Limbal relaxing incision kit simplifies task of treating residual astigmatism

September 15, 2008

The Donnenfeld Limbal Relaxing Incision (LRI) kit (Accutome) contains a set of tools to simplify LRI surgery, including the Donnenfeld LRI Diamond Knife that enables patient treatment at the slit-lamp.

Key Points

New York-The Donnenfeld Limbal Relaxing Incision (LRI) kit (Accutome) provides surgeons with a comprehensive set of tools that makes treatment of residual astigmatism by incisional surgery easier than ever before, said Eric D. Donnenfeld, MD.

The Donnenfeld LRI kit contains the Donnenfeld LRI diamond knife, which was designed to enable surgery at the slit-lamp. It also includes the Donnenfeld LRI nomogram and the Donnenfeld LRI marker.

"LRIs are an integral part of the surgical armamentarium for the comprehensive refractive specialist and have a role in optimizing results after both corneal and refractive IOL surgery. In fact, the growth of the presbyopia-correcting IOL market has led to a resurgence of interest in LRIs," Dr. Donnenfeld told Ophthalmology Times.

In-office a plus

When performing LRIs as an enhancement technique to improve refractive outcomes, doing the surgery as an in-office procedure at the slit-lamp has significant advantages. There are benefits relating to cost, convenience, and accessibility. In addition, compared with an operating microscope, the slit-lamp provides stereopsis and depth perception for excellent visualization of the cornea and anterior segment.

"Based on these features, I have been performing LRIs at the slit-lamp for 20 years. Historically, however, one of the drawbacks of this procedure was that it is sometimes difficult to access the cornea optimally with the diamond knife when the patient is in the sitting position. The Donnenfeld LRI diamond knife addresses that issue," said Dr. Donnenfeld, clinical professor of ophthalmology at New York University, and founding partner of Ophthalmic Consultants of Long Island, NY.

This instrument is a pre-set diamond knife configured with a 15° degree angulation of the knife head that improves access to the cornea in areas that are difficult to reach using a straight diamond knife. It also features a shortened titanium handle for improved surgeon control.

Dr. Donnenfeld noted he and his practice partners have been using the Donnenfeld LRI Diamond Knife for 18 months and found it affords comfortable positioning of the hand and easy access to the necessary incision location.

"The procedure is done using topical anesthesia, in about 30 seconds. Patients really appreciate the convenience of having LRIs done in the office and perceive it as less of a procedure, per se, because it is performed without the need for lying down," he said.

Simplifying the procedure

Dr. Donnenfeld's nomogram was developed with the aims of simplifying the LRI procedure. It recommends incision number and length based on the amount of astigmatism to be treated, but with slight length adjustments (5°) depending on patient age or the presence of against-the-rule astigmatism.

"Other nomograms incorporate specific adjustments for age and cylinder axis, and because of their complexity, these tools may incorrectly create the impression that LRI surgery yields consistently precise results. Rather, LRIs are probably more art than science. For this reason, surgeons should personalize my nomogram based on their instruments and surgical outcomes," Dr. Donnenfeld said.

According to the Donnenfeld nomogram, only one incision measuring 1.5 clock hours in length (45°) is needed to correct 0.5 D of cylinder. Correction of 0.75 D, 1.50 D, and 3.00 D of cylinder is achieved using two paired incisions made at the steep axis measuring 1 clock hour (30°), 2 clock hours (60°), and 3 clock hours (90°) each, respectively.

The nomogram is accessible online at http://www.lricalculator.com/. The Web site includes a demonstration of nomogram use and also provides vector analysis so that surgeons can create surgical plans taking into account surgically induced astigmatism to achieve better outcomes.

The Donnenfeld LRI marker is a Dell-style marker created to mark the eye with a blueprint for incisions that correspond to the Donnenfeld nomogram. The marker features a rotating bezel to align marks in the proper meridian, provides good visualization, and creates markings on the eye for the incision lengths specified in the Donnenfeld nomogram.