Premium IOLs in corneal disease an individualized decision

Patients with concurrent corneal disease may be candidates for premium IOLs to correct presbyopia and/or astigmatism, but often these individuals need corneal surgery before or after the cataract procedure, said William B. Trattler, MD.

The first step in planning the cataract surgery and choosing an appropriate IOL is to identify the presence of corneal disease, and making the diagnosis will require the use of topography.

“When examined at the slit-lamp, eyes with keratoconus or pellucid marginal degeneration (PMD) may show no signs of their corneal disorder, and even epithelial basement membrane dystrophy (EBMD) can be subtle," said Dr. Trattler, director of Cornea Center for Excellence in Eye Care, Miami. "These conditions all affect corneal shape, and so topography is key.”

Once the diagnosis is made, the question becomes whether it is possible to normalize the cornea so that the patient becomes a candidate for a premium IOL. The answer may be "yes."

Superficial keratectomy can be performed to regularize the cornea in an eye with EBMD, Descemet stripping endothelial keratoplasty or Descemet membrane endothelial keratoplasty can be performed for eyes with Fuchs disease. Surgery can also be performed to remove the pathology and make eyes with pterygia or Salzmann nodular degeneration a candidate for premium IOLs, while eyes with corneal irregularity associated with dry eye disease should also be managed prior to cataract surgery.

Dr. Trattler presented several case examples to illustrate the outcomes of corneal surgery prior to a cataract procedure in eyes with corneal disease. One example involved a patient whose astigmatism was reduced from +3.5 to +1.3 D after surgery to remove a nasal pterygium.

“This patient was now eligible to be implanted with a toric presbyopia-correcting IOL,” Dr. Trattler said.

Challenges of keratoconus

Eyes with keratoconus or PMD are not candidates for a presbyopia-correcting IOL, but may be considered for a toric IOL. The decision of whether or not to proceed with the premium implant, however, depends on whether or not it is possible to accurately determine the axis of astigmatism that in turn guides alignment of the toric IOL.

“When there is significant irregular astigmatism, it can be difficult to know the axis to place a toric IOL, and in that situation, I will avoid a toric implant,” Dr. Trattler said.

As a contrast, he presented a case involving a patient with PMD and 3.58 D astigmatism at 172° as measured by optical biometry. The topography image showed regular astigmatism in the center of the visual axis, and on that basis, the patient was expected to have a good visual outcome with a toric IOL.

Since CXL may be needed in an eye with keratoconus, another question that arises is whether to perform cataract surgery before or after the corneal procedure.
“Patients with a visually significant cataract and significant astigmatism from the corneal disease may be happy with their vision after cataract surgery, but we also need to anticipate the possibility that the patient will need CXL in the future,” Dr. Trattler said.

Dr. Trattler said that in a patient with an advanced cataract, he advocates for performing cataract surgery first.

“Corneal shape continues to change for many, many years after CXL, and so performing CXL first will not result in a stable corneal shape,” he explained.

However, he recommended targeting 1 to 2 D of myopia when performing cataract surgery, recognizing that CXL, if it is needed, can cause a hyperopic shift.