To understand more about minimally invasive glaucoma surgery (MIGS), Dr Margaret Lam interviewed Sujan Hong, an optometrist and surgical glaucoma specialist for Alcon with expert knowledge on the Hydrus Microstent.
Cataract and glaucoma are the two leading causes of blindness. While cataracts are usually easily treated with cataract surgery, the damage and blindness from glaucoma is usually irreversible.1 MIGS can be an effective way to slow the development and progression of optic nerve damage for glaucoma patients and is often performed in conjunction with cataract surgery.
When it comes to glaucoma management, I am sure many turn to drops as the first line of treatment, but should that change?
According to an email poll conducted by Healio for Ocular Surgery News, MIGS was voted as one of the most important ophthalmic innovations of the last few decades by hundreds of ophthalmologists.2
It is, therefore, imperative for optometrists and ophthalmologists co-managing glaucoma patients to maintain an understanding of innovations in this space.
Armed with the latest knowledge, we can better advise our patients about treatment options for their condition.
Q. What can patients expect during the recovery process?
MIGS in the anterior chamber – known as ab-interno surgery – takes minutes to perform and enables glaucoma patients to go for a longer period with no or fewer drops or secondary surgical intervention, so there is really no reason why this option shouldn’t be offered at the time of cataract surgery, if a patient is suitable for a MIGS device.
Post-operative protocols are the same. The recovery time typically takes no longer than cataract surgery alone, and patients should not feel anything.3
Q. How effective is Hydrus Microstent at reducing intraocular pressure (IOP), and how would you measure success in patients?
To measure the success of a MIGS device we would look to three factors:
Firstly, the decrease in IOP.
Secondly, lessening dependency on IOP lowering drops post-surgery, and whether this benefits the patient.
And thirdly, a reduced need for secondary surgical intervention to manage IOP post-surgery.
The five-year HORIZON randomised clinical trial showed that 66% of combination cataract and Hydrus Microstent surgery patients remained medication-free at five years, vs 46% of the cataract surgery only group.4
Additionally, there was a more than 50% relative reduction in incisional secondary surgical intervention with cataract and Hydrus Microstent surgery patients vs the cataract surgery only group.
Q. How do you address common concerns or anxieties patients have about undergoing a MIGS procedure?
As with any surgery, there may be risks but MIGS procedures use tiny incisions and microscopic devices. They generally provide improved safety compared with other glaucoma surgical intervention methods, while providing mild-to-moderate IOP lowering effects.5
Other common concerns may be around efficacy and cost.
When it comes to efficacy, it really depends on the stage of glaucoma at the time of the surgery, as well as the type of MIGS procedure they have.
Q. How does Hydrus Microstent fit in within the MIGS space?
Hydrus Microstent is an ab-interno, canal based, MIGS approach, designed to optimise aqueous drainage, and reduce intraocular pressure for adult patients with open-angle glaucoma.
When it comes to cost concerns, Hydrus Microstent is fully covered for those with private health insurance with prosthesis cover. This should allay cost concerns if patients have appropriate cover.6 But I think the practitioner and patient should also consider the benefit of an improved ocular surface – most often without the need for eye drops, improved quality of life and better controlled disease. All of this presents significant savings long term.
Q. What are the considerations for recommending a MIGS procedure?
There are different ways a MIGS works:7
• By enhancing fluid outflow using the eye’s inherent drainage system (if the drainage system is functional),
• By shunting fluid to the outside of the eye (ab-externo), and
• By decreasing the production of fluid within the eye.
We know that compliance with topical eye drops is one of the biggest challenges with glaucoma patients, and non-adherence is associated with progression.8 If glaucoma is progressing despite the patient being prescribed drops, we need to consider whether non-adherence is at play, and in such cases, a surgical procedure may better control the condition.
Another factor is ocular surface disease (OSD). It is estimated that up to 75% of patients being treated for glaucoma also have OSD.9 Both prostaglandin analogues and beta-blockers can negatively impact meibomian glands,9 which are crucial in maintaining a healthy lipid layer in a tear film. For patients with significant OSD, reducing the number of glaucoma drops with procedures such as selective laser trabeculoplasty (SLT) or MIGS, could significantly improve their quality of life.
Different MIGS devices have different indications for different types of glaucoma.
Hydrus Microstent is indicated for patients with mild-to-moderate primary open angle glaucoma. Patients with moderate-to-severe glaucoma may need a more invasive surgical procedure that can achieve a greater IOP reduction.
Q. Can you share a patient story that demonstrates the benefits of MIGS?
Beverly* presented in 2015 with preoperative visual acuity (VA) of 6/24-36 and IOP of 19mmHg. She had been prescribed prostaglandins, a beta blocker, an alpha agonist and a carbonic anhydrase inhibitor. Her ocular surface was poor.
She had combined cataract and Hydrus Microstent surgery in 2015, after which her VA was 6/9, and her IOP was 14mmHg with no medications.
Generally, patients can be off medications immediately after the surgery, with reduced IOP, and can be monitored.
In 2022, when Beverly presented for her regular eye examination, her VA was still 6/9 and her IOP was 14mmHg. Seven years on, having had Hydrus Microstent, she still had no need for any topical medications.
This was an excellent result given her improved VA, IOP, and ocular surface, and she no longer had to deal with the logistical and financial burden of four medications.
Q. What are the most common postoperative complications associated with Hydrus Microstent?
In clinical studies of the Hydrus Microstent, intraoperative complications have been uncommon and typically involve transient hyphema10 (which resolves over one week post-operatively) or malpositioning of the device4,10 (which can be re-captured and re-deployed at the time of surgery with the same delivery system if detected). In the 2020 American Academy of Ophthalmology (AAO) Primary Open-Angle Glaucoma Preferred Practice Pattern guidelines, the Hydrus Microstent received a data rating of “moderate quality, strong recommendation”. This was the highest rating given among all MIGS.11
Q. What are some considerations for surgeons when considering when to perform a standalone glaucoma MIGS procedure vs combining it with cataract surgery or other ocular surgeries?
I think this is where the paradigm shift comes in. If a patient has difficulty with compliance, or known poor compliance, and their pressure is not being controlled adequately with drops, and if other surgical interventions such as SLT have not worked, then it would be great to consider MIGS.
If the patient is already having cataract surgery, it will only take minutes to implant Hydrus Microstent at the time of surgery. As glaucoma progression has a high degree of unpredictability, giving a patient extra support to manage their pressure at the time of cataract should definitely be considered for all eligible patients.
Q. What training do surgeons undertake before performing MIGS procedures?
We certify surgeons using a three-step process:
1. A didactic presentation, where we walk through the device, surgical steps, tips and tricks, and present the clinical data around Hydrus Microstent efficacy and safety,
2. A wet lab in the operating theatre, where we demonstrate the implantation process on model eyes, and
3. Surgical case proctoring, during which we provide surgical support in theatre with the first series of cases.
We continue to support the surgeon until they are comfortable with the surgical technique.
I got to try Hydrus Microstent implantation on model eyes for the first time in this role and I was impressed at how easy the process was. Holding on to the gonio lens – which I hadn’t done for a number of years – was the hardest part!
It would obviously be different on human eyes with so many variabilities, but studies have shown a relationship between significant hospital volume and patient outcomes.12
Dr Tatham, an award winning cataract and glaucoma surgeon from Scotland who was recently in Australia, said that inserting Hydrus Microstent is “a lot easier than you might think”.
Q. What advice do you have for ophthalmologists working in the cataract and glaucoma space?
I think the common misconception is that MIGS needs to be performed by a glaucoma surgeon, but any surgeon who performs cataract surgery can incorporate MIGS into their practice with the right training and support from ophthalmic companies. The only additional surgical items required when doing a cataract surgery would be a Hydrus Microstent, a gonioprism, and a 1.5mm blade for a corneal incision.
Q. What new developments in glaucoma MIGS technology can we expect in the coming years?
The pace of innovation is accelerating, however before we look for new developments and future advancements, I think we need to fully embrace and understand the innovations we have at our fingertips. When it comes to glaucoma management, I am sure many turn to drops as the first line of treatment, but should that change?
Professor Ahmed, who is also a director of the Alan S. Crandall Center for Glaucoma, said: “In the past, the benefits of early glaucoma surgical intervention were insufficient and the significant risks too great to justify the early use of traditional procedures such as trabeculectomy or tube shunts. The emergence of MIGS procedures, however, has potentially tipped the risk-benefit scale in favour of early surgery to afford quality of life benefits to patients who otherwise would not be considered appropriate surgical candidates. Furthermore, decreased IOP fluctuation and the likelihood of improved adherence may reduce the risk of visual field progression and/or need to progress to further, more invasive surgery3 This is a paradigm shift that I am hopeful more surgeons will continue to consider.”13
Q. Lastly, as the glaucoma specialist representing Hydrus Microstent, how does this technology differ from other MIGS devices?
Hydrus Microstent employs a tri-modal mechanism of action:
1. It is designed to span approximately 90º of Schlemm’s canal, ensuring access to collector channels in the nasal region,
2. It uses an open scaffold design, which precisely dilates and scaffolds Schlemm’s canal, gently expanding the cross-sectional area without obstructing outflow access to collect channel ostia, and
3. It bypasses the trabecular meshwork to restore flow of aqueous from the anterior chamber through the inlet of the Microstent into Schlemm’s canal.
We don’t know the exact locations of the collector channels, but we do know that there are more collector channels present in the nasal inferior quadrant, so having a stent that spans over a quarter of your Schlemm’s canal will only help increase your chances of accessing as many collector channels as possible.
I’d like to conclude by saying that although MIGS is a relatively new innovation in the glaucoma space, it has an excellent safety profile, is minimally disruptive and efficacious.7
MIGS can enhance quality of life and alleviate ocular surface disorders in eligible patients when conducted alongside cataract surgery. Additionally, it can be independently performed as a standalone procedure.
*Patient name changed for privacy. Thanks to Dr Brendan Cronin for providing the case.
Sujan Hong is a surgical glaucoma specialist for Alcon based in NSW. She graduated from Auckland University with a Bachelor of Optometry and practised as an optometrist before heading to the United States of America to pursue a management career in information technology. Ms Hong returned to clinical optometry in Australia before joining Alcon Vision Care as a Professional Education and Development Manager in 2018.
Dr Margaret Lam is the National President of Optometry Australia. She practises optometry at 1001 Optical in Bondi Junction in Sydney, and teaches at the School of Optometry at UNSW as an Adjunct Senior Lecturer.
References
1. Allison, K., Patel, D., and Alabi, O., Epidemiology of Glaucoma: The past, present, and predictions for the future. Cureus, 2020. 12(11): p. e11686.
2. Dreisbach, E.N., Phacoemulsification, MIGS voted most important recent innovations in ophthalmology. 2022 [cited 21July 2023]; Available from: healio.com/news/ophthalmology/20220411/phacoemulsification-migs-voted-most-important-recent-innovations-inophthalmology
3. VEI. Minimally invasive glaucoma surgery (MIGS). Vision Eye Institute eyeMatters: Bringing you the latest news and resources in eye health 2020 [cited 2 Aug 2023]. Available from: visioneyeinstitute.com.au/eyematters/minimally-invasive-glaucoma-surgery-migs.
4. Ahmed, I.I.K., et al., Long-term outcomes from the HORIZON randomized trial for a Schlemm’s canal microstent in combination cataract and glaucoma surgery. Ophthalmology, 2022. 129(7): p. 742-751.
5. Pillunat, L.E., et al., Micro-invasive glaucoma surgery (MIGS): a review of surgical procedures using stents. Clin Ophthalmol, 2017. 11: p. 1583-1600.
6. Prostheses cover under private health insurance [cited 21 July 2023]. Available from: health.gov.au/topics/private-health-insurance/what-private-healthinsurance-covers/prostheses-cover-under-private-health-insurance.
7. Ahmad A., Aref, Tripathy K., Faisal R., et al., 2023, American Academy of Ophthalmology: eyewiki.aao.org/Microinvasive_Glaucoma_Surgery_(MIGS)#MIGS_Approaches.
8. Shu, Y.H., et al., Topical Medication adherence and visual field progression in open-angle glaucoma: Analysis of a large US Health care system. J Glaucoma, 2021. 30(12): p.1047-1055.
9. Lappin, C.J., The intertwining story of glaucoma treatment and ocular surface burden. 2023 [cited 21 July 2023]. Available from: eyesoneyecare.com/resources/intertwining-story-of-glaucoma-treatment-and-ocularsurface-burden.
10. Safety and effectiveness study of the Hydrus microstent for lowering IOP in glaucoma patients. ClinTrials.gov (NCT01539239).
11. Alcon. Hydrus Microstent – Your MIGS choice matters [cited 21 July 2023]; Available from: www.myalcon.com/professional/cataract-surgery/hydrus-microstent.
12. Levaillant, M., et al., Assessing the hospital volume-outcome relationship in surgery: a scoping review. BMC Med Res Methodol, 2021. 21(1): p. 204.
13. Ahmed, I.I.K., MIGS Beyond Cataract Surgery. Glaucoma Today, 2022 (May/ June Insert).
