Treating astigmatism

Due to differences in healing and post-transplant stretch, high astigmatism is difficult to prevent in both penetrating and lamellar keratoplasty, and glasses or contact lenses are not always possible. David S Rootman MD, of the University of Toronto, Canada, offered tips for treating it during Cornea Day at the 2016 American Academy of Ophthalmology Annual Meeting in Chicago. For patients with 6.0D or less, surface ablation is often an option, Dr Rootman said. For higher astigmatism, astigmatic keratotomy (AK), stitches or reoperation may help bring the patient’s astigmatism down to a treatable level. ARCUATE KERATOPLASTY In a cognitively challenged young man with about 10.0D astigmatism after deep anterior lamellar keratoplasty (DALK) for keratoconus, Dr Rootman used manual AK because the patient could not cooperate for a femtosecond laser procedure. “This is often successful in reducing astigmatism down to the level where a patient can wear glasses and function without further treatment,” he said. A second patient who had undergone penetrating keratoplasty (PK) 25 years earlier for keratoconus presented with cataract and about 15.0D astigmatism. Dr Rootman used femtosecond laser AK to bring the astigmatism down to a treatable range. He typically uses an optical zone of the graft diameter minus 1mm, with incisions of 80-90% over arcs of 45 to 80 degrees. After two months to allow the results to stabilise, Dr Rootman removed the cataract and inserted a toric intraocular lens (IOL). The patient was 20/100 uncorrected with about 4.0D cylinder one day after surgery. STITCHING A third patient with severe keratoconus had undergone PK, then AK and photorefractive keratectomy. After 10 years he had a cataract developing and 16.0D cylinder due to stretching of the host cornea. In this case Dr Rootman opted for a wedge resection with stitches left in place for several months to allow complete healing, followed by cataract extraction and implanting a toric IOL. Going back to the second case, the patient later experienced a Descemet’s membrane detachment. After Descemet’s membrane endothelial keratoplasty (DMEK), he returned to 20/80 uncorrected outcome, Dr Rootman said. Endothelial keratoplasty is usually effective in such cases, Dr Rootman said. However, PK may be required in cases of stromal scarring, or astigmatism cannot be corrected. “Astigmatism challenges us all. However, there are valuable surgical tools available, and in many of these cases we can obtain good vision without having to repeat the graft,” Dr Rootman concluded. David S Rootman: d.rootman@utoronto.ca

Tags: astigmatism