Dry eye disease is often accompanied by painful ocular sensation, but conventional dry eye therapy doesn’t always resolve the issue. That’s when clinicians may begin to suspect ocular pain. According to the Tear Film and Ocular Surface Society’s DEWS II report, ocular neuropathic pain is a separate entity from dry eye, but the two may coincide. Some studies have reported dry eye patients describing features of neuropathic pain, such as spontaneous pain, dysesthesias, allodynia and hyperalgesia.

A recent study aimed to identify more overlapping characteristics between dry eye and ocular neuropathic pain, since there isn’t currently any gold standard for its diagnosis. The team found that patients with central-dominant sensitization may experience more intense pain.

The cross-sectional study included 33 patients with dry eye and ocular neuropathic pain. The patients underwent comprehensive testing, including tear film, ocular surface and meibomian gland examination.

The researchers divided patients into two groups: those with less than 50% improvement in pain intensity after a proparacaine challenge test were placed in the central-dominant sensitization group, and those with 50% or more improvement were placed in the peripheral-dominant sensitization group.

The researchers observed no significant differences between the two groups in terms of age, sex, underlying disease, history of ocular surgery, duration of ocular pain, tear film, ocular surface or meibomian gland parameters. They did note, however, that ocular and non-ocular pain severity and time spent thinking about non-ocular pain were significantly higher in the central-dominant group. This group also voiced more complaints of a burning sensation.

The researchers concluded that dry eye patients with central-dominant sensitization may experience more intense ocular and non-ocular pain than others. They identified burning sensation as a key ocular pain symptom. “The Ocular Pain Assessment Survey questionnaire can be a good option for evaluating whether patients have ocular neuropathic features,” the researchers wrote in their paper. They suggested further studies on the corneal nervous system and on peripheral and central sensitization associated with dry eye to aid in the management of those with ocular neuropathic pain.

Kim J, Yoon HJ, You IC, et al. Clinical characteristics of dry eye with ocular neuropathic pain features: Comparison according to the types of sensitization based on the Ocular Pain Assessment Survey. BMC Ophthalmol. 2020;20:455.