The OD’s Role in Glaucoma Surgical Care

The utility of microinvasive glaucoma surgery (MIGS) has increased dramatically during the past decade. For most glaucoma surgeons, this has meant more time in the OR and less time for clinic, and optometrists are stepping in to fill the gap. It is therefore important that ODs know what to expect after glaucoma surgery. This article outlines some key areas of focus in postoperative care.

TRABECULAR STENTS, GONIOTOMY, AND CANALOPLASTY

Postoperative Day 1

Immediate postoperative management is similar for these procedures. IOP should be stable or slightly reduced, and patients should notice minimal to no effect on their vision. As with any incisional procedure, the initial evaluation should include checking for proper wound closure via Seidel testing and looking for excess inflammation in the anterior chamber, which could suggest the development of toxic anterior segment syndrome or endophthalmitis. A wound leak or significant inflammation with fibrin or hypopyon warrants contacting the surgeon for prompt intervention.

Hyphema, usually microhyphema to grade 1, is common after surgery with a trabecular stent, goniotomy, and canaloplasty and may be an initial cause of blurred vision (Figure 1). IOP should be monitored closely, and patients should be instructed to keep their head elevated and to avoid strenuous activity. Management is conservative with close monitoring and management of any IOP elevation with topical medications.

Postoperative Week 1

Patients are typically seen again 1 week after surgery, at which point some reduction in IOP is expected. For individuals who received a trabecular stent or a goniotomy, gonioscopy is performed to evaluate the angle, especially if IOP is elevated. Proficiency with gonioscopy is imperative for the management of MIGS patients because this examination permits direct assessment of the surgical site for problems that can decrease the procedure’s efficacy. A four-mirror gonio lens is preferred for efficiency and patient comfort.

Trabecular stents such as the iStent series (Glaukos) and Hydrus Microstent (Ivantis) are typically placed in the nasal quadrant and should be evaluated for proper positioning at the level of the trabecular meshwork into Schlemm canal. Devices that are placed improperly or that slip out of position may lower IOP inadequately or cause persistent anterior uveitis from iris chafing. These findings necessitate surgical revision. If iris tissue plugs the lumen of the stent, fluid outflow may be blocked, leading to IOP elevation; this problem can be alleviated surgically or with Nd:YAG laser ablation to clear the obstructive tissue. Sometimes, iris tissue only partially plugs the lumen, and IOP may be within the target range. In this situation, patients may be monitored without intervention.

Patients who underwent a goniotomy with a Trabectome (MicroSurgical Technology), Kahook Dual Blade (New World Medical), or the Omni Surgical System (Sight Sciences) should be evaluated for the formation of peripheral anterior synechiae that may obstruct aqueous outflow. Pilocarpine is often included in the postoperative drug regimen to prevent the formation of peripheral anterior synechiae, although the necessity of doing this is being studied.^1,2

One of the major draws of MIGS is its potential to decrease the medication burden on patients. The process of discontinuing glaucoma medications differs from one clinician to another. At our practice, my colleagues and I tend to wait until the 1-month visit to begin tapering medications to mitigate a steroid response. Hypotensive drops should be removed one at a time so that the clinician may gauge the efficacy of surgery more easily and prevent large pressure spikes.

Additional Notes

Throughout the early postoperative period, clinicians should remain watchful for a steroid response because patients with glaucoma are at increased risk of this complication.³ When a spike occurs, IOP-lowering medications may be added, and steroid therapy should be decreased—but not too quickly, as this may trigger rebound inflammation. One may also consider switching to a steroid such as loteprednol (various) that is associated with lower response levels.⁴ Patients should be reassured that IOP spikes are typically transient in nature and that pressure should return to normal after steroid therapy ceases.

Rarely, patients who receive a trabecular stent or goniotomy experience sporadic hyphemas months to years after surgery. This is thought to be secondary to manipulation of the eye in the presence of low IOP, which allows blood reflux into the anterior chamber.⁵ Episodes may lead to blurred vision, often upon waking, and significant IOP spikes. These hyphemas can be managed with IOP-lowering drops until the blood clears.

SUBCONJUNCTIVAL STENT

Postoperative Day 1

An ab externo approach and its higher risk-reward profile have led some to classify the Xen Gel Stent (Allergan) as “MIGS-plus.” Expectations for postoperative day 1 differ greatly for this device compared with other MIGS procedures. IOP should be in the single digits, and visual acuity is often reduced.⁶ Flow through the stent should result in the formation of a diffuse bleb. Stent obstruction is a concern if, on examination, the IOP is high or the conjunctiva around the device is flat. If the anterior chamber appears to be shallow, as may happen if IOP is low, atropine should be added to the drop regimen to deepen and stabilize the chamber. Because IOP is expected to decrease significantly, all hypotensive medications are discontinued immediately after surgery to avoid hypotony.

Postoperative Weeks 1 and 2

IOP should increase to the high single digits or low teens during the first 2 weeks after surgery. If the IOP rises higher, the first step is to prescribe aqueous suppressants. Limiting aqueous production and flow is thought to reduce the amount of inflammatory factors introduced to the bleb that may contribute to scarring.⁷ Conversely, IOP that is too low (low single digits) may indicate overly robust flow, and hypotony may result. Whereas steroid-induced IOP spikes are a concern with other MIGS procedures, these agents may keep pressure low after the placement of a Xen implant by preventing bleb scarring. Steroids may therefore be decreased in these patients to lessen aqueous outflow.

My colleagues and I have found that a very slow (ie, over the course of 2 to 3 months) taper of steroids helps to ensure good bleb formation after the placement of a Xen Gel Stent (Figure 2). Tapering steroids too quickly may lead to scarring, which can seal off the distal end of the stent. If excessive conjunctival injection is noted over the area of filtration, steroids can be increased to prevent scarring.

Additional Notes

Encapsulation of the bleb can occur months to years after surgery and limit aqueous outflow, leading to an IOP spike. In this situation, bleb needling and the application of antifibrotics such as mitomycin C may help to break apart fibrotic adhesions and improve filtration.⁸ The stent may also become exposed, increasing the risk of infection and bleb leak.⁹ The device should be evaluated at every visit for these issues.

WHY SHOULD ODS TAKE PART?

Although postoperative care may not be the most lucrative type of visit, playing an active role during this period gives optometrists an opportunity to build rapport with patients. Patients are often comforted to know that they have a provider in addition to their surgeon whom they can trust with their care. Extended facetime with patients and proper management of their eyes during the postoperative period has led many of them to elect to continue care with me. As such, I have found this to be an effective way to build my patient base and establish a niche within my practice.