Decreased corneal sensitivity and tear production in fibromyalgia.

PURPOSE To investigate corneal sensitivity to selective mechanical, chemical, heat, and cold stimulation in patients with fibromyalgia (FM). METHODS Twenty patients with FM (18 women, 2 men; 51.9 +/- 2.3 years old) and 18 control subjects (16 women, 2 men; 51.7 +/- 2.4 years) participated voluntarily in the study. Subjective symptoms of ocular dryness were explored and a Schirmer I test was performed. The response to selective stimulation of the central cornea with the Belmonte gas esthesiometer was measured. RESULTS The majority (18/20) of patients with FM reported dry eye symptoms, with the ocular dryness score significantly higher in affected subjects than in healthy ones (2.3 +/- 0.1 vs. 0.05 +/- 0.02; P < 0.001). The Schirmer test results were significantly lower in patients with FM than in those in the control group (10.5 +/- 2.2 and 30.6 +/- 1.6 mm, respectively; P < 0.001). Mean corneal threshold sensitivity values to chemical stimulation (31.16% +/- 2.04% CO(2) FM; 15.72% +/- 0.67% CO(2) control), heat (1.87 +/- 0.11 degrees C FM; 0.99 +/- 0.05 degrees C control), and cold (-2.53 +/- 0.11 degrees C FM; -0.76 +/- 0.05 degrees C control) were increased in patients with FM, whereas threshold responses to mechanical stimulation did not vary significantly (123.0 +/- 8.0 mL/min FM; 107.8 +/- 4.4 mL/min control). CONCLUSIONS The reduced corneal sensitivity of patients with fibromyalgia is attributable to a moderate decrease in corneal polymodal and cold nociceptor sensitivity, which may be the consequence or the cause of the chronic reduction in tear secretion also observed in these patients.