Clinical efficacy evaluation of accelerated epithelium-off corneal collagen cross-linking on corneal ectasia after keratorefractive surgery

Objective

To investigate the efficacy and safety of accelerated epithelium-off corneal collagen cross-linking (CXL) in the treatment of corneal ectasia after keratorefractive surgery.

Methods

An observational case series study was performed.Twelve patients (22 eyes) diagnosed with corneal ectasia after keratorefractive surgery in the First Affiliated Hospital of Army Medical University were enrolled from January 2016 to December 2018.All the patients received accelerated epithelium-off CXL and were followed up for 12 months.Before and 1 week, 1, 3, 6, and 12 months after the operation, the uncorrected visual acuity (UCVA) and best corrected visual acuity (BCVA) converted to the logarithm of the minimum angle of resolution (LogMAR) unit were measured.The sphericity, cylindricity, and spherical equivalent were examined by Topcon auto refractor.The maximum keratometry (Kmax) of the front surface, mean keratometry (Km) of the front surface, Km of the back surface, symmetry index of front surface (SIf), symmetry index of back surface (SIb), thinnest corneal thickness (TCT), total aberrations, total high-order aberrations, coma aberration, trefoil aberration and spherical aberration were detected by the Sirius analyzer.The depth of corneal demarcation lines was determined by optical coherence tomography.The intraocular pressure was measured by the non-contact tonometry.The corneal endothelial cell density was assayed by the endothelial cell densitometry.The inflammatory reaction and haze were observed with a slit lamp at different time points after surgery.This study adhered to the Declaration of Helsinki.The study protocol was approved by the First Affiliated Hospital of Army Medical University (No.KY2020063). Written informed consent was obtained from each patient before entering the cohort.

Results

Among the 22 eyes of 12 cases, 3 eyes of 2 cases (13.64%) underwent small incision lenticule extraction, and 19 eyes of 10 cases (86.36%) underwent excimer laser in situ keratomileusis.The UCVA (LogMAR), BCVA (LogMAR), cylindricity and spherical equivalent before the operation were 0.61±0.42, 0.24±0.23, (-2.83±2.39)D, (-3.60±2.66)D, which were significantly worse than 0.45±0.31, 0.12±0.15, (-2.11±1.67)D, (-3.12±2.31)D at 12 months after the operation (t=4.054, 4.956, -3.728, -2.742; all at P<0.05). The front surface Kmax, front surface Km and SIf at 12 months after the operation were (48.37±5.80), (41.49±3.04), (5.36±4.07)D, which were significantly lower than (49.61±5.97), (41.66±2.97), (5.85±4.18)D before the operation (t=5.949, 2.278, 2.719; all at P<0.05). There was no significant difference in sphericity, Km of the back surface, SIb, TCT, total aberrations, total high-order aberrations, coma aberration, trefoil aberration, spherical aberration, intraocular pressure and endothelial cell density between before and 12 months after the operation (all at P>0.05). Grade 0.5-2 haze occurred in 8 eyes of 4 patients one month postoperatively.After administration of prednisolone acetate eye drops, haze decreased or disappeared 3 months postoperatively, with UCVA and BCVA unchanged.A corneal demarcation line with a depth of (285.40±51.61)μm was found in 11 eyes of 6 cases at 1 month after operation.

Conclusions

Accelerated epithelium-off CXL can significantly improve visual acuity, reduce corneal astigmatism and corneal curvature, as well as effectively prevent the progress of corneal ectasia.

Keratorefractive surgical procedures; Ectasia, cornea; Epithelium-off corneal cross-linking