EyeWorld Asia-Pacific March 2020 Issue

30 EWAP MARCH 2020 SECONDARY FEATURE a classic bullseye pattern of RPE loss, Dr. Dugel said, but by the time you see it, it’s quite late and there’s some evidence that it stays behind in the RPE cells even after you stop using the medication. “We know now with the OCT that there are subtle changes to look for early on in the ellipsoid zone to allow us to identify before seeing the bullseye pattern,” he said. “What we’ll see is the ellipsoid loss that has a kind of parafoveal distribution.” The classic appearance may change a bit because toxicity may be more parafoveal in Caucasians but more peripheral in Asians, he added. The point is that it’s really important to screen patients on a regular basis with the OCT and catch the potential toxicity earlier, Dr. Dugel said. Ethambutol Another drug with the potential for ocular toxicity is ethambutol, which is used in tuberculosis treatment. It causes what is sometimes mistaken for a retinal problem, Dr. Dugel said, but it really damages the optic nerve. It’s usually bilateral and symmetric, he added, and can cause photophobia, poor dark adaptation, and color changes. For patients on this drug, Dr. Dugel suggested regular assessment. Changes may be noticed in vision, visual field, and color vision, and it may also be helpful to look at the OCT, he said. This can lead to a pretty severe optic neuropathy, Dr. Weng said. She added that while there are no formal screening guidelines, patients will generally have toxicity appear 4–12 months after starting the medication. As such, many physicians bring patients in monthly during the first year. There have been reports of toxic effects being reversible, if detected early enough, Dr. Weng said, so time is of the essence in these cases. She added that this drug isn’t often used long term. Pentosan Pentosan is another potentially toxic drug, used to treat bladder issues such as interstitial cystitis. It was only recently learned that pentosan can cause pigmentary maculopathy, Dr. Weng said, which can cause damage to the outer retina and RPE. This was found incidentally by an ophthalmologist, Dr. Nieraj Jain at Emory University, who noticed that there was something that looked similar to macular degeneration and identified this drug as the common thread, she said. This is a maculopathy that is located in the central macula, which is very unfortunate, Dr. Weng added, because that’s the area most responsible for central and sharp vision. This toxicity can closely mimic macular degeneration or geographic atrophy, she said, so many of these patients potentially had a previous diagnosis of macular degeneration when it could have actually represented pentosan pigmentary maculopathy. No current screening guidelines exist, Dr. Weng said, and the full extent of damage or abnormality it can cause is still unknown. She added that it’s important to work together with urology colleauges as we learn more about this condition. Dr. Dugel said that changes may look like dry macular degeneration and patients may be misdiagnosed. Patients with this type of maculopathy are often younger (40s and 50s), so if someone is on Pentosan, they should be looked at, he said. Other drugs Dr. Dugel also mentioned the possible toxicity of drugs used for cancer, specifically several used to treat breast cancer. Additionally, he mentioned MEK inhibitors and immune checkpoint inhibitors. MEK inhibitors can disrupt the outer blood retinal barrier and cause fluid to accumulate in the subretinal space, he said. If you stop the medication, the fluid usually resolves, Dr. Dugel added. However, a lot of these cancer drugs are being used in patients with advanced disease, so it may not be possible to stop them, he added. Meanwhile, immune checkpoint inhibitors target the tumor by increasing T-cell function. The T-cells attack the tumors but can also trigger uveitis. Additionally, Dr. Dugel said these can cause VKH-like conditions, which can cause multiple subretinal fluid accumulations and RPE detachments. Dr. Noecker mentioned drugs that alter blood flow as potentially problematic. For example, anti-impotence drugs can change the circulation and may cause a drop in circulation around the eye. In those cases, you worry about dropping the blood supply too much to the optic nerve or parts of the retina, he said. This could potentially cause vein occlusion in the retina. There are often symptomatic changes in the vision, which may be transient, Dr. Noecker said. Additionally, blood pressure medications may also be something to look out for, Dr. Noecker said, as these may also impact the optic nerve and good circulation of the retina. In glaucoma, we’re worrying about drugs that drop diastolic pressure too low, he said. EWAP Editors’ note: Dr. Weng is affiliated with Baylor College of Medicine, Houston, Texas. Dr. Dugel is affiliated with the Retinal Consultants of Arizona, Phoenix, Arizona. Dr. Noecker is affiliated with the Ophthalmic Consultants of Connecticut, Fairfield, Connecticut. None of the doctors declared any relevant financial interests. Fundus autofluorescence illustrates the “bullseye” parafoveal ring of hyper-aut- ofluorescence thought to represent pho- toreceptor damage preceding significant retinal pigment epithelium degeneration. Source (all): Christina Weng, MD