Surgery after corneal grafts

Abstract

There is one available donor per 70 patients so we need to identify those whose vision would benefit from corneal transplantation and minimize risks that could jeopardize corneal graft survival possibility1.The two leading causes of graft failure post Penetrating Keratoplasty (PKP) are graft rejection and secondary glaucoma development. The existence of preoperative glaucoma increases two to three times the chances of graft rejections in any corneal transplantation2,3. The 10‐year Cornea Donor Study also confirmed that pre‐existing glaucoma is a risk factor for graft failure4. The 3‐year graft survival rate has been shown to be 71% in patients with preop glaucoma and 89% in patients without preop glaucoma5.In cases following Descemet Striping Endothelial Keratoplasty (DSAEK), Ocular Hypertension (OHT) ranges in otherwise healthy eyes from 29 to 47% and increases to 43 to 54% in cases with pre‐existing glaucoma or high‐risk eyes. Glaucoma can be presented in up to 15% in post‐DSAEK cases which increases twice the relative risk of rejection. Concurrent gonio‐synechiolysis is considered an additional risk factor whereas 18.6% of high IOP cases considered as secondary to steroid administration. Acute raise in IOP can be attributed in pupillary block at an estimated rate of 13%6,7.In cases of Descemet Membrane Endothelial Keratoplasty (DMEK) OHT or intraocular pressure (IOP) elevation is presented to 6.5 up to 11.1% and de novo glaucoma can be found from 2.8 to 6.5%, whereas progression of pre‐existing glaucoma is less than 2.5%8. In cases with simultaneous DMEK and cataract surgery there is greater likelihood of post‐op OHT or glaucoma. In DMEK cases the early postoperative increase in pressure is usually due to a combination of anterior (inferior) and posterior (superior) pupillary blocks when patient is sitting upright9.The late post‐DMEK IOP increase is attributed to Blockage of TM by inflammatory cells, PAS formation or steroid use. However, steroid‐induced glaucoma post‐DMEK is not as common as that in post‐PKP or post‐DSAEK due to the shortest steroid regime post‐DMEK cases. Treatment methods include medical treatment, trabeculectomy or tubes. Some cases with Xen®10 and Micropulse cyclodidode11 laser have been reported in endothelial cases, however with little degree of evidence.Controversy still exists to which surgical procedure is the best for graft survival and IOP control, as well as when is the best time of the surgery in patients with pre‐existing glaucoma, before, simultaneously or after, and if needed, graft surgery. Certainly a “try not to create glaucoma” strategy needs always to be followed by not producing additional iatrogenic risk factors with improved technique(s) and by respecting the tissue(s).