Purchase this article with an account.
Priyanka Chhadva, Tinthu Lee, Abigail Hackam, Allison Louise McClellan, Elizabeth Felix, Constantine Sarantopoulos, Roy Levitt, Anat Galor; Human Tear Serotonin Levels and Neuropathic Ocular Pain in Dry Eye. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):352.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Serotonin is a neurotransmitter known to be involved in nociceptor activation and to be present in human tears. The purpose of this study was to evaluate whether tear levels of serotonin are associated with certain aspects of dry eye, including symptoms, signs, and clinical descriptors of neuropathic ocular pain.
Sixty-six patients with normal eyelid and corneal anatomy were prospectively recruited from a Veterans Administration Hospital over 11 months. Dry eye symptoms (Ocular Surface Disease Index [OSDI]), signs (tear break-up time, corneal staining, and Schirmer score), and presence of any clinical descriptors of neuropathic ocular pain (NOP) (sensitivity to wind, sensitivity to light, and/or ocular pain characterized as hot-burning) were assessed. Patients were divided into 3 groups based on the above: (1) OSDI≥6 and Schirmer < 10 (+symp/+sign group; n=16), (2) OSDI ≥ 6 and Schirmer ≥ 10 (+symp/-sign group; n=34), and (3) OSDI< 6 (-Symp group; n=16). For tear analysis, each patient’s tears were collected after instilling 50μl of sterile saline to the lower cul-de-sac of each eye and using capillary action microcaps to collect the ocular wash. Tear serotonin levels were measured using enzyme-linked immunosorbent assay (ELISA).
Serotonin concentration was significantly different between groups, with the +Symp/+Sign group having the highest value (2.12ng/ml±1.03) compared to the +Symp/-Sign (1.41ng/ml±0.83) and -Symp (1.66ng/ml±1.03) group; p=0.046. The +Symp/-Sign group reported more clinical descriptors of NOP including sensitivity to wind (68%), photosensitivity (71%), and burning (44%) than the +Symp/+Sign (31%, 44%, 19% respectively) and -Symp group (13%, 6%, 13% respectively); p=0.03, 0.001, and 0.001 respectively. Serotonin concentrations did not correlate with dry eye symptoms, clinical descriptors of NOP, tear break up time or staining, but correlated with Schirmer score (r=-0.307; p=0.01).
Patients with dry eye symptoms and reduced tear production have higher tear serotonin levels than those with dry eye symptoms and normal tear production. Patients with dry eye symptoms and normal tear production more frequently describe features of NOP. This suggests that this group may have central abnormalities in their ocular sensory apparatus (i.e. central sensitization) driving their symptoms.
This PDF is available to Subscribers Only