of ±0.3 mm for a normal mesopic pupil (∼4.5 mm). 1,5 In panel B, when the target is moved near the eye to the intermediate distance (67 cm, orange vertical line), the image moves to the right. This can also be accomplished with a À1.50 D lens in front of the eye with the target at infinity.…”