Lamellar-based keratoplasty procedures

With corneal transplant surgery shifting towards more lamellar-based keratoplasty procedures, surgeons need to be aware of a host of early postoperative complications that may potentially compromise long-term graft survival and visual function, according to Frank Larkin FRCS, FRCOphth. “The complications that modern corneal transplant surgeons are seeing today are quite different to those that surgeons were seeing in the era before lamellar surgery. That is why we need strategies to be able to deal with these immediate postoperative problems and prevent them from undermining long-term graft survival and visual outcomes,” he said. Dr Larkin, Consultant Ophthalmic Surgeon at Moorfields Eye Hospital, London, UK, highlighted a fundamental difference between complications associated with penetrating keratoplasty (PK) compared to lamellar procedures such as deep anterior lamellar keratoplasty (DALK), Descemet’s stripping endothelial keratoplasty (DSEK), and Descemet’s membrane endothelial keratoplasty (DMEK). “With PK, we know that the complications of most importance for transplant survival and function such as graft rejection, glaucoma, and refractive errors, usually occur much later after the surgery. In contrast, those patients having lamellar surgery may experience complications that manifest very early following surgery, often within the first week, which will have a very significant impact on the fate of the graft and long-term outcome,” he said. Complications to watch for in PK procedures include Uretts-Zavalia syndrome, epithelial toxicity and persistent epithelial defects, atopic sclerokeratitis and recurrent infection, said Dr Larkin. Uretts-Zavalia syndrome will usually manifest through an acute intraocular pressure rises within hours of surgery. “The syndrome gives rise to long-term problems such as fixed mydriasis, chronic low grade uveitis, and secondary cataract,” he said. Epithelial toxicity and persistent epithelial defects are also easily overlooked, warned Dr Larkin. “Prior to the surgery patients with uncertain limbus function, limbus disease after a chemical burn or long-term contact lens wearers with epitheliopathy are the ones most at risk and the problems can be significant if there is secondary infection present,” he said. Atopic sclerokeratitis is very rare and is only seen in genuinely atopic patients, said Dr Larkin. “These patients all have atopic dermatitis with keratoconus and they usually present several weeks after the surgery with pan anterior ocular inflammation. It is not donor specific inflammation and it is not graft rejection. Management is systemic immunosuppression, and if I suspect the risk is high, I will try to treat prophylactically with oral prednisolone for 3 weeks post-graft. If they need to continue steroids for more than a month, cyclosporine is a better option for patients who need more long-term management,” he said. Recurrent infection in PK is particularly difficult to manage in the absence of a preoperative microbial diagnosis, said Dr Larkin. “In those whom the pathogen is identified they need to be treated for as long as you can afford to wait before surgery with appropriate anti-microbial agents. If the diagnosis is after the graft, then culture the excised cornea and continue antimicrobial treatment. Management includes scrapings for polymerase chain reaction (PCR) analysis, culture, biopsy and confocal microscopy,” he said. DALK COMPLICATIONS Early DALK complications include double anterior chamber or interface infection. For the former, prevention is intraoperative conversion to PK if a large tear is present and air bubble tamponade with or without iridotomy in the case of a small tear, said Dr Larkin. For interface infection, treatment is usually a graft lift followed by amikacin and vancomycin irrigation followed by topical intensive moxifloxacin application. Early post-DSEK complications to watch for are partial graft detachment or dislocation, acute glaucoma, intraocular infection and haemorrhage. “Detachments almost all extend to dislocation. Management is re-bubble without delay, preferably while the graft is partially attached. This is usually successful and has no impact on graft function or survival,” said Dr Larkin. In acute glaucoma, which manifests 24 to 36 hours post-DSEK, the goal should be to lower the IOP urgently, said Dr Larkin. Possible complications post-DMEK could include partial graft detachment or dislocation, inverted graft and pupil block glaucoma, he added. Primary graft failure with no evidence of endothelial function within one month of transplant may also be a problem post DSEK and post DMEK, said Dr Larkin. “Definition of graft failure post endothelial keratoplasty is difficult on account of possible unrecognised surgical complications such as inverted graft or surgical trauma to the endothelium. A better definition would be no evidence of endothelial function within one month of transplant in the absence of surgical complications,” he concluded. Frank Larkin: frank.larkin@moorfields.nhs.uk;  f.larkin@ucl.ac.uk