• YO Need to Know: 6 Pearls for Glaucoma Diagnosis and Management

    Glaucoma diagnosis and management present unique challenges to ophthalmologists in training and to those early in comprehensive practice. A broad spectrum of disease manifestations, our reliance on multiple ancillary tests and the availability of medical, laser and surgical treatment options can be daunting. These six pearls will help you better diagnose and manage glaucoma.

    Perform gonioscopy

    Gonioscopy remains an integral part of a comprehensive eye exam even in our modern era of imaging. Unlike anterior segment optical coherence tomography (AS-OCT), a careful gonioscopic examination yields subtle clues to the presence of secondary causes of glaucoma (e.g., pigment dispersion, pseudoexfoliation and angle neovascularization). Gonioscopy requires the examiner to be fluid and dynamic; for example, a convex iris approach might require tilting the gonioprism toward the quadrant being examined or asking the patient to look slightly toward the mirror. Compression gonioscopy can help identify areas of peripheral anterior synechiae in eyes with primary angle closure disease. Gonioscopy.org is an invaluable resource for learning additional techniques. Remember: The more you do, the better you’ll get! 

    Repeat the visual field 

    Visual fields (VFs) can be onerous for patients and often have a steep learning curve. When establishing a baseline — or in the setting of unreliability, artifact or suspected progression — repeat the VF to confirm or refute changes before altering treatment. In the Ocular Hypertension Treatment Study, abnormalities on reliable VFs were not confirmed in 85.9% of repeat tests!1 Set your patients up for success by explaining the test well and choosing an appropriate testing strategy (e.g., consider a 10-2 for patients with defects close to or involving fixation and a stimulus V for those with visual acuity < 20/200).

    Additional tips to troubleshoot VF artifacts include taping ptotic eyelids, ensuring the correct refraction is used and testing only one eye on a given day for easily fatigued patients. Artifacts have become common during the pandemic due to face masks and lens fogging; we recommend taping the superior edge of each patient’s mask to the nasal bridge to mitigate this. Finally, if pupil size is < 3 mm, consider pharmacologic dilation prior to testing. 

    Beware of “red disease” and “green disease”

    Spectral-domain OCT of the retinal nerve fiber layer (RNFL) has become an essential tool for diagnosing glaucoma and monitoring progression. However, like VFs, OCT RNFL is subject to artifact, and the normative databases by which different machines define normal (i.e., green) versus abnormal (i.e., red) have inherent limitations. Accurate interpretation of an OCT RNFL report therefore requires looking beyond the color coding to analyze the RNFL thickness and deviation maps, horizontal and vertical B-scan tomograms, and temporal, superior, nasal, inferior, temporal (TSNIT) plot to identify artifacts, “red disease” and “green disease.” 

    False-positive “red disease” (i.e., when the OCT RNFL reads normal as abnormal) may result from segmentation errors (e.g., due to a posterior vitreous detachment or blink artifact), high myopia, and retinal findings like age-related macular degeneration or panretinal photocoagulation. “Green disease” refers to false negatives – the inability of OCT RNFL to pick up damage when it’s focal (see Figure 1) or in the presence of confounding factors like optic nerve head edema and/or macular edema. Be mindful of “progression in the green,” whereby the OCT RNFL is progressively thinning in a given sector but remains green as it's still in the wide normal range. Remember, OCT RNFL is a supplement to, not a replacement for, your clinical examination and should always be interpreted in the context of other data points (e.g., VF and macular imaging). By looking at the big picture, you’ll avoid overtreating “red disease” and undertreating “green disease.”

    Figure 1A. In this example of a spectral-domain OCT RNFL (left), the TSNIT plot indicates inferotemporal thinning of the left ONH (blue arrow) and an inferotemporal wedge defect is seen in the RNFL thickness map (red arrow) and RNFL deviation map (purple arrow). A cursory look at the normal average RNFL thickness of 93 um in the summary statistics and green color coding in the quadrant and clock-hour analyses would miss this subtle, focal damage. Color fundus photograph of the left ONH (bottom right) shows thinning of the inferotemporal neuroretinal rim that correlates to the OCT RNFL.
    Figure 1B. This example of a spectral-domain OCT ganglion cell analysis from the patient shown in Figure 1a demonstrates inferotemporal thinning in the ganglion cell layer-inner plexiform layer thickness map (red arrow) and deviation map (purple arrow) of the left eye that correlates to the clinical examination and OCT RNFL of the left ONH. The yellow inferotemporal sector also indicates thinning (blue star).

    Don’t neglect the ocular surface 

    Ocular surface disease (OSD) is prevalent among patients with glaucoma and its effects on quality of life contribute to medication nonadherence. Ask your patients about medication tolerability and assess the eyelids, ocular surface and tear film at each visit. Keep in mind both benzalkonium chloride-free alternatives (e.g., Alphagan P, Travatan Z and Xelpros) and preservative-free options (e.g., dorzolamide-timolol, timolol and tafluprost). In addition, a newer sustained release intracameral implant (bimatoprost SR; Durysta) may mitigate ocular surface toxicity. Selective laser trabeculoplasty and incisional glaucoma surgery can also be considered to relieve medication burden in patients with comorbid OSD and glaucoma. 

    Consider primary SLT

    The LiGHT trial was a landmark randomized clinical trial demonstrating the safety, efficacy and cost-effectiveness of primary 360-degree selective laser trabeculoplasty (SLT) in treatment-naïve patients with OHTN and (mostly) mild OAG. At 3 years, 74.2% of eyes in the SLT group maintained target IOP without medications and none required glaucoma surgery.2 We consequently now have high-quality evidence supporting the use of SLT as an initial treatment for OHTN and OAG, rather than waiting until maximum medical therapy fails as has been done historically.

    Refer early 

    If in doubt about an equivocal diagnosis or the best next step in management for your patient, refer early to a glaucoma specialist. Developing relationships with glaucoma specialists in your practice and community will go a long way toward providing the best possible care to your patients.

    1. Keltner JL, Johnson CA, Quigg JM, et al. Confirmation of visual field abnormalities in the Ocular Hypertension Treatment Study. Ocular Hypertension Treatment Study Group. Arch Ophthalmol. 2000 Sep;118(9):1187-1194.

    2. Gazzard G, Konstantakopoulou E, Garway-Heath D, et al; LiGHT Trial Study Group. Selective laser trabeculoplasty versus eye drops for first-line treatment of ocular hypertension and glaucoma (LiGHT): a multicentre randomised controlled trial. Lancet. 2019 Apr 13;393(10180):1505-1516.

    The Academy’s YO Info Editorial Board is collaborating with YO leaders from our subspecialty society partners and thanks the American Glaucoma Society Jr. Members at Large, Kateki Vinod, MD, and Angela Turalba, MD, for contributing this article.

    About the Authors

    Kateki Vinod, MD, is an assistant professor of ophthalmology at the Icahn School of Medicine at Mount Sinai and the glaucoma fellowship director at New York Eye and Ear Infirmary of Mount Sinai in New York City.
     
    Angela Turalba, MD, is chief of ophthalmology at Atrius Health in Boston. Drs. Vinod and Turalba are currently the American Glaucoma Society’s Junior Members-at-Large.