Descemetorhexis Without Endothelial Keratoplasty
Descemetorhexis Without Endothelial Keratoplasty (DWEK) is a proposed term to describe the surgical removal of Descemet membrane (DM) without subsequent endothelial transplantation, in the treatment of Fuchs Endothelial Corneal Dystrophy (FECD). Other used names include Descemet's stripping only (DSO), Descemet stripping without endothelial keratoplasty, descemetorhexis without grafting and descemetorhexis without graft placement.
While over the past years selective endothelial transplantation has replaced penetrating keratoplasty as the preferred technique to manage FECD (Descemet stripping endothelial keratoplasty [DSEK] and Descemet membrane endothelial keratoplasty [DMEK]), there are still issues with rejection (albeit reduced), postoperative complications (primary graft failure, graft dislocation) and tissue availability.
The concept of performing DWEK was based on several case reports of spontaneous resolution of corneal edema after iatrogenic (during intraocular surgery, after DSEK/DMEK graft detachment) and deliberate removal of DM in patients with FECD. As the sole presence of guttae contributes to intraocular light scatter, decrease in contrast sensitivity and visual acuity in these patients, the removal of central guttae could theoretically be a viable option in selected patients with FECD, reducing the need for corneal transplantation. Central cornea edema resolution is thought to occur secondary to migration and regeneration of peripheral endothelial cells. This potential for endothelial “rejuvenation” in FECD contrasts with bullous keratopathy, thought to be an endothelial depletion disease.
While the optimal patients characteristics for predicting favorable outcomes are not yet fully identified, careful patient selection is likely required in this treatment modality. The most adequate candidates appear to be patients with FECD with central focal edema and a clear peripheral cornea with densely populated peripheral endothelium.
The following criteria are adapted from the study by Moloney et al.
FECD diagnosed clinically and on confocal microscopy with the following characteristics:
- Presence of central guttae deemed to be the chief cause of visual symptoms (decreased visual acuity, contrast sensitivity, glare).
- Clear peripheral cornea with an endothelial cell count > 1000 cells/mm2 on confocal or specular microscopy.
- The patient is otherwise contemplating endothelial keratoplasty.
- Phakic or pseudophakic.
- Advanced corneal stroma edema (haze, bullae, DM folds).
- Peripheral endothelial cell count < 1000 cells/mm2.
- Presence of secondary corneal pathology.
- History of herpes simplex virus or cytomegalovirus keratitis.
This procedure can be done under local or general anesthesia and typical surgery time is around 6 minutes. Previous pupil dilation may provide a better red reflex and allow easier visualization of DM.
Under viscoelastic, a central circular 4 mm descemetorhexis is performed using a reverse Sinskey hook or a Foglat DM stripping hook followed by Utrata forceps or MST forceps. Care should be taken in peeling and not scraping DM, avoid engaging corneal stroma and to limit the size of the descemetorhexis. A recent recommended technique described as "two-flaps" uses smooth forceps to create a nick that creates two flaps of two clock hours. There is no need to inject air or gas in the anterior chamber at the time of the procedure.
The procedure can be done after standard phacoemulsification and insertion of a posterior chamber intraocular lens (a “triple-DWEK”).
Postoperative care should include topical antibiotic, steroid and hypertonic saline drops. Recent studies suggest the use of a topical Rho kinase inhibitor (Ripasudil) may improve endothelial proliferation and corneal clearance. There have been also attempts at using postoperative Netarsudil because of easier commercial availability.
In one of the original case series, DWEK provided corneal clearance in 14 of 17 eyes (82.4%), with mean time for resolution of corneal edema of around 3 months. The 3 eyes that failed to clear after 8 months underwent subsequent DMEK. In one case series, the use of topical Ripasudil as a salvage agent in 2 eyes resulted in complete corneal clearance , suggesting the possibility of a broader application for this surgery. A recent subsequent study of DWEK supplemented with Ripasudil resulted in clearing of 22/23 corneas at a mean time of 4.1 weeks. In this study, 21 out of 23 patinets were satisfied with the visual outcome. 
Other cases series and case reports have provided conflicting results. Bleyen et al reported poor results in combined DWEK with cataract surgery, with only 3 of 8 patients achieving corneal clarity. On the opposite hand, Borkar et al reported satisfactory results, with 10 of 13 eyes obtaining corneal clearance.
According to Borkar et al, cases can be classified as fast responders, responders, and slow responders if there is resolution of corneal edema with visible central endothelial mosaic by the first, third and after the third postoperative month, respectively. Cases with persistent corneal edema requiring endothelial keratoplasty were classified as nonresponders.
A small retrospective study comparing DMEK to DWEK in patients with mild to moderate Fuchs showed equivalent visual outcomes, with a prolonged time to recovery but fewer adverse events in DWEK patients .
There seems to be a trend toward better outcomes for smaller central descemetorhexis (4mm), while thicker central corneas and higher central endothelial cell counts are observed, although not universally, in nonresponding patients. Some authors have reported young age to be a positive prognostic factor in DWEK, but it is not consistently reported in the literature. Irregular astigmatism from deep stromal opacities at the margin of the descmetorhexis was reported in a series of patients, possibly from baring of central stroma. Concomitant cataract extraction and intraocular lens implantation do not seem to influence DWEK outcomes.
- Descemetorhexis decentration.
- Descemet membrane detachment. These cases can undergo a rebubble procedure.
- Posterior stromal opacities at the margin of the descemetorhexis from iatrogenic intraoperative stromal indentation, that can preclude endothelial cells migration.
- Abnormal corneal topography and irregular corneal astigmatism, that can be improved with rigid gas-permeable contact lens fitting. It is not currently known whether endothelial keratoplasty is useful in these cases.
- Persistent corneal edema. Nonresponders can undergo endothelial keratoplasty to achieve corneal clarity. Apart from Arbelaez, which had issues with DMEK detachments, successful DMEK and DSAEK procedures were described in these cases.
DWEK is still a controversial technique, as not all patients achieve lasting corneal clarity. Despite that, there is evidence that supports its use for select cases of FECD patients, providing a useful option for achieving corneal clearance for patients with visual symptoms caused by central guttae, in the absence of advanced corneal edema, while helping to reduce the need for endothelial keratoplasty in these cases.
(Video used with permission from Dr. Gregory Moloney)
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