Eyeworld

Nomograms used by Dr. Mackool when performing double penetrating incisions for astigmatism Source: Richard Mackool, M.D. 32 Techniques aim to improve surgical outcomes, exceed patient expectations T here are different treatment approaches that surgeons can take when treating residual corneal astigma- tism after presbyopia-cor- recting surgery. Here's an outline of three approaches—limbal relaxing incisions (LRIs), double penetrating incisions, and arcuate incisions with a femtosecond laser. The surgeons profiled here commonly use the ap- proach that they describe. LRIs With patient expectations higher than ever, the goal of presbyopia- correcting surgery is to make the pa- tient as emmetropic as possible, said Louis D. "Skip" Nichamin, M.D., medical director, Laurel Eye Clinic, Brookville, Pa. That said, LRIs can help surgeons and their patients achieve better refractive outcomes. Commonly used for 1-2 D of astig- matism, Dr. Nichamin believes that LRIs can correct a greater degree of astigmatism. "I've been an LRI advo- cate for a long time, and I'm com- fortable correcting 2 or more diopters," he said. If the patient has greater than 3 D of astigmatism, he will use LRIs and a toric IOL or ex- cimer ablation in a bioptics fashion. Dr. Nichamin believes that skep- ticism about the use of LRIs for higher degrees of astigmatism may relate to improper technique. He makes several moves to ensure proper technique. "LRIs take invest- ment in technique," he said. First, "as with any astigmatism correction, the treatment has to be centered precisely over the steep meridian," he said. Additionally, the incisions have to be perpendicular to the corneal surface. Quality knives are key to well- done LRIs, and Dr. Nichamin be- lieves the incisions are best made with a thin diamond blade. "If it's beveled, the incision may not be deep enough," he said. Old radial keratotomy knives, steel blades, and double-edge blades do not usually perform well, he said. A thin dia- mond blade designed for LRI can prevent regression and help produce predictable incisions, he said. Surgeons should also be sure to measure the cornea before making an incision. "A 550-micron incision doesn't fit everyone," he said. LRIs are a valuable part of a surgeon's technique toolkit, Dr. Nichamin said. "I think they have gotten a bad reputation because not everyone understands their sub- tleties," he said. Penetrating limbal relaxing incisions (PLRI) Richard Mackool, M.D., Astoria, N.Y., jokingly says that PLRIs are "so easy a caveman can do it." "If you can make a phaco incision, you can do this and do it reproducibly," he said. He noted that PLRIs obviously achieve reliable depth compared with LRIs. Dr. Mackool will use PLRIs for up to 2 D of astigmatism. The inci- sions are 2 mm in length, start just inside the conjunctiva, and their width varies depending on the amount of astigmatism. He creates them just before viscoelastic mate- rial is removed at the end of a case, with the I/A handpiece in the eye (foot pedal position one). "You never have to do stromal hydration, the incisions self-seal immediately," he said. He calculates incisions with the assistance of his nomogram. A backup plan is key if you make the incision and the astigma- tism doesn't improve, Dr. Mackool said. "Don't do what you did be- EW REFRACTIVE SURGERY 32 June 2011 by Vanessa Caceres EyeWorld Contributing Editor Reducing pre-existing corneal astigmatism I n this month's inaugural refractive cor- ner, I'd like to give some food for thought on the topic of astigmatism. Astigmatism is one of the most common conditions a cataract and refractive surgeon deals with. It's more common than dry eye and even more common than blepharitis. In fact, more than 70% of the adult population has more than 0.5 D of pre-existing astig- matism. Interestingly, our incidence of cor- recting pre-existing astigmatism varies by procedure. With laser vision correction (LASIK, PRK, LASEK), we correct any amount of astigmatism 100% of the time. If it's there, it's addressed. Why? To provide patients the best opportunity to see without being dependent on glasses or contacts lenses. That's the mission of today's refrac- tive surgeon. With cataract surgery, how- ever, there is still a transition of traditional surgeons converting to refractive cataract surgery. Yet time is moving things very quickly in that direction. Astigmatism treat- ments associated with cataract surgery vary from 0-40% or higher in 2011, de- pending on the practice and the individual surgeon's preference. A common question we ask ourselves is, "How much astigmatism warrants our attention?" It wasn't that long ago that FDA-sponsored clinical trials considered less than 1.5 D to be "not clinically significant." This was re- duced to 1 D, then 0.75 D, and now many of our peers consider 0.5 D, especially in the setting of presbyopia-correcting IOLs, to be the cut-off point for clinically significant astigmatism. Our refractive colleagues would suggest any amount is too much, and surgical inci- sions and the astigmatism they induce need to be taken into account. Do they treat a tenth (0.1) of a diopter on wavefront testing with their LASIK or PRK procedures? They absolutely do, every patient, every day when indicated. As refractive cataract sur- geons, we may soon evolve to that line of thinking as well. The paradigm is shifting and refractive cataract surgery is truly com- ing of age. I've asked three experts, Skip Nichamin, M.D., Richard Mackool, M.D., and Eric Donnenfeld, M.D., to share their thoughts and pearls on the treatment op- tions for modern astigmatism procedures that can be performed at the time of cataract surgery (limbal relaxing incisions, penetrating limbal relaxing incisions, and arcuate incisions with the new femtosecond lasers). These techniques, in association with presbyopic, monofocal, or toric IOLs, should permit today's refractive cataract surgeons to provide their patients with the same degree of spectacle independence as our laser vision refractive colleagues. Kerry Solomon, M.D., refractive editor Refractive editor's corner of the world Horizontal PLRI(s) nomogram Length Mean (range) 1 incision Mean (range) 2 incisions 2.75 0.3 (0-.5) 0.7 (0-1.1) 3.0 0.4 (0-.7) 1.1 (0-1.8) 3.2 0.6 (0-1.0) 1.5 (0-2.1) Vertical PLRI(s) nomogram Length Mean (range) 1 incision Mean (range) 2 incisions 2.75 0.4 (0-.8) 1.0 (0-1.5) 3.0 0.6 (0-1.0) 1.4 (0-2.0) 3.2 0.8 (0-1.2) 1.8 (0-2.4) continued on page 34

• Cover