An Analysis of Scheimpflug Holladay-Equivalent Keratometry Readings Following Corneal Collagen Cross-Linking

The aim of this research was to compare Holladay equivalent keratometry readings (EKR) and anterior corneal simulated keratometry (SimK) values in keratoconus cases following corneal collagen cross-linking (CXL) treatment.

This study included 42 eyes of 30 patients with progressive keratoconus. Scheimpflug imaging was performed pre-CXL and at post-CXL months 6 and 12. The mean Holladay EKR and SimK measurements from 1mm to 7mm were compared and repeated variance analysis was performed.

The mean age of the patients was 18.93±3.82 years (range: 12-27 years). A reduction was observed in the EKR and SimK values at 6 and 12 months postoperatively compared with the preoperative values, but the difference was not statistically significant (p>0.05). In the mild keratoconus group, the keratometric measurements were lower after treatment. Similar measurements were obtained in the moderate and severe keratoconus groups before and after treatment. In 1 patient, there was an increase of >1 diopter in the maximum keratometry value. No complications developed that would lead to vision loss.

Corneal collagen CXL treatment is known to be effective to a depth of two-thirds of the anterior corneal stroma. The results of this study showed that Holladay EKR measurements differed from SimK measurements, especially in cases of mild keratoconus. In addition to anterior corneal surface measurements, methods that can evaluate anterior and posterior surface curves could provide more accurate results in progression analysis.