Corneal confocal and topographical changes with use of rigid contact lens in keratoconus patients following collagen cross linking

Abstract

 

Purpose

 

To assess corneal confocal and topographical changes with use of rigid gas permeable contact lens (CL) in keratoconus (KC) patients following collagen cross linking (CXL).

 

Methods

 

A prospective comparative case series was performed in which three groups of eyes with primary KC were recruited: Group 1 (CXL-CL), 26 eyes which were newly fitted with CL three months after CXL; Group 2 (CXL-SL), 21 eyes with CXL done three months back, not fitted with CL; Group 3 (KC-CL), 25 eyes that had never undergone CXL and were newly fitted with CL. All eyes were followed up for six months after recruitment. Confoscan CS4 (NIDEK, Gamagori, Japan), Pentacam (Oculus, Lynnwood, WA, USA), Videokeratography (Atlas 9000, Carl Zeiss Meditec, Dublin, CA, USA) and Specular endothelial microscopy (EM 1000, Tomey corp, Nagoya, Japan) were performed in all eyes at baseline and at one; three and six months follow up.

 

Results

 

CXL-CL and KC-CL showed increase in the superficial epithelial cell size, decrease in basal epithelial cell density and decrease in the sub-basal nerve plexus fibre count and branching count over follow up; whereas CXL-SL showed decrease in superficial epithelial cell sizes, increase in basal epithelial density and regeneration of sub-basal nerve plexus (Table 1). CXL-CL had a regression of 0.93D in mean keratometry and 1.99D in maximum keratometry (P=0.00 in both); no significant keratometric flattening was seen in other groups (Figure 1). Uncorrected visual acuity (UCVA) improved only in CXL-CL from 0.97 ± 0.25 logarithm of the minimum angle of resolution (logMAR) units at baseline to logMAR 0.86 ± 0.30 at 6 months (P=0.00). CL users had better BCVA (P=0.00) than patients using spectacles. Over-refraction showed a myopic shift of 0.37D in CXL-CL (P=0.00), no significant change in over-refraction was seen in KC-CL.

 

Conclusions

 

CL use after CXL is associated with changes in corneal epithelium and delayed recovery of corneal sub-basal nerve plexus on confocal microscopy. It is also associated with significant cornea flattening and improvement in UCVA.

 

 

Confocal microscopy epithelial and sub-basal nerve plexus parameters.

 

 

Pentacam subtraction maps. a) CXL-CL patient showing central flattening after 6 months follow up. b) CXL-SL patient showing minimal change after 6 months follow up. c) KC-CL patient showing inferior and central steepening after 6 months follow up.

 

Keywords: 484 cornea: stroma and keratocytes • 477 contact lens • 596 microscopy: confocal/tunneling