Article

MIGS, in defense of the tear film

Although a Gallup study1 estimates that 55 million Americans have dry eye, a recent epidemiology study2 found that only 17 million patients had been diagnosed with dry eye. This lack of awareness — and, consequently, treatment — lead to exacerbated conditions, disappointing surgical outcomes and worsening symptoms. This holds particularly true for glaucoma patients, whose medications often cause or worsen existing conditions.

It follows that a way to reduce the frequency of glaucoma medications should reduce patients’ likelihood of developing DED. And that’s where MIGS comes in.

PREVALENCE IN CATARACT, GLAUCOMA PATIENTS

Cataract and refractive surgery advances provide dramatic improvements in surgical safety and improve patients’ quality of vision. However, these advances are lost with even a minimal disruption of the tear film. The tear film is the first refractive interface. The anterior surface of the precorneal tear film has the greatest optical power of any ocular surface, providing two thirds of the eye’s optical power, along with the cornea. Any irregularities in the tear film will scatter light and possibly degrade retinal image quality by 20% to 40%. Irregularities also cause an increase in higher-order aberrations (HOA) and impaired visual acuity between blinks in dry eyes.3

Within the glaucoma community, patients have a high risk of dry eye due to their typically advanced age, often multiple long-term ocular glaucoma medications and likely epithelial toxicity from those medications, many of which contain the preservative benzalkonium chloride (BAK). One study found 60% of glaucoma patients on medications reporting dry eye symptoms.4 Other studies determined the prevalence of OSD signs or symptoms in 30% to 70% of glaucoma patients,5-8 also finding a significant correlation between the prevalence of OSD and the number of BAK-preserved medications used by the patient.9

The negative effect of BAK in glaucoma patients has been well documented. Studies show that the frequency of ocular surface changes is twice as high in those who receive preserved drops and that frequency of signs and symptoms is dose related.10 In other words, the more BAK-preserved drops a patient administers, the more likely that patient develops OSD. Also, patients on BAK-preserved drops are twice as likely to have lissamine green staining of the corneal conjunctiva.8 The reduction or elimination of topical medications, particularly BAK-preserved medications, minimizes these effects.

MIGS AS A PRIMARY TREATMENT OPTION

Treating OSD improves symptoms as well as post surgical outcomes, patient satisfaction and quality of life. Multiple therapies provide relief and improvement in tear film and function, including Omega 3 nutritional supplements, punctal occlusion, office mechanical therapy and thermal pulsation and doxycycline (50 mg QD or 20 mg BID.). Nonpreservative tears, gels, ointments, and medications are also beneficial. However, these treatments do not address the burden of daily glaucoma medications.

As an alternative, microinvasive glaucoma surgeries (MIGS) provide multiple advantages. MIGS can be performed, even at the time of cataract surgery, with minimal risk or morbidity and rapid recovery times. They do not affect ocular structures, allowing for future surgical procedures if necessary. For example, implantation of the iStent trabecular microbypass (Glaukos) reduces or even eliminates glaucoma medications while improving the ocular surface and visual outcomes. The iStent reduces pressure via bypassing the trabecular meshwork, allowing aqueous to egress into Schlemm’s canal from the anterior chamber. The pivotal and more recent trials11,12 have proved its safety and efficacy, and a recent meta-analysis illustrated improved long-term results when combined with cataract surgery.13

With or without OSD, most patients with glaucoma and cataract are perfect candidates for an iStent given the significant benefits. Patients are only ruled out if they have an abnormal angle that might interfere with implantation.

Many clinicians still tend to under-diagnose and fail to aggressively treat OSD. For cataract patients whose outcomes may be significantly affected and glaucoma patients who may experience debilitating effects as glaucoma medications may cause or worsen dry eye, this under-diagnosis can be devastating. However, MIGS treatments will relieve glaucoma effects without placing more burden on the patient. OM

MIGS can help manage more than IOP

BY ELIZABETH YEU, MD

Glaucoma physicians are no longer surprised to find that their patients have concomitant ocular surface disease. Glaucoma patients have a high risk of dry eye due to their typically advanced age, often multiple, long-term ocular glaucoma medications and likely epithelial toxicity from those medications, many of which contain the preservative benzalkonium chloride (BAK). One study found 60% of glaucoma patients on medications reporting dry eye symptoms.1 Mocan and colleagues determined that the prevalence of meibomian gland dysfunction (MGD) is associated with an astonishing 96% of topical prostaglandin analogue users with 58% of patients using topical non-prostaglandin glaucoma medications.2 Researchers are also finding a significant correlation between the prevalence of OSD and the number of BAK-preserved medications used by the patient.3

MIGS as a primary treatment option

Microinvasive glaucoma surgeries (MIGS) provide multiple advantages. MIGS, of which there are several classes, can be performed as a standalone procedure, or simultaneously at the time of cataract surgery, with less risk of severe complications of traditional glaucoma surgeries (i.e., suprachoroidal hemorrhage, hypotony with flat anterior chamber), more rapid recovery times and decreased dependency on topical glaucoma agents.4-10 MIGS are positioned for mild-to-moderate glaucoma. There often exists a trade-off between lower complication profile and its decreased efficacy as compared to traditional glaucoma procedures. A major benefit to a MIGS procedure is that aqueous outflow structures are often less disturbed, thus allowing for future surgical procedures if necessary.

The MIGS procedures include trabecular bypass implants (iStent, the as-yet unapproved Hydrus); trabeculotomy-based (Kahook dual blade, Trabectome, Trab360); suprachoroidal implant (CyPass); ab interno canaloplasty (Visco360); and subconjunctival stents (Xen). As most are more recent FDA-approved technologies, reimbursement can be a challenge, and certain MIGS procedures (i.e. iStent, CyPass) can only be reimbursed if performed simultaneously with cataract surgery. The established safety and efficacy profiles vary among the MIGS procedures, as evidenced by different studies that demonstrate an IOP reduction.5

While cataract surgery alone can decrease IOP, a meta-analysis illustrates improved long-term results when a MIGS procedure is combined with cataract surgery.4,7 The main contraindication to a MIGS procedure is an abnormal angle that would prohibit the surgical technique, or placement of the stent or shunt. The incidence of OSD in those presenting for cataract surgery evaluations is all too prevalent as well, with 77% of eyes demonstrating defined moderate DED with positive corneal staining.11

REFERENCES

  1. Moss SE, Klein R, Klein BE. Prevalence of and risk factors for dry eye syndrome. Arch Ophthalmol 2000;118:9:1264-1268.
  2. Mocan MC, et al. The Association of Chronic Topical Prostaglandin Analog Use With Meibomian Gland Dysfunction. J Glaucoma. 2016 Sep;25:770-774.
  3. Pisella PJ, Pouliquen P, Baudouin C. Prevalence of ocular symptoms and signs with preserved and preservative free glaucoma medication. Br J Ophthalmol. 2002;86:418-423.
  4. Ansari E. An Update on Implants for Minimally Invasive Glaucoma Surgery (MIGS). Ophthalmol Ther. 2017 Dec;6:233-241.
  5. Batlle JF, Fantes F, Riss I, et al. Three-Year Follow-up of a Novel Aqueous Humor MicroShunt. J Glaucoma. 2016 Feb;25(2):e58-65.
  6. Saheb H, Ianchulev T, Ahmed II. Optical coherence tomography of the suprachoroid after CyPass Micro-Stent implantation for the treatment of open-angle glaucoma. Br J Ophthalmol. 2014 Jan; 98:19-23.
  7. Samuelson TW, Katz LJ, Wells JM, Duh YJ, Giamporcaro JE, US iStent Study Group. Randomized evaluation of the trabecular micro-bypass stent with phacoemulsification in patients with glaucoma and cataract. Ophthalmology 2011;118:459-467.
  8. Arriola-Villalobos P, Martínez-de-la-Casa JM, Díaz-Valle D, et al. Combined iStent trabecular micro-bypass stent implantation and phacoemulsification for coexistent open-angle glaucoma and cataract: a long-term study. Br J Ophthalmol. 2012;96(5):645-649.
  9. Fea AM, Consolandi G, Zola M, et al. Micro-bypass implantation for primary open-angle glaucoma combined with phacoemulsification: 4-year follow-up. Journal of Ophthalmology. 2015;2015: 795357.
  10. Neuhann TH. Trabecular micro-bypass stent implantation during small-incision cataract surgery for open-angle glaucoma or ocular hypertension: long-term results. Journal of Cataract & Refractive Surgery. 2015;41(12):2664-2671.
  11. Trattler WB, Majmudar PA, Donnenfeld ED, et al. The prospective health assessment of cataract patients’ ocular surface (PHACO) study: the effect of dry eye. Clin Ophthalmol. 2017 Aug 7;11:1423-1430.

Disclosures: Dr. Holland consults for Aerie, Azura, Glaukos, Katena, Kala, Mati, Novartis, Omeros, Precision Lens, Senju, Shire, Sight Sciences, SightLife Surgical, TearLab and Vomaris. He is also a researcher for Mati, Novartis, Omeros and Senju, and a speaker for Novartis, Omeros, Senju and Shire.

REFERENCES

  1. The Gallup Organization, Inc. The 2004 Gallup Study of Dry Eye Sufferers. Princeton, NJ: Multi-Sponsor Surveys, Inc; 2004.
  2. The Mattson Jack Group, Inc. “Epidemiology Analysis”. 2005.
  3. Tutt R, Bradley A, Begley C, Thibos LN. Optical and visual impact of tear break-up in human eyes. Invest Ophthalmol Vis Sci. 2000 Dec;41(13):4117-23.
  4. Moss SE, Klein R, Klein BE. Prevalence of and risk factors for dry eye syndrome. Arch Ophthalmol 2000; 118:9:1264-1268.
  5. Rossi GC, Pasinetti GM, Scudeller L, Raimondi M, Lanteri S, et al. Risk factors to develop ocular surface disease in treated glaucoma or ocular hypertension patients. Eur J Ophthalmol 2013;23: 296-302.
  6. Labbe A, Terry O, Brasnu E, Van Went C, Baudouin C. Tear film osmolarity in patients treated for glaucoma or ocular hypertension. Cornea. 2012;31:994-999.
  7. Ghosh S, O’Hare F, Lamoureux E, Vajpayee RB, Crowston JG. Prevalence of signs and symptoms of ocular surface disease in individuals treated and not treated with glaucoma medication. Clin Experiment Ophthalmol. 2012;40:675-681.
  8. Leung EW, Medeiros FA, Weinreb RN. Prevalence of ocular surface disease in glaucoma patients. J Glaucoma. 2008;17:350-355.
  9. Pisella PJ, Pouliquen P, Baudouin C. Prevalence of ocular symptoms and signs with preserved and preservative free glaucoma medication. Br J Ophthalmol. 2002;86:418-423.
  10. Mocan MC, et al. The Association of Chronic Topical Prostaglandin Analog Use With Meibomian Gland Dysfunction. J Glaucoma. 2016 Sep;25:770-774.
  11. Samuelson TW, Katz LJ, Wells JM, Duh YJ, Giamporcaro JE, US iStent Study Group. Randomized evaluation of the trabecular micro-bypass stent with phacoemulsification in patients with glaucoma and cataract. Ophthalmology 2011;118:459-467.
  12. Arriola-Villalobos P, Martínez-de-la-Casa JM, Díaz-Valle D, et al. Combined iStent trabecular micro-bypass stent implantation and phacoemulsification for coexistent open-angle glaucoma and cataract: a long-term study. Br J Ophthalmol. 2012;96(5):645-9.
  13. Malvankar-Mehta M. S., Iordanous Y., Chen Y. N., et al. iStent with phacoemulsification versus phacoemulsification alone for patients with glaucoma and cataract: a meta-analysis. PLoS ONE. 2015;10(7) doi: 10.1371/journal.pone.0131770.e0131770.

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