Corneal CXL seems to be safe and effective in halting the progression of keratoconus in pediatric patients at 4-year follow-up. In addition, the procedure provides improvements in visual, refractive, topographic, and corneal aberrometric measurements.

In diseases which affect the posterior corneal surface, such as keratoconus, it is thought that because of the asymmetrical peripheral placement of the corneal apex, as the corneal diameter increases there could be an error increase of 1-3 mm in keratometric systems evaluating the anterior surface.

Objectives: This study examined changes in the levels of organic acids, which are important tear metabolites, after corneal collagen crosslinking (CXL) treatment for keratoconus. Methods: This prospective, nonrandomized, interventional case series included a single eye from 24 patients who were scheduled to receive CXL treatment (Dresden protocol) for progressive keratoconus. Before CXL treatment and at 6 months after treatment, tears were collected in capillary tubes. The patients were separated into four groups as males, females, and ages 18 years younger and >18 older. The organic acid profiles of the tear samples were analyzed using mass spectrometry. Results: An evaluation was made of 12 females and 12 males with a mean age of 19.20±4.06 years (range: 12‒27 years). The greatest percentage increase in organic acids after CXL treatment was observed for N-acetyl-L-aspartic acid (66% increase). The organic acid showing the greatest decrease was 3-OH butyric acid (61% decrease). A decrease of 46% was found (P=0.263) in the lactic acid/malic acid ratio. Conclusion: Metabolomic studies of tears could facilitate a new and objective process in the follow-up period or in the determination of prognosis after CXL treatment for diseases such as keratoconus, which has a multifactorial etiology.

To evaluate the ABCD grading system used in follow-up of keratoconus progression after the corneal collagen cross-linking (CXL) treatment in different Kmax groups. Methods: This study included 57 eyes of 43 patients applied with CXL treatment for progressive keratoconus. All the patients were applied with the standard CXL protocol (Dresden). According to the changes in the Kmax value at the end of 12 months postoperatively (0-1D, 1-2D, >2D), the groups were separated as steepening and flattening. Scheimpflug progression parameters, such as ABCD keratoconus grading systems, were evaluated in six different groups. The Paired Samples t-test was used in the evaluation of parameters with normal distribution and the Wilcoxon test for parameters not showing normal distribution. A value of p<0.05 was accepted as statistically significant. Results: Mean age of patients was 18.37±3.86 years (11-28 years). According to the ABCD grading system, 0.19 significant regression was determined in grade A (p=0.014) and 0.24 in grade D (p<0.0001). 0.10 progression was seen in grade B (p=0.089), and 0.11 in grade C (p=0.011). In the mean Kmax value 0.25±0.42, D flattening was seen (p=0.137). Conclusion: The anterior corneal surface grade in ABCD system is correlated with Kmax in different groups. However, the posterior corneal surface parameter is not correlated with Kmax in 1-2 D steepening and >2D flattening groups. Although there is an increase in posterior elevation after CXL, despite excessive Kmax flattening, it would be inaccurate to consider this increase as an indicator of topographic progress.