Ocular Neuropathic Pain

Ocular neuropathic pain is a diagnosis of exclusion which refers to the heightened perception of pain in response to normally non-painful stimuli. It usually presents without any visible objective exam findings, making it extremely difficult to identify. For this reason, it often gets misdiagnosed as dry eye disease. Ocular neuropathic pain may present with accompanying visible damage to tissue; however, it can also occur as a result of a physiological dysfunction of the nervous system. With other corneal pathologies, the intensity of corneal pain often correlates with vital dye staining. However, in patients with ocular neuropathic pain, symptoms are severe and unaccompanied by equivalent signs, which is why ocular neuropathic pain is sometimes referred to as “corneal pain without stain” or “phantom cornea.” This is the ocular analog of complex regional pain syndrome, systemic neuropathic pain, or reflex sympathetic dystrophy. Other names for this condition include, but are not limited to corneal neuropathic pain, corneal neuralgia, ocular pain syndrome, keratoneuralgia, corneal neuropathic disease, and corneal allodynia. Ocular neuropathic pain is an important differential to consider because many patients get misdiagnosed due to its significant overlap with dry eye disease. The disparity between signs and symptoms often results in patients being dismissed or considered malingering, hysterical, or psychosomatic. As demonstrated by case reports, patients with extreme cases of this condition have even committed to suicide due to the severity of chronic pain. An important first step in treating ocular neuropathic pain is to communicate the belief that the condition and the symptoms are real. The objective of this article is to provide a summary of the condition and review approaches for its treatment and management, as well as increase awareness of this underrecognized disease.