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EUROTIMES | Volume 17/18 | Issue 12/1

Measuring retinal image quality in a model eyeWhat is the ideal configuration for a realistic reproduction of the pseudophakic retinal image quality in a model eye? Researchers in the US have introduced a new adaptive optics IOL metrology system comprising a model eye, wavefront sensor, deformable mirror, and an image-capturing device that acquires through-focus images of a letter chart with 3.0mm and 5.0mm pupil diameters. They noted that to simulate pseudophakic retinal image quality on an optical bench, it is critical to reproduce real-life conditions. Corneal lower-order aberrations and higher order aberrations are present in all eyes to a varying degree and have a significant impact on pseudophakic through-focus visual performance. Furthermore, corneal aberrations interact with the aberrations of the IOL to yield the complete ocular aberrations, which increase with pupil size. The researchers used the new system to induce corneal astigmatism and higher-order aberrations in previously measured pseudophakic presbyopic eyes. A single-optic accommodating IOL (Crystalens HD (HD500), an apodised (ReSTOR +3.0 D SN6AD1) and full-aperture (Tecnis ZM900) diffractive multifocal IOL, and a monofocal IOL (AcrySof SN60AT) were evaluated. Image quality was quantified using the correlation-coefficient image-quality metric. The single-optic accommodating IOL and monofocal IOL performed similarly. However, with a 3.0mm pupil, the former had better intermediate (1.50 D) image quality. The multifocal IOLs had bimodal through-focus image quality trends. Corneal astigmatism reduced through-focus image quality and depth of focus with all IOLs. However, the multifocal IOLs had the most severe decline in depth of focus. Ocular spherical aberration had the strongest impact on image quality when typical pseudophakic corneal HOAs were present.

n L Zheleznyak et al., JCRS, “Impact of corneal aberrations on through-focus image quality of presbyopia-correcting intraocular lenses using an adaptive optics bench system,” Volume 38, Issue 10, 1724-1733.

Learning to do femtosecond LASIKFemtosecond lasers are now used by more than 50 per cent of LASIK surgeons in the US. It appears that the introduction of femtosecond laser systems for flap creation may improve the learning curve for newly trained surgeons because many of the more visually threatening flap complications, such as free caps, irregular flaps, buttonholes, decentred flaps and epithelial defects, occur much less frequently. British researchers looked at the learning curve of the first 200 consecutive myopic LASIK procedures using the Visumax femtosecond laser and the MEL 80 excimer laser by an expert surgeon (11,637 previous microkeratome LASIK procedures) and a fellowship-trained surgeon (observed 1057, performed 155 supervised LASIK procedures) following a standardised surgical technique. They observed no statistically significant differences in outcome measures between surgeons. Preoperatively, the mean SE was −4.00 D ± 1.83 (SD) and −3.97 ± 1.98 D and the mean cylinder was 0.81 ± 0.67 D and 0.79 ± 0.66 D for the expert surgeon and fellowship-trained surgeon, respectively. Postoperatively, the SE was ±0.50 D in 79 per cent and 74 per cent, uncorrected distance visual acuity was 20/20 or better in 96 per cent and 96 per cent, and one line of CDVA was lost in 3.5 per cent and 1.5 per cent for the expert surgeon and fellowship-trained surgeon, respectively. Contrast sensitivity increased or was unchanged.

n D Reinstein et al., JCRS, “Transitioning from mechanical microkeratome to femtosecond laser flap creation: Visual outcomes of an experienced and a novice LASIK surgeon,” Volume 38, Issue 10, 1788-1795.

Review

JCrS HiGHLiGHtSJournal of Cataract and Refractive Surgery

Thomas Kohnenassociate editor of jcrs

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Don’t miss Ophthalmologica Highlights, see page 43