Morphological characterization and clinical effects of stromal alterations after intracorneal ring segment implantation in keratoconus

Abstract

Purpose To analyze the histological and (ultra)structural stromal tissue changes after femtosecond (Fs) laser–assisted intra corneal ring segment (ICRS) implantation and their refractive and topographic efects in patients with keratoconus. Methods This monocentric retrospective case series included 15 consecutive patients with clinical peri-segmental lamellar channel deposits after treatment with Fs-ICRS implantation for keratoconus. The stromal changes were investigated using in vivo confocal microscopy. Two patients underwent a penetrating keratoplasty after the Fs-ICRS implantation; the explanted corneas were processed for histopathology and transmission electron microscopy (TEM). Refractive and topographic efects were investigated comparing the uncorrected (UDVA) and corrected (CDVA) distance visual acuity, spherical equivalent (SE), fat (K1), steep (K2), and steepest (Kmax) keratometry before and after detection of lamellar channel deposits. Results In vivo confocal microscopy revealed difuse linear and focal granular hyperrefective structures. Histologically, there was mild proliferation of fbroblasts and fbrosis. TEM demonstrated focal accumulations of degenerated keratocytes with cytoplasmic lipid inclusions. There were no signifcant changes for UDVA (Δ=0.0±0.2 logMAR; p=0.67), CDVA (Δ=0.0±0.1 logMAR; p=0.32), SE (Δ 0.1±0.9 D; p=0.22), K1 (Δ=0.3±1.0 D; p=0.28), K2 (Δ=0.1±0.9 D; p=0.51), and Kmax (Δ=0.3±1.5 D; p=0.17). Conclusions Two types of structural stromal changes were identifed: (1) difuse peri-segmental fbrosis and (2) lamellar channel deposits. These structural changes showed no evidence of a relevant refractive or topographic efect.