Abstract
Purpose :
To study the changes of corneal epithelial thickness after FS-LASIK (Femtosecond Laser-assisted In Situ Keratomileusis) in different regions in high astigmatism patients.
Methods :
This study involved 42 eyes of 28 patients (19 male and 9 female). The astigmatism of all eyes was at least 2.00 D and the optical zone was 6.19±0.38 mm. Corneal epithelial thickness was measured by AngioVue OCT preoperatively and one month postoperatively. Concentric circles were marked as auxiliary measuring tools with radius within range of 0.5-3.5 mm. Corneal epithelial thickness was recorded at every intersection of concentric circles and specific axes, including the astigmatic axis (K1) and the perpendicular meridian (K2). The central, paracentral and peripheral regions were defined as the area of central 2 mm, 2-5 mm and 5-7mm respectively. Corneal epithelial thickness in different axes and their correlations with preoperative diopter were analyzed.
Results :
1.There were significant differences in epithelial thickness changes of K1 and K2 in paracentral and peripheral regions （K1para=4.29±2.93μm VS K2para=3.54±2.52μm，P=0.014; K1peri=1.12±3.69μm，K2peri=-2.32±3.24μm,P<0.001). 2. The difference of epithelial thickness changes in K1, and K2 were significant at 2.5, 3 and 3.5 mm from corneal vertex (K12.5=2.50±3.06μm VS K22.5=1.35±2.84μm，P=0.011; K13.0=0.30±3.81μm VS K23.0=-3.76±3.21μm，P<0.001; K13.5=1.93±4.22μm VS K23.5=-2.64±2.84μm，P<0.001). 3. There were correlations between the epithelial thickness changes (central and paracentral regions) and preoperative diopter（central r=0.439，paracentral r=0.258). 4.The ratio of epithelial thickness changes and diopters in K1 were significantly less than K2 in central and paracentral regions (RK1cent=0.68±0.65 VS RK2cent=0.75±0.73，P<0.001，RK1para=0.55±0.47 VS RK2para=0.76±0.68，P<0.001）.
Conclusions :
The corneal epithelial thickness increased significantly both in central and paracentral regions one month postoperatively in high astigmatism patients. Furthermore, the increase in astigmatism axis of paracentral region was larger than that in perpendicular meridian. Diopter was one of the factors that affected growth of corneal epithelium. The impact on the central region was greater than the paracentral region. On the contrary, the corneal epithelial thickness decreased in peripheral region, which might be due to the epithelial damage when creating flap.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.