Eyeworld

EW FEATURE 44 Intersection of refractive surgery and MIGS • April 2018 aggressive procedures if the MIGS procedure fails to adequately control the disease process. Intraoperative gonioscopy Dr. Brubaker said that there is a learning curve with gonioscopy. "This can be practiced on non-MIGS patients initially," he said. "It is crucial to tilt the head and micro- scope enough to obtain an enface view of the angle." A challenge that he often sees with beginning MIGS surgeons is they don't get the right angle and the TM or ciliary body is viewed at an oblique angle. "This makes visualization and treatment much more difficult than it needs to be," he said. "In addition to this the dominant hand that is holding the intraoperative devices and instru- ments needs to have adequate sup- port to prevent posterior or anterior wound stretch, which can also cause corneal distortions." Dr. Brubaker said that he will use a standard Swan-Jacob lens for most of his cases. It is nice if it has a cutout at the apex of the prism to allow for a free insertion of the in- traocular instruments, he said. "The single use iPrism in conjunction with the iClip from Glaukos has an enhanced viewing angle," Dr. Bru- baker said. "The clip helps to move and stabilize the eye if necessary." He finds this prism especially useful for procedures that treat a wider portion of the angle such as KDB, GATT, or if placing multiple stents. Dr. Huang noted that intraop- erative gonioscopy can be a barrier, as good visualization is needed for implantation of devices. "However, once intraoperative gonioscopy is learned and mastered, it can be a skill that is useful in many differ- ent types of MIGS procedures," she said. "I recommend a direct gonio lens to visualize the angle, such as a Swan-Jacob lens." She added that certain direct lenses have a ring that contacts the limbus, which allows for stabilization and control of the globe. The ring also allows the gonio lens to float over the cornea, Dr. Huang said, minimizing pres- sure and distortion of the cornea and thus allowing a clear view. "Intraoperative gonioscopy, how- ever, is easy to practice at the end of cataract surgery," she said. "For surgeons who wish to master the skill, I recommend that at the end of a cataract case, they rotate the pa- tient's head and microscope and use the gonio lens to view the angle." Then, she said to use a cannula to gently touch the TM and mimic the motion of device implantation. How refractive cataract surgery patients resemble MIGS candidates Dr. Samuelson said that one aspect of MIGS surgery that will appeal to refractive cataract surgeons is that MIGS surgery by definition is microinvasive. "For example, canal- based surgery does not influence the postoperative refractive result," he said. "Moreover, for the canal device surgery, such as the iStent or Hydrus [Ivantis, Irvine, California], the intraoperative and perioperative adverse event and complication rate in the pivotal trials was not statisti- cally different from cataract surgery alone." Therefore, Dr. Samuelson said that adding MIGS surgery to refractive cataract surgery follows a similar, premium visual outcomes mindset and strategy. "That said, I am cautious about the use of multi- focal implants in patients with man- ifest glaucoma and visual field loss, primarily due to loss of contrast sensitivity as well as the possibility that the glaucoma could progress in years to come, which could further compromise the visual function," Dr. Samuelson said. Many MIGS procedures are for patients with mild to moderate glau- coma and are often coupled with cataract surgery, Dr. Huang said. "Often MIGS procedures do not re- quire an additional incision and are easily performed after the cataract is removed," she said. "MIGS proce- dures have been shown to decrease intraocular pressures and may also decrease medication burden." Standalone MIGS surgeries with refractive patients "Some MIGS procedures are per- formed in conjunction with cataract surgery," Dr. Huang said. If done as a standalone, the patient's insurance may not cover the procedure, she noted. In those instances, Dr. Huang usually offers a self-pay option or may offer a MIGS procedure that is approved as a standalone procedure. MIGS procedures may be useful in patients who are pseudophakic or post-refractive surgery as they often involve small corneal incisions and are sutureless, she said. "Compared to traditional filtering surgery, MIGS procedures will likely cause less astigmatism and also affect the tear film less." Dr. Samuelson thinks that standalone MIGS surgeries will play a more important role in the future. "Currently, both the iStent and CyPass are approved only in conjunction with cataract surgery," Adopting continued from page 43 Kahook Dual Blade goniotomy CyPass insertion iStent insertion Source (all): Michael Patterson, DO

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