Treatment for Neuropathic Corneal Pain

Compassionate comprehensive care required for adequate management. Cheryl Guttman Krader reports from ASCRS 2021 in Las Vegas, USA. Neuropathic corneal pain (NCP) can present a treatment challenge, but patients suffering from this disorder can do well when they receive compassionate multimodal and multidisciplinary care, Majid Moshirfar MD told a Cornea Day session. “Most patients can lead functional lives whilst managing their debilitating neuropathic pain. My take-home messages are to show compassion, provide diligent care, use rating scales to char-acterise pain severity, adjust the treatment regimen accordingly, and try to get other disciplines involved,” Dr Moshirfar said. PRESENTATION AND RISK FACTORS Patients with NCP complain subjectively of severe ocular pain and symptoms associated with dry eye disease that are greatly out of proportion to clinical findings. “Some patients might have mild meibomian gland disease or ocular surface staining, but overall, the ocular surface condition will be very good. Because of the benign clinical picture, clinicians may doubt whether patients are telling the truth about their symptoms,” Dr Moshirfar said. “Now we know these are neuralgic symptoms.” NCP diagnosis is made by exclusion. Although confocal microscopy can reveal aberrations in corneal nerve architecture consistent with the concept that the pathophysiology of NCP involves aberrant regeneration of injured nerves, the findings are not sensitive or specific. “I have also seen the same nerve abnormalities in post-LASIK patients without NCP. Furthermore, a normal appearance of the corneal nerves on confocal microscopy does not rule out NCP,” Dr Moshirfar said. He discussed a recently published paper in which he undertook a retrospective review of his LASIK cases to identify and characterise patients with NCP (Moshirfar M, et al. Ophthalmol Ther. 2021; 10: 677–689). A total of 18 patients were found in a medical search encompassing 26 years, translating into a prevalence of approximately 1 in 900. All patients with NCP had uncomplicated LASIK. Fifty percent of patients had a prior neuropsychiatric disorder, including depression and anxiety. Other common medical history findings included functional pain syndromes, autoimmune diseases, and endocrinological abnormalities. “These comorbidities have been noted by other authors, and NCP may occur more often in females than males,” Dr Moshirfar said. COMPONENTS OF CARE Dr Moshirfar said his treatment for NCP includes autologous blood serum at a concentration ranging from 20% to 50%. Noting the therapeutic benefit of the autologous serum is likely related to the delivery of neurotrophic growth factors, Dr Moshirfar said he once sought authorisation to prescribe recombinant human nerve growth factor (cenegermin, Oxervate) for a patient but could not gain approval. “There are two different thoughts about using neurotrophic growth factors. On the one hand, it may be beneficial by acting as a ‘fertilizer’ to enhance the growth of nerve endings and induce regeneration. On the other hand, perhaps the treatment may lead to more aberration and make the micro-neuromas worse. In terms of providing nerve growth factors, I truly think we should try to help these patients by using autologous blood serum.” Other therapeutic modalities include artificial tears, anti-inflammatory agents, and other treatments typically used to manage dry eye, along with ocular surface protection (scleral contact lenses, bandage contact lenses, amniotic membrane). Oral treatments include nutritional supplementation with omega-3 fatty acids and vitamins D3 and B12 that may have neuroprotective activity, tricyclic antidepressant medications, and anticonvulsants, particularly gabapentin. In addition, Dr Moshirfar said he prescribed naltrexone 1.5 mg at bedtime for some patients. He has also referred patients with peripheral hypersensitivity to see an anaesthesiologist for trigeminal nerve ganglion ablation, which has provided transient benefit. Other interventions include meditation, biofeedback, acupuncture, and botulinum toxin injections. “Although I have not personally done so, there are also reports intrathecal injection with fentanyl and bupivacaine at the level of C1 has been helpful for patients with a presynaptic condition who are refractory to other treatments,” Dr Moshirfar said. He emphasised the importance of identifying mental health problems in patients with NCP and encouraging them to seek help from a psychiatrist. “Neuropathic corneal pain can worsen underlying neuropsychiatric conditions. There are reports of suicide and suicidal ideation among these patients. Some patients may ask for enucleation, which is shocking,” Dr Moshirfar said. INFORMED CONSENT CAUTION Refractive surgery can be a trigger for NCP. This underscores the importance of obtaining a thorough medical history preoperatively, with an awareness that certain conditions may be predisposing factors. This can help in identifying patients who may be at risk for developing NCP after refractive surgery. “If I see that a patient has functional pain syndrome, fibromyalgia, or is on chronic pain medications, I talk to them specifically about this rare postoperative complication and tell them I think they are at high risk,” Dr Moshirfar said. Majid Moshirfar MD is Director of Clinical Research at Hoopes Vision and Adjunct Professor at John A Moran Eye Center, University of Utah, Salt Lake City, USA. He is also co-director of the Utah Lions Eye Bank, Murray, Utah. cornea2020@me.com

Tags: cornea, corneal