Corneal transplantation by ultra-thin DSAEK: thinner grafts, better vision?

Objective(s) / research question(s):

Corneal transplantation improves vision and quality of life in patients with corneal disease. Currently, the predominant technique for patients with corneal endothelial disease is Descemet Stripping Automated Endothelial Keratoplasty (DSAEK), in which only the posterior side of the cornea is transplanted. However, visual rehabilitation after DSAEK may be variable. In ultra-thin DSAEK, the donor tissue is thinner, which results in better visual outcomes and, consequently, a better quality of life. The objective of this project is to assess the effects and costs of ultra-thin DSAEK vs. standard DSAEK in order to determine whether the new technique is effective and cost-effective over the standard technique.



Study design:

Multicenter randomized clinical trial.



Study population(s) / datasets:

The study population will consist of 66 patients with irreversible corneal endothelial failure due to Fuchs’ endothelial dystrophy who need corneal transplantation.



Intervention:

The intervention consists of the performance of standard DSAEK (grafts of approximately 200 microns) or ultra-thin DSAEK (grafts of approximately 100 microns).



Outcome measures:

Primary outcome measure is best corrected visual acuity 12 months postoperatively. Secondary outcome measures are contrast acuity, astigmatism, quality of vision, endothelial cell loss, incidence of graft rejection, primary graft failure, cornea donor loss due to preparation, and generic and vision-related quality of life.



Sample size calculation / data analysis:

Sample size calculation for the outcome measure best corrected visual acuity 12 months postoperatively is based on an expected mean

difference in BSCVA of 0.15 LogMAR between DSAEK and UT-DSAEK with a standard deviation of 0.2

LogMAR. Assuming alpha of 0.05 and power of 80% yields a sample size of 58 patients. Accounting for

an anticipated dropout rate of 15%, 33 patients need to be included in both the experimental and the control group. Data analysis will be performed using point estimates and 95% confidence intervals.

Economic evaluation: An economic evaluation will be performed from a societal and a health care perspective with a time horizon of 12 months. Incremental cost-effectiveness ratios will be calculated. Standard sensitivity analyses and bootstrap analysis will be performed to investigate the uncertainty surrounding the cost-effectiveness ratios.



Time schedule:

Patients will be included during the first 9 months of the study. After a follow-up of 12 months, data analysis will be performed in the final 3 months.

In patients with irreversible corneal endothelial failure, corneal transplantation is the only effective treatment. Currently, the predominant transplantation technique for patients with corneal endothelial disease is Descemet Stripping Automated Endothelial Keratoplasty (DSAEK) where a donor lamellar disk consisting of posterior stroma, Descemet’s membrane and endothelium is dissected with the use of a microkeratome. However, visual rehabilitation after DSAEK may be variable. Better visual outcomes are achieved by using Descemet Membrane Endothelial Keratoplasty (DMEK) in which a very thin disk of isolated donor Descemet’s membrane with endothelium is transplanted. Although DMEK results in better restoration of vision, the surgical technique is more demanding and may lead to higher levels of corneal donor loss and primary graft failure. A hybrid technology, ultra-thin DSAEK, is now available that combines the functional advantages of DMEK with the established safety of DSAEK. In ultra-thin DSAEK, the thickness of the lamellar grafts is 100 microns vs. 200 microns in standard DSAEK grafts. Early clinical studies with ultra-thin DSAEK show promising results, but preparation of the pre-cut ultrathin lamellar disks involves the use of a mechanical microkeratome to make a second cut or a femtosecond laser microkeratome which will generate additional costs per patient.

A randomized clinical trial will evaluate ultra-thin DSAEK as compared to standard DSAEK to demonstrate whether this innovation is effective and cost-effective.

Measurements are performed before and 3, 6 and 12 months after the intervention

The intervention consists of the performance of standard DSAEK or ultra-thin DSAEK.