Correcting astigmatism

Preparation of lenticule backside: Oval shape of opaque bubble layer for correction of high astigmatism. Courtesy of Suphi Taneri MD Small-incision lenticule extraction (SMILE) appears to be safe and effective for astigmatism correction, although cyclotorsion could be an issue, according to two early studies presented at the XXXV Congress of the ESCRS in Lisbon, Portugal. Suphi Taneri MD reported outcomes from follow-up of up to three months for a consecutive series of 157 eyes with astigmatism of at least 1.0D treated at the Centre for Refractive Surgery, St Francis Hospital, Muenster, Germany, with the VisuMax femtosecond laser (ZEISS). They represent the first eyes in an ongoing observational case series treated with SMILE and having this level of astigmatism. The eyes had myopia between -0.5 and -10.0D and corrected distance visual acuity (CDVA) of 1.0 or better. The treatment target was plano in all cases. Preoperative marking of the axis was done only in eyes with astigmatism of greater than 3.0D, which accounted for 4.5% of the study cohort. Analysis of the refractive outcomes showed very good predictability and stability. Mean spherical equivalent was -5.52D preoperatively, +0.07D at one week and -0.06D at three months. Spherical equivalent at three months was ±0.50D of intended target in 85% of eyes and ±1.0D in 97%. An analysis of refractive astigmatism showed that at three months, 99% of eyes had less than 1.0D of astigmatism. “We found a tendency for undercorrection in the eyes with very high astigmatism, greater than 3.0D, but considering that we had so few such eyes in our series, we are waiting to adjust our nomogram because we do not want to risk overcorrection,” Dr Taneri said. Data on the refractive astigmatism angle of error showed the axis was well targeted. “Of course, you have to align the patient correctly before starting the treatment,” Dr Taneri said. Snellen uncorrected distance visual acuity (UDVA) at three months was 20/25 or better in 90% of eyes and 20/20 or better in 76%. A loss of ≥2 lines of CDVA occurred in 2% of eyes. “SMILE outcomes may be improved in the future with automated compensation of cyclotorsional eye movements, but they are similar to those reported for modern femto-LASIK with automated eye tracking,” Dr Taneri said. COMPARATIVE STUDY OUTCOMES Dr Taneri’s conclusion was supported by the findings of a comparative study presented by Sherif Tolees MD. The retrospective, non-randomised study analysed data from 43 SMILE eyes and 49 eyes treated with femto-LASIK (OPA software, Quest excimer laser; Nidek) at the Magrabi Eye Hospital, Jeddah, Saudi Arabia. The eyes had between -1.0 and -5.0D of astigmatism preoperatively, and they all completed follow-up to six months. In the femto-LASIK group, mean cylinder was reduced from -1.63±0.48D preoperatively to -0.38±0.32D. In the SMILE group, mean cylinder was -1.84±0.64D preoperatively and was reduced to -0.47±0.35D at six months. Refractive astigmatism was ≤0.25Ds in 59% of femto-LASIK eyes and in 43% of eyes in the SMILE group, and it was ≤ 1.0D in 98% of femto-LASIK eyes and 96% of SMILE eyes. Angle-of-error analysis showed treatment alignment in about 70% of eyes in both groups. Spherical equivalent results were stable from month one to month six and showed mild undercorrection of about 0.5D in both groups. “We believe this undercorrection should be considered in our nomogram. In addition, eye marking is very important when performing SMILE because docking and suction manoeuvres may create cyclotorsion,” said Dr Tolees. No eyes lost more than one line of CDVA, and CDVA was unchanged or improved in 94% of femto-LASIK eyes and 91% of SMILE eyes. Uncorrected distance visual acuity at six months was 20/16 or better in 33% of femto-LASIK eyes and 19% of SMILE eyes, with 88% of femto-LASIK patients achieving of 20/20 or better compared with 81% in the SMILE group. Sherif Tolees: sheriff.tolees@magrabi.com.sa Suphi Taneri: taneri@refraktives-zentrum.de

Tags: astigmatism