EyeWorld India December 2014 Issue

December 2014 42 EWAP GLAUCOMA by Ellen Stodola EyeWorld Staff Writer Femto for glaucoma Indications for the new technology possible W ith the femtosecond laser being explored for a multitude of uses, indications for the technology in glaucoma surgery could be a possibility. Many factors are still being evaluated, including cost and when the laser can be applied. Malik Kahook, MD , Slater Family Endowed Chair in Ophthalmology, and professor of ophthalmology, University of Colorado School of Medicine, Aurora, Colo., U.S., and Michael S. Berlin, MD , professor of clinical ophthalmology, Jules Stein Eye Institute, University of California, Los Angeles, Calif., U.S., and director of the Glaucoma Institute of Beverly Hills, discussed the possibilities for femtosecond laser-assisted glaucoma surgery (FLAGS). How it would work Dr. Berlin has been exploring applications using femto lasers in a variety of glaucoma surgeries for a number of years. Because femto laser wavelengths are corneal transmissible, FLAGS procedures could be approached transcorneally, ab interno, in a manner similar to femto cataract procedures, and ab externo, in a manner similar to corneal lamellar flap procedures, he said. Applications for the femto laser ab externo include creating trabeculectomy flaps, non- penetrating procedure flaps, near-perforating deep excisions under flaps, removal or thinning of trabecular meshwork and the inner wall of Schlemm’s canal, and creating suprachoroidal fistulae, as the sclera, like the cornea, can be almost transparent to these wavelengths, targeting tissues by controlling the depth of focus. Applications for ab interno procedures include an ELT (excimer laser trabeculostomy) equivalent using docked gonio lens delivery systems, for creating full thickness or near full thickness scleral windows for trabeculectomy equivalent ab interno procedures, and for creating suprachoroidal fistulae. “Femtosecond lasers have the advantages that they are both corneal transparent and almost scleral transparent and can be used on any of the tissue that we want to target in glaucoma by controlled focusing from the inside or the outside,” he said. “FLAGS just requires the correct docking and scanning devices to enable this to happen.” Performing an excimer laser procedure to remove outflow obstruction in glaucoma and relieve pressure or using a femto laser could affect similar outcomes as it is almost as non-traumatic. Since the femto laser is corneal transparent, a visible wavelength can pass through the cornea with a large optical aperture beam so the energy does not injure the cornea. With the beam focused onto a small optical aperture to micro- photodisrupt the target tissue, in this case trabecular meshwork, the pattern of this photodisruption would effectively create an opening, Dr. Berlin said. Dr. Kahook said that currently the femtosecond lasers that are used in both cataract and cornea surgeries are optimized specifically for those particular tissues. “FLAGS would require modifications to the system, which would be readily achievable with some effort and time,” he said. Another possibility for using the laser in glaucoma surgery would be to combine it with femtosecond laser-assisted cataract surgery (FLACS) so that the trabecular meshwork could be targeted after the cataract surgery is complete. “The trabecular meshwork can be removed, or targeted holes can be created in full thickness fashion to enhance outflow of aqueous humor,” Dr. Kahook said. “An alternative would be to create a partial thickness intrascleral channel that would receive aqueous humor from the anterior chamber and allow it to drain away through the sclera, thus decreasing IOP.” He added that there are a number of potential applications for FLAGS, like assisting in scleral flap formation and creating novel geometries in ocular tissues to enhance implantation of devices. Benefits of FLAGS Benefits of using the femtosecond laser in glaucoma surgery are similar to those associated with using the technology in cataract surgery. These include enhancing precision of surgery and hopefully enhancing outcomes by decreasing surgical time and obviating the need for excessive tissue manipulation, Dr. Kahook said. “FLAGS also has the potential to make the use of femtosecond lasers for cataract surgery more economical for practices by allowing the device more utility across different diseases outside of refractive surgery,” he said. “If there are more applications for a given laser, practices are more likely to be able to afford the costs associated with buying and maintaining these expensive systems.” Ideal patients A number of patients could