Early clinical outcomes of laser in situ keratomileusis concurrent with accelerated corneal collagen crosslinking for myopia and astigmatism with thin cornea

Background

Keratectasia after laser in situ keratomileusis (LASIK) is a rare but severe complication, which threatens the visual acuity and corneal strength.Corneal collagen crosslinking (CXL) is a new therapy that increases the security and decreases the risk of complication.However, the effectiveness and safety of LASIK-CXL is still need to be concerned.

Objective

This study was to evaluate the safety of LASIK-CXL for myopia and astigmatism with thin cornea.

Methods

A prospective cohort study was designed.A total of 128 eyes of 64 patients with thin corneal and myopic astigmatism enrolled in Beijing Tongren Eye Center from January 2014 to January 2015.The patients were assigned to LASIK group (74 eyes of 37 patients) and LASIK-CXL group (54 eyes of 27 patients). Refractive surgery was performed by Visumax femtosecond lasrer and VISX S4 excimer laser.Eyes of LASIK-CXL group applied accelerated CXL immediately after LASIK.The follow-up was 6 months.Manifest refraction, uncorrected (UDVA) and corrected distance visual acuity (CDVA), average keratometry values (AveK), anterior segment OCT (AS-OCT), corneal hysteresis (CH) and corneal resistance factor (CRF) were examined before and after operation.This research passed through Ethics Committee of Beijing Tongren Hospital.

Results

The spherical equivalent (SE) of the LASIK group and LASIK-CXL group were (-6.49±2.41)D and (-6.97±2.41)D before operation and decreased to (-0.68±0.88)D and (-0.75±0.94)D 6 months after operation.The UDVA (LogMAR) was 1.18±0.28 and 1.05±0.38 before operation and elevated to -0.06±0.09 and -0.03±0.186 months after operation in the LASIK group and LASIK-CXL group.The preoperative AveK values were (44.37±1.46)D and (44.47±1.50)D in the LASIK group and LASIK-CXL group and reduced to postoperative (39.30±2.06)D and (38.66±1.80)D.The preoperative SRI of LASIK group and LASIK-CXL group were 0.25±0.21 and 0.24±0.22, which increased to 0.29±0.24 and 0.28±0.24.The SAI values were 0.36±0.16 and 0.39±0.15 before operation, which increased to 0.57±0.31 and 0.75±0.376 months after operation, and the SAI value of the LASIK-CXL group was significantly higher than that of LASIK (F=10.220, P=0.002). CRF values of LASIK and LASIK-CXL were (8.44±1.44)mmHg and (8.63±1.35)mmHg in preoperation, which decreased to (5.74±1.31)mmHg and (6.25±1.24)mmHg in postoperation.The result of LASIK-CXL was higher than that of LASIK (F=8.650, P=0.040). CH values were 8.78±1.51 and 8.69±1.62 in preoperation, which decreased to (7.23±1.08)mmHg and (6.50±1.32)mmHg.The value of LASIK-CXL was lower than that of LASIK (F=5.860, P=0.017). The mean depth of demarcation line was (228.45±28.24) μm (range 165 to 310 μm) on OCT, which was presented in 45 eyes (81.82%) at 1 month in postoperation.

Conclusions

Accelerated CXL with FS-LASIK is effective and safe in improving visual acuity in myopic astigmatism patients with thin cornea, which also can increase the rigidity of the cornea.

Keratomileusis, laser in situ/methods; Lasers, excimer/therapeutic use; Combined modality therapy Collagen/metabolism; Cross-linking reagents/therapeutic use; Biomechanical phenomena; Prospective srudies; Corneal collagen cross-linking