EyeWorld Asia-Pacific September 2013 Issue

34 EWAP CAtArACt/IOL September 2013 “T oday, cataract surgery is refractive surgery,” said Sri Ganesh, MD , chairman, Nethradhama Superspeciality Eye Hospital, Bangalore, India. The availability of newer technologies, from delivery systems to lenses, he said, has led to an increase in patients’ expectations. “Patients expect very good uncor- rected vision and freedom from glasses after cataract surgery.” Dr. Ganesh chaired a lunch symposium sponsored by Hoya Surgical Optics (HOYA Corporation, Tokyo) at the 26th APACRS Annual Meeting in Singapore focusing on refractive cataract topics. While surgeons need to be comfortable with all the new technology, he said, safety is foremost. Surgeons need to be attentive to issues, such as postoperative inflammation, that affect outcomes and, ultimately, the ability to meet patients’ increasingly high expectations. Toxic anterior segment syndrome (TASS) is therefore a topic that cannot be ignored. According to Nick Mamalis, MD , professor of ophthalmology, John A. Moran Eye Center, and director, Intermountain Ocular Research Center, Salt Lake City, TASS is acute, sterile postoperative inflammation. “What sets TASS apart from endophthalmitis is TASS occurs immediately after surgery,” said Dr. Mamalis. “Usually cases of TASS occur anywhere from 12 to 48 hours after surgery.” Clinically, TASS is characterized by diffuse limbus-to-limbus corneal edema —this distinguishes the condition from more focal inflammation resulting from incisions or localized stress from instruments during surgery. Clinical findings may also include increased cell, increased flare, hypopyon formation, and even fibrin on the surface of the iris and in the anterior chamber. Notably, TASS can potentially damage the iris and trabecular meshwork, leading to fixed, dilated pupils that don’t constrict well to light, or even, in the worst cases, secondary glaucoma, highlighting the importance of not just identify- ing and treating the condition as soon as it occurs, but preventing it from occur- ring in the first place. “It’s critical to understand what can cause TASS and how we go about preventing it,” said Dr. Mamalis. The list of potential causative factors, he added, includes just about anything: “Anything that gets into the eye during cataract surgery or after cataract surgery is potentially a source of inflammation.” Over the years as co-chair of the ASCRS TASS Task Force, Dr. Mamalis has seen outbreaks caused by a number of different factors, including endotoxins in balanced salt solution resulting from contamination during the manufacturing process, preservatives such as benzalkonium chloride in ophthalmic solutions, stabilizing agents such as sodium bisulfite and metabisulfite in epinephrine solutions, improperly mixed intracameral antibiotics and anesthetics, topical ointments used when a wound leak is present, and remnant OVD, especially in reused small-bore cannulas and instrument tips. In a study of 1,500 cases of TASS out of 69,000 concomitant cataract cases, Dr. Mamalis and his colleagues found the most common factor involved with TASS to be poor instrument cleaning and sterilization—inadequate flushing of handpieces, use of enzymatic cleaners and detergents. “It’s critical that we clean and process our instruments properly,” he said. “Try and use single-use cannulas if you can; try not to reuse cannulas if you can avoid it.” Another way surgeons can minimize the risk of TASS and other complica- tions during surgery is by using preloaded injectors to implant IOLs after cataract surgery. With preloaded injectors, said Tetsuro Oshika, MD , professor and chairman, Department of Ophthalmology, Faculty of Medicine, University of Tsukuba, Japan, IOL implantation is consistent, easy to manipulate, and safe—“Damage [to the lens] is avoided, and there is less chance of endophthalmitis and TASS, theoretically,” he said. Dr. Oshika favors Hoya’s iSert preloaded IOL delivery system, calling it “the best preloaded product in the market.” The delivery system, he said, allows surgeons to implant IOLs through a 2.2-mm scleral tunnel incision; a screw-type plunger ensures very smooth, controlled implantation, avoiding the “explosive” IOL implantation that can occur with push-type plungers. In addition, the inner surface of the system’s IOL cartridge is coated with hy- drophilic macromolecules that provide lubrication such that, according to Dr. Oshika, there is no noticeable difference whether you fill the cartridge with viscoelastic material or plain balanced salt solution. Dr. Oshika also highlighted the advantages of Hoya’s IOL design, which features soft PMMA haptic tips that aid visualization and prevent haptic-optic adhesion, and an optic material that stays “crystal clear for many years”—making the lens suitable, he said, even for pediatric cases. In terms of the optic itself, Hoya has introduced another innovation with a special line of IOLs. “Optimum quality vision is not just about resolution,” said Graham Barrett, MD , clinical professor, Lions Eye Institute and Sir Charles Gairdner Hospital, Nedlands, Western Australia. “Based on this concept, Hoya has produced a monofo- cal lens with an extended depth of focus. “This lens has a unique aspheric design that produces a controlled amount of positive spherical aberration, constant for each lens power,” he added. “This provides about 1 D additional depth of focus.” The lens is manufactured using blue light-ab- sorbing material and is compatible with the iSert delivery system. Dr. Barrett began a study of the extended depth of focus (EDF) lens in February 2012 together with colleague Yokrat Ton, MD . They implanted the lens in 59 eyes (42 patients) in two clinical scenarios: one group with modest monovision, and another where emmetropia was targeted in both eyes. At the time of the symposium, all patients had been followed up for three months. Patients in the monovision group achieved good near and excellent intermediate vision, and the distance vision was well preserved, with 6/9 Snellen equivalent. The emmetropic patients had excellent distance and good intermediate vision, and while their near vision was better than expected, they still required modest monovision to read unaided. Corrected acuity was excellent for both groups, and within the first week Dr. Barrett said they realized that the quality of vision was not compromised. Most interesting were the results of defocus curve testing, performed with distance correction in place and the addition of lenses in ±0.5 D increments to demonstrate enhancement, if any, in the depth of focus. In 18 patients acting as their own matched controls—a negative aspheric in one eye and an EDF lens in the other—defocus curve testing revealed an enhanced depth of focus equivalent to an additional one and a half lines of unaided near vision with the EDF lens. To provide patients receiving IOLs with better reading vision, traditional monovision is often used. However, said Dr. Barrett, overlap between the eyes is mini- mal, and some patients have problems adjusting to anisometropia. “That’s why I have always been an advocate of modest monovision,” he said. “By reducing the difference between the two eyes, aiming for –1.25 D, you do have some overlap between the two eyes.” Cataract surgery: The most common Tetsuro Oshika, MD Graham Barrett, MD Sri Ganesh, MD Geoff M. Whitehouse, MD Rohit Shetty, MD Nick Mamalis, MD APACRS Supplement to EyeWorld Asia-Pacific Fall 2013