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In the ongoing debate over which endothelial keratoplasty procedure corneal surgeons should perform, Massimo Busin MD is taking the middle ground.

At the 5th EuCornea Congress in London, UK, Dr Busin advocated ultra-thin DSAEK (UT-DSAEK) for its ability to provide the best of DSAEK (descemet stripping automated endothelial keratoplasty) and DMEK (descemet membrane endothelial keratoplasty).

“In medio stat virtus – in the middle stands virtue,” said Dr Busin, quoting Aristotle and Horace. “UT-DSAEK shares DMEK's advantages over conventional DSAEK of faster visual recovery, better visual outcomes, and reduced immunologic rejection risk. At the same time, UT-DSAEK is simpler surgery than DMEK and minimises all types of postoperative complications.”

According to Dr Busin, consistently better quality graft tissue is the reason why UT-DSAEK provides better vision outcomes than conventional DSAEK. He explained that central thickness is not the only parameter that matters.

“The simple value of central thickness is not sufficient to evaluate the ‘quality’ of a DSAEK graft, which is why a DSAEK lenticule with a 'good' stromal component is perfectly compatible with 20/20 vision, probably regardless of its central thickness. Surface regularity and planar shape must also be taken into account,” said Dr Busin, professor of ophthalmology, Villa Igea Hospital, Forli, Italy.

“Therefore, corneal surgeons advocating DMEK for its better vision outcomes should not be comparing DMEK against DSAEK in general, but against ‘good DSAEK’, which is DSAEK using a graft with a good quality
stromal component.”

Dr Busin undertook the comparison between DMEK and ‘good DSAEK’ using data from his own UT-DSAEK series.

The first issue he considered was best spectacle-corrected visual acuity (BSCVA) at one year among eyes with 6/6 potential. He reported that in his UT-DSAEK cohort, 39 per cent of eyes achieved BSCVA ≥6/6, 71 per cent saw ≥6/7.5, and 95 per cent achieved ≥6/9.

Proportions of eyes achieving those BSCVA thresholds after DMEK were 41 per cent, 80 per cent and 98 per cent, respectively. Endothelial cell loss rates in the UT-DSAEK and DMEK groups were similar as well (34 per cent and 36 per
cent, respectively).

Presenting data on speed of visual recovery, Dr Busin showed that UT-DSAEK had a clear advantage over DSAEK. Although mean BSCVA levels at three and six months were slightly better after DMEK than UT-DSAEK, Dr Busin pointed out that mean preoperative logMAR BSCVA was also better in the DMEK versus UT-DSAEK group, 0.51 versus 0.76.

Compared to the same DMEK group, a better-matched UT-DSAEK cohort (phakic eyes with an average preoperative BSCVA of 0.55 in logMAR units) achieved better levels of vision in a shorter time.

“I am convinced that it is the preoperative condition of the patient and not a thin layer of stroma that makes a difference in vision outcomes,” Dr Busin said.

The outcome of Dr Busin’s UT-DSAEK series also reduces concern about increased risk of immunologic rejection with DSAEK versus DMEK, although he emphasised the importance of an appropriate corticosteroid treatment regimen postoperatively.

He reported that the Kaplan-Meier cumulative probability of immunologic rejection was 2.5 per cent after UT-DSAEK at one and two years, one per cent for DMEK at both follow-up intervals, and six per cent and 10 per cent at one and two years, respectively, post-DSAEK of the conventional type.

“Numerically, the rejection rate for UT-DSAEK is twofold higher than DMEK, but the difference represents just one more case of rejection per 100 patients per year. And, if we consider other possible complications, including the need for air re-injection, primary failure and tissue loss, then UT-DSAEK compares quite well against DMEK,” said Dr Busin.

In his UT-DSAEK series with Fuchs or pseudophakic bullous keratopathy, three per cent of eyes needed air re-injection, while both primary failure and tissue loss occurred at a rate of just one per cent. Data from DMEK series show air re-injection rates between 17 per cent and 77 per cent, a nine per cent primary failure rate and a tissue loss rate of up to 13 per cent.

Dr Busin explained that different techniques could be used to harvest the UT-DSAEK graft. Initially, he used a double pass technique with a pivoting microkeratome.

“Accurate thickness could not be achieved after a single pass technique because of the instrument’s tendency to cut deeper at the beginning of the dissection. To compensate for that effect, a second pass was performed in the opposite direction of the first,” he explained.

Now, with the introduction of new linear microkeratomes that cut at a uniform depth throughout the dissection, Dr Busin prepares UT-DSAEK grafts with a single pass technique.


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