Clinical, Refractive and Histological Reversibility of Corneal Additive Surgery in Deep Stroma in an Animal Model

ABSTRACT

Purpose: The aim was to evaluate the reversibility of the clinical and histological changes induced in the corneas of an animal model after removing an intracorneal ring segment (ICRS).

Methods: Surgery for this study was performed in 38 eyes of an experimental animal model (Gallus domesticus) for ICRS surgery (Ferrara technique). The animals without complications were randomized to two groups; in all of them, 1 segment was implanted in each eye and later removed at different times (1 and 3 months after implantation). In each group, after explantation, corneas were processed at different times for histological analysis with hematoxylin and eosin (H&E) stain and electronic microscopy. The refractive state of the eyes was also measured.

Results: In corneas without complications (88.23%), explantation was performed correctly. During the first few days, around the area where the ICRS was implanted we observed deposits of cells and a moderate degree of corneal opacity (haze). These signs decreased progressively without disappearing completely. Histologically, at 7 days, we observed hyperplasia and abnormal arrangement of collagen fibers. Later, these findings also decreased in both groups, albeit at a faster rate in group 1. Minimal changes were observed in electron microscopy up to the end of the study in both groups. Preoperative refractive state was achieved at 1 month after explantation in both groups.

Conclusions: ICRS can safely be explanted from the cornea. Refractive reversibility was achieved at 1 month after explantation. However, the clinical and histological findings after ICRS explantation depend on the time from implantation to explantation.

KEYWORDS:

• Additive surgery
• corneal wound healing
• intrastromal corneal ring segments
• keratoconus
• reversibility

Acknowledgments

We would like to thank Dr Angel García Barcia, Félix Gómez and Juanjo Arribas for caring for the animals used in this study. Ferrara Rings and AJL Ophthalmics provided both PMMA segments and surgical instruments. We would like to thanks Manuel Avellla and Luis Santiago as technical assistance from the Microscopy department of the University of Valladolid for the electron microscopy images. We would also like to thank Dr Alfonso and the staff of SECOIR (Spanish Society of Implant-Refractive Ocular Surgery) for their help during the closing stages of this study. We also thank Carmina Sanchis and Laura López Giménez from MSC for her advice on methodology. This work was supported by the CENIT-CeyeC (Customized Eye Care Technology) program, and also by profit cit-300100-2007-50 “Desarrollo de nuevos implantes intracorneales para la corrección de ametropias y tratamiento de ectasias corneales”.

Declaration of interests

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper. All authors certify that they have no affiliations with or involvement in any organization or entity with any financial interest (such as honoraria; educational grants; participation in speakers’ bureaus; membership, employment, consultancies, stock ownership, or other equity interest; and expert testimony or patent-licensing arrangements), or non-financial interest (such as personal or professional relationships, affiliations, knowledge or beliefs) in the subject matter or materials discussed in this manuscript.