Why Is The Cornea Often Much Thinner Than Expected After Dmek? – A Retrospective Review And Discussion Of The Clinical Implications

DMEK is effective in surgically treating endothelial dysfunction, with visual improvement following oedema resolution. It has been our observation that post-operative DMEK corneas are often much thinner than anticipated. We wished to review our recent cases and discuss potential explanations and implications.

This is a retrospective case series of consecutive patients who have undergone DMEK at Gartnavel General Hospital in Glasgow, Scotland. 

Retrospective case-note review of 50 consecutive DMEK patients, including demographics and serial ultrasound central corneal thickness (CCT) measurements.

63 eyes from 50 patients were identified (29 male, 21 female; median age 74 (range 34-87)). 85.7% (54/63) had Fuch’s endothelial dystrophy (32 phaco/DMEK; 31 DMEK alone). 

Mean preoperative CCT was 684µm (median 670um, range 582-934um), significantly reduced at 3 months postoperatively by 22.4% (524µm; median 523um; 404-801um) and maintained by 6 months 26.3%. Mean CCT was significantly lower than expected (524.3µm vs 540µm; p=0.04 (one sided t-test)), with 60% under 540µm and 32% less than 500µm.

Using a linear regression model no association was found between 3 month CCT and donor cell count (p=0.49; median 2600cells/mm² (2200-3600)), or age of donor (p=0.87; median 71 (49-88)).

15.9% of eyes required topical ocular hypotensives at 6 months.

Approximately one-third of our cases resulted in sub-500um corneal thickness following DMEK. This phenomenon is not explainable solely due to a normalization of anatomy (Descemet/endothelial pump, corneal dehydration and epithelial re-modelling), but likely related to stromal atrophy and keratocyte death. While histo-pathological research is required to confirm these findings, this awareness has clinical implications for IOP measurements and subsequent management in DMEK patients.