Decreased corneal sensitivity and tear production in Fibromyalgia Syndrome

A recent study by researchers in Spain has shown that people with Fibromyalgia Syndrome suffer from dry eyes, with decreased corneal sensitivity to a number of stimuli. ¹

The aim of the study was to investigate corneal sensitivity various stimuli in Fibromyalgia Syndrome (Fibro) patients.

Twenty Fibro patients and 18 control subjects participated in the study. Of the Fibro patients, 18 were female and 2 male, with an average age of 51.9 years old +/- 2.3 years. Of the control subjects, 16 were female and 2 male, with an average age of 51.7 years old +/- 2.4 years old.

Subjective symptoms of ocular dryness were explored and Schirmer's 1 test (where tear production is measured using paper test strips) was performed. The response to selective stimulation of the central cornea with the Belmonte gas esthesiometer was measured.

The majority (18 out of 20) of the Fibro patients reported dry eye symptoms, with the ocular dryness score being significantly higher than in healthy subjects (2.3 +/-0.1 vs. 0.05 +/-0/02; p<0.001). ¹

Schirmer's test values were significantly reduced in the Fibro patients compared to those of the control group (10.5 +/- 0.2 mm and 30.6 +/- 1.6 mm, respectively; p<0.001). ¹

The Fibro patients were found to have a raised average threshold of corneal sensitivity (so decreased sensitivity) to chemical stimulation (31.16 +/- 2.04 % CO2 vs. 15.72 +/- 0.67 % CO2 for controls), heating (1.87 +/- 0.11 degrees C vs. 0.99 +/- 0.05 degrees C for controls) and cooling (-2.53 +/- 0.11 degrees C vs. -0.76 +/- 0.05 degrees C for controls). The threshold to mechanical stimulation did not vary significantly for Fibro patients (123.0 +/- 8.0 ml/min vs. 107.8 +/- 4.4 ml/min for controls). ¹

The researchers concluded that:

"The reduced corneal sensitivity of patients with fibromyalgia is attributable to a moderate decrease of corneal polymodal and cold nociceptor sensitivity, that may be the consequence or the cause of the chronic reduction in tear secretion also observed in these patients." ¹

References:

1. Gallar J, Morales C, Freire V, Acosta MC, Belmonte C, Duran JA. Decreased corneal sensitivity and tear production in fibromyalgia. Invest Ophthalmol Vis Sci. 2009 Mar 25. [Epub ahead of print]