EyeWorld India March 2020 Issue

EWAP MARCH 2020 41 CORNEA Gerard Sutton, MD Professor, Vision Eye Institute Level 3 270 Victoria Avenue, Chatswood, NSW, Australia 2067 Gerard.sutton@vei.com.au ASIA-PACIFIC PERSPECTIVES T he significant variation within keratoconus patients suggests an individual approach is required to optimize both refractive and surgical outcomes following cataract surgery. The recent discussion by Drs. Aldave, Beckman, and Trattler highlight a number of key considerations. Without prior patient history, it may be difficult to identify the relative contribution of keratoconus to reduced vision and therefore a definitive treatment path. The authors suggest that crosslinking should be considered to strengthen the cornea and improve regularity in progressive cases; however, disease progression in elderly patients is limited and, in our experience, this is rarely necessary. Crosslinking also carries some risk and it should be avoided unless there are exceptional circumstances. The use of corresponding corneal procedures such as intracorneal stromal rings or topography-guided PRK was also discussed. We believe that there is a limited role for these procedures. Intracorneal stromal rings can be used to further reduce astigmatism after the use of a toric IOL. Topographic PRK in these cases requires further clinical assessment. Refractive outcomes in keratoconus eyes often result in a residual hyperopic surprise, therefore a myopic target for mild to moderate keratoconus is our preferred practice. Toric IOLs are a valid option to minimize postoperative astigmatism but only for low to moderate keratoconic patients who have had demonstrable reasonable vision in spectacles prior to the onset of cataract. The authors suggest that the greater corneal irregularity, the less effect toric IOLs will have and this reflects our experience. Corneal topography is essential in determining both toric suitability and IOL axis. As indicated, the use of toric IOLs must be avoided in patients who either wish to remain in rigid contact lenses following surgery or if keratoplasty may be required following cataract surgery. A strategy to treat residual astigmatic error is important. The Berdahl-Hardten IOL Astigmatism Fix calculator is useful to determine if IOL rotation may further reduce residual error. I have used the AddOn Sulcus IOLs (1stQ, Germany) with success in several cases which now represents my preference when astigmatic corrections are needed. Technically, cataract surgery in keratoconus patients should be straightforward albeit with the occasional challenge. A highly irregular cornea may lead to an incomplete dock and reduced energy delivery in femtosecond laser-assisted cases. Very advanced cones can impact visualization and I have used a rigid contact lens to provide a clearer image intraoperatively. The authors have identified several approaches and raised some important concerns in these patients. Patient counseling is essential as there is a much higher risk of residual error and the possibility of additional procedures. Editors’ note: Dr. Sutton declared no relevant financial interests. surgery, he stressed that the most important step is choosing the correct IOL power. Kenneth Beckman, MD, stressed the importance of optimizing the ocular surface before any treatment decisions are made and also ensuring the patient is out of their contacts ahead of the preoperative evaluation. Once you’re past the hurdle of cleaning up the cornea, he said there are several options. First of all, you need to take into account that the measurements that we take may not be entirely accurate particularly in a very steep cornea, he said. “In my experience, we tend to see, in severe corneas, that the topography can really fluctuate, and you tend to find a hyperopic surprise in postop refraction,” Dr. Beckman said. Therefore, he usually targets slight myopia in these patients to get them closer to plano. If you’re going to be doing a premium procedure on a patient, you have to take into account that the accuracy, forgetting about all the aberrations of the lens, of the power calculation may be off, he said. Intacs, crosslinking, or topography-guided ablations are all good options, Dr. Beckman said, adding that he personally does not use topography- guided ablation at the time of crosslinking, because he doesn’t know if the cornea is going to change. “I would rather treat the cornea, let it stabilize, and then see if they need refractive surgery later,” he said. Dr. Beckman pointed out that Intacs do not slow progression, but they can significantly reshape the eye. “Their benefit is correcting residual astigmatism to give a patient better uncorrected or spectacle corrected vision,” he said. Crosslinking is going to remodel the cornea for months and months, Dr. Beckman said. “I’d probably lean towards getting the cataract out and seeing where I am and then determining if I want to crosslink,” he said, adding that if you had a pediatric cataract and the patient is progressing rapidly, you may want to crosslink first and then do that cataract. When there are this many options, it’s because none of them are perfect, Dr. Beckman said, but he believes the techniques are getting better and insurance coverage is getting better, so there’s more access. Which lens options are available for these patients? When looking at lens options for these patients, Dr. Aldave said that if the patient was satisfied with glasses-corrected visual acuity prior to the development of the cataract, he will usually place a monofocal IOL targeting emmetropia based on the measured keratometry values. However, if the patient is a contact lens wearer or may need a corneal transplant in the future, he usually places a spherical monofocal IOL targeting emmetropia based on his average keratometry values after a corneal transplant. Dr. Aldave said he personally