Localized changes in stromal reflectivity after corneal collagen cross-linking observed with different imaging techniques.

PURPOSE To report changes observed in the corneal stroma using confocal microscopy and Scheimpflug imaging following epithelium-off collagen cross-linking (CXL) in cases of progressive keratoconus. METHODS Fifteen eyes of 14 patients were examined before and after CXL using slit-lamp biomicroscopy, Scheimpflug imaging, and confocal microscopy. A subset of patients also had optical coherence tomography imaging performed. RESULTS After CXL, confocal microscopy revealed a discrete layer of increased reflectivity in the mid to deep stroma. This layer was visible from as early as 1 week following treatment with patchy changes persisting until 12 months. This posterior reflective zone was found to consist of numerous linear or striate reflective structures (intrastromal striate reflections [ISRs]). ISRs were not observed in any of the eyes before the CXL procedure. High-resolution Scheimpflug and optical coherence tomography images also demonstrated a narrow zone of increased reflectivity at a similar depth. A layer-by-layer match was possible between the confocal and Scheimpflug images. The location of the ISR layer appears to correlate with a zone of increased reflectivity visible on postoperative slit-lamp examinations. CONCLUSION Altered stromal reflectivity after CXL can be observed with modern diagnostic imaging technologies. These findings seem to correlate not only among the different devices but also with biomicroscopic observations and could potentially provide a non-invasive tool to monitor the cross-linking effect in individual corneas.