LRIs good option for pre-existing astigmatism in phaco surgery

Dorado, Puerto Rico-Cataract surgeons should learn how to perform limbal peripheral arcuate astigmatic relaxing incisions (LRIs), a good approach for correcting pre-existing astigmatism in patients undergoing cataract surgery or refractive lens exchange (RLE) at the time of surgery, according to Louis D. "Skip" Nichamin, MD.

"In our practice, exactly one out of three traditional cataract patients has his or her astigmatism treated. In the RLE population, or those patients who will receive a presbyopia-correcting IOL, one out of two patients are treated," said Dr. Nichamin, who spoke about his LRI technique during the Current Concepts in Ophthalmology meeting in Dorado, Puerto Rico. The meeting was sponsored by Johns Hopkins University School of Medicine, Baltimore and Ophthalmology Times.

While LRIs produce less effect because of their peripheral placement, the surgeon can still correct up to 3 D of astigmatism using them, he said.

How to proceed

Cataract surgeons new to LRIs will need to familiarize themselves with an appropriate nomogram, proper instrumentation, and the surgical technique, Dr. Nichamin advised.

Dr. Nichamin has developed two nomograms-one for cataract surgery patients, which is conservative, and another for RLE patients, which is a little more aggressive, he said.

The more conservative nomogram, "Intralimbal relaxing incision nomogram for modern phaco surgery," (Table 1) has age adjustments for correction of against-the-rule astigmatism and with-the-rule astigmatism. It utilizes an empiric blade-depth setting of 600 μm.

The more aggressive nomogram, "The Nichamin age and pachymetry-adjusted intralimbal arcuate astigmatic nomogram," (Table 2) is also adjusted for age, but also incorporates pachymetry for the younger RLE patients. "Both nomograms vary slightly for with-the-rule astigmatism versus against-the-rule astigmatism," explained Dr. Nichamin. "We perform pachymetry intraoperatively or preoperatively, and set an adjustable micrometer blade to 90% of the thickness reading obtained. Of course, this figure will depend on the type of blade used."

Instrumentation

Surgeons have a variety of options in terms of blades for the incision and markers for delineating the incision placement. Dr. Nichamin suggests investing in a quality diamond blade, such as those produced by Mastel Precision, Storz, Rhein Medical, or other reputable instrument manufacturers.