In Dr. Starr’s practice, dry eye is the most common etiology of abnormal corneas.
“Corneal staining, hyperosmolarity, and rapid tear film break-up time can significantly affect topography and keratometry calculations, creating IOL errors,” he said.
“The pearl in patients with dry eye is to treat aggressively preoperatively (and) delay biometry and surgery until the ocular surface has normalized,” Dr. Starr said. “This can sometimes take a long time.”
However, some patients with advanced cataracts may not want to wait for the cornea to reach its optimal status and demand cataract surgery despite significant dry eye disease. In one such patient in his practice, implantation of toric IOLs after cataract surgery resulted in a plano refraction but substantial visual fluctuations during the day.
Epithelial basement membrane, Salzmann nodules, subepithelial fibrosis, and pterygia can cause substantial irregular astigmatism, fluctuate, and recur after removal. However, the big clinical decision associated with these is “to scrape or not to scrape.”
“For patients with high expectations and who want to reduce spectacle dependence, the rule of thumb is to scrape but well before surgery,” Dr. Starr said. “Allow at least 6 to 8 weeks after superficial keratectomy or phototherapeutic keratectomy, repeat keratometry and topography. After another 2 to 4 weeks, repeat these measurements again. When the cornea is stable and regular, a toric IOL can be implanted.”
In certain scenarios, the best approach may be not to scrape.
“In patients with stable mild peripheral lesions, regular astigmatism in the central cornea, normal-sized scotopic pupils, and good spectacle-corrected vision preoperatively, cataract surgery with implantation of a toric IOL can be performed successfully without a superficial keratectomy,” he said.