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Different corneal diseases present different challenges to achieving the desired refractive outcome after cataract surgery. Cornea specialist Dasa V. Gangadhar, MD, highlights measures to consider in various situations.
Dr. GangadharWichita, KS-Achieving the desired refractive outcome after cataract surgery can be a challenge in eyes with corneal disease. However, excellent results are possible with careful preoperative evaluation coupled with attention to IOL selection and surgical technique, according to Dasa V. Gangadhar, MD.
Dr. Gangadhar-a cornea specialist, Grene Vision Group, Wichita, KS, and assistant clinical professor of surgery, University of Kansas School of Medicine, Kansas City-provided pearls for performing cataract surgery in eyes with irregular astigmatism, Fuchs corneal endothelial dystrophy/endothelial compromise, keratoconus, a history of penetrating keratoplasty (PK), and prior keratorefractive surgery.
“These are special situations that often require a change in technique,” Dr. Gangadhar said. “It is important for surgeons to tailor their approach to the circumstance and not use a cookie-cutter approach for all procedures.”
Next: Irregular astigmatism
Irregular astigmatism can be caused by a number of different conditions, including basement membrane dystrophy, Salzmann nodules, pterygia, and ocular surface disease among others.
Dr. Gangadhar’s pearl for managing these cases is to teach the office technicians performing the preoperative testing to spot irregular astigmatism and alert the surgeon to the condition prior to dilating the patient. Technicians in Dr. Gangadhar’s office know to review the manual keratometry for any sign of irregularity.
“The irregular astigmatism can be subtle and easily missed in a busy cataract practice, especially if the patient (eyes are) dilated prior to the surgeon’s examination,” he explained. “However, even subtle irregular astigmatism can lead to IOL calculation errors and subsequently a patient who is dissatisfied with the visual outcome after cataract surgery.”
Once the cause of irregular astigmatism is identified, it is addressed prior to cataract surgery. For example, keratectomy is performed for basement membrane dystrophy, dry eye is treated aggressively, and pterygia or Salzmann nodules are removed. Dr. Gangadhar encouraged use of intraoperative mitomycin-C during Salzmann nodule surgery to reduce the risk of recurrence and waiting at least 6 weeks after keratectomy to obtain keratometry measurements for the IOL calculation, he said.
Next: Fuchs corneal endothelial dystrophy/endothelial compromise
Dr. Gangadhar’s pearl for these cases pertained to eyes with moderate or high risk for corneal decompensation. He advised targeting a final refraction 1.0 to 1.5 D more myopic than the final intended refraction, anticipating a need for Descemets stripping (automated) endothelial keratoplasty [DS(A)EK] that will create a hyperopic shift.
He noted that while cataract surgery should be combined with corneal surgery in some cases, when the need for corneal surgery is in doubt, cataract surgery should be done alone first.
He also advised obtaining preoperative pachymetry and endothelial cell counts for risk analysis and using the information to counsel the patient. Documenting the discussion is important for medicolegal protection.
Furthermore, he suggested using a scleral incision, as it may be more protective of the endothelium than a clear cornea approach. Other surgical tips are to use a softshell technique with a cohesive and dispersive viscoelastic and low-flow, low-energy, in-the-bag phacoemulsification.
Use of a scleral incision was Dr. Gangadhar’s pearl for operating on eyes with keratoconus.
“A clear corneal incision in this setting can act as a limbal relaxing incision on steroids, creating unpredictable shifts in astigmatism axis and magnitude,” he explained.
He also noted a toric IOL can be useful for correcting astigmatism. However, it should only be selected if reasonable congruity of axis can be established preoperatively with multiple modalities of astigmatism measurement (manual keratometry, automated keratormetry, topography) and if rigid-gas permeable contact lens wear is not anticipated after cataract surgery.
Dr. Gangadhar’s pearl for these eyes identified toric IOLs as a “gamechanger” for managing astigmatism.
Considering the potential for refractive surprises, he advised performing sequential surgery whenever possible, beginning with PK, rather than undertaking a triple procedure. Cataract surgery should be delayed for 12 to 18 months after the graft sutures are removed, and then toric IOL implantation may provide a reliable means of fine-tuning the final refractive error.
Obtaining endothelial cell counts, using measures for protecting the endothelium at the time of cataract surgery, and aiming for a more myopic refraction is also recommended in these cases if graft decompensation and future DS(A)EK is considered a possibility.
Next: Postkeratorefractive surgery
For these cases of “iatrogenic corneal disease,” for which accurate IOL power calculation is particularly challenging and patients have especially high demands, Dr. Gangadhar had a series of tips:
“Document your preoperative discussions on outcome carefully and set realistic expectations,” he said. “For IOL power calculations, try to obtain reliable historical data in eyes with prior LASIK or PRK and use multiple methods to predict corneal refractive power along with the latest generation IOL formulas and the ASCRS online calculator.”
The preoperative discussion should advise patients about the potential for a refractive surprise and the possibility for needing a secondary procedure, such as IOL exchange, a piggyback lens, or laser enhancement. He noted that intraoperative aberrometry may also play a role for achieving the desired refractive outcome in these difficult cases.
In eyes with prior RK, Dr. Gangadhar advised using a scleral incision to avoid the risk of intersecting with an RK incision, which can create significant irregular astigmatism.
Dr. Gangadhar has no relevant financial interests to disclose.