Treatment Considerations for Controlling IOP in Pigmentary Glaucoma

In this episode of Pressure Points Glaucoma, Justin Schweitzer, OD, FAAO, sits down with Judy Hu, OD, to discuss a case of pigmentary glaucoma and important treatment considerations for these patients.

Dr. Hu is an optometrist at The Glaucoma Center, a tertiary referral center in Bowie, Maryland, that offers medical, laser, and surgical glaucoma care.

Case report

A 40-year-old Caucasian male patient was referred to the clinic for a glaucoma evaluation, as the referring optometrist noted that his eye pressures were elevated. The patient’s best-corrected visual acuity (BCVA) was 20/20 in the right eye (OD) and 20/20 in the left eye (OS), and he had not been prescribed glaucoma medication previously.

The clinical examination revealed:

Intraocular pressure (IOP): 30mmHg OD, 31mmHg OS
Corneal hysteresis: 7.5mmHg OD, 7.6mmHg OS
Pachymetry: 550μm OD, 550μm OS
Refractive status: Myopic

Figures 1 and 2: Fundus images of the optic nerve head OD and OS, respectively, demonstrating signs of atrophy and optic disc tilt.

^{Figure 1: Courtesy of Justin Schweitzer, OD, FAAO.}

^{Figure 2: Courtesy of Justin Schweitzer, OD, FAAO.}

Figure 3: Slit lamp image of the patient at baseline showing pigment on the corneal endothelium.

^{Figure 3: Courtesy of Justin Schweitzer, OD, FAAO.}

Figure 4: Slit lamp image at baseline displaying iris transillumination defects.

^{Figure 4: Courtesy of Justin Schweitzer, OD, FAAO.}
Figure 5: Gonioscopy exam at baseline revealing a heavily pigmented trabecular meshwork.

^{Figure 5: Courtesy of Justin Schweitzer, OD, FAAO.}

OCT and VF testing

Interpreting glaucomatous changes in myopic eyes can be difficult as structural and functional defects due to myopia, such as thinning of the lamina cribrosa and optic nerve changes, can be challenging to distinguish from true glaucomatous signs.^1,2

Dr. Schweitzer noted that he was cautious when analyzing the optical coherence tomography (OCT) image, as the TSNIT curve was “bouncing around,” which suggested that it was not a reliable scan.

Figures 6 and 7: OCT imaging of the patient, OD and OS, respectively, showing fluctuating TSNIT curves.

^{Figure 6: Courtesy of Justin Schweitzer, OD, FAAO.}

^{Figure 7: Courtesy of Justin Schweitzer, OD, FAAO.}

Figures 8 and 9: VF testing OD and OS, respectively, demonstrating a classic glaucomatous VF defect OD.

^{Figure 8: Courtesy of Justin Schweitzer, OD, FAAO.}

^{Figure 9: Courtesy of Justin Schweitzer, OD, FAAO.}

Initial reflections on the case

Dr. Hu’s key takeaways from this case:

Based on the clinical examination, imaging, and testing, she would diagnose the patient with pigmentary glaucoma, moderate OD and mild OS
Aggressive IOP control will be one of the top priorities, and given the patient’s relatively young age (40 years old) and IOP levels (30mmHg OD, 31mmHg OS), she would target a mid-teens IOP OD and high-teens IOP OS
The slit lamp image showed that the patient had hazel eyes, so she would mention that prostaglandin analogs (PGAs) have been shown to cause increased pigmentation of the iris, resulting in a darker eye color³
- This may be a deterrent for patients with hazel eyes.

Tips for diagnosing pigment dispersion syndrome

Pigment dispersion syndrome (PDS) and subsequent pigmentary glaucoma are characterized by the liberation of iris pigment due to contact between a posteriorly bowed iris and lens zonules.⁴ This pigment circulates into the anterior chamber and deposits into the angle, resulting in an obstruction of aqueous outflow.

The classic clinical triad of indications include:⁴

Pigment deposition on the posterior surface of the central cornea (known as a Krukenberg spindle and shown in the first slit lamp image)
Mid-peripheral iris transillumination defects (show in the second slit lamp image)
Dense trabecular meshwork pigmentation (seen in the gonioscopy exam)

Treatment approaches for this patient

Dr. Hu noted that, in her experience, individuals with hazel eyes typically do not want to risk changing their eye color. So, if this patient did not want a PGA, she would recommend a fixed-combination agent OU and a noninvasive laser procedure - selective laser trabeculotomy (SLT) OD. However, for a patient with a different eye color, she would recommend a PGA OU and SLT OD.

She added that she would likely reach for Combigan (brimonidine tartrate 0.2% / timolol maleate 0.5%, Allergan) or dorzolamide-timolol as long as there were no contraindications, such as asthma, respiratory problems, or bradycardia.

Dr. Hu explained that she would recommend a fixed-dose combination drop to minimize the number of total drop bottles, especially because this patient is treatment-naïve. Moreover, she would propose that the patient initiate topical therapy and return in 4 weeks to reassess IOP levels.

Dr. Schweitzer noted that he often leans on laser for these patients as well, and because the patient was young, he would be aggressive with treatment. However, he advised that optometrists keep in mind that patients with heavily pigmented trabecular meshwork are at higher risk of post-SLT IOP spikes.⁵

As such, he usually follows up with patients 1 week after the procedure to check for pressure elevation. Dr. Hu added that, in her experience, these IOP elevations tend to level out by the 4- to 6-week mark.

LPI for pigmentary glaucoma

Another potential laser-based treatment for pigmentary glaucoma is laser peripheral iridotomy (LPI), which aims to decrease the lens-zonular interaction by eliminating reverse pupillary block in the presence of a posteriorly bowed iris.⁶

However, both doctors remarked that they have observed inconsistent treatment outcomes with LPI for pigmentary glaucoma, and studies have not yet established its long-term effects on visual function and other patient-important outcomes.⁶

Dr. Schweitzer added that it is important to weigh the risks and rewards, as doing an LPI may cause glare or halos in a young patient.

Conclusion

Ultimately, Dr. Schweitzer recommended that the patient undergo standalone SLT initially and observed an IOP reduction to the low twenties.

He is currently monitoring the patient’s IOP levels, and both doctors agreed that another therapy would be required to get the patient’s IOP to the teens if any progression is noted.