Speaker: Andrew Tatham

In the context of cataract surgery, combining it with Minimally Invasive Glaucoma Surgery (MIGS), such as phaco-MIGS, offers a valuable opportunity to better manage intraocular pressure (IOP) in glaucoma patients. However, patient selection is crucial. MIGS should not be offered universally to all cataract patients with glaucoma due to factors like cost and suitability. Ideal candidates for MIGS include patients struggling with the tolerance of glaucoma medications, those with systemic issues caused by medications, and those experiencing poor IOP control or non-compliance with their treatment regimen. In particular, patients with early-stage glaucoma are prime candidates for phaco-MIGS, as this population often benefits the most from the combined procedure.

When considering the safety profile of glaucoma surgeries, trabeculectomy remains the most powerful intraocular pressure (IOP)-lowering procedure but is associated with notable risks, including hypotony, choroidal effusion, and bleb-related complications such as bleb leaks and potential endophthalmitis. In contrast, MIGS is defined by its minimally invasive nature, offering a better safety profile and faster recovery compared to traditional glaucoma surgeries. However, not all MIGS procedures are the same, and safety varies based on the technique. Canal-based MIGS procedures, such as the iStent and Hydrus stents, are designed to restore physiological outflow through Schlemm’s canal, reducing the risk of severe complications like hypotony. Evidence from randomized controlled trials, including the pivotal Food and Drug Administration (FDA) study for the iStent inject published in 2019, supports the safety of these procedures. In the two-year follow-up, phaco-iStent inject showed a similar safety profile to cataract surgery alone, with no reports of hypotony, corneal decompensation, or choroidal hemorrhage. Common complications included self-limiting microhyphema and focal synechiae, which are more related to long-term efficacy than safety concerns. Though some bleeding may occur due to blood reflux from Schlemm's canal, this is typically self-limiting. In the pivotal trial, the most common adverse event was a loss of visual acuity by two or more lines, but this was slightly more frequent in the cataract-only group. Overall, MIGS, particularly canal-based procedures, presents a safer alternative with fewer complications for patients with early glaucoma and medication tolerance issues, offering a favorable option for enhancing glaucoma management during cataract surgery.

In terms of intraocular inflammation, the incidence is similar between the phaco-iStent group and the phaco-alone group. As for IOP spikes, both groups showed a low incidence, with only 2% in the phaco-iStent group experiencing these spikes. This aligns with concerns about endothelial cell safety, especially following the complications seen with the CyPass stent. Fortunately, long-term safety data on the iStent inject show that endothelial cell loss remains comparable to phaco alone, as demonstrated in a five-year extension of the pivotal study. There was no difference in the proportion of eyes experiencing more than 30% endothelial cell loss over three to five years, reaffirming the high safety level of the iStent. Similarly, for the Hydrus Microstent, data from the five-year Horizon study revealed a comparable safety profile. Some minor complications, such as intraoperative hyphema and a cyclodialysis cleft, were observed but resolved quickly without long-term consequences. The Hydrus also demonstrated a lower incidence of IOP spikes compared to cataract surgery alone, with no reports of serious complications like hypotony, endophthalmitis, or choroidal effusion. Long-term concerns like synechiae, which may obstruct the stent, were noted but are more related to efficacy than safety. The study also showed no significant difference in visual acuity loss between the phaco-hydrus and phaco-alone groups, and the inflammation rates were low, dispelling concerns about intracameral inflammation caused by metallic implants.

Endothelial cell loss occurs with both phaco and phaco-Hydrus procedures, but the long-term rate of loss post-surgery was similar between the two groups. Overall, trabecular stenting devices like iStent and Hydrus have demonstrated high safety profiles in trials up to five years, and with over a million iStent devices implanted worldwide, real-world experience confirms these findings. These devices avoid the bleb-related complications seen with more invasive glaucoma surgeries, though they may not achieve the same level of IOP reduction as bleb-forming procedures. When discussing other trabecular procedures, such as trabecular dilation (e.g., canaloplasty) and trabecular tearing (e.g., trabeculotomy), these techniques lack the same level of randomized trial data. For example, the Omni procedure, which combines 360-degree canaloplasty with 180-degree trabeculotomy, showed promising results in the non-randomized GEMINI study, but the risk of hyphema was higher compared to stent devices. Additionally, newer techniques like excimer laser trabeculostomy (ELT) may hold promise for restoring outflow but still lack robust safety data. Finally, procedures targeting the suprachoroidal or supraciliary space aim to bypass the limitations of episcleral venous pressure by increasing aqueous outflow. These procedures, while potentially allowing for lower IOP, carry added risks due to the highly vascular nature of the suprachoroidal space. Thus, more research is needed to fully understand their safety profiles.

Suprachoroidal devices, such as the CyPass and Miniject, offer greater IOP-lowering potential but carry a higher risk of complications. CyPass was withdrawn in 2018 due to significant endothelial cell loss, particularly in cases where the device was improperly inserted. The Miniject, a softer material, remains the only commercially available suprachoroidal device, though it has been associated with higher rates of complications, including anterior chamber inflammation (24%), hyphema (13%), and some cases of explantation in earlier designs. Endothelial cell loss in standalone procedures without phaco has been minimal, suggesting that phaco may contribute more to cell loss in mixed procedures. Subconjunctival MIGS, like the PreserFlo and Xen45, present a more invasive option but with a favorable safety profile compared to traditional trabeculectomy. In a RCT, PreserFlo demonstrated lower rates of hypotony (3.8% vs. 15%) and choroidal effusions (4.8% vs. 7.6%) compared to trabeculectomy, while also providing faster visual recovery. However, bleb-related complications, such as bleb leaks and rare cases of endophthalmitis and choroidal hemorrhage, can still occur, highlighting the importance of surgical experience in bleb management.

Overall, the canal-based MIGS offer a higher level of safety compared to bleb-forming procedures, while suprachoroidal devices may provide more powerful IOP lowering but with an increased risk of complications. Bleb-forming procedures, though effective, carry the highest risk, particularly for hypotony and bleb-related issues. The trade-off between safety and efficacy remains a key consideration, and more long-term data is needed to fully assess these evolving procedures. Regulatory bodies, like the European Glaucoma Society (EGS) and the Royal College of Surgeons, urge caution and thorough evaluation of long-term outcomes to mitigate enthusiasm bias.

42nd Congress of the European Society of Cataract and Refractive Surgeons, 6 – 10 September 2024, Fira de Barcelona, Spain.