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BLOG: Surgical treatment of Fuchs’ dystrophy
Last month we talked about how to monitor your patients with Fuchs’ and some findings in nonvisually significant disease.
We talked about sodium chloride ointment and how it’s best for epithelial edema and less effective for deeper, stromal edema. We talked about taking corneal pachymetry values and repeating this over time. We talked about looking for Descemet’s membrane folds and even evaluating endothelial cell density if you have access to a specular microscope.
Also, don’t forget about the IOP. We know the cornea can swell in cases of high IOP like angle closure glaucoma. The reason this happens is that the endothelial pumps start to change and shut down in the presence of high IOP, thus deturgescence stops and the cornea starts to decompensate. It’s been shown that lowering IOP can (sometimes quickly) resolve corneal edema in certain etiologies. So consider medically lowering your Fuchs’ patient with borderline IOP; just be sure to avoid carbonic anhydrase inhibitors, as they can decrease endothelial pump function. And we’ve all heard of the hair-dryer-at-arm’s-length-in-the-morning treatment. Sounds odd, but it certainly works for some patients.
This month, as promised, we’ll discuss what to do when the patient’s vision starts to get worse, when the cornea starts to decompensate, we can’t bring it back medically and surgical options are necessary for the Fuchs’ dystrophy.
The first corneal transplant was performed over 100 years ago, so this field is not particularly new. But many amazing changes have taken place over the last 10 years. Penetrating keratoplasty (PKP) has given way to a more focused approach for many diseases, and Fuchs’ is certainly one of them. The rationale is: Why replace the entire tissue when only a part of it is diseased? For instance, in keratoconus or any case of stromal scarring, surgeons will often prefer not a PKP but a deep anterior lamellar keratoplasty, where the host Descemet’s membrane (DM) and endothelium is left untouched, but the epithelium and stroma are removed and replaced with a donor’s. In Fuchs’, the preference is to leave the epithelium and stroma and to replace the DM and endothelium in a procedure known as endothelial keratoplasty (EK).
There are several types of EK, and I apologize in advance for all the acronyms. Posterior lamellar keratoplasty (PLK) and its sister procedure, deep lamellar endothelial keratoplasty (DLEK), were relatively revolutionary as recently as the early 2000s, but both are used infrequently currently. PLK and DLEK were endothelial transplants, but would keep a lot of the donor stromal bed and adhere it to the host stromal bed. This would create a very thick final cornea with a donor-stroma-to-host-stroma interface that was prone to corneal haze and scarring. This interface would decrease contrast sensitivity and visual acuity potential, making a great PLK or DLEK outcome around 20/40 or 20/50. The big difference between these two procedures was that DLEK required a smaller incision wound (around 9 mm vs, 5 mm) and used a foldable donor insertion.
Next came Descemet’s stripping endothelial keratoplasty (DSEK), where only a thin layer of stroma was transplanted along with the DM and endothelium. This reduced a lot of the complications of DLEK, and best potential visual acuity was improved in comparison.
Descemet’s stripping automated endothelial keratoplasty (DSAEK) came after that and is essentially the same procedure, but instead of the surgeon manually dissecting the donor stromal bed by hand, in DSAEK a microkeratome or femtosecond laser is used on the donor, hence the term “automated.”
Descemet’s membrane endothelial keratoplasty (DMEK) has taken the next logical step and has done away with any stromal bed altogether and only transplants DM and endothelium. In DMEK and DSAEK, after the donor tissue is centered in place, an air bubble is injected underneath the graft to create apposition between the donor and host tissue. Cycloplegic drops are given to reduce risk of pupillary block, and some surgeons put an inferiorly placed iridectomy (inferior because there’s less risk of an air bubble occluding it). Patients are typically advised to lie flat for 6 to 24 hours, depending on the surgeon’s preference.
Almost all of the endothelial keratoplasties performed in the U.S. today are either DSAEK or DMEK. Different surgeons have their preferences, and while potential acuities are likely best with DMEK, new surgical procedures have steep learning curves, and many surgeons can achieve good results with DSAEK. The DMEK procedure is still relatively new, so final acuity outcomes and complication rates vary from surgeon to surgeon. But in DMEK and DSAEK, the speed of visual recovery is much superior to PKP, with patients generally recovering excellent vision in a matter of weeks rather than months or years.
There are complications with DMEK/DSAEK, of course. In order to have the best bond between host and donor, the DM of the host must be completely stripped away, and the posterior stroma laid bare. If any host DM remnants remain, the seal of the donor DM can become weak. As one might imagine though, if the host cornea is very edematous, ensuring all the DM has been removed can be a difficult task. The donor can also dislocate due to interface fluid and patient’s overly vigorous eye rubbing. Additionally, the bubble can cause pupillary block and angle closure. This should be caught at post-op day 1 and must be immediately treated by partially evacuating the bubble.
Finally, of course, DMEK and DSAEK can also fall victim to primary graft failure and graft rejection, just like any transplant. The overall rejection rate is lowest with DMEK, presumably because there is less tissue involved, and has been found by some studies to be 15 times less than those with DSAEK (Guerra and colleagues).
Corneal guttae are a common finding in our eye exams, especially in our older patients. But knowing the difference between typical guttae and worrisome Fuchs’ is important. Follow these patients closely, especially in the beginning, to monitor how their disease progresses. And be aware of the relatively recent changes in endothelial keratoplasty that can give your patient a better chance at great vision postoperatively, compared to surgical alternatives in the past.
References:
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Guerra FP, et al. Ophthalmology. 2011;118(12):2368-2373. doi: 10.1016/j.ophtha.2011.06.002.
Krachmer JH, et al. Cornea. 3rd ed. Mosby Elsevier; 2011.
Melamed S, et al. Br J Ophthalmol. 1980;64:164-169. doi:10.1136/bjo.64.3.164.
Ytteborg J, et al. Arch Ophthalmol. 1965;74:375-381.
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