Fuchs’ endothelial corneal dystrophy (FECD) is a progressive disease that affects the endothelial layer of the cornea, resulting in decreased vision and discomfort. FECD can occur sporadically or be inherited in an autosomal dominant manner.1
The hallmark of FECD is the development of corneal guttae, which are small, round excrescences that accumulate on the endothelium. As the disease progresses, the guttae become larger and more numerous, leading to corneal thickening, swelling, and opacification.2
Corneal transplantation is the definitive treatment to restore vision in cases of FECD and is a primary indication for the procedure in the United States.3 The most common types of corneal transplant procedures are penetrating keratoplasty (PK), Descemet's stripping endothelial keratoplasty (DSEK), and Descemet's membrane endothelial keratoplasty (DMEK).4
A brief overview of DSEK
DSEK is a highly favored treatment option for patients with FECD, offering lower rejection rates, fewer intra-operative and post-operative complications, and improved visual acuity when compared to PK.5 The procedure involves the removal and replacement of the damaged endothelial layer of the cornea by utilizing the Descemet's membrane exclusively as a transport mechanism.6
The thin layer of donor graft tissue is inserted into the anterior chamber through a small incision and held in place by the placement of an air bubble at the time of surgery. Although DSEK offers many advantages, some limitations of the procedure include the risk of inadequate donor attachment, subsequent detachment, and graft failure.7
DMEK to treat FECD
In the past decade, DMEK has become the preferred surgical technique for the treatment of FECD. DMEK involves transplanting only the donor's Descemet's membrane and the endothelial cells. The surgeon carefully separates a donor Descemet's membrane from a corneoscleral rim. The stripped membrane is then rolled and inserted into the recipient's anterior segment, which had been stripped of its own Descemet's membrane through a 3-mm clear corneal incision.
Unlike DSEK, DMEK does not involve transplanting any stromal tissue.8,9,10 DMEK offers many advantages, particularly in cases with minimal pathology, while providing superior visual outcomes and a reduced risk of graft rejection.8,11,12 Additionally, early post-operative studies indicate higher cell loss within the first 6 months for DMEK compared to DSEK, but long-term data suggest comparable endothelial cell loss between the two procedures.13,14,15
Despite its many advantages, DMEK does have disadvantages, including its technical complexity, creating a steep learning curve for surgeons.16 Furthermore, DMEK had a greater potential for graft detachment compared to DSEK, requiring re-bubbling.17,18
Descemetorhexis without endothelial keratoplasty
Descemetorhexis without endothelial keratoplasty (DWEK), also referred to as Descemet's stripping only (DSO), is a newer surgical technique that involves removing the diseased Descemet’s and leaving the remaining Descemet's membrane intact.
In DSO/DWEK, a circular portion of the central Descemet's membrane is removed, and the peripheral portion is left intact. After the removal of the diseased endothelium, the cornea is allowed to heal, causing the remaining healthy endothelial cells in the periphery to spread and cover the exposed Descemet's membrane.19,20
Indications for DSO/DWEK
Indications for DSO/DWEK include patients with mild to moderate FECD with good visual potential, intact Descemet's membrane, and no significant peripheral corneal abnormalities.21 While some studies have indicated that age might be a beneficial prognostic factor for surgical outcomes, the results have not been consistent across different studies.19,22,23
Moreover, a trend towards improved outcomes has been observed in cases of smaller central descemetorhexis and thinner corneas prior to surgery, but these factors were not universally associated with positive outcomes.23
Patients with a peripheral endothelial cell count below 1,800 cells/mm2 are contraindicated for DSO/DWEK, as studies have demonstrated a correlation with poor corneal clearance outcomes.22 DWEK is also not recommended for patients with severe FECD, advanced corneal stromal edema, or secondary corneal pathology.
Advantages of DSO/DWEK
The benefits of DSO/DWEK include reduced risk of post-operative complications as this surgery involves the removal of only the diseased layer of the cornea, leaving healthy tissue intact. Compared to traditional corneal transplant surgeries, DSO/DWEK does not involve a donor graft, removing the risk of graft rejection, which can lead to better long-term outcomes. Multiple studies have shown that DWEK can achieve improved visual acuity compared to baseline.23,24
Finally, DSO/DWEK requires fewer post-operative medications compared to other corneal transplant procedures, reducing the risk of complications associated with long-term use of steroids (e.g., cataract, glaucoma) and antibiotic medications.25
Limitations of DSO/DWEK
Potential limitations of DSO/DWEK include delayed healing or persistent corneal edema, formation of posterior stromal opacities, abnormal corneal topography and irregular astigmatism, and variable patient responsiveness.19,23,26 In some cases, additional surgical procedures, such as conversion to DSEK, may be necessary to treat these complications.23
DSO/DWEK is a procedure that relies on the patient's natural ability to heal the corneal endothelium, as opposed to using a donor graft. Consequently, the recovery period following DSO/DWEK may be longer in comparison to conventional corneal transplant methods. A study comparing DSO to DMEK revealed that the average time required to achieve 20/40 vision was 7.1 weeks in the DSO group, whereas it was only 2.2 weeks for those who underwent DMEK.26
Additionally, multiple studies have demonstrated varying levels of patient responsiveness. It is critical that all patients be educated that recovery is expected to be longer than “traditional transplant surgery.” In a retrospective case series, patients were categorized into three groups: fast responders, slow responders, and nonresponders based on the time it took for corneal edema to resolve and visible central endothelial mosaic to appear post-operatively.19
Further considerations for DSO/DWEK
The success of DWEK is influenced by surgical technique, with manual stripping potentially causing small detachments of Descemet's membrane that lead to edema, and/or scarring of the stromal tissue that can impede central migration.27
Furthermore, it is possible that a Descemetorhexis size exceeding 4.0mm in diameter may hinder remaining corneal endothelial cells from repopulating the entire surface area of the corneal endothelium in the majority of FECD patients.19,23,26,27 Recent studies have demonstrated that the incorporation of topical Rho-associated kinase inhibitor may enhance outcomes in patients with slow responsiveness to DWEK.28,29,30
This promising finding has the potential to expand the use of DWEK as a viable surgical option for a broader patient population. Although initial studies suggest that DSO/DWEK may have a lower risk of complications than DSEK, additional research and clinical trials are required to identify the optimal patient population for this technique.26
Final thoughts
DSO/DWEK is a promising alternative to DSEK and DMEK for mild to moderate FECD cases. This technique offers several benefits, including a shorter surgical time, fewer complications such as corneal transplant rejection, and preservation of the recipient corneal tissue.
However, patient selection and appropriate surgical technique are crucial to achieving good outcomes. Further research is needed to determine the long-term outcomes and efficacy of DSO/DWEK in treating FECD.
