Over the last decade, there has been a significant shift in management of glaucoma patients. Historically, ophthalmologists have initiated treatment with topical therapy and titrated the number of medications based on the patients’ stage of glaucoma and target intraocular pressure (IOP), followed by laser trabeculoplasty and/or filtration surgery if target IOP was not achieved. Filtration procedures were typically limited to those with moderate to severe glaucoma due to their aggressive nature and complication profile, which include hypotony, choroidal effusions, maculopathy, bleb leaks, and endophthalmitis. Intraoperative complications were reported in up to 10% of cases, while perioperative complications were estimated to occur in approximately 50%.¹ Due to the overall challenges with surgical technique and postoperative management, glaucoma procedures have historically been performed by glaucoma subspecialists.²

Minimally invasive glaucoma surgery (MIGS) has emerged as a promising approach to managing previously challenging aspects of glaucoma, while offering improved safety and efficacy compared to traditional surgical methods. With the explosion in the research and development of MIGS devices and procedures, there has been a significant upsurge in the volume of glaucoma procedures performed over the last decade — from 2012 to 2016 alone, there was a 426% increase in the use of MIGS, and its use continues to exponentially grow.² Most MIGS procedures target the conventional outflow system, which offers a safer, bleb-free approach. Despite the improved safety profile, no surgery is without risk, because each MIGS procedure, although rare, can have unfavorable intraoperative and postoperative complications.

Of the postoperative complications, hyphema is the one most frequently encountered with the various MIGS devices and procedures collectively. A recent review article discussed the rates of hyphema after the following MIGS procedures: iStent Inject (Glaukos) 0% to 5%, Hydrus Microstent (Alcon) 1.92% to 6.45%, Kahook Dual Blade (New World Medical) goniotomy 0% to 34.9%, Trabectome (MicroSurgical Technology) 4.72% to 95%, gonioscopy-assisted transluminal trabeculotomy (GATT) 0.97% to 38%, Omni Surgical System (Sight Sciences) 3.7%, ab interno canaloplasty 1.9% to 20%, and Xen gel stent (Allergan/AbbVie) 0.9% to 6%.¹ Unlike guidelines for traumatic hyphema management, formal treatment guidelines on MIGS-associated postoperative hyphema management are absent and are currently based on clinical expertise. Fortunately, most postoperative hyphemas resolve with conservative measures (routine postoperative care) and without any long-term sequelae.

Intraoperative Hyphema Development and Management

The etiology of hyphema development associated with MIGS procedures targeting the conventional outflow system can vary among the devices used for outflow manipulation, but the disruption of the integrity of the inner wall of Schlemm’s canal, which is a blood-aqueous-barrier, allows for blood in the distal outflow system to regurgitate into the anterior chamber (AC). This can be seen intraoperatively when blood emanates through trabecular microbypass stent ostia (Figure 1) or directly into the AC following excisional goniotomy/trabecular ablative procedures (Figure 2). Surgeons often consider this to be a confirmation that a direct unhindered communication has been established between the AC and a patent distal outflow system. Like the prognostic findings of the episcleral fluid venous wave described by Grover et al following trabecular ablative procedures, blood regurgitation through stents or directly through collector channels into the AC can be a positive prognostic indicator that angle manipulation yielded a favorable treatment.³ However, bleeding can also occur due to iatrogenic trauma to tissues and vasculature adjacent to Schlemm’s canal (eg, bridging vessels, iris root, ciliary body). This is very different from a simple reflux of blood and more challenging to manage. With blood regurgitation, hyperpressurizing the eye with balanced salt solution (BSS) to an IOP in the mid-20s can alleviate the presence of blood in the AC. With tissue damage, however, pressurization with BSS may be insufficient to impede bleeding, and tamponade with a viscoelastic agent may be necessary. In extreme cases, use of an argon laser or thermocautery may be necessary. Glaucoma surgeons encounter traumatic bleeding more frequently with procedures that tear through large sections of the trabecular meshwork, like the GATT procedure, regardless of the goniotomy device used. These procedures may be associated with larger hyphemas, clot formation (Figure 3), IOP spikes, corneal blood staining, and potential vision loss.¹

Intraoperative techniques may also lower the rate of postoperative hyphema. In our center, we typically attempt to leave the IOP between 20 mmHg and 25 mmHg upon leaving the operating room to minimize risk for perioperative hyphema development. With excisional goniotomy or other procedures that disrupt large areas of the blood-aqueous barrier, we may opt to leave a small amount of viscoelastic in the angle to tamponade the collector channels. This can minimize blood regurgitation directly into the anterior chamber.

Immediate Postoperative Hyphema Patterns and Management

Temporary visual impairment may be encountered, even with modest amounts of circulating red blood cells in the AC, especially in a pseudophakic patient. With larger hyphemas or clots, the schedule of postoperative visits are usually modified because of these potential consequences. In the setting of hyphema and elevated IOP (even as low as the high 20s), aggressive pressure management and close follow-up are merited. There are differing opinions among glaucoma specialists on the methods for pressure reduction, with some advocating for rapid depressurization by releasing aqueous via AC tap/wound burping or with pharmacologic administration of topical aqueous suppressants and oral carbonic anhydrase inhibitors. In our practice, aqueous release is limited to patients with elevated IOP associated with clots obstructing the angle, those in pain, or those with contraindications to oral carbonic anhydrase inhibitors. There is some fear that rapid depressurization can lead to further regurgitation of blood from the distal collector system back into the AC, which can exacerbate the patient’s condition. Patients are also followed much closer until the pressure stabilizes without oral medications to ensure that harmful adverse events like corneal blood staining do not occur.

Other potential complications associated with postoperative hyphema include formation of a retrolenticular hematoma, which can take months to resolve (Figure 4). If the retrolenticular hematoma is treated with a capsulotomy using an Nd:YAG laser, the blood can dissipate into the vitreous, forming a vitreous hemorrhage. We have also encountered a case of a primary vitreous hemorrhage during goniotomy with the Omni Surgical System, which necessitated a trans pars plana vitrectomy for blood clearance. Thankfully, these cases are very rare, but it is important to know that the risk exists.

Anticoagulation and MIGS

No clinical trials have established standard preoperative use of blood thinners or well-defined postoperative management algorithms. Preoperative cessation of antiplatelet and anticoagulation medications is a topic of debate within the surgical community, again with no literature-based consensus. At the 2023 American Glaucoma Society meeting, Teejus Pradeep presented a survey of glaucoma specialists that showed 48% had “high concern” for performing excisional goniotomy on patients unable to hold their anticoagulants or antiplatelets prior to surgery.^4,5 Pratte et al looked at patients undergoing combined phacoemulsification and Kahook Dual Blade goniotomy with 42 eyes on anticoagulation and 90 eyes off anticoagulation and found no difference in postoperative hyphema rate. The main factor associated with hyphema was found to be a postoperative day 1 IOP of 10 mmHg or less (17.2% developing hyphema) vs patients with IOP above 10 mmHg (2.0% developing hyphema). These data suggest that low IOP is a greater risk factor for hyphema development rather than preoperative bleeding risk.⁶ The coagulative ability of patients may be more critical if the iris or ciliary body are damaged during a procedure, which is a known risk factor of any angle-based procedure, including trabecular bypass stents. In our practice we tend to avoid procedures that shear through the TM, like the GATT procedure or goniotomy with the Omni Surgical System, in patients who are on anticoagulants. Proper intraoperative identification of angle structures is critical to reduce the risk of damaging adjacent structures and almost certainly reduces the risk of postoperative hyphema unrelated to low IOP. Regardless of a surgeon’s preference on preoperative medication management, safe practice may involve consulting the patient’s cardiologist or primary care provider during the preoperative planning process to determine if medication cessation is safe and appropriate.

Long-term Outcomes of Postoperative Hyphema

The primary goal of treating postoperative hyphema is to prevent the development of vision-threatening complications such as IOP spikes, surgical failure, and corneal blood staining. The mainstay of initial medical treatment for hyphemas includes topical steroids with or without cycloplegic agents, which typically leads to resolution of the hyphema. Reasons for early IOP spikes from 1 to 14 days after 360° GATT were explored by Rao et al in a 2023 retrospective study that found hyphema led to early IOP spikes in 25% of cases.⁷ This study also found the formation of a fibrotic membrane via anterior-segment optical coherence tomography in 12% of GATT patients, and that this significantly increased chances of needing additional IOP-lowering therapy after surgery. It seems likely that postoperative hyphema could contribute to the formation of this fibrotic membrane and thus early treatment with steroids is imperative to try to prevent this complication.⁸ To make things even more challenging, MIGS patients can still get a steroid-related IOP spike, so it is critical to evaluate whether hyphema and inflammation is the cause of high IOP or if it is due to prolonged steroid use.

Delayed onset hyphema is rare but can arise many months or even years after a MIGS surgery. In a 2012 retrospective study, Ahuja et al looked at 262 eyes undergoing Trabectome sugery, with a total of 12 patients (4.6%) experiencing a hyphema at least 2 months after surgery. Median time to delayed onset hyphema was 8.6 months, and 1 patient required trabeculectomy for refractory IOP spikes. The underlying etiology for recurrent hyphema development is a period whereby the episcleral venous pressure exceeds the IOP (ie, hypotony, valsalva maneuvers, and head-down positions). Life-style modifications to minimize or eliminate blood regurgitation into the AC may be merited if tolerated by the patient (ie, minimize head-down yoga positions). If lifestyle modifications are ineffective, more invasive measures may be required.⁸ There have been published cases requiring surgical intervention due to IOP spikes from hyphemas, but this has been a rare occurrence.^8,9 There is a single case report describing the successful use of endoscopic cyclophotocoagulation (ECP) in treating a chronic recurrent hyphema after 360° trabeculotomy, as well as a report of argon laser to stop a recurrent traumatic hyphema, so laser approaches may be a reasonable option, especially if bleeding can be localized to certain collector channels.^10,11 Anterior-chamber washout could also be indicated if hyphema is not clearing over time to get a sufficient view to use argon or ECP, or if vision-threatening IOP spikes occur secondary to the hyphema.

Conclusion

Minimally invasive glaucoma surgery has emerged as a promising approach to managing previously challenging aspects of glaucoma, with improvements in safety and efficacy. Consequently, there has been a shift in the practice of glaucoma management and increase in volume of procedures. Although MIGS offer improved safety profiles compared with traditional glaucoma surgeries, complications, such as hyphema, can occur and need to be managed appropriately to ensure optimal patient outcomes. Additionally, more clinical data on postoperative MIGS complications would be helpful in establishing better medical and surgical management guidelines. GP

Declan Kirk, MD, and Carl Pellerin, MD, are ophthalmology residents at Texas Tech University Health Sciences Center in Lubbock, Texas. They report no relevant disclosures.

Matt Porter, MD, is a glaucoma specialist and assistant professor at Texas Tech University Health Sciences Center. Dr. Porter reports consultancy to Glaukos.

Mark J. Gallardo, MD, is a glaucoma specialist with El Paso Eye Surgeons in El Paso, Texas. Dr. Gallardo reports consultancy, speaker’s fees, and clinical trials with Glaukos, Alcon, and Ellex; clinical trials with Sight Sciences, New World Medical, and Ivantis; and speaker’s fees from Aerie Pharmaceuticals and Bausch + Lomb. Reach him at gallardomark@hotmail.com.

References

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