Affecting factors of corneal epithelial healing following de-epithelized corneal collagen cross linking in keratoconus patients

Background

Corneal collagen cross-linking (CXL) shows good clinical effects for keratoconus, and de-epithelized CXL appears to be benefit to the distribution and absorption of riboflavin in cornea stroma.However, de-epithelization of CXL will increase the infective risk and corneal healing time.It is very important to understand and control the affecting factors of corneal repair after de-epithelization of CXL.

Objective

This study was to evaluate the characteristics of corneal epithelial repair and analyze the relevant factors affecting corneal healing time after de-epithelized CXL.

Methods

A series-cases observational study was performed.De-epithelized CXL was performed on 77 eyes of 68 keratoconus patients in Shandong Eye Hospital from September 2013 to September 2015 under the approval of Ethic Committee of this hospital and informed consent of each patient.The age, corneal curvature, corneal thickness, breakup time of tear film (BUT), corneal front astigmatism (Astig) and epithelial healing time of the patients were recorded after surgery.The correlations between corneal epithelium healing time and above-mentioned factors were analyzed.

Results

De-epithelized CXL was smoothly finished in all the eyes.The corneal epithelium healing time was 2-12 days after surgery, with the average healing time 5 (4, 6) days.The mean age, thickness at corneal thinnest point, minimal cornea curvature (Kf), maximal corneal curvature (Ks), corneal average curvature (Km) and Astig was 22.00 (18.00, 25.00) years, 436 (412, 470)μm, 47.40 (44.70, 50.45)D, 52.10 (49.00, 54.55)D, 50.00 (47.15, 53.15)D and -3.30 (-5.45, 1.70)D, respectively.Spearman rank correlation analysis showed significant negative correlations between corneal epithelium healing time and BUT or the thickness at corneal thinnest point (BUT: r_s=-0.334, P=0.003; corneal thickness: r_s=-0.417, P=0.000), and the significant positive correlations were found between corneal epithelium healing time and Km, Kf and Ks (Km: r_s=0.449, P=0.000; Kf: r_s=0.300, P=0.008; Ks: r_s=0.432, P=0.000). There were no considerable correlarions between corneal epithelium healing time and age or Astig (age: r_s=0.023, P=0.845; Astig: r_s=-0.190, P=0.098). Multiple linear regression analysis were carried out to study the dependent variable and independent factors.Because of the multiple co-linearity between variables, this paper corrects the model by using ridge regression.There is significant negative correlation between BUT, corneal thickness and corneal healing time, respectively(both at P<0.05), corneal curvature Km and Kf is positively correlated with corneal healing time (both at P<0.05).

Conclusions

The corneal thickness, Kf, Km, as well as BUT are influencing factors of epithelial healing after CXL.