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Minimally invasive glaucoma surgery (MIGS)


What is MIGS?

Minimally invasive (also known as micro-invasive or micro-bypass) glaucoma surgery refers to a class of surgical treatment used to manage mild-to-moderate cases of primary open-angle glaucoma.

This is the most common type of glaucoma and results when the trabecular meshwork that drains aqueous fluid from the front of the eye is not working properly. As a result, pressure in the eye (also called intraocular pressure or IOP) increases and pushes on the optic nerve. Over time, damage to the nerve fibres results in peripheral (side) and eventually central vision loss.

MIGS procedures involve placing tiny medical devices in the eye to improve fluid outflow through the trabecular meshwork. The resultant decline in IOP reduces stress on the optic nerve and prevents further damage.

MIGS is occasionally used to treat some secondary glaucomas, such as pseudoexfoliation glaucoma or pigmentary glaucoma.

MIGS in Australia

Three implants are approved for use in Australia:

  • iStent inject®
    The iStent inject consists of two tiny (less than 0.4 mm) titanium stents that are implanted using a preloaded injector.1 These stents bypass the blockage in the trabecular meshwork, allowing the aqueous humour to drain from the eye at the same rate it is produced.
  • Hydrus®
    Hydrus is a curved, flexible stent that is roughly the size of an eyelash. Once inserted, it bypasses the trabecular meshwork and acts as a scaffold to widen the natural drainage canal.2 More fluid can flow via the canal into collector channels, thereby reducing the pressure in the front of the eye.
  • XEN®
    The XEN gel stent is a small, 6 mm shunt made from non-degradable gelatin that softens and conforms to the shape of the eye once inserted in the front chamber of the eye.3 It diverts fluid through the trabecular meshwork into a small blister (bleb) under the conjunctiva (skin of the eye) just below the upper eyelid.

Medicare rebate for MIGS as a standalone procedure

MIGS is typically offered after conventional treatments (medicated eye drops, laser therapy) have failed to achieve a satisfactory reduction in IOP. This type of surgery has a good safety profile and can delay the need for more invasive surgical procedures (trabeculectomy, drainage devices) in some people.

Previously, patients could only qualify for a Medicare rebate for MIGS when it was combined with cataract surgery. However, as of 1 May 2020, a standalone MIGS rebate (not performed in conjunction with another surgery) is available for patients with glaucoma who fail or are not eligible for conventional treatment with drops or laser therapy.4

Eligible patients can receive the Medicare rebate for MIGS when it is performed by an ophthalmologist with recognised training in these procedures.

Comparing MIGS to other glaucoma treatment options

While the mechanism varies, all treatment options aim to manage glaucoma by reducing IOP.

  • Medicated eye drops are a first-line treatment for patients with mild-to-moderate glaucoma. Although eye drops can effectively reduce IOP, adherence is often a problem. A high number of patients discontinue use due to side-effects, cost, forgetting to take the medication regularly (especially if they are taking multiple glaucoma eye drops), or developing a tolerance to treatment and experiencing a visual decline. Drops may be contraindicated in patients with pre-existing corneal conditions, such as dry eye or allergies.
  • Selective laser trabeculoplasty (SLT) is often added to the treatment plan when eye drops by themselves have not achieved sufficient reduction in IOP. The laser is applied to the trabecular meshwork to improve drainage. SLT is considered safe, effective and low risk. It does not cause tissue damage and can be repeated every 12 to 24 months as needed.
  • Trabeculectomy surgery is considered the most effective treatment option to prevent further vision loss from glaucoma. It is typically only used when other treatments have failed to sufficiently reduce IOP and in advanced causes where very low pressure is needed. Compared to MIGS, trabeculectomy is a more complicated procedure that requires greater tissue manipulation and has a slower, more intensive recovery period.5
  • Glaucoma drainage devices are used to manage patients with more severe glaucoma where other interventions (including trabeculectomy) have not worked or are unlikely to, and for cases linked to trauma, injury or complications of diabetes.6


How long does a MIGS procedure take?

Combined MIGS and cataract surgery typically takes 30–40 minutes operating time, while standalone MIGS may only take 5–10 minutes. Allowing for admission, preparation and recovery time, you should expect to be in the day surgery for around 2–3 hours.

Will the procedure hurt?

MIGS is performed under a local anaesthetic. You may feel some slight pressure on your eye during the operation, but there won’t be any pain.

Will I be able to feel the stent in my eye?

No, stents cannot be felt once placed in the eye.

What’s the recovery period like?

Recovery is rapid and typically no longer than the recovery period for cataract surgery (approximately 2–4 weeks). You will be prescribed medicated eye drops after the surgery to treat any swelling and inflammation. Your doctor will advise you on how often and how long to use the drops. You should be able to resume normal activities after 2 weeks.

Is MIGS safe?

The MIGS devices that are currently approved for use in Australia are safe. However, as with all surgical procedures, there are potential risks.

Minor postoperative complications include:

  • Increase in IOP
  • Low IOP (hypotony) with XEN compared to iStent and Hydrus
  • A bleed inside the eye (hyphema) is common with the iStent and Hydrus – this typically resolves a few days after surgery
  • Endothelial cell loss (uncommon)

An uncommon but serious complication that can occur after MIGS is endophthalmitis (infection within the eye). If left untreated, this can lead to irreversible vision loss.

Will I still need eye drops after MIGS?

After a MIGS procedure, you will temporarily stop all your regular glaucoma medication so that your eye pressure can be reassessed and monitored. Many patients find that they no longer need glaucoma medication or can reduce the number of drops they take, but this is not guaranteed. Some patients may also need to restart eye drops or laser treatment in the future if their eye pressure goes back up.


When deciding the best course of treatment, your ophthalmologist will take into account your lifestyle, pre-existing eye conditions, type and severity of glaucoma and initial eye pressure. Regardless of whether medication, laser therapy or surgery is recommended, it’s important that you don’t stop treatment without speaking to your ophthalmologist first. Glaucoma requires long-term management by an ophthalmologist to keep your eye pressure controlled and prevent or minimise vision loss.

iStent inject® is a registered trademark of Glaukos Corporation.
Hydrus® is a registered trademark of Ivantis, Inc.
Xen® is a registered trademark of AqueSys, Inc., an Allergan affiliate.


  1. Glaukos. iStent Inject. Glaukos (date unknown). Available at https://www.glaukos.com/au/healthcare-professionals/istent-inject/ [Accessed 13 August 2020]. ↩︎
  2. Ivantis. Healthcare professionals. Ivantis Inc (date unknown). Available at https://www.ivantisinc.com/au/healthcare-professionals/ [Accessed 13 August 2020].↩︎
  3. XEN Gel Stent. What is the XEN gel stent? Allergan (date unknown). Available at: https://www.xengelstent.com/XENGelStent [Accessed 10 August 2020].↩︎
  4. Glaucoma Australia. MIGS approved as standalone procedure. Glaucoma Australia (date unknown). Available at: https://www.glaucoma.org.au/articles/migs-approved-as-standalone-procedure-article/ [Accessed 23 July 2020].↩︎
  5. Chen DZ, Sng CCA. Safety and Efficacy of Microinvasive Glaucoma Surgery. J Ophthalmol. 2017. Article ID 3182935. Available at http://downloads.hindawi.com/journals/joph/2017/3182935.pdf [Accessed 13 August 2020].↩︎
  6. A/Prof Michael A Coote. Glaucoma drainage devices. Glaucoma Australia (date unknown). Available at https://www.glaucoma.org.au/articles/glaucoma-drainage-devices-article/ [Accessed 23 July 2020].↩︎
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