Purpose: To investigate corneal sensitivity to selective mechanical, chemical, heat and cold stimulation in fibromyalgia (FM) patients.
Methods: Twenty FM patients (18 female, 2 male; 51,9+/-2,3 years old) and 18 control subjects (16 female, 2 male; 51,7+/-2,4 years) participated voluntarily in the study. Subjective symptoms of ocular dryness were explored and Schirmer’s 1 test was performed. The response to selective stimulation of the central cornea with the Belmonte gas esthesiometer was measured.
Results: The majority (18 out of 20) of FM patients reported dry eye symptoms, being the ocular dryness score significantly higher than in healthy subjects (2.3+/-0.1 vs. 0.05+/-0.02; p<0.001). Schirmer's test values were significantly reduced in FM patients compared to those of the control group (10.5+/-.2 mm and 30.6+/-1.6 mm, respectively; p<0.001).
Mean corneal threshold sensitivity to chemical stimulation (31.16+/-2.04 %CO2 FM; 15.72+/-0.67 %CO2 control), to heating (1.87+/-0.11 degrees C FM; 0.99+/-0.05 degrees C control), and to cooling (-2.53+/-0.11 degrees C FM; -0.76+/-0.05 degrees C control) were increased in FM patients while threshold 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 of corneal polymodal and cold nociceptor [sensory receptors] sensitivity, that may be the consequence or the cause of the chronic reduction in tear secretion also observed in these patients.
Source: Investigative Ophthalmaology & Visual Science, Mar 25, 2009. PMID: 19324850, by Gallar J, Morales C, Freire V, Acosta MC, Belmonte C, Duran JA. Instituto de Neurociencias, Universidad Miguel Hernandez-CSIC, San Juan de Alicante, Spain.