“As ophthalmologists, regardless of your specialty, you will see glaucoma patients,” warns Alyson L. Hall, MD of The Glaucoma Center, Annapolis, Md. “You can run from them, but you cannot hide.” Given this unfortunate reality, the ASCRS’s “Glaucoma Essentials” symposium at its virtual annual meeting in May, armed clinicians against what is still one of the leading causes of irreversible blindness worldwide.
Michael F. Oats, MD, Jody R. Piltz-Seymour, MD and Amy D. Zhang, MD, ABO, led the May 16 session.
Definition and types of glaucoma
Aakriti Garg Shukla, MD, ABO, of Wills Eye Hospital, Philadelphia, detailed the definition and types of glaucoma. In addition to basic glaucoma classifications, Dr. Shukla emphasized the importance of ruling out other conditions through differential diagnosis. “These include compressive lesions and congenital abnormalities” she said.
Pachymetry, gonioscopy and corneal hysteresis in glaucoma diagnosis
Nathan M. Radcliffe, MD, ABQ, Mt. Sinai Hospital, New York City, examined the roles of these technologies in the glaucoma diagnosis.
Gonioscopy remains “priceless,” he said, and should be performed on all patients at baseline, then periodically thereafter. As for corneal thickness, he noted that OHTS demonstrated it dominates glaucoma risk. It is a stronger predictor of glaucoma development than IOP and is the current standard for IOP and glaucoma risk and interpretation. He described corneal hysteresis as the “next level of corneal thickness. Hysteresis is the newest and frankly more powerful risk assessment that can allow us to better characterize our patient’s risk for glaucoma and progression.
Clinical observations of the optic nerve
While glaucoma care entails heavy reliance on optic nerve analysis with OCT, Jody Piltz-Seymour, MD, of Wills Eye, made the case that “it’s vitally important that every ophthalmologist know how to examine the optic nerve clinically.” A systematic approach is critical. “Most optic nerves follow the ‘ISNT rule,’” she explained. “That means the inferior rim is thickest, followed by the superior, then the nasal, and the temporal rim is the thinnest.”
With that in mind, she shifts to another acronym: SHIP. “We look for size, we look for hemorrhages, we look at the ISNT evaluation of the optic nerve rim, we look at parapapillary atrophy.” As a bonus, the physician can also look at the retinal nerve fiber layer (RNFL). Be on the lookout for changes in these parameters as well as shifts in blood vessels, Dr. Piltz-Seymour instructed.
“In assessing the optic nerve, the first thing you need to know is the size of the discs. If you don’t pay attention to disc size, you risk missing the diagnosis of glaucoma in the small optic nerve and misdiagnosing glaucoma in normal eyes that are either large or have asymmetric-sized optic nerves.”
When it comes to evaluating progression, the clinician must look for hemorrhages, progressive rim thinning, widening of notches in the retinal fiber layer defects, vessel shifts, increased peripapillary atrophy and pallor, Dr. Piltz-Seymour said. With regard to hemorrhages, “it’s very good to say at one point when you’re examining the optic, ‘I am going to look for hemorrhages now,’” she said. “Because sometimes at quick glance, it can just look like a little blood vessel. Look for true contour changes compared to the normal or contralateral eye.”
Interpreting visual fields
Tom Patrianakos, DO, of Northwest Chicago Eye Specialists, offered six tips for better interpretation of visual fields.
Be sure you pick the correct test
Understand the reliability indices
Be able to use global indices
Recognize glaucomatous scotomas, and learn to differentiate them from other types of scatomas,
Be well versed in common artifacts as well as testing errors
Put it all together to determine what progression is.
Posterior segment OCT for glaucoma detection
Brian A. Francis, MD, MS, Doheny Eye Center UCLA in Pasadena, Calif., offered different ways to check for scan quality and detailed various artifacts to identify and potentially fix. “One of the first things we look for is signal strength,” he said. “Poor signal strength will tend to give you a test that shows artificial thinning of the RNFL.”
Scan signal pattern should be evenly strong throughout the test with a solid segmentation red line extending across the entire scan, he added. Another tip: Scan alignment is very important.
Summing up, Dr. Francis said, “The OCT is useful in earlier detection of optic nerve damage in glaucoma suspects, in following glaucoma suspects for mild to moderate glaucoma, and for detection of progression or conversion. The GCC [ganglion cell complex] may be more sensitive in early disease and more useful in advanced disease than the peripapillary RNFL.” As always, he warned, the information from OCT must be put into context with the clinical exam findings as well as the results of the visual field testing and optic nerve appearance.
Stratifying stage and risk for glaucoma
Accurately identifying the stage of glaucoma is important, said Douglas J. Rhee, MD, chair, Department of Ophthalmology and Visual Sciences, Case Western, Cleveland, because it helps physicians zero-in on the most appropriate interventions. “Patients with advanced stage disease have a worse prognosis for progression, and advanced stage disease may benefit from trabeculectomy earlier in the treatment protocol.”
It’s also helpful to know the risk factors for converting from ocular hypertension to actual glaucoma. Accurate assessment of the patient’s stage is valuable for billing and coding, as well, Dr. Rhee added. For example, for advanced stages of the disease, RNFL testing is not reimbursed.
When to treat, when to refer
“Prior to the advent of the NEI trials and MIGS, this would have been a very short conversation,” Dr. Hall said. “We maximize drops, we offer laser trabeculoplasty, and then we refer patients for trabeculectomy or aqueous shunt procedures if you don’t perform them yourself.” The NEI trials and MIGS have changed that, however, with the result that clinicians recognize the need to more aggressively lower IOP. Innovations such intracameral injections may allow some patients to avoid surgery altogether, she noted, while MIGS has opened up opportunity for ophthalmologists who don’t perform “trabs and tubes” and so would previously have referred out.
Despite these advances, however, some patients will continue to progress. “These need to be referred before they fall off a cliff,” Dr. Hall said. Risk factors that warrant referral, she continued, include uncontrolled IOP, race, a strong family history of blindness from glaucoma, anyone who needs to be dilated regularly for diabetes; refer patients who are progressing or are at moderate to high risk of progressing.
“Evaluate the patient’s risk for developing glaucoma andthe risk for getting worse,” she said.
Differential diagnosis in glaucoma
To distinguish between glaucoma and a “masquerader,” Amy D. Zhang, MD, ABO, of Kellogg Eye Institute said it is crucial to get a thorough and detailed patient history and to note the speed of progression of the disease. Further, Dr. Zhang explained, it is important to not just rely on one single piece of information but to include all signs and testing to help evaluate the patient. A “very careful” exam is also a necessity, she said, specifically for pallor of the optic nerve. “And finally, to remember that the patient may have more than one disease.” OM