EyeWorld India September 2017 Issue

by Liz Hillman EyeWorld Staff Writer Microscope settings for cataract surgery Minimizing accommodation, scope position, illumination type, maximizing red reflex, and more T hough not the sexiest of topics when it comes to pearls for perfecting cata- ract surgery, basic micro- scope settings are one of the most fundamental and foundational steps to set the stage for a clear operation. “I often work with residents who are new to using the operating microscope. They are often nervous and can easily over-accommodate during the surgery,” said Matthew Wade, MD , assistant professor, Gavin Herbert Eye Institute, Uni- versity of California, Irvine. One trick that Dr. Wade offered to avoid over accommodating is to have those in training zoom in all the way. Then, using the micro- scope handles, adjust the focus so the cornea is in focus. From there, zoom back out until the field of view is sufficient. “Any further fine focus with the microscope pedal should be mi- nor,” Dr. Wade said. “If they press on the fine focus for an extended period of time they are likely ac- commodating. This method helps them get the case started correctly.” “Being young has many advantages, but accommodating during cataract surgery is not one of them,” said Robert Cionni, MD , The Eye Institute of Utah, Salt Lake City. “After a day in the OR, headaches are certain if accommo- dating all day long. I have a routine that helps me minimize accommo- dation.” This routine, Dr. Cionni said, includes adjusting his PD start- ing with the oculars wider than his expected PD. From there he brings them together slowly until he achieves binocularity. When adjusting the microscope’s focus, he starts with the focus point above the eye and slowly focuses the scope down until the eye is just in focus. “The concept is similar to start- ing a refraction in the ‘+’ range to prevent a young patient from accommodating during the refrac- tion,” Dr. Cionni explained. Sumit “Sam” Garg, MD , vice chair of clinical ophthalmol- ogy, and medical director, Gavin Herbert Eye Institute, University of California, Irvine, advised dialing in a little minus (–0.75 to –1 D). Start high and focus down, he said. Dr. Garg also suggested looking across the room prior to starting a case. As for the microscope’s actual position, Dr. Cionni said he finds tilting more comfortable and less likely to produce neck strain. “It also allows me to get my knees under the stretcher comfort- ably. The only limit to tilt is my arm length. I prefer to keep my arms bent instead of stretched out far,” he said. Drs. Wade and Garg, in con- trast, said they prefer leaving it perpendicular to the floor. Dr. Garg said this position can help prevent parallax, while Dr. Wade likes the red reflex this position provides. To maximize red reflex while making the capsulorhexis, Dr. Garg said he uses coaxial light and minimizes the surround light. “I also make sure the scope is aligned with the eye as much as possible,” he said. Dr. Wade provided similar advice. “If needed, I will decrease the oblique light to improve the red reflex or decrease the aperture if light reflecting from outside of the cornea is bothersome,” Dr. Wade said. Dr. Wade cited a study by Cionni et al. that evaluated the red reflex and surgeon preference between nearly collimated beam illumination and focused beam illumination microscope systems. 1 The research determined via a survey that surgeons found the red reflex was maintained over greater distances from the pupillary center and at a greater depth of focus with the nearly collimated illumi- nation. “Most participating surgeons ( * 64%) reported a preference for the microscope with nearly-colli- mated illumination with regard to red reflex stability, depth of focus, visualization, surgical working distance, and perceived patient comfort,” Cionni et al. wrote. “The larger red reflex of the nearly collimated microscope can be helpful in the case of patient movement,” Dr. Wade said. “The paper showed that focused beam microscopes have a usable red reflex to be 8.7 mm. For a relatively stable patient, this is sufficient to perform a 5 mm to 5.5 mm capsu- lorhexis.” Dr. Wade said he prefers the Lumera microscope (Carl Zeiss Meditec, Jena, Germany), which has a focused illumination beam, but “at the end of the day it comes down to surgeon (and surgical center) preference.” Dr. Cionni said he finds that the focused beam of light pro- vides for a slightly crisper, detailed focus. There is a compromise, however, with the smaller depth of focus and loss of red reflex when not centered or if the eye is tilted, he added. “The advantage of a collimated beam is a broader red reflex so that the areas outside of the center of focus are well visualized, even if at the edge of the field of view or if the eye is tilted. One small compromise is the possibility of glare off of instruments such as continued on page 40 39 EWAP CATARACT/IOL September 2017