Combined or separate cataract, DSAEK procedures in Fuchs' dystrophy?

Vail, CO-In patients who present with both cataract and Fuchs’ endothelial corneal dystrophy, ophthalmologists have the option of performing cataract extraction alone or simultaneously with Descemet’s stripping automated endothelial keratoplasty (DSAEK), said Anthony Aldave, MD, at the 29th annual Current Concepts in Ophthalmology conference. Careful patient selection and informed consent are vital to choosing the proper approach.

Dr. Aldave explored how to determine the best options for these patients. Should surgeons perform just cataract surgery or cataract surgery and DSAEK?

“If there’s any epithelial edema at all, that patient should have a combined procedure,” said Dr. Aldave, who is associate professor of ophthalmology, The Jules Stein Eye Institute, University of California-Los Angeles. “When patients come to us with corneal edema and subepithelial scarring, it’s from epithelial edema that has been present for a few months. You don’t typically get subepithelial scarring from stromal edema. That patient should have cataract surgery and DSAEK.”

What about in the patient without epithelial edema, but with stromal edema?

“If they have to wait a while every morning before their vision is optimized (to read the newspaper, for example), then the corneal edema is interfering with their lifestyle,” Dr. Aldave said. In these patients, he recommends a combined procedure.

When performing an exam in these patients, which measurements are significant? According to Dr. Aldave, the cutoff for pachymetry measurements is not absolute, although he uses a cutoff of approximately 640 µm.

“If the cornea is thicker than that, I do a combined procedure,” he said, adding that if pachymetry is less than 640 µm, without epithelial edema, cataract surgery alone is typically recommended.

“But if the pachymetry is borderline, I target a myopic postoperative refractive error, knowing that if they subsequently require DSAEK, it will induce a hyperopic shift,” he added.

Dr. Aldave explained that he does not typically use endothelial cell counts to make the decision between performing cataract surgery versus a combined procedure, but if the endothelial cell density is less than 500 cells/mm², perhaps a combined procedure should be considered.

Dr. Aldave also offered some valuable advice about choosing the IOL type and power in patients with Fuchs’ dystrophy:

Multifocal IOLs are contraindicated in these patients because of the visual aberrations that result from endothelial guttae (when cataract surgery alone is performed) and decreased contrast sensitivity following DSAEK (when a combined surgery is performed).

Toric IOLs are appropriate to place, as long as that patient remains a candidate for DSAEK should corneal endothelial compensation occur post-operatively.

“Although the astigmatic effects of DSAEK are somewhat unpredictable, especially if a clear corneal incision is used, we have found that the effect is fairly small in the majority of patients. As long as you have good informed consent, I think that’s appropriate,” he noted.

Accommodating IOLs may also be considered, with good informed consent, although, stressed Dr. Aldave, patients must be informed that a refractive touch-up will likely be needed if DSAEK surgery is subsequently required due to the hyperopic shift that typically occurs with DSAEK surgery.

“I typically target a residual refractive error of about –1.00 to –1.25 D when choosing an IOL for a patient undergoing a combined cataract surgery and DSAEK. With the move to ultra-thin DSAEK, and now with the advent of Descemet’s membrane endothelial keratoplasty, surgeons should probably target a little less myopia, perhaps –0.75 to –1.00 D,” he explained.

Dr. Aldave also touched upon the performance of YAG capsulotomy in patients with Fuchs’ corneal dystrophy. During DSAEK, he related, he has noted the presentation of vitreous into the anterior chamber during surgery in approximately 5% to 10% of patients. Some of these patients have an IOL in the bag, but have had either a large-sized or eccentric YAG capsulotomy, which allows the movement of vitreous around the lens optic into the anterior chamber when the lens-iris diaphragm moves posteriorly during DSAEK surgery, he said.

“If you decide a YAG capsulotomy is needed in a patient who has Fuchs’ dystrophy, keep it small and keep it centered so that if they come to me for DSAEK, I won’t have to do a vitrectomy during the procedure,” Dr. Aldave added.

When performing both cataract surgery and DSAEK, consider how to get reliable K values, continued Dr. Aldave. Topography should be done prior to the onset of corneal epithelial edema in phakic patients who have Fuchs’ dystrophy. Prior topographies are important, especially in patients who go on to develop epithelial edema, because topography performed after edema has developed will not be accurate, and could be a full diopter off, he noted.

In the setting of fine microcystic edema, when prior topography has not been performed, glycerin application in the clinic can be very helpful, he continued. This may be successful in resolving the epithelial edema, resulting in a reliable topography. In patients who present with epithelial bullae, glycerin will not help, however. In these cases, Dr. Aldave has patients come in for a pre-op visit 1 week before surgery, he performs corneal epithelial debridement, and then he performs corneal topography.

Simultaneous surgeries have many advantages, including a single surgery and faster rehabilitation for the patient, although sequential surgery may be indicated in particular circumstances, Dr. Aldave continued.

“The downside when you are doing DSAEK and cataract surgery simultaneously is that you must keep your capsulorrhexis small so the IOL stays in the bag when you insert the donor cornea,” he said. “If you’ve got a dense cataract, trying to remove it safely through a small capsulorrhexis can be problematic. You absolutely cannot have an anterior capsule tear, because the significant posterior movement of the IOL and capsular bag that occurs during air injection into the anterior chamber could cause the tear to extend posteriorly.”

“The advantage of performing cataract surgery as an initial separate procedure prior to DSAEK is that a larger capsulorrhexis can be made, so that at the time of DSAEK surgery, which will be a couple months later, the lens will be fibrosed in the bag,“ he noted. “The downside is two trips to the operating room, which is less convenient for out-of-town patients and more expensive for self-pay patients.”

His preference is simultaneous cataract and DSAEK for all patients, except in those who are at high risk for intraoperative floppy iris syndrome, who have high hyperopia secondary to a short axial length, and eyes with known zonular instability.

“I use a 5-mm clear coronal incision for DSAEK surgery. The last thing I want is iris prolapsing out of that incision as I’m trying to bring the DSAEK lenticle into the eye,” he noted.

“I’ve noted the movement of the residual air bubble that remains at the end of the procedure posterior to the iris in a number of cases of combined DSAEK and cataract in patients with high hyperopia and very short eyes,” he added. “Thus, in someone who has very high hyperopia, typically an eye that is more than +4 D hyperopic, I will perform sequential procedures,” he said. “If there is any concern regarding zonular integrity, I will also perform cataract surgery and DSAEK as sequential procedures as well.”

Dr. Aldave has no financial disclosures relevant to the topic.

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