Penetrating keratoplasty and graft rejection in eight horses.

This research aimed to observe the outcomes of a surgical procedure known as penetrating keratoplasty in horses. The goal was to compare different types of preserved corneal grafts used in the procedure, and analyse the reactions to these grafts in terms of immune responses in tear film. Despite different treatment methods, all grafts were partially rejected.

Research Approaches and Procedures

• This study involved eight horses with normal vision as subjects. The scientists sought to analyze the outcomes of penetrating keratoplasty (PK) using varying types of preserved corneal grafts—freshly collected from donors, frozen, or preserved in tissue culture mediums.
• The procedures for taking the graft, cornea storage methods, PK surgery, aftercare treatments and any related complications were documented and analyzed in the research.
• The researchers tracked the horses’ recovery progress closely, with an average follow-up period of 286 days.
• Another important part of the study involved monitoring the immunological response within the tear film over time. This involved taking regular samples of the tear film before and at different stages after the surgery. The samples were tested with an ELISA (enzyme-linked immunosorbent assay) to measure levels of three types of immunoglobulins (Ig)—IgA, IgG, and IgM.

Research Findings

• The study revealed that regardless of the type of cornea graft used, all animals showed some degree of rejection. There was no difference in healing outcomes or appearances among the various graft types.
• The low risk of graft failure was associated with clear corneas before surgery. This indicated that both fresh and preserved corneal tissues were able to provide healthy endothelium, an essential layer of the cornea.
• However, in all horses, studies post-surgery showed that the graft did not remain clear.
• The ELISA tests showed the presence of all three types of immunoglobulins from early after surgery. The IgG level was much lower than the levels of the other two immunoglobulins, but showed a consistently stable baseline over time. The IgA and IgM levels, however, were quite variable and showed unique patterns in each individual eye.