One would only ever consider corneal transplantation if the patient’s ocular health is at risk or if the vision is affected.
Following the introduction to the different corneal transplant surgeries in our previous post, this entry will outline some preoperative considerations.
It is important to ask ourselves if a specialty contact lens would do the job. In no way should these corneal transplant surgeries be treated as a way to avoid correction. I have my patients verbalize that they understand that best-corrected visual acuity will likely be with updated spectacles or gas-permeable lenses after surgery (and even then only after months of healing, fluctuating refraction and a contact lens re-fit). Descemet’s membrane endothelial keratoplasty (DMEK), Descemet’s stripping automated endothelial keratoplasty (DSAEK) and deep anterior lamellar keratoplasty (DALK) can have some amazing refractive outcomes, but in every case I would prefer my patients be pleasantly surprised that glasses provide good vision rather than upset that their doctor is now recommending GP lenses.
And that’s just in the long run. More immediately, it is always helpful if patients go into surgery understanding that vision will be plenty blurry until the air bubble and/or cornea clears, depending on the type of transplant. Once again, preoperative education for corneal transplant patients is paramount and can help set reasonable postoperative expectations. Many patients are surprised when I stress that they will be on steroid drops for 9 to 12 months after surgery on the short end (DALK) or for years or even life in certain cases (eyes that have undergone penetrating keratoplasty with a history of repeat episodes of rejection).
DMEK patients should also be informed that they will have a short laser procedure 1 to 2 weeks prior to their transplant; many surgeons require a laser peripheral iridotomy (LPI) prior to endothelial transplantation to prevent pupillary block from the anterior chamber air bubble following transplant surgery. For this reason, our surgeons place the LPI at 6:00.
DMEK and DSAEK patients should also expect to lay supine for several days after their procedure, spending some of that time hyperextended in order to best utilize the air bubble and ensure good graft adherence (inferior adhesion can be the trickiest). This can be a little more relaxed in DSAEK cases, and the surgeon may inform them that it is OK to remain upright after observing their appearance at the 1-day follow-up. However, even with good compliance, up to one-third of DMEK patients have to be re-bubbled several days later. With this in mind, when considering a referral for either of these endothelial keratoplasties (especially DMEK), patients with back or neck issues who are unable to lie on their back for extended periods should be carefully screened.
Looking beyond the cornea itself, Fuchs’ dystrophy can be exacerbated during cataract extraction, where phacoemulsification can stress the endothelium, causing further damage and cell loss. At the least, Fuchs’ patients undergoing cataract extraction are at risk of longer healing time with significant postop corneal edema and, at worst, can experience corneal decompensation. (An argument could be made to treat cataracts earlier in these patients so they are more easily removed with less subsequent risk to the cornea, in addition to overall earlier corneal disease.)
More advanced Fuchs’ cases, for example those with pachymetries of greater than 640 microns, may benefit from a combined endothelial keratoplasty/cataract surgery if considering cataract extraction. Even when anticipating staged cataract surgery, cataract surgery first then DMEK or DSAEK surgery to follow when needed, one should consider altering the patient’s refractive target when selecting their IOL. Due to an often hyperopic outcome from endothelial keratoplasties, the surgeon might place a lens with a slightly myopic target such as about -0.50 D used for a more overall plano outcome if DMEK is planned in conjunction with cataract extraction or a -1.50 D target with DSAEK for a more emmetropic outcome.
Join us next month as we go into postop management, focusing on different corneal transplant rejection rates and keeping rejection from becoming failure.