39 EyeWorld Asia Pacific | June 2024 GLAUCOMA Current Perspectives on NTG and Progression at Low IOPs by Liz Hillman, Editorial Co-Director It’s heartbreaking and hard to understand: a patient has glaucoma and their disease continues to progress, despite having a normal or low IOP. Marlene Moster, MD, and Pradeep Ramulu, MD, PhD, provided their thoughts on diagnosis of normal tension glaucoma (NTG), establishing true progression, and how to manage worsening disease in this patient population. According to Dr. Ramulu, half or more glaucomas develop at low pressures. “Once you start getting to really low pressures, it can be a bit of a surprise that someone has glaucoma … because most of the people who have glaucoma developing at low pressures are still in the upper half of what’s normal, usually 15 mmHg and above,” Dr. Ramulu said. “When you start getting below that, it becomes relatively uncommon. The more troubling, and less common, scenario is someone who appears to be getting worse when their eye pressure is well controlled.” Is it really NTG? When it comes to establishing an initial diagnosis of NTG, Dr. Moster and Dr. Ramulu said it’s important to ensure that it’s truly NTG. Dr. Moster said when a patient is sent in for a diagnosis and treatment of NTG, it’s important to look for red flags so that other treatable optic neuropathies are not missed. “For example, we look very carefully for an atypical visual field with temporal loss. If the cupping is similar in both eyes but there is a large afferent pupillary defect, I’m concerned there is a neurologic process going on. We look for color loss, dyschromatopsia, because there is not much color loss in glaucoma, but there is profound loss in neurologic disease,” she said. “I look for pallor of the rim of the optic nerve more than cupping; asymmetric pallor is indicative of neurologic disease.” She said that other neurologic symptoms to watch out for are headache, motility defects, and diplopia. “Also, I look for decreased vision out of proportion to what I would expect looking at the optic nerve because with neurologic disease, vision is usually poor, but with glaucoma, even at the end, there is good central vision. I also look for ganglion cell layer loss that is atypical on OCT, looking for an atypical paracentral defect that will show up on the ganglion cell complex or nasal defect that is atypical. Also, very young patients are unlikely to have normal tension glaucoma and may instead have neurologic disease,” she said. If a patient has a red flag, Dr. Moster said she refers the patient to neuro-ophthalmology for further testing. Establishing progression When visual fields and/or OCT suggest that a patient with NTG is progressing despite a low IOP, Dr. Ramulu said he likes to first establish that it’s true progression. He asks the patients about their symptoms. Are they experiencing a drop in vision that is commensurate with what he would expect from the imaging and visual fields? He has a discussion with patients about whether they’re using their topical IOP-lowering medications as directed. “I say, ‘We’re going to start talking about operations, and if you’re not using your medicines properly, please tell me because I don’t want to do an operation if you’re just not using your medications as you should be,’” he said of his patient conversation. “Usually at that point when faced with something tangible that has some risks, patients say, ‘I haven’t been using them consistently.’” He’ll also check ability to administer drops. Patients might in fact be taking their drops, but if they’re not getting onto the eye correctly, they’re not working. You need to make sure they’re taking what you say they should take, when you say, how often, and that the drop is making it into their eye, Dr. Ramulu said.
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