Histopathological findings after intracorneal ring segment implantation in keratoconic human corneas

Abstract

Intacs induced keratocyte apoptosis, probably through a switch to a collagenous synthetic phenotype. Although histological changes seem to be entirely reversible after implant removal, longer follow-up is necessary to determine whether they accelerate corneal thinning and keratoconus progression via apoptosis and release of metalloprotease.

Clinical and pathological effects of different acrylic intracorneal ring segments in corneal additive surgery

“…Histologically, several findings underline the biocompatibility of both groups, since there was no evidence of an inflammatory response at 30 and 90 days. All the samples showed hypoplasia of the epithelium over the segments and an increased keratocyte density at the edges of the rings, these findings being in agreement with previous works [14,15]. Several studies reported that the deposits observed on biomicroscopic examination consist of intracellular lipid accumulations and new collagen formation.…”

“…Currently, intracorneal ring segments are manufactured from PMMA, since different in vivo biocompatibility studies have showed a low rejection rate and acceptable predictability [11,30]. However, other studies described intrastromal deposits in the lamellar channel around the ring [14,31] and a decrease of the keratocyte density above and below the ring [15] as common clinical and histological findings, respectively. Also, anterior stromal aseptic necrosis, infiltrative keratitis or stromal thinning was reported [32][33][34].…”

“…Samini et al reported [15] a decrease in keratocyte density above and below the segment. In the PMMA group a decrease of keratocyte density was detected in the anterior stroma over the implant; however, this finding was detected in a lesser degree in the MMA/EHA groups.…”

“…However, this is a rigid and hard material that differs from the composition of the cornea; it shows different clinical and histological complications and its stability is difficult to predict [12,13]. Several studies of PMMA intracorneal rings described an extracellular intrastromal deposit in the lamellar channel around the implant [14] and a decrease of the keratocyte density anterior to the implant [15] as common clinical and histological findings respectively. Therefore, in this paper we assessed the potential use of hydrophobic acrylic copolymers as a new material for intracorneal rings based on the fact that these copolymers present a high longterm biostability and might be more biocompatible than PMMA, and it has been verified that the flexibility of the macromolecular chains could be precisely controlled.…”

Corneal Cross-linking in Combination with Intracorneal Ring Segments

“…This theory is supported by a publication showing that the keratocyte density in the anterior part of the stroma above the rings, decreased dramatically after ICRS insertion. 18 The same phenomenon was observed with CXL during the initial 6 months postoperatively, in the first anterior half of the cornea treated. 19 Several studies have evaluated the rational for performing the ICRS implantation and collagen crosslinking the same day.…”