Two surgical techniques for corneal transplant (replacing the clear part of the eye with donor tissue)

What is the aim of this review?
The aim of this Cochrane Review was to compare two different ways of doing corneal transplant surgery: Descemet’s membrane endothelial keratoplasty (DMEK) and Descemet’s stripping automated endothelial keratoplasty (DSAEK). Cochrane Review authors collected and analysed all relevant studies to answer this question and found four studies.

Key messages
DMEK may result in better vision compared with DSAEK. DMEK may be associated with more complications but these complications do not occur often and can be managed without further surgery.

What was studied in the review?
The cornea is the clear (transparent) front part of the eye. In some conditions, for example, Fuch's endothelial dystrophy, the cells that line the inside of the cornea (endothelium) stop working so well. This can lead to cloudy vision. Doctors can restore vision by doing a corneal transplant which means replacing the corneal tissue with donor tissue. When the endothelium only is replaced this is known as 'Descemet’s membrane endothelial keratoplasty' or DMEK. An alternative corneal transplant is to replace the endothelium and the next layer of tissue in the cornea as well. This is known as 'Descemet’s stripping automated endothelial keratoplasty' or DSAEK.

Cochrane Review authors aimed to find out whether vision is better after DMEK or DSAEK, and how the techniques compare with respect to surgical complications.

What are the main results of the review?
The Cochrane Review authors found four studies. These studies included people who had DSAEK in their first eye to receive a corneal transplant followed by DMEK in their second eye to have a transplant. The studies were from Canada, Germany, India and the USA. None of the studies were supported by sponsors with a commercial interest.

The Cochrane Review authors judged the evidence to be low- or very low-certainty because there may be differences between the first eye and second eye surgeries (other than DMEK or DSAEK) and, in some cases, the data were limited or inconsistent.

The results were:

• DMEK may result in better vision compared with DSAEK (low-certainty evidence). This difference is equivalent to reading one or two lines more on a vision chart.

• None of the people taking part in these studies had severe vision loss after surgery. Severe vision loss was defined as vision worse than 6/60 or 20/200. There were not enough people enrolled in these studies to measure reliably this infrequent outcome (very low-certainty evidence)..

• The studies measured how many cells there were in the endothelium after surgery but found inconsistent results (very low-certainty evidence).

• Almost everyone taking part in the studies had good graft survival, with very few graft rejections and no graft failures. There were not enough people enrolled in these studies to measure reliably these infrequent outcomes (very low-certainty evidence)..

• DMEK may be associated with more early surgical complications. Graft dislocation may happen in one or two out of 100 people with DSAEK and about five times more often with DMEK. This difference was not measured reliably and could be smaller or much larger (very low-certainty evidence). Graft dislocation occurs within days or weeks after surgery and is usually treated with an injection of air into the eye ('re-bubbling').

How up-to-date is this review?
Cochrane Review authors searched for studies that had been published up to August 2017.

Authors' conclusions: 

This review included studies conducted on people with corneal endothelium failure due to FED for whom both DMEK and DSAEK can be considered, and found low-certainty evidence that DMEK provides some advantage in terms of final BCVA, at the cost of more graft dislocations needing 're-bubbling' (very low-certainty of evidence).

Read the full abstract...
Background: 

Corneal endothelial transplantation has become the gold standard for the treatment of corneal endothelial dysfunctions, replacing full thickness transplantation, known as penetrating keratoplasty. Corneal endothelial transplantation has been described using two different techniques: Descemet’s membrane endothelial keratoplasty (DMEK) and Descemet’s stripping automated endothelial keratoplasty (DSAEK). Both are still performed worldwide.

Objectives: 

To compare the effectiveness and safety of Descemet's membrane endothelial keratoplasty (DMEK) versus Descemet's stripping automated endothelial keratoplasty (DSAEK) for the treatment of corneal endothelial failure in people with Fuch’s endothelial dystropy (FED) and pseudophakic bullous keratopathy (PBK).

Search strategy: 

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Trials Register) (2017, Issue 7); MEDLINE Ovid; Embase Ovid; LILACS BIREME; the ISRCTN registry; ClinicalTrials.gov and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP). The date of the search was 11 August 2017.

Selection criteria: 

We included randomised controlled trials (RCTs) and non-randomised paired, contralateral-eye studies in any setting where DMEK was compared with DSAEK to treat people with corneal endothelial failure.

Data collection and analysis: 

Two review authors independently screened the search results, assessed trial quality and extracted data using the standard methodological procedures expected by Cochrane. Our primary outcome was best corrected visual acuity (BCVA) measured in logarithm of the Minimum Angle of Resolution (logMAR). Secondary outcomes were endothelial cell count, graft rejection, primary graft failure and graft dislocation. We graded the risk of bias of non-randomised studies (NRSs) using ROBINS-I.

Main results: 

We did not identify any RCTs but found four non-randomised studies (NRSs) including 72 participants (144 eyes), who had received DSAEK in the first eye followed by DMEK in the fellow eye. All the studies included adult participants where there was evidence of FED and endothelial failure requiring a corneal transplant for the treatment of visual impairment. We did not find any studies that included PBK. The trials were published between 2011 and 2015, and we assessed them as high risk of bias due to potential unknown confounding factors since DSAEK preceded DMEK in all participants. Two studies reported results at 12 months, one at 6 months, and one between 6 and 24 months. At one year, using DMEK in cases of endothelial failure may result in better BCVA compared with DSAEK (mean difference (MD) -0.14, 95% confidence interval (CI) -0.18 to -0.10 logMAR, 4 studies, 140 eyes, low-certainty evidence). None of the participants had severe visual loss (BCVA of 1.0 logMAR or more; very low-certainty evidence). Regarding endothelial cell count data (4 studies, 134 eyes) it is hard to draw any conclusions since two studies suggested no difference and the other two reported that DMEK provides a higher cell density at one year (very low-certainty evidence). No primary graft failure and only one graft rejection were recorded over four studies (144 eyes) (very low-certainty evidence). The most common complications reported were graft dislocations, which were recorded in one or two out of 100 participants with DSAEK but were more common using DMEK, although this difference could not be precisely estimated (risk ratio (RR) 5.40, 95% CI 1.51 to 19.3; 4 studies, 144 eyes, very low-certainty evidence).

Share/Save