November 2019

IN FOCUS

Managing Irregular Corneas Prior to Cataract Surgery
Cataract surgery and addressing irregular astigmatism in Fuchs’


by Liz Hillman EyeWorld Editorial Co-Director

“We are increasingly doing DMEK surgery first in patients who present with Fuchs’ and
waiting to do the cataract.”
—Winston Chamberlain, MD



Changes in corneal topography after DMEK. This patient had DMEK in both eyes. Both corneas had a change in the pattern of the axial map. Both corneas had a reduction in the total refractive power as measured by Scheimpflug photography with a net flattening (hyperopic shift), much greater in the left eye. The topographic
astigmatism changed more in the left eye as well. This example demonstrates the challenges in predicting both conventional and toric IOLs before DMEK is done.
Source: Winston Chamberlain, MD

 

In general, there is an underappreciation for the astigmatism associated with Fuchs’ dystrophy, according to Kathryn Colby, MD, PhD.
“There are some cases—the really sick corneas with blisters and things like that—where it’s visually significant,” Dr. Colby said, but a paper published in Ophthalmology determined that irregular astigmatism associated with Fuchs’ might not be so obvious.1 It could have implications if a Fuchs’ patient needed cataract surgery.
The paper by Sun et al. looked at loss of parallel isopachs, displacement of the thinnest part of the cornea, and focal posterior corneal surface depression, using tomographic pachymetry and Scheimpflug images in 93 eyes that had a range of Fuchs’ dystrophy severity. The study authors concluded that subclinical corneal edema could be identified with Scheimpflug tomography and suggested classifying corneas in Fuchs’ patients as clinically definite edema based on a slit lamp exam, subclinical edema based on tomography, or no edema. “This classification is independent of [central corneal thickness] and should be considered when evaluating [Fuchs’ dystrophy] eyes for cataract surgery or EK,” the study authors wrote.
Winston Chamberlain, MD, said most of the irregular astigmatism in patients with Fuchs’ is associated with advanced disease and stromal swelling.
“Epithelium can become uneven and thickened with edema and basement membrane changes and can generate an irregular topography. If advanced enough, some patients develop scarring from microstructural changes in the stroma and recurrent bullae and microcysts,” Dr. Chamberlain said.
When Fuchs’ patients need cataract surgery, deciding whether to do a combined procedure (if a corneal procedure is needed) or staged procedure depends on the patient. And if it’s combined, how does the physician determine IOL power?
Mark Terry, MD, described a recent case where a patient with Fuchs’ put off cataract and transplant surgery. The patient had massive corneal swelling, blistering, and scarring on the surface. The patient’s other eye also had Fuchs’, though less severe, and its axial length was the same as the other eye. Dr. Terry asked the patient how his vision was 10–20 years prior, finding out that the patient could see well without glasses in both eyes. As such, Dr. Terry planned an IOL based on the patient’s healthier eye and performed a triple procedure where he removed the scar, performed phaco, and followed with DMEK.
“I took the keratometry on the eye that did not have swelling and used that for my calculations on the eye that had terrible swelling, that way I could feel confident that the IOL I put in would have the same outcome as if he didn’t have the horrible swelling,” Dr. Terry said.
But what if the patient hadn’t seen well without glasses prior? What if the axial lengths were different? In cases where you can’t obtain accurate keratometry in the face of known irregular astigmatism, Drs. Terry, Colby, and Chamberlain said cataract surgery would be staged after DMEK, DSEK, or Descemet’s stripping only (DSO), the corneal procedure depending on the patient’s situation and the surgeon’s capabilities.
“We are increasingly doing DMEK surgery first in patients who present with Fuchs’ and waiting to do the cataract,” Dr. Chamberlain said. “This step normalizes the cornea and creates a more predictive refractive outcome when cataract surgery is done.”
The benefit of a combined cataract and corneal procedure is time, expense, and saved endothelial cells.
“You always worry about doing phaco [later] with an endothelial keratoplasty graft. Are you going to damage some of those endothelial cells that you transplanted?” Dr. Colby said.
If irregular astigmatism cannot be corrected or if Fuchs’ is not being addressed with endothelial keratoplasty or DSO, Dr. Chamberlain said he would choose a monofocal lens. Dr. Chamberlain cited analysis of a randomized, controlled patient population of DMEK and DSEK patients that found the cornea flattened or lost power in two-thirds of cases and steepened or gained power in the remaining third.
“Granted, these shifts are small but can be enough to create greater than 1 D of refractive surprise. For this reason, when combining cases, I typically use monofocal lenses,” he said. He also advised making a smaller capsulorhexis in combined cases and noted the importance of a clear enough cornea for safe cataract surgery. “Use aids such as trypan blue, if necessary. Dilate the pupil only with intracameral, preservative-free epinephrine so that it is easy to reduce pupil size later in the surgery when beginning the endothelial keratoplasty.”
Dr. Terry said he would use a toric lens in some patients.
“I use toric lenses in combined cases with DMEK, but I let the patient know it’s not quite as accurate. … They may need to have the lens rotated if their astigmatism changes after the swelling is gone,” he said.
Multifocal IOLs in this subset of patients gave the surgeons pause.
“I think there are situations where you could get away with a multifocal, but why?” Dr. Colby said. “If someone has a corneal disease that is significant enough to need corneal surgery … glasses independence is just not a reasonable expectation.”
Dr. Chamberlain said he would consider a premium lens in a patient who has had prior DMEK.
Dr. Terry bases his IOL calculations on the likelihood of a hyperopic shift, aiming for –0.8 for DMEK, –1.25 for DSAEK, and –0.5 for DSO. Dr. Colby targets her IOL calculations to 0.75–1 D myopic, knowing that DSEK would bring them closer to plano, while with DMEK or DSO she leaves them 0.5–0.75 myopic. Dr. Chamberlain said that he targets –0.5 D with DMEK and ultra-thin DSAEK. DSO can have an early myopic shift in the cornea, Dr. Chamberlain continued, adding that more long-term data is needed about how it stabilizes.
None of the doctors saw a distinct benefit for using the femtosecond laser for cataract surgery in these cases. Dr. Colby said that while, theoretically, softening the lens with a femtosecond laser could reduce phaco time in the eye and thus spare endothelial cells, its benefits are not born out in peer-reviewed literature. Studies have compared conventional phaco and femtosecond laser-assisted cataract surgery in eyes with Fuchs’, finding less endothelial cell loss in the FLACS group,2,3 but a study of 207 eyes with Fuchs’ comparing conventional phaco and FLACS did not see a difference in corneal decompensation rates.4
Dr. Terry also pointed out that if you were doing a combined procedure, sparing recipient endothelial cells of a cornea that is about to have an endothelial keratoplasty procedure that removes them is not a concern.
“If you think you can get away with cataract surgery without having to do a transplant, I think you should use whatever technique you think causes the least amount of damage,” Dr. Terry said.
The doctors provided a few final thoughts on the topic of irregular astigmatism in patients with Fuchs’ who need cataract surgery. Dr. Colby stressed the Sun et al. paper because it “has the potential to change the way we evaluate Fuchs’ patients.” Dr. Terry said it’s important to address Salzmann’s nodules and pterygia, which could be the cause of significant irregular astigmatism.
Dr. Chamberlain noted increasing numbers of phakic DMEK surgeries and emphasized how DMEK grafting first can normalize the cornea and allow for better refractive IOL prediction staged at a later date.
“We’ve also been surprised to see that some of our Fuchs’ patients are able to postpone cataract surgery for a considerable period of time because their vision improves so much from the DMEK alone,” he said.

At a glance

• How to handle IOL calculations and cataract surgery in a patient with Fuchs’ dystrophy and irregular astigmatism varies by patient.
• In some cases, a combined endothelial keratoplasty and phaco procedure can produce fair refractive outcomes.
• In other cases, a staged procedure is needed with endothelial keratoplasty to regularize the cornea for accurate IOL power calculations.
• In combined procedures, surgeons target the IOL powers with a hyperopic shift in mind.

About the doctors

Winston Chamberlain, MD
Associate professor of ophthalmology
Oregon Health Sciences University
Portland, Oregon

Kathryn Colby, MD, PhD
Louis Block Professor and Chair, Department of Ophthalmology and Visual Science
University of Chicago Medicine & Biological Sciences
Chicago

Mark Terry, MD
Professor of ophthalmology
Oregon Health Sciences University
Portland, Oregon

References

1. Sun SY, et al. Determining subclinical edema in Fuchs’ endothelial corneal dystrophy: Revised classification using Scheimpflug tomography for preoperative assessment. Ophthalmology. 2019;126:195–204.
2. Fan W, et al. Femtosecond laser-assisted cataract surgery in Fuchs’ endothelial corneal dystrophy: Long-term outcomes. J Cataract Refract Surg. 2018;44:864–870.
3. Yong WWD, et al. Comparing outcomes of phacoemulsification with femtosecond laser-assisted cataract surgery in patients with Fuchs’ endothelial dystrophy. Am J Ophthalmol. 2018;196:173–180.
4. Zhu DC, et al. Outcomes of conventional phacoemulsification versus femtosecond laser-assisted cataract surgery in eyes with Fuchs’ endothelial corneal dystrophy. J Cataract Refract Surg. 2018;44:534–540.

Relevant financial interests

Chamberlain: None
Colby: None
Terry: None

Contact information

Chamberlain: chamberw@ohsu.edu
Colby: kcolby@bsd.uchicago.edu
Terry: MTerry@deverseye.org

Cataract surgery and addressing irregular astigmatism in Fuchs’ Cataract surgery and addressing irregular astigmatism in Fuchs’
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