Previous studies have shown keratoconus patients have formed corneal deep stromal opacity months following corneal crosslinking (CXL), and researchers decided to dive into this issue and evaluate the predictive factors for stromal scar formation after receiving this treatment.

In this comparative cohort study, the medical records of 295 progressive keratoconus patients who had undergone accelerated CXL were reviewed. Patients were split into two groups—the scar group, which included 32 patients who still had a corneal scar in the first year, and the control group, which included 75 patients without any scar.

The patients’ demographic characteristics, preoperative uncorrected distance visual acuity (UCVA) and corrected distance visual acuity (CDVA), slit-lamp biomicroscopy and corneal topographic parameters data were acquired from their files. Multivariable logistic regression analysis and receiver operating characteristic (ROC) curves were used for the purpose of evaluating predictive factors for corneal scar formation.

The UCVA and CDVA, which were determined to be similar between the groups during the preoperative period, improved postoperatively in both groups (p = .98, p = .10, respectively). The thinnest point of corneal thickness was statistically lower in the scar group (p = .03). In multivariable logistic regression analysis, preoperative keratometric astigmatism was a predictive value showing postoperative scar development. Keratometric astigmatism had the highest sensitivity (90%), specificity (86.7%), and accuracy (95%) for scar formation at the best cut-off point of 5.61D according to the ROC curve.

Researchers found the preoperative corneal thickness in the scar group to be significantly lower compared to the control group, and keratometric astigmatism to be significantly higher, but there was no stage 3 keratoconus in any of the cases.

These findings are comparable with previous studies, which have indicated a significant complication of permanent stromal haze.

“The severity of keratoconus was similar in the scar and the control group,” the authors concluded in their study. “A higher tendency for stromal scar development following CXL was determined in eyes with thinner corneas and higher keratometric astigmatism. Keratometric astigmatism had an excellent ability to predict corneal scar formation after CXL. A cut-off value of 5.61 D for keratometric astigmatism would predict corneal scar formation with the highest sensitivity, specificity and accuracy. Moreover, the development of a corneal scar, which is resistant to steroid treatment, does not cause visual impairment but leads to a significant reduction in the postoperative corneal thickness.”