DMEK graft detachment

Graft detachment is one of the most common complications after Descemet membrane endothelial keratoplasty (DMEK), but in determining the best approach to management, corneal surgeons must use the proper technology to make the diagnosis and recognise that not all graft detachments are the same, said Isabel Dapena MD, PhD, at the 4th EuCornea Congress in Amsterdam, The Netherlands. “Remember that the presence of corneal oedema does not always mean there is a graft detachment as patients may have an attached graft with delayed corneal clearance that will spontaneously resolve. And not all graft detachments require secondary surgery,” said Dr Dapena, cornea specialist, Melles Cornea Clinic, Netherlands Institute for Innovative Ocular Surgery, Rotterdam, The Netherlands. “If vision is not affected, the detachment is not clinically significant and it does not require surgical repair.” Although by definition, a graft detachment is lack of adherence between the Descemet graft and the posterior stroma of the host, the extent of the detachment generally predicts whether the detachment is clinically significant and will require intervention. Small graft detachments, defined as those involving no more than one-third of the graft surface area, are generally benign and can be left alone. These grafts usually reattach spontaneously and the cornea clears without any additional treatment, Dr Dapena said. In contrast, graft detachments involving more than one-third of the graft surface area are generally clinically significant, but do not always require intervention. This group of detachments is comprised of large partial detachments, upside down grafts or complete detachments with a free-floating Descemet roll in the anterior chamber. “It is important to be discriminative about the need for intervention in an eye with a larger detachment. In some large partial detachment cases, the cornea clears by itself and the patient achieves very good visual acuity,” Dr Dapena said. Dr Dapena recommended the use of anterior segment optical coherence tomography (AS-OCT) to diagnose graft detachment as it enables the surgeon to distinguish between true detachment and delayed corneal clearance. Slit-lamp photographs of the same transplanted cornea 3 (A, B), 8 (C, D), and 12 weeks (E, F) after DMEK. Notice that the oedema (yellow arrows) overlying the detachment (white arrows) resolves with time and that stromal thinning with coincident corneal clearance progresses from the periphery toward the corneal centre (green arrows) [Image reprinted with permission of Elsevier, Am J Ophthalmol. 2011;152:543-555. Dirisamer M, Dapena I, Ham L, van Dijk K, Oganes O, Frank LE, van der Wees J, Melles GR. Patterns of corneal endothelialization and corneal clearance after Descemet membrane endothelial keratoplasty for Fuchs’ endothelial dystrophy.] She noted that slit lamp biomicroscopy does not always allow a conclusive diagnosis, and the presence of corneal oedema can obscure visualisation of a graft detachment through Pentacam imaging (Oculus). “Importantly, the findings from AS-OCT can also allow us to predict if the detachment will reattach, which is important for determining what treatment to do,” Dr Dapena added. “In a published study [Yeh RY, et al. Ophthalmology 2013;120(2):240-5], we reported that about 30 per cent of patients had some kind of graft detachment at one week. However, many of those resolved with time, which we believe was the result of some kind of healing process. We also found that the one-hour AS-OCT was the most important aid for predicting whether a graft that was detached at one week remained detached in the longer term.” If a detachment is seen on AS-OCT at one week after surgery and was also visible in the image taken after one hour, surgeons should assume that spontaneous reattachment is unlikely. In these cases, the next step is to consider whether the detachment is visually significant. If it is not, no intervention is required. However, even if the patient has decreased vision, it is worth waiting a few weeks to see if there is spontaneous corneal clearance/reattachment, Dr Dapena said. If there is no improvement, intervention (rebubbling or retransplantation) is indicated. “Remember not to rush into a rebubbling. However, if you come to the decision that rebubbling is necessary, then it is better to do it early or not at all.” Dr Dapena also presented information on the rate of DMEK graft detachments and their management from a series of 300 eyes operated on at the Melles Cornea Clinic. At six months after surgery, detachment involving less than one-third of the graft area was identified in 34 eyes (11 per cent) and 44 eyes (15 per cent) had a larger, clinically significant graft detachment. However, when the latter rate was analysed with eyes divided into two groups representing the first 100 eyes and the subsequent 200 cases, it was clear that increasing surgeon experience with DMEK and the opportunity to refine the surgical protocol led to an important reduction in the detachment rate. “We saw a clear learning curve effect with a 25 per cent rate of larger graft detachments in the first 100 cases and a decline in the rate to just nine per cent after the learning curve period,” Dr Dapena explained. None of the eyes with a small detachment needed any treatment. Among eyes with a larger detachment within the initial 100 cases, rates of rebubbling and retransplantation were about four per cent and five per cent, respectively. In a paper published in 2012, Dr Dapena and colleagues describe the incidence and type of graft detachments observed in the first 150 consecutive DMEK cases, their management and strategies for prevention [Dirisamer M, et al. Arch Ophthalmol. 2012;130(3):280-91]. Isabel Dapena: dapena@niios.com