Scheimpflug Corneal Densitometry Changes After the Intrastromal Corneal Ring Segment Implantation

Purpose: To investigate the changes in corneal backward scattering using Scheimpflug tomography (densitometry) 6 months after intrastromal corneal ring segments (Keraring) implant for keratoconus and to correlate with clinical results. Methods: Along with standard ophthalmic examination, Scheimpflug tomography using Pentacam HR was performed to document corneal densitometry and corneal shape. A densitometry map was displayed using grayscale units (GSUs) ranging from 0 to 100 (minimum to maximum light scattering) in 4 concentric annuluses: central 2-, 2- to 6-, 6- to 10-, 10- to 12-, and total 12-mm corneal diameter and at 3 different depths: anterior 120 mu m, posterior 60 mu m, middle (varying accordingly to the total thickness), and total thickness. Results: The changes in mean corneal densitometry values for anterior, central, and posterior layers were 3.82 +/- 3.13, 2.70 +/- 1.78, and 1.68 +/- 1.52 GSU, respectively, and for annuluses of 0 to 2, 2 to 6, 6 to 10, and 10 to 12 mm were 2.96 +/- 2.60, 4.53 +/- 2.28, 2.09 +/- 1.74, and 0.45 +/- 3.93 GSU, respectively. The mean values increased for all corneal layers (P< 0.05), except in the peripheral 10- to 12-mm annulus (P> 0.05). The highest increase was in the annulus 2 to 6 mm of the anterior layer (5.72 +/- 3.70 GSU). Changes in the mean densitometry showed a significant correlation with the mean of average keratometry changes only for the front corneal surface and changes in the Q-values for both corneal surfaces in the 2- to 6-mm annulus for all layers. Conclusions: Significant increase in the corneal densitometry mainly in the anterior 2- to 6-mm annulus of the cornea is associated with the position of the ring segment implant. More studies are needed to elucidate the relevance of such findings.