Microinvasive glaucoma surgery

The micro-invasive glaucoma surgery (MIGS) is a new option in the surgical treatment of glaucoma (glaucoma). With minimally invasive glaucoma surgery (also called microincisional glaucoma surgery), intraocular pressure, the most important risk factor for glaucoma, is reduced. The interventions carried out with small implants do not lower the intraocular pressure as significantly as classic glaucoma surgery, especially trabeculectomy , but are less prone to complications according to the current state of clinical studies.

method

As with most glaucoma surgical procedures, the aim is to improve the drainage of the aqueous humor and thus lower the intraocular pressure. There are various ways of increasing or redirecting this outflow:

• Trabecular: Small stents , the iStent , the iStent inject or the Hydrus stent, create a connection between the anterior chamber of the eye and the natural drainage path, Schlemm's canal , through the trabecular meshwork
• uveoscleral: the aqueous humor is diverted into the branched network of blood vessels in the choroid using implants such as the CyPass ( withdrawn from the market since September 2018) and (in future) the iStent supra and drained from the eye via their veins
• subconjunctival: a XEN implant is used to create a drain under the conjunctiva. This is the same principle as in the most common “classic” glaucoma operation, the trabeculectomy, with the difference that a fistula is created from the outside (from externo) and from the inside of the eye (from interno) in MIGS

Results

The MIGS was initially - and will continue to be - used as part of a cataract operation: in patients who have cataracts (cataracts) and glaucoma (glaucoma) at the same time and whose cataract operation is already indicated an additional, no further trauma and hardly any additional surgery Effort-requiring intervention with the implantation of a stent takes place. In the meantime, MIGS interventions are also carried out as independent operations ("stand-alone procedures"). The mini-implant is inserted into the anterior chamber and the desired position through an opening only 1 to 2 mm in size. Suturing the micro-incision is not necessary; iStent and iStent inject, for example, are considered to be the smallest implants in medicine today.

MIGS interventions that reduce intraocular pressure or intraocular pressure (IOP) by at least 20% are considered effective; The aim is also to reduce the number of hypotensive eye drops that the patient has to take - ideally, the patient can even get by without further medication.

This requirement is met or exceeded in most of the studies on the subject. In an American publication, 42 eyes are reported to have an average intraocular pressure of 20.2 mm Hg preoperatively. One year after implantation of an iStent, this value had fallen to 16.3 mm Hg; after two years a further slight reduction to 13.6 mm Hg could be determined. This resulted in a total pressure reduction of a good 33%, which is close to the theoretical maximum of a drug-based glaucoma therapy. In a Munich study group of 62 patients who had an average intraocular pressure of 24 mm Hg before the operation, this value averaged 14.2 mm Hg three months after the implantation. The pressure reduction is apparently permanent: after three years it had Collectively, an average intraocular pressure of 14.9 mm Hg. The creation of the micro-bypass from the anterior chamber into Schlemm's canal thus led to a long-term reduction in intraocular pressure of around 33 percent in this group. This roughly corresponds to the maximum effect of drugs used to treat glaucoma.

Compared to drug therapy with a prostaglandin analogue, the implantation of two iStents was found to be more effective in reducing intraocular pressure to a level that can be classified as safe: in a study with 101 glaucoma patients, three years after the implantation of the small stents, 91% an intraocular pressure of 18 mm Hg or less and 62% of 15 mm Hg and less - with drug therapy this was only the case in 79% and 21%, respectively.

In an American multicenter study in which a CyPass was implanted as part of a cataract operation, the average pressure reduction of 7.4 mm Hg compared to the initial pressure was slightly more pronounced than the pressure-lowering effect of the cataract operation alone with an average of 5.4 mm Hg.

There are still no comprehensive clinical results based on larger patient groups for other MIGS options.

As MIGS is a new method, its exact place in glaucoma surgery is still unclear, but the consensus among glaucoma specialists is that it has a permanent place in the treatment of patients with moderate increases in IOP because of faster recovery and less frequent, less severe side effects .

Complications

Postoperative problems are apparently extremely rare after MIGS; There are practically no serious complications that threaten eyesight to date in the literature. Occasionally blood (hyphema) can appear in the anterior chamber, which is absorbed within a few days. After CyPass implantation, a temporary low pressure in the eye (hypotension) was reported in 13.8%.

Sources and literature

• Grace Richter, Anne Coleman: Minimally invasive glaucoma surgery: current status and future prospects. Clin Ophthalmol 2016: 10 189-206.
• Ronald D. Barley: Glaucoma - Miniaturization in Diagnostics and Therapy. Deutsches Ärzteblatt 2016; 113: A1710-1711.
• Ronald D. Gerste: Micro-invasive glaucoma surgery - a suitable addition to small-incision cataract surgery. Ophthalmic surgery 2015; 27: 103.
• Saheb H and Ahmed II: Micro-invasive glaucoma surgery: current perspective and future directions. Curr Opin Ophthalmol 2012; 23: 96-104.
• Khan M and Saheb H et al .: Efficacy and safety of combined cataract surgery with 2 trabecular microbypass stents versus ab interno trabeculotomy. J Cataract Refract Surg 2015; 41: 1716-1724.

Web links

• A stent in the eye. Neue Zürcher Zeitung from February 13, 2016.
• Article about glaucoma and modern surgical therapy in the NDR

Individual evidence

1. ↑ Caprioli J, Kim JH, Friedman DS, Kiang T et al .: Special Commentary: Supporting Innovation for Safe and Effective Minimally Invasive Glaucoma Surgery: Summary of a Joint Meeting of the American Glaucoma Society and the Food and Drug Administration, Washington, DC , February 26, 2014. Ophthalmology. 2015 Sep; 122 (9): 1795-1801
2. ↑ Ferguson TJ, Berdahl JP, Schweizer JA et al .: Evaluation of a Trabecular Micro-Bypass Stent in Pseudophakic Patients With Open-Angle Glaucoma. J Glaucoma 2016, published online on August 22nd
3. ↑ Neuhann T: Trabecular micro-bypass stent implantation during small-incision cataract surgery for open-angle glaucoma or ocular hypertension: Long-term results. J Cataract Refract Surg 2015; 41: 2664-2671
4. ↑ Vold SD, Voskanyan L, Tetz M, Auffarth G et al .: Newly Diagnosed Primary Open-Angle Glaucoma Randomized to 2 Trabecular Bypass Stents or Prostaglandin: Outcomes Through 36 Months. Ophthalmol Ther 2016, published online on September 12th
5. ↑ Vold S, Ahmed II, Craven ER et al .: Two-Year COMPASS Trial Results: Supraciliary Microstenting with Phacoemulsification in Patients with Open-Angle Glaucoma and Cataracts. Ophthalmology 2016 Oct; 123: 2103-2112.
6. ↑ Töteberg-Harms M: Glaucoma surgery: Is minimally invasive automatically better? Ophthalmic surgery 2015; 27: 5-6.
7. ↑ Hoeh H, Ahmed IK, Grisanti S et al. Early postoperative safety and surgical outcomes after implantation of a suprachoroidal micro-stent for the treatment of open-angle glaucoma concomitant with cataract surgery. J Cataract Refract Surg. 2013; 39: 431-437.

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