This article in the May-June issue of Survey of Ophthalmology provides of a review of endothelial keratoplasty (EK), including its history, evolution of procedures and techniques, indications, outcomes, complications and future.
EK allows selective replacement of diseased endothelium and is continually evolving both in surgical technique and clinical outcome. Historically, from the mid-1950s through the mid-1990s, the anterior approach was tried. Initially, the graft was sutured, but now modern techniques use air, which has allowed longer graft survival with greater endothelial density.
Descemet’s stripping endothelial keratoplasty (DSEK) has replaced penetrating keratoplasty (PK) as the treatment of choice for corneal endothelial dysfunction. It is safe and predictable and offers early visual rehabilitation.
Newer iterations include Descemet’s membrane endothelial keratoplasty (DMEK), Descemet’s membrane automated endothelial keratoplasty (DSAEK) and other hybrid techniques. Some DMEK variants are not mentioned in the article: DMAEK (Descemet’s membrane automated endothelial keratoplasty), ultrathin DSAEK, and DMAEK with stromal rim. DMAEK consists of a central graft with only Descemet’s and endothelium and a peripheral stromal ring.
Early data on these newer EK techniques suggest that they provide significantly better visual outcomes compared to DSEK. Initial five-year survival data indicates that EK is at least comparable to PK. However, further work is needed to simultaneously optimize visual outcomes, refractive predictability and endothelial cell survival, as well as surgical techniques of donor preparation and insertion.
DMEK indications are any endothelial dysfunction without stromal scarring, such as Fuchs’ dystrophy, posterior polymorphous dystrophy, pseudophakic bulbous keratopathy, endothelial failure from trauma, iridocorneal endothelial syndrome, or failed PK.
Cataract surgery can be performed at the same time as EK (the new “triple procedure”) or after. Most surgeons perform these procedures concurrently, except in children with a clear lens and patients with mild to borderline endothelial dystrophy who may benefit from IOL implantation alone. Staging the cataract surgery after the EK allows for more accurate refractive effect, although most surgeons know their range of induced refractive error, and staged procedures are more inconvenient for the patient.
EK is challenging in eyes with apakia and pupillary anomalies, aniridia, peripheral anterior synechiae and shallow anterior chambers. Most EK surgeons replace an anterior chamber IOL with an iris-fixated or a scleral-sutured posterior chamber IOL before proceeding with EK due to the chance of graft failure. The major issue in eyes with previous trabeculectomies and glaucoma drainage devices is to maintain an air fill intraoperatively because the air tends to escape into the trabeculectomy or tube.
Visual outcomes with DSEK can be limited by irregularities in the donor stroma resulting from the lamellar dissection or folding from conforming to the back of the recipient cornea. DMEK provides the fastest and best visual recovery of all current EK procedures but is more technically challenging to perform. Therefore it has not been widely adopted yet. DMAEK results exceed those of DSEK.
There is a hyperopic shift after EK. If DASEK is anticipated, the cataract surgeon should determine the range of the usual hyperopic shift by the corneal surgeon so the proper amount of myopia can be aimed for.
Graft dislocation can be a problem, requiring re-bubbling of the graft. Primary graft failure is rare. Post-keratoplasty glaucoma, especially in eyes with long duration of corticosteroid use has been reported. Those with pre-existing glaucoma are particularly at risk, regardless of steroid use.