Histologic Evaluation of Corneal Stroma in Rabbits After Intrastromal Corneal Ring Implantation

Abstract

Tissue response to these corneal inserts includes keratocyte activation, intracellular lipid accumulation, and new collagen formation. Our histologic findings suggest that these deposit formations are not lipofuscin accumulations.

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.…”

“…Several studies reported that the deposits observed on biomicroscopic examination consist of intracellular lipid accumulations and new collagen formation. These deposits were observed in the edges of the segment where increased cell density was present, being a connection between the deposits and the keratocyte activation stimulated by the wound-healing response [14]. The presence of myofibroblast in this zone suggested an active wound-healing process.…”

“…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].…”

“…Previous studies have explored the effects of intracorneal ring segments on a variety of alternative animal models, selecting rabbits as the animal more suitable for evaluating the safety of the intracorneal rings effects [14,24,43]. However, in this study we chose the hen as the experimental animal since, histologically, its cornea resembles human cornea in size and structure: it is thinnest centrally and it thickens toward the periphery.…”

“…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.…”