EyeWorld Asia-Pacific June 2018 issue

by Stefanie Petrou Binder, MD EyeWorld Contributing Writer Managing eyes with long axial lengths Figures 1A and 1B. As the phaco tip is withdrawn from the anterior chamber, air is injected through the paracentesis (A) in order to keep the chamber formed and prevent collapse of the chamber with anterior movement of the vitreous body (B). EWAP CATARACT/IOL June 2018 47 continued on page 48 Challenges of cataract surgery in long eyes H ighly myopic eyes require special care when being considered for cataract surgery. Although there is no real con- sensus on the axial length that constitutes a “long eye,” most eye doctors would want to pay care- ful attention to eyes approaching 30 mm in axial length. Cataract surgeons need to be aware of the challenges associated with long eyes before, during, and after sur- gery. Speaking on long eye cataract surgery at the XXXV Congress of the ESCRS, Daniel Badoza, MD , medical director, Instituto de la Visión, Buenos Aires, Argentina, shared his pearls. Preoperative pearls One of the first challenges in long eyes in need of cataract surgery is obtaining a reliable measure- ment of axial length, which is ultimately essential for IOL power calculations. Axial length is hard to measure accurately in long eyes. Consequently, postoperative refractive error is one of the major complications in highly myopic eyes. “In patients with long eyes, we focus primarily on the biom- etry, IOL power calculations, and the right formula,” Dr. Badoza said. “When we perform an axial length measurement, we usually find posterior staphylomata, which are a source of error. They are common and we spot them with ultrasound biometry, using either contact or immersion techniques. Staphylomata can cause inaccu- rate biometry outcomes. Optical biometers are our best option for good measurements. We think they are mandatory in these eyes. Ultrasound imaging can help us to visualize a posterior staphyloma. However, even with an expert operator performing ultrasound biometry, we can end up with a 2-mm range in axial length results, which will cause problems in the estimation of the IOL power.” The classic IOL power calcu- lation formulas have a tendency toward hyperopic error in long eyes. Although the SRK/T formula is widely used, Dr. Badoza thinks it is imprecise. His preferences are the Olsen, Haigis, and Barrett formulas for higher accuracy, as they consider the anterior chamber depth (ACD) in the estimation of the effective lens position (ELP). Many IOL power calculations in patients with long eyes will result in a minus diopter IOL. To prevent postoperative refractive surprises due to the different architecture of the optic, the surgeon must use specific A-constants for these lenses. Intraoperative pearls Considerations intraoperatively begin with choosing the safest form of anesthesia. Dr. Badoza considers intracameral anesthesia best for these cases, as it is safer than retrobulbar or peribulbar, which have been associated with the risk of globe perforation in long eyes. Intracameral anesthesia would also reduce the patient’s discomfort in case a fluctuation in ACD occurs. Long eyes are at an increased risk for lens-iris diaphragm retro- pulsion syndrome (LIDRS), charac- terized by adhesions between the iris and anterior capsule rim along 360 degrees. Dr. Badoza explained that LIDRS tends to appear just af- ter the infusion starts intraopera- tively, producing reverse pupillary block, pupil dilation, deepening of the anterior chamber, posterior bowing of the iris, and patient discomfort. Regarding the man- agement of LIDRS, the surgeon can learn to mechanically break the iridocapsular block to restore normal chamber depth and relieve patient discomfort. 1 “What you usually see is right after you introduce the phaco tip, there is a sudden dilatation of the pupil and a deepening of the AC,” Dr. Badoza. “You can use your second hand instrument to softly push back the capsule rim to return the diaphragm to its normal position and start phaco- emulsification comfortably. Also, the syndrome can often appear when introducing the irrigation/ aspiration tip. You see a wide and abrupt dilation of the pupil along with other classic symptoms. By carefully pushing back the capsule with the irrigation/ aspiration tip, which is made of soft silicone, you reverse the block and can start the cortical cleanup.”