Patients with neuropathic corneal pain demonstrate decrease in their relative centralized component of pain with therapy

Abstract

Purpose : Neuropathic corneal pain (NCP) occurs due to neurosensory abnormalities in the peripheral and/or central nervous systems. The proparacaine challenge test (PCT) isolates the presumed centralized component of NCP, by silencing the peripheral component using topical anesthesia. The pain or discomfort that persists after topical anesthesia is a presumed centralized pain (PCP). This study aims to assess if the relative PCP component of NCP, when assessed using the PCT, can decrease longitudinally.

Methods : This retrospective study of a database containing clinically diagnosed NCP patients who had undergone the PCT at two separate visits at least one month apart. During the PCT, patients were asked to rate their pain or discomfort on the visual analogue scale (1 to 10) before and after instillation of 0.5% proparacaine hydrochloride. The percent PCP was calculated as post-PCT rating/pre-PCT rating x 100. All subjects were required to have at least 10% of PCP at the first visit. Statistical models were used to assess if change in PCT results between the visits were significant and if those changes were associated with clinical factors.

Results : The analysis included 18 subjects, with mean age (±SD) of 52.4±22.4 years and a female percentage of 77.8%. The mean time between PCTs was 12.3±9.0 months. The average pre- and post-PCT pain levels were 6.8±1.8 and 4.9±1.6 for visit 1, respectively, and 5.2±2.6 and 2.7±2.2 for visit 2. The mean PCP level was 73.3±21.0% and 44.1±30.2% for visits 1 and 2, respectively. The change in PCP (visit 2-visit 1) was -29.2±37.0%, which was significant (p=0.0005). The pre-instillation VAS scores were also found to have a significant effect on PCP in the mixed model (p<0.0001). While in patients with depression/anxiety, increased age resulted in smaller reductions in PCP, in patients without depression/anxiety, increased age resulted in a larger reduction in PCP (interaction term: depression/anxiety x age; p=0.0062).

Conclusions : The relative component of centralized pain in patients with NCP can decrease over time with treatment. This change is affected by a history of anxiety/depression depending on patient age.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.