BLOG: What to expect during corneal transplant postop
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The final entry for this corneal transplant miniseries will explore transplant-specific risks, recovery and expected time to visual stability of the different transplants, as well as postoperative astigmatism and suture manipulation.
Penetrating keratoplasty (PK) has the longest recovery period with 2 years to 3 years for complete visual stabilization, largely due to the need to wait 1 year to 2 years for suture removal with an additional 6 months before the corneal stabilizes.
However, prior to the removal of all PK sutures, one can manipulate a few sutures to regularize and reduce transplant astigmatism. Several months after a PK, guided by corneal topography, the surgeon or comanaging optometrist may remove a few interrupted sutures along the steep meridian in an attempt to flatten the transplant. In the case of a running suture, the specialist can redistribute suture tension to relax along the steep meridian.
An analogy I like is a tied shoe: the shoelaces are tied, a closed system, but they’re too tight at the top and too loose at the bottom. We all know you can redistribute the tension without untying the shoes, and adjusting a running suture isn’t much different. Depending on the amount of suture manipulation, the patient may be prescribed a prophylactic antibiotic for several days.
Outside of adjusting sutures for reduced graft astigmatism is the need to address suture-related complications. If an interrupted suture is loose or broken it should be removed immediately, regardless of the amount of time from surgery. A broken suture is not just a discomfort to the patient but is a possible route for infection and subsequent graft rejection. Along these lines, a good practitioner remembers to observe their transplant patients closely for neovascularization. This may call for corneal Avastin (bevacizumab, Genentech) injections or cautery because with faulty blood vessel growth, lymphatics, immune response and rejection are all the more likely to follow. If an injection is performed, it continues to work for 3 months to 4 months and should therefore be observed before recommending repeat treatment. However, in cases when the angiogenesis is spurred by the presence of sutures, the suture itself may be removed, addressing the source of the problem rather than the neo itself.
Some other PK risks include post-surgical glaucoma, higher graft failure in patients with glaucoma prior to transplant and microbial keratitis, especially in eyes with dryness. This highlights the importance of epithelial healing and maintaining ocular surface health in corneal transplant eyes. There are many tools available to help these patients including artificial tears, prescription dry eye therapy, punctal plugs/cautery, bandage contact lenses, scleral lenses and even tarsorrhaphy when needed.
With Descemet stripping automated endothelial keratoplasty (DSAEK) we see visual recovery in 3 months to 1 year, much faster than PK but on average longer than DMEK’s 1 month to 6 months. There are several factors that infer such a quick recovery for endothelial transplants including minimal corneal alteration by only transplanting the inner lining and leaving the majority of the host’s cornea intact, and the “sutureless” status of DSAEK and Descemet membrane endothelial keratoplasty (DMEK). Compared with PK, it’s easy to see why both endothelial keratoplasties are considered sutureless despite the few stitches a surgeon will use to close the wound. For DMEK/DSAEK, it is usual to remove these few sutures after only 1 month.
There is more risk for corneal opacification in a DSAEK compared with a DMEK due to the host-donor stromal interface; DMEK is a very thin graft, just replacing Descemet’s and endothelium. Both DMEK and DSAEK can experience inverted donor tissue, where the endothelium is inserted facing the anterior chamber (although this can be avoided by marking the tissue), or primary failure where the graft just will not adhere to host cornea during surgery. Even after surgery, patients can suffer a free-floating graft putting them at risk for pupillary block glaucoma (pretransplant laser peripheral iridotomy reduces this risk).
Additional complications include risk for unsuccessful donor peel that can be avoided with tissue precut by the eye bank, although doing so incurs additional cost. For both endothelial keratoplasties, there is risk for inducing cataract depending on anterior chamber depth and the gas used. For this reason, you’ll notice most corneal transplant studies only included pseudophakic eyes. Again, some cases will call for a joint cataract extraction/endothelial keratoplasty procedure.
DMEK clearly has a few advantages over DSEAK (shorter visual recovery, superior visual outcome and a lower rejection rate). So why isn’t DMEK the default treatment for our endothelially compromised patients?
First of all, DMEK is considered a more difficult surgery than DSAEK and is historically thought to have a higher rate of postop complications, although with continued improved surgical technique this is debatable. Surgeons do avoid DMEK in eyes with difficult anatomy such as “soft eyes” and those with shunts or filters. DMEK has higher incidence of donor contraction, scroll or dehiscence. Even with DMEK postop patients undergoing longer periods in the supine position to have the air bubble adhere to the graft than DSAEK patients do, DMEK transplants have a higher need for rebubble.
Compared with all corneal transplants, deep anterior lamellar keratoplasty (DALK) has the fastest recovery and lowest rejection rate. Sutures can be manipulated at the steep axis as early as 4 months postop, especially if they are loose, however with less “bang for your buck” than PK suture manipulation. With adequate healing and surgeon approval, all sutures may be removed as early as 9 months with relative visual stability after only 1 year.
DALK is a more complex and difficult to perform surgery than PK with a risk for penetrating Descemet’s; in such a case, the surgery can become a full-thickness PK. And like DSEAK, there is the possibility of opacification at the stromal interface between the graft and the host and subsequent lower best corrected visual acuity than a fully healed and corrected PK.
With different indications, recovery rates, rejection rates, graft longevity, risks, strengths and weaknesses, there are a lot of factors to consider when planning corneal transplant surgery for a patient. Where there can be a lot of work and commitment from both provider and patient, corneal transplants can be life-changing surgeries.