Glaucoma The advantages of minimally invasive glaucoma surgery (MIGS) include that it is a micro-invasive approach that inflicts minimal trauma to tissues while providing both a rapid recovery and a higher safety profile than traditional invasive surgery, said Dr. Bryan ANG (Singapore). While there are numerous devices that fall under the MIGS category, Dr. Ang said there are about 53 million people worldwide with glaucoma, “and that’s why MIGS are so important. We know that most of the patients fall under the mild to moderate category of glaucoma, and about 25% of them have moderate to severe disease.” The Hydrus Microstent, a flexible microstent made of nitinol (the same material used in cardiovascular stents) that is used to enhance the outflow of aqueous from the anterior chamber through the Schlemm's canal, is indicated for use in conjunction with cataract surgery for the reduction of intraocular pressure (IOP). Studies have shown devices using the conventional outflow through Schlemm’s canal have a more favorable safety profile than bypass devices that use the suprachoroidal or subconjunctival space. 16 "More than 100,000 eyes have been implanted with the HYDRUS. and there have been no reported cases of chronic redness, irritation or intraocular inflammation attributable to an allergic reaction or intolerance to the nitinol material,” Dr. Ang said. The trimodal device (1) bypasses the trabecular meshwork through the inlet of the device to allow fluid to pass from the anterior chamber into Schlemm’s canal, (2) dilates and scaffolds Schlemm’s canal, allowing a permanent scaffold in the canal to augment flow, and (3) is the only MIGS implant that spans 90 degrees of the canal. The HORIZON study remains the largest of the MIGS pivotal trials (38 sites/9 countries, N=556), comparing the combination of cataract surgery (phaco) and Hydrus implantation (n=369) to phaco alone (n=187). Inclusion criteria was mild/moderate primary open-angle glaucoma (POAG), on 1-4 medications, with no prior glaucoma surgery, although selective laser trabeculoplasty was allowed. There were no statistically significant differences between the two groups at baseline; washed out diurnal IOP was 25.5±3.0 mmHg in the Hydrus group and 25.4±2.9 mmHg in the phaco-only group. The primary endpoint was the percentage of patients who achieved a ≥20% IOP reduction at the end of 2 years. “HORIZON found 78% in the Hydrus group and 60% in the phaco-only group met the primary endpoint,” Dr. Ang said, which was statistically significant (p<0.001). 17 Further, the Hydrus group showed an absolute reduction of -7.6 mmHg compared to only -5.3 mmHg in the phaco-only group (p<0.001).17 Of equal importance, “almost 80% of eyes in the Hydrus group got off medications and stayed off medications up to 24 months after surgery compared to less than 50% in the phaco-only group,” Dr. Ang said. In his practice, where a good majority of patients are only on one medication, he said if those patients met the inclusion criteria for HORIZON, “you could confidently tell patients that References 1. Modi S, Lehmann R, Maxwell A, et al. Visual and Patient-Reported Outcomes of a Diffractive Trifocal Intraocular Lens Compared with Those of a Monofocal Intraocular Lens. Ophthalmology. Feb 2021;128(2):197-207. doi:10.1016/j.ophtha.2020.07.015 2. Kohnen T, Herzog M, Hemkeppler E, et al. Visual Performance of a Quadrifocal (Trifocal) Intraocular Lens Following Removal of the Crystalline Lens. Am J Ophthalmol. Dec 2017;184:52-62. doi:10.1016/j. ajo.2017.09.016 3. Bohm M, Petermann K, Hemkeppler E, Kohnen T. Defocus curves of 4 presbyopia-correcting IOL designs: Diffractive panfocal, diffractive trifocal, segmental refractive, and extended-depth-of-focus. J Cataract Refract Surg. Nov 2019;45(11):16251636. doi:10.1016/j.jcrs.2019.07.014 4. Ribeiro FJ, Ferreira TB. Comparison of visual and refractive outcomes of 2 trifocal intraocular lenses. J Cataract Refract Surg. May 2020;46(5):694-699. doi:10.1097/j.jcrs.0000000000000118 5. Tran DB, Owyang A, Hwang J, Potvin R. Visual Acuity, Quality of Vision, and Patient-Reported Outcomes After Bilateral Implantation with a Trifocal or Extended Depth of Focus Intraocular Lens. Clin Ophthalmol. 2021;15:403-412. doi:10.2147/OPTH. S295503 6. Bala C, Poyales F, Guarro M, et al. Multicountry clinical outcomes of a new nondiffractive presbyopia-correcting IOL. J Cataract Refract Surg. Feb 1 2022;48(2):136-143. doi:10.1097/j. jcrs.0000000000000712 7. Kohnen T, Suryakumar R. Extended depth-of-focus technology in intraocular lenses. J Cataract Refract Surg. Feb 2020;46(2):298-304. doi:10.1097/j. jcrs.0000000000000109 8. Kohnen T, Petermann K, Bohm M, et al. Nondiffractive wavefront-shaping extended depthof-focus intraocular lens: visual performance and patient-reported outcomes. J Cataract Refract Surg. Feb 1 2022;48(2):144-150. doi:10.1097/j. jcrs.0000000000000826 9. Cionni RJ, Pei R, Dimalanta R, Lubeck D. Evaluating Red Reflex and Surgeon Preference Between Nearly-Collimated and Focused Beam Microscope Illumination Systems. Transl Vis Sci Technol. Aug 2015;4(4):7. doi:10.1167/tvst.4.4.7 10. Shammas HJ, Ortiz S, Shammas MC, Kim SH, Chong C. Biometry measurements using a new large-coherence-length swept-source optical coherence tomographer. J Cataract Refract Surg. Jan 2016;42(1):50-61. doi:10.1016/j.jcrs.2015.07.042 FIGURE 6. HORIZON Study 5-Year IOP reduction in eyes remaining medication-free 11. Whang WJ, Yoo YS, Kang MJ, Joo CK. Predictive accuracy of partial coherence interferometry and swept-source optical coherence tomography for intraocular lens power calculation. Sci Rep. Sep 13 2018;8(1):13732. doi:10.1038/s41598-01832246-z 12. Tamaoki A, Kojima T, Hasegawa A, et al. Clinical Evaluation of a New Swept-Source Optical Coherence Biometer That Uses Individual Refractive Indices to Measure Axial Length in Cataract Patients. Ophthalmic Res. 2019;62(1):11-23. doi:10.1159/000496690 13. Hussaindeen JR, Mariam EG, Arunachalam S, et al. Comparison of axial length using a new swept-source optical coherence tomography-based biometer - ARGOS with partial coherence interferometry- based biometer -IOLMaster among school children. PLoS One. 2018;13(12):e0209356. doi:10.1371/journal.pone.0209356 14. Shammas HJ, Shammas MC, Jivrajka RV, Cooke DL, Potvin R. Effects on IOL Power Calculation and Expected Clinical Outcomes of Axial Length Measurements Based on Multiple vs Single Refractive Indices. Clin Ophthalmol. 2020;14:1511-1519. doi:10.2147/OPTH.S256851 15. Woodard L, Pan LC, Timmons S, et al. PSU9 Time Efficiencies Associated with an Innovative Optical Biometer in Cataract Surgery Planning: A Timeand-Motion Study. Value in Health. 2020;23(Virtual ISPOR Europe 2020)(2):S399-S772. doi:10.1016/j. jval.2020.08.1995 16. Chen DZ, Sng CCA. Safety and Efficacy of Microinvasive Glaucoma Surgery. J Ophthalmol. 2017;2017:3182935. doi:10.1155/2017/3182935 17. Samuelson TW, Chang DF, Marquis R, et al. A Schlemm Canal Microstent for Intraocular Pressure Reduction in Primary Open-Angle Glaucoma and Cataract: The HORIZON Study. Ophthalmology. Jan 2019;126(1):29-37. doi:10.1016/j.ophtha.2018.05.012 18. Ahmed IIK, De Francesco T, Rhee D, et al. Longterm Outcomes from the HORIZON Randomized Trial for a Schlemm's Canal Microstent in Combination Cataract and Glaucoma Surgery. Ophthalmology. Jul 2022;129(7):742-751. doi:10.1016/j.ophtha.2022.02.021 19. American Academy of Ophthalmology Glaucoma Preferred Practice Pattern Panel: Primary Open-Angle Glaucoma (2020). 20 . Alcon Vision LLC ILE871-P001 A Real World Evidence (RWE) Clinical study protocol. Alcon Data on File, 2023 almost 90% would be able to get off medications and stay off them for at least 2 years,” he said. At 5 years, 66% of the overall patients in the Hydrus group remained medication-free, and 72% of those who were only on one medication at baseline remained medication-free. 18 Additionally, fewer than 1% of patients in the Hydrus group had an IOP spike after surgery (compared to 3% in the phaco-only group), and there was no hypotony (≤ 6 mmHg for ≥ 1 day) reported in either group. At 5 years, 5.3% of those in the phaco-only group needed a secondary surgery (trabeculectomy, tube shunt, gel stent, etc.), which was halved to only 2.4% for those in the Hydrus group. 18 “I think it’s no surprise that the AAO’s Preferred Practice Pattern POAG guidelines 19 granted the Hydrus a ‘moderate quality, strong recommendation,’ the highest rating of any MIGS to date,” Dr. Ang said. Other surgical pearls: ensure the gonioscope and the patient’s head are tilted about 30-40º so landmarks are highly visible, use the gonio lens over viscoelastic, ensure an en face view of the angle rather than a top-down view, tilt the cannula about 15-20 º anteriorly toward the cornea at the juncture between pigmented and non-pigmented trabecular meshwork. The Hydrus should appear “dull” during advancement and stay behind the trabecular meshwork; it it appears “shiny,” the stent is in front of the trabecular meshwork and not in Schlemm’s canal, he said. Postoperatively, he prescribes a tapering dose of steroids and antibiotics and halts all glaucoma medications, with exceptions for patients with severe glaucoma or who have a heavy glaucoma medication burden. Supplement to EyeWorld Asia-Pacific December 2023 Media placement sponsored by Alcon
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