Modification of the Neuropathic Pain Symptom Inventory for use in eye pain (NPSI-Eye)

Abstract

Chronic eye pain, which has previously been assumed to be due to ocular surface abnormalities (ie, "dry eye [DE] disease"), has recently garnered attention as a potential indicator of neuropathic ocular pain in some patients. The purpose of this study was to evaluate the psychometric properties of a modified version of the Neuropathic Pain Symptom Inventory in individuals with eye pain (NPSI-Eye). Enrolled participants (n = 397) completed the NPSI-Eye, general pain severity questionnaires, DE symptom report, and psychological health indices. Participants also underwent mechanical pain sensitivity testing of the cornea, tear film assessment, and evaluation of the efficacy of anesthetic eye drops to relieve pain. Short-term test-retest reliability of the NPSI-Eye was excellent (intraclass correlation coefficient = 0.98, P < 0.001). Correlations between the NPSI-Eye and indicators of general eye pain were ≥0.65 (P < 0.001), whereas correlations between the NPSI-Eye and DE symptom severity and psychological health indices were lower (rho = 0.56, 0.32, 0.37; all P < 0.001). Individuals who reported little or no decrease in pain after anesthetic eye drops (hypothesized to indicate eye pain with at least partial central involvement) had significantly higher NPSI-Eye scores than participants whose eye pain was completely relieved by anesthetic (P < 0.05). Overall, our results support preliminary validation of the NPSI-Eye, yielding similar metrics to those reported in Bouhassira et al.'s original NPSI publication (2004). However, additional evaluation and refinement of some questions may be desirable, including the potential elimination of items that were not highly endorsed.

Figures

Figure 1. Relationship between NPSI-Eye and DE symptoms/signs discordance score.

Participants were rank ordered based on the difference in severity of their reported DE symptoms and a composite measure of signs of tear dysfunction. A higher number on the DE discordance score reflects a greater difference in the severity of symptoms compared to signs. A higher score on the NPSI-Eye reflects greater neuropathic-like pain symptoms. The Spearman correlation coefficient was significant at p

Figure 2. NPSI-Eye total score across subgroups based on response to eye drop anesthetic.

NSPI-Eye total scores were compared across three groups of participants based on their response to anesthetic eye drops: 1) those with intermittent eye pain symptoms (“no pain before”); 2) those with eye pain presumably due to peripheral mechanisms alone (“complete response”); and 3) those with eye pain presumably including at least partial central pain mechanisms (“no, or partial, response”). The box plots show the median (bold horizontal line inside the box), the limits of the 25th and 75th percentile (lower and upper limits of the boxes, respectively), and the upper and lower error bars indicate the limits of 95% of scores. Open circles indicate outliers. Significant comparisons between groups are noted with * (p< 0.05).

Figure 3. Relationship between change in total NPSI-Eye and NRS comparing 2 points in time.

A subgroup of study participants (n = 26) completed repeated measurement (approximately 4 months after the initial visit) of the NPSI-Eye and ratings (NRS) of average eye pain intensity. Filled circles represent changes in scores across this time period on these measures, with a regression line fitted to the data. The Spearman correlation coefficient was significant at p