EyeWorld India March 2020 Issue

CORNEA 42 EWAP MARCH 2020 does not use toric lenses for patients with keratoconus but noted that these lenses may be used in the setting of topographic stability, orthogonal astigmatism, and in patients who are not rigid gas permeable or scleral lens wearers. Dr. Aldave does not recommend the use of multifocal IOLs for keratoconus patients. Dr. Beckman agreed that he’s “not a big fan” of a multifocal lens in these patients. Potential problems are the obvious aberrations from the cornea, the cornea may be changing, and you also may be “way off in power just by virtue of the inaccuracy of their measurements preoperatively.” For this reason, Dr. Beckman said this choice would be a riskier option, but some doctors may choose this option if the astigmatism is mild. Dr. Beckman said that a toric lens is an option that he has used in patients with keratoconus. “But you want to make sure they’re fairly regular and fairly stable,” he said. “A lot of these patients have a lot of astigmatism, and you may not be able to fully correct the astigmatism with a toric.” He added that the patient may appreciate the option of debulking the astigmatism with a toric and then wearing weak glasses or contacts. “The concern is if you put a toric lens on these patients, they may then may not be able to wear a gas permeable or scleral lens,” Dr. Beckman said, adding that those lenses correct all of the corneal astigmatism (but some of that has been corrected inside of the eye) so you might get an overcorrection with the contact lens. For patients with keratoconus, a multifocal will not be effective, Dr. Trattler said. “They already have a multifocal cornea, so you want to avoid a multifocal or EDOF lens.” If the astigmatism is irregular, astigmatism-correcting IOLs are often not the best option for patients with keratoconus, Dr. Trattler continued. Toric IOLs can be used if the astigmatism is regular but not if there’s a significant skew in the axis. If the axis is skewed, there is no clear axis to orient the toric IOL, he said. Dr. Trattler said that you also have to consider if the patient wears a scleral lens, RGP lens, or hybrid lens and plans to continue to wear one after cataract surgery, then a toric intraocular lens is not the best plan of action. A monofocal lens will be the better option, but Dr. Trattler said to choose one without negative asphericity. A steep cornea means that the cornea already has significant negative asphericity, he said, and there is no need to use a monofocal IOL that provides additional negative asphericity. Instead, consider a monofocal IOL with neutral asphericity. EWAP Editors’ note: Dr. Aldave is professor of ophthalmology, Walton Li Chair in Cornea and Uveitis, chief, Cornea and Uveitis Division, The Stein Eye Institute, UCLA, Los Angeles, and declared no relevant financial interests. Dr. Beckman is affiliated with the Columbus Eye Surgery Center, Columbus, Ohio, and has relevant financial interests with Avedro. Dr. Trattler is affiliated with the Center for Excellence in Eye Care, Miami, and has relevant financial interests with Avedro, CXLO, and Oculus. Rohit Shetty, MD Vice Chairman and Head, Narayana Nethralaya drrohitshetty@yahoo.com ASIA-PACIFIC PERSPECTIVES T here are two aspects to consider. First is timing, second is choice of intraocular lens (IOL). With the timing of cataract surgery in keratoconus patients, there are two primary considerations. In older patients (>40 years) who are incidentally found to have keratoconus at the time of cataract surgery, there are no concerns of progression. In young patients, unless they have significant cataract and are in the amblyogenic age group, arresting keratoconus progression takes priority over cataract. We prefer to perform cataract surgery after at least 6 months of crosslinking and two consecutive visits demonstrating stability in keratometry. Performing crosslinking after cataract surgery leads to deterioration of vision due to hyperopic shift. Another factor to consider is the stability of ocular surface with respect to allergy, ocular surface inflammation, and dry eye. When these are associated, a 4–6-week course of topical low-potency steroids with cyclosporine is preferred before cataract surgery. When considering choice of IOL, a multifocal IOL is not considered in view of expected worsening of contrast. We are left to decide between a monofocal and a toric IOL, which requires an understanding of whether the corneal astigmatism is regular or irregular, the patient is a rigid permeable lens user, and they are willing to undergo PRK/ Intacs. Corneal irregularity can be decided by three methods. First, a look at the topography map can suggest. Second, in the EKR Holladay map using a Pentacam, if the distribution of corneal powers follows a single peak and if the zonal standard deviation at 4.5 mm is less than 1.1 D, then the cornea is regular. Thirdly, if the difference between best corrected spectacle vision and best RGP lens vision is greater than 2-Snellen lines, then cornea is considered irregular. To decrease corneal irregularity, patient can be given an option of either a topography-guided PRK with CXL or asymmetric Intacs insertion depending on whether the cone is centered or decentred. Performing either of these procedures makes better sense before 6 months of cataract surgery, as they can help enable an appropriate toric IOL with better keratometric reliability. If performed after cataract surgery, they tend to induce hyperopia and a drop in uncorrected vision. We do not prefer to follow one particular concept of Dr. Beckman, i.e, crosslinking followed by refractive surgery later. This ablates already crosslinked anterior cornea, with possibility of decreasing the effect of CXL, compared to PRK with CXL done simultaneously. Editors’ note: Drs. Shetty and Lalgudi declared no relevant financial interests. Vaitheeswaran G. Lalgudi, MD Consultant & Research Associate Cornea and Refractive surgery department, Narayana Nethralaya, Bengaluru, India 121/C, Chord road, Rajaji Nagar, Bengaluru, India kanthjipmer@gmail.com