Surprise Spikes

Selective laser trabeculoplasty (SLT) is a safe and effective method for lowering IOP. First introduced in 1995 and FDA approved in 2001, SLT is increasingly becoming the first-line treatment for open-angle glaucoma.¹ The term “selective” refers to the laser’s precision in targeting pigmented trabecular meshwork (TM) cells while sparing adjacent nonpigmented tissue.¹ Using a low-energy, frequency-doubled Q-switched Nd:YAG laser (532 nm), SLT induces a biological response that enhances aqueous outflow through the TM—achieved not by ablating tissue, but by stimulating cellular and cytokine-mediated remodeling.¹

Traditionally performed by anterior segment surgeons, SLT is now being adopted by a growing number of optometrists in 11 states and counting, as the scope of practice expands.² Despite its strong safety profile, the procedure can lead to rare complications, such as corneal haze, hyphema, and persistent inflammation.³ However, the biggest concern remains transient post-procedural IOP elevation.³ Identifying appropriate candidates for SLT is key to minimizing adverse outcomes.

Although IOP spikes following SLT are rare, I recently encountered a noteworthy case featuring a significant post-laser IOP spike. Interestingly, this patient demonstrated substantial ganglion cell complex (GCC) loss in the absence of a corresponding visual field defect. This article explores the clinical course of this case and reviews the incidence, pathophysiology, risk factors, and management strategies for increases in IOP following SLT.

CASE PRESENTATION

A 58-year-old Asian man with a history of mild bilateral primary open-angle glaucoma was referred for a glaucoma evaluation. He had been managed with multiple IOP-lowering agents, including brimonidine tartrate 0.2%/timolol maleate ophthalmic solution 0.5% (Combigan, Allergan/AbbVie) and latanoprost ophthalmic solution 0.005% (Xalatan, Viatris).

On initial examination, the patient’s BCVA was 20/20 OU and his IOP was 10 mm Hg OD and 8 mm Hg OS. Slit-lamp examination revealed periocular dermatitis localized to the right upper eyelid. Posterior segment evaluation demonstrated healthy optic nerves with cup-to-disc ratios of 0.7 OD and 0.6 OS and no other notable posterior pole pathology (Figures 1 and 2).

The periocular dermatitis was suspected to be an allergic contact dermatitis secondary to chronic use of brimonidine. To reduce the patient’s topical medication burden and manage the suspected allergic reaction, SLT was recommended and subsequently performed in his right eye. The brimonidine/timolol combination treatment was discontinued, while timolol by itself was continued once daily in the right eye and latanoprost was maintained once nightly in each eye.

At the 1-month post-SLT follow-up, the patient’s IOP was acutely elevated to 36 mm Hg OD. He was treated in-office with 500 mg of oral acetazolamide (Diamox, Teva Pharmaceuticals) and was instructed to increase timolol to twice daily in the right eye. Additionally, topical bromfenac ophthalmic solution 0.07% (Prolensa, Bausch + Lomb) was initiated to address possible post-SLT inflammation or trabeculitis.

After 1 week, the patient’s IOP had decreased to 30 mm Hg OD. Although still elevated, the downward trend was encouraging, and he was advised to maintain the same regimen. A repeat evaluation was scheduled for 3 weeks later, and the patient was informed that if his IOP did not improve, further surgical intervention would be recommended.

At the subsequent follow-up visit, the patient’s IOP had decreased significantly to 15 mm Hg OD and 14 mm Hg OS, indicating successful control was achieved with the revised treatment plan. He was directed to continue all glaucoma medications and to return in 3 months for updated glaucoma testing.

DISCUSSION

IOP can rise for many reasons, including due to an inflammatory response, TM dysfunction, hypersensitivity to laser energy, and pre-existing ocular conditions. Understanding the causes of these IOP spikes is essential for developing effective strategies for monitoring, managing, and ensuring optimal patient outcomes.

Inflammatory Response

Mechanism: SLT causes a controlled, selective disruption of the TM cells and collagen matrix, leading to a mild inflammatory response.⁴ The laser energy induces the release of inflammatory mediators such as prostaglandins and cytokines, which can cause temporary alterations in the outflow facility.⁴

Management: Short-term antiinflammatory medications such as topical corticosteroids or NSAIDs are commonly prescribed to mitigate this effect.⁴ Close monitoring of IOP is necessary to ensure the spike resolves or remains manageable.

TM Dysfunction

Mechanism: SLT selectively targets pigmented cells in the TM, aiming to stimulate the outflow of aqueous humor.⁵ However, in some cases, this laser treatment can cause irreversible damage to the TM cells or collagen structure, impairing the outflow facility.⁵ Additionally, laser energy can lead to an increase in extracellular matrix deposition, causing increased resistance to aqueous outflow.⁵

Management: If TM dysfunction is suspected, a more conservative approach should be taken when managing IOP spikes, with medications being used to reduce the pressure.⁵ Long-term follow-up is important to assess whether the TM’s function improves over time or further interventions, such as MIGS, are required.

Hypersensitivity to Laser Energy

Mechanism: Although SLT is a selective procedure, individual variation in ocular tissue response to the laser energy can lead to an exaggerated inflammatory or healing response.⁶ Some eyes may be more sensitive to the laser’s thermal effects, especially those with a heavily pigmented TM, leading to a greater inflammatory reaction or excessive scar tissue formation.⁶

Management: If hypersensitivity is suspected, antiinflammatory therapy, such as corticosteroids or NSAIDs, can be employed to reduce the severity of the inflammatory response.⁶ To decrease the risk of IOP spikes, lower energy settings are recommended in patients who exhibit greater angle pigmentation.⁶

Pre-Existing Ocular Conditions

Mechanism: Certain pre-existing conditions (eg, narrow or closed angles, pseudoexfoliation, and previous trabeculectomy or glaucoma surgery) can predispose the eye to a greater risk of postoperative IOP spikes after SLT.

• Narrow or Closed Angles: Eyes with narrow angles may have a more difficult time achieving sufficient TM exposure for SLT, which can reduce the effectiveness of treatment and result in transient IOP spikes due to insufficient aqueous outflow.⁷
• Pseudoexfoliation: In eyes with pseudoexfoliation syndrome, there may be a structural abnormality or added resistance to aqueous outflow that becomes exacerbated after SLT.⁸
• Previous Trabeculectomy or Glaucoma Surgery: Eyes that have previously undergone glaucoma surgery may have altered TM physiology or altered healing, which could affect the success of SLT and contribute to IOP spikes.⁹

Management: A comprehensive preoperative evaluation is essential to identify any risk factors or pre-existing conditions that could predispose the patient to IOP spikes. In such cases, the SLT procedure should be performed with caution, and postoperative care should be more closely monitored. Medication adjustments or other treatments (eg, laser peripheral iridotomy in narrow-angle patients, incisional surgery in patients with advanced glaucoma) may be necessary.

PREPARE FOR POSTOP

Spikes in IOP that occur after SLT are multifactorial in origin, with causes ranging from transient inflammatory responses to more complex anatomic and biochemical alterations. The variability in response to SLT among individuals underscores the importance of a personalized approach to preoperative assessment, surgical technique, and postoperative management. Timely detection and appropriate management of these spikes is crucial to ensuring favorable long-term outcomes for patients undergoing this procedure for glaucoma treatment.