Incidence of CME high in patients with retinitis pigmentosa
SEATTLE – Up to 70% of patients with retinitis pigmentosa can have cystoid macular edema, so thorough subjective and objective testing is advised, a presenter said here at Optometry’s Meeting.
Lindsay T. Gibney, OD, FAAO, a resident at Omni Eye Specialists in Baltimore, shared a case report here during a “live poster presentation.” She also presented the case in a poster at the meeting.
A 27-year-old white, healthy male with no systemic conditions presented with complaints of worsening central vision, Gibney said. He had been diagnosed with retinitis pigmentosa (RP) by a retina specialist prior to relocating, but he said he had previously been told he had age-related macular degeneration. He was taking dorzolamide.
The patient’s best-corrected visual acuity was 20/200 OD and 20/400 OS, full to finger-counting. He had no afferent pupillary defect, intraocular pressure was normal, the anterior segment exam was unremarkable and he had no cataracts.
“You could tell he had cystoid macular edema (CME),” Gibney said; “he had no foveal light reflex. In his periphery you could see subtle bone spicules. Red-free photos showed the CME better. Overall, the retina and nerves looked good.
“This was upsetting to think that his vision was affected by the macular edema,” she continued. “We see this in so many diabetic patients. You send them to the retina specialist, and there are a lot of treatments for it, but you can’t always restore vision.”
RP is a genetic disease, with inherited symptoms, Gibney said. Difficulty with night vision is the initial complaint, and progressive peripheral visual field loss occurs. Retinal signs include bone spicules, mottling and granularity of the retinal pigment epithelium, attenuated vessels and waxy pallor of the optic nerve head.
“It distorts peripheral vision, but not central vision so much,” she said. “However, there are things that can happen with the disease to affect the central vision, especially later in the disease, such as posterior subcapsular cataract, central retinal degeneration and macular edema.”
She noted about 100 different genetic mutations have been identified as causing RP.
“We are not sure what causes macular edema in RP and not exactly sure why carbonic anhydrase inhibitors (CAIs) seem to be an effective treatment,” Gibney said. “It could be that CME and RP have a chronic low-grade inflammation. You could see the vitreous cells.”
Patients are also more prone to developing pseudophakic CME and epiretinal membranes after cataract surgery.
“Antiretinal antibodies are found in patients with RP and seen a lot in patients with autoimmune diseases,” she said.
The mechanism of action of CAIs, the main treatment for CME in RP, is increasing the passage of fluid through the RPE, possibly improving the extrafoveal sensitivity.
“Sometimes you won’t see an improvement in the optical coherence tomography, but the patients often feel like they see better,” Gibney said. “It may improve their contrast sensitivity.”
Between 20% and 56% of patients will see an improvement, she said.
She recommended starting with topical CAIs, gauging the response and stepping up to orals if necessary.
“Other possible options for treatment could be steroids,” Gibney said. “Intravitreal injections have been found to benefit, but the benefits are short-lived, and repeated injection are needed. Nonsteroidal anti-inflammatories can be used, but they are not as effective as CAIs.”
Because a third of patients with RP will have CME, perform an OCT on these patients, Gibney advised.
“If they have pretty good central vision, you’ll want to do a visual field to be sure they’re still legal to drive,” she said. “Our patient could not drive.”
Other testing includes fluorescein angiography to test for macular edema and confirm the diagnosis, in addition to ERG and microperimetry.
“In the future, this will probably be more important, but genetic counseling can help guide therapy and help determine a prognosis,” Gibney said. “Consider a low vision consult and psychological counseling.”
She said she recommends that all patients with AMD quit smoking, use UV protection, consider blue light filtering and avoid isotretinoin and Viagra (sildenafil citrate, Pfizer).
Future treatments could include vitamin, gene and stem cell therapy, Gibney said.
“Vitamin A has been shown to slow progress, but effects are modest, and the dosages in studies are high,” she said. “It’s not safe in women of child-bearing age. DHA in fish oil and lutein, just like with AMD, may help, but there are not a lot of studies.”
RP patients do not respond well to anti-VEGF therapy, in contrast to those with vascular disease, Gibney said.
“There’s some question if it’s safe, because you get vessel attenuation in CME with RP, and anti-VEGFs can cause vessel attenuation,” she said. “And it hasn’t been shown to be more effective than CAIs.”
Gene therapy may help, but only if damage has not already been done to the retina, Gibney said. “Stem cell therapy can help replace cells that have been destroyed by disease. A 3-D retinal layer grown in a lab may be a future treatment.”
The Argus II (Second Sight) was approved in February 2013. “It doesn’t give sight back, but it provides shadows and can help patients maneuver around,” she said. – by Nancy Hemphill, ELS, FAAO
Disclosure: Gibney reports no financial disclosures.