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Alexandra Levitt, WAN CHEN, Anat Galor, Jin Yuan, Constantine D Sarantopoulos, Nabeel Shalabi, Hatim Ismail Batawi, Allison Louise McClellan, William J Feuer, Roy C Levitt, Jianhua Wang; Microvascular responses of the bulbar conjunctiva in dry eye. Invest. Ophthalmol. Vis. Sci. 201657(12):.
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© ARVO (1962-2015); The Authors (2016-present)
Many patients with dry eye (DE) describe features of neuropathic ocular pain, including burning and evoked pain to wind and light, yet we have limited knowledge of the efferent innervation of the ocular surface. Our previous work utilizing a novel functional slit-lamp biomicroscope (FSLB) demonstrated that changes in conjunctival blood flow velocity (BFV) are neurally mediated, suggesting that microvascular changes may be a useful surrogate for the study of the neural response of the ocular surface. We performed a prospective, cross-sectional study to better characterize microvascular alterations of the bulbar conjunctiva in response to trigeminal nerve stimulation and learn whether they correlate with symptoms and signs of dry eye.
Forty DE patients were prospectively recruited over 8 months from a Veterans Administration eye clinic. Symptoms of DE and ocular pain were assessed and an ocular surface evaluation for objective signs of DE was performed. A FSLB was used to image the temporal bulbar conjunctiva from the right eye before and after central corneal stimulation with an air puff. BFV was measured and non-invasive microvascular perfusion maps (nMPMs) were created.
The bulbar BFV was 0.56±0.14 mm/s at baseline and increased significantly to 0.60±0.16 mm/s after stimulation (P=0.008). nMPMs values did not significantly increase after stimulation (1.63±0.05 at baseline, 1.65±0.03 after stimulation, P=0.93). Baseline BFV positively associated with Schirmer test scores (r=0.33, P=0.04) and baseline vessel diameter positively associated with evoked pain (r=0.34, P=0.03). Those with higher self-rated wind hyperalgesia demonstrated less change in BFV (r=-0.354, P=0.025) after air stimulation on the central cornea. No other DE symptom, ocular pain complaint, or objective ocular surface parameter significantly correlated with change in BFV.
Conjunctival BFV increases after wind stimulus, but this response is diminished in correlation with neuropathic pain measures. Additionally, the baseline differences in vessel parameters in patients with reduced tear production versus neuropathic pain symptoms suggest a dichotomous DE population and a potential role for autonomic dysregulation in the pathogenesis of DE symptoms. Microvascular responses may be a useful surrogate marker of the efferent innervation of the ocular surface, thus FSLB may be a useful technique to better characterize DE phenotypes.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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