Corneal allograft rejection: has the time come for intravenous pulsed methylprednisolone? A debate

Case-control study of subconjunctival triamcinolone acetonide injection vs intravenous methylprednisolone pulse in the treatment of endothelial corneal allograft rejection

PURPOSE

To assess the safety and effectiveness of treating corneal endothelial rejection with a subconjunctival injection of 20 mg triamcinolone acetonide in combination with topical application of 1% prednisolone acetate, as compared to treatment with an intravenous pulse of 500 mg methylprednisolone in combination with topical application of 1% prednisolone acetate.

METHODS

A case-controlled study including a literature review was performed. Patients who presented with an initial episode of corneal endothelial rejection were treated with subconjunctival injection of 20 mg triamcinolone in combination with topically applied 1% prednisolone and were retrospectively matched for age and diagnosis to patients who received a single intravenous injection of 500 mg methylprednisolone in combination with topical 1% prednisolone. Patients were analysed regarding reversion of the rejection episode, intraocular pressure, and visual acuity after 1 year.

RESULTS

Overall, the triamcinolone group had a better outcome regarding reversion of corneal transplant rejection (P=0.025), with 15 of 16 patients in the triamcinolone group having clear grafts, compared to only 10 of 16 patients in the methylprednisolone group. Intraocular pressure (IOP) was increased in both groups at day 30 (P=0.002), although there was no statistically significant difference in IOP between the groups (P=0.433). Visual acuity improved in both groups after 1 year (P=0.049), although slightly more improvement was observed in the triamcinolone group (P=0.002).

CONCLUSIONS

The results observed in this case-controlled study suggest that the use of subconjunctival triamcinolone acetonide may benefit patients with corneal transplant rejection.

The potential of antibody-based immunosuppressive agents for corneal transplantation

Corneal transplantation is a sight-restorative procedure but its success is limited by irreversible graft rejection, which accounts for up to 50 per cent of failures. The normal eye is an immune-privileged site. Multiple mechanisms maintain ocular privilege, including the blood-eye barrier, the lack of blood vessels and lymphatics in the normal cornea, the relative paucity of mature antigen-presenting cells in the central cornea, the presence of immunomodulatory factors in ocular fluids, and the constitutive expressive of CD95L (Fas ligand) within the eye. However, privilege can be eroded by the sequelae of inflammation and neovascularization. Corneal graft rejection in humans is currently suppressed with topical glucocorticosteroids, which are moderately effective. Systemically administered immunosuppressive therapy is of limited efficacy and may be accompanied by unacceptable morbidity. Alternative therapies are needed to improve outcomes. Corneal graft rejection is primarily a cell-mediated response controlled by the CD4+ T cell, and thus CD4 and costimulatory molecule blockade are appealing targets for new therapeutic interventions. A number of monoclonal antibodies have shown promise as immunosuppressants to prolong corneal graft survival in experimental animal models, and may eventually prove to be useful adjuncts to corticosteroids.