Treating ocular surface may not be enough in dry eye

CHICAGO – Evaluating the ocular surface for local treatment is not enough, according to Anat Galor, MD. Nerve dysfunction must also be considered in cases of stubborn dry eye.

Galor, an associate professor of clinical ophthalmology at Bascom Palmer Eye Institute, Miami, spoke on neuropathic pain here at the American Academy of Optometry’s Anterior Segment Section Symposium, which was cosponsored by Primary Care Optometry News.

“Many patients with dry eye symptoms have evidence of nerve dysfunction and central sensitization,” Galor said. “Even though we know this, there’s a disconnect. Patients come in complaining of dry eyes, and the clinician says, ‘You must have a tear problem.’

“We spend a lot of time measuring tear parameters in a methodical way,” she continued. “But even in the best circumstances, 8% of variability in symptoms is explained by what we’re seeing on the ocular surface. That’s terrible. There has to be more.”

Galor said patients with dry eye sensation may have aqueous deficiency or evaporative tears.

“But other patients can have neuropathic pain, such as post-LASIK, post-trauma, post-herpetic neuralgia, migraine, traumatic brain injury, fibromyalgia, depression and anxiety,” she said. “When I see these comorbidities, I start thinking about neuropathic pain.”

Pain specialists have been evaluating for sensitization in the clinic “for ages,” Galor said. “We don’t have to reinvent the wheel. They’re looking for specific descriptors of pain to indicate a neuropathic origin.”

Galor said she and her colleagues have adapted the Neuropathic Pain Symptom Inventory questionnaire to include: hot and burning, sensitivity to light, and sensitivity to wind. Clinicians should also ask how long the symptoms have existed.

Patients who indicate these symptoms have more severe, chronic disease and are less likely to respond to topical therapies, she said.

“There are lots of symptoms, but few signs of disease,” Galor said.

She recommended that eye care providers test potential neuropathic pain patients with proparacaine.

“We ask patients to rank their pain before and after proparacaine,” she said. “If they have persistent pain after proparacaine, this could be a manifestation of neuropathic pain.”

Galor said clinicians are already making headway in helping these patients.

“When we protect the ocular surface, we’re protecting nerves,” she said. “When we treat inflammation, we make nerves happier, improve aqueous health, improve lipid health and address anatomy.

“Do we need to modulate somatosensory function in patients with neuropathic pain?” she asked.

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Galor said her first-line therapy focuses on topical modulation with autologous serum tears, “which seems to work,” she said.

These patients also respond well to drugs such as Neurontin (gabapentin, Pfizer), Lyrica (pregabalin, Pfizer) and Cymbalta (duloxetine, Eli Lilly), used off-label, Galor noted.

“Prevention is better than treatment,” she said. “In anesthesia, there’s an idea of preemptive analgesia. If you give people drugs that protect the nerves before the surgery, they’ll have less pain a year out. We thought maybe this would work in eye pain.”

Galor and colleagues are enrolling patients in a study to determine if presurgically dosed Lyrica would be effective in preventing neuropathic pain in LASIK patients.

“If we see a signal, this could be a way to open up new ways to prevent dry eye symptoms and pain,” she said.

She noted that pain specialists use transcutaneous electrical nerve stimulation (TENS) to shut down the pain in the nociceptive nerves.

“There’s also an emotional component to the pain,” she said. “Many of our patients with dry eye have anxiety and depression, and there are strategies that are more effective in dealing with chronic pain, such as cognitive behavioral therapy, as an alternative to drugs.”

Galor suggested forming relationships with other specialists, such as dermatologists for rosacea and rheumatologists for systemic uveitis.

“We found the best connections are finding a great pain specialist and a mental health professional with neuropathic pain experience, and you can focus on the eye and let them do the other parts,” she said. – by Nancy Hemphill, ELS, FAAO

Reference:

Galor A, et al. New perspectives in dry eye: Neuropathic corneal pain. Presented at: American Academy of Optometry; Chicago; Oct. 10-14, 2017.

Disclosure: Galor’s research is supported by funding from the National Eye Institute and the Veterans Administration.