Abstract
Purpose :
Small incision lenticule extraction (SMILE) is now commonly performed for correction of myopic astigmatism. However, SMILE is currently unsuitable for treatment of mixed astigmatism and astigmatism more than 5 Diopters (D). In this study, we evaluated the feasibility and precision of intrastromal lenticule rotation (ISLR) for treatment of astigmatism up to 10 Diopters.
Methods :
Eighteen human donor corneas were mounted on an artificial anterior chamber containing organ culture media and 8% dextran. After laser application and dissection, the lenticule was rotated 90° in the intrastromal pocket. The attempted astigmatic correction was twice the cylindrical magnitude of the lenticule; 5.0D (5D group, n=9) and 10.0D (10D group, n=9), respectively. Pre- and postoperative Total Corneal Refractive Power was measured in the 4mm apex zone (Pentacam HR, Oculus). The change in keratometric astigmatism was evaluated by vector analysis. Anterior segment optical coherence tomography (AS-OCT, Heidelberg) was performed postoperatively in the axis of the preoperative steep and flat meridian, respectively.
Results :
In the 5D group, ISLR caused a mean absolute surgical induced astigmatism (SIA) of 5.30 ±1.14D [3.78D ; 7.68D] with a correction index of 1.06 ±0.23 [0.76, 1.36] and an angle of error of -0.80 ±4.61°[-6.33°; 6.93°]. In the 10D group, the mean absolute SIA averaged 9.57 ±1.10D [7.45D ; 11.60D] with a correction index of 0.96 ±0.11 [ 0.75; 1.16 ] and an Angle of Error of 2.75 ±3.60°[-1.67°; 7.69°]. The average Km increased 1.36 ±0.67D [ 0.60D ; 2.50D ] and 1.95 ±1.57D [0.25D ; 4.95D] in the 5D group and 10D group, respectively. On AS-OCT, ISLR caused a stromal redistribution in the periphery of the optical zone with tissue addition in the preoperative steep meridian and tissue reduction in the preoperative flat meridian.
Conclusions :
Intrastromal lenticule rotation seems precise and efficient for correcting regular astigmatism up to 10D. We found ISLR easily performed ex vivo, with an angle of error less than ±10%. A myopic shift was observed in the average keratometry. The in vivo corneal remodeling after ISLR warrants further investigation.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.