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Jianhua Wang, Hong Jiang, Aizhu Tao, Delia DeBuc, Yilei Shao, Jianguang Zhong, Sandra Pineda; Limbal capillary perfusion and blood flow velocity as a potential biomarker for evaluating dry eye. Invest. Ophthalmol. Vis. Sci. 2013;54(15):4335.
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Dry eye syndrome is a chronic inflammation of the ocular surface due to lack of sufficient lubrication and moisture. As a result, an individual suffering from the dry eye syndrome will experience uncomfortable symptoms of dryness, itchiness, and a burning sensation in the eyes. The goal of this study was to develop a sensitive biomarker to quantitatively evaluate the severity in dry eyes by imaging limbal capillary perfusion and calculating the velocity of blood flow.
A retinal function imager (RFI, Optical Imaging Ltd, Rehovot, Israel) was used to capture reflectance changes as a function of time under stroboscopic illumination. The system was further adapted from its original use of retinal imaging to being utilized in anterior surface imaging. Hemoglobin in red blood cells was used as an intrinsic motion-contrast agent in the generation of detailed noninvasive capillary-perfusion maps (nCPMs) and the calculation of the velocity of blood flow. Nine healthy subjects (3 males and 6 females, age 29.8 ± 10.4 years) and nine previously diagnosed dry eye patients (4 males and 5 females, age 51.0 ± 17.5 years) were recruited. The temporal conjunctivas of the patient’s right eyes were imaged with the RFI device. The velocity of blood flow in arteries and veins was measured at selected vessel segments in the temporal conjunctivas.
The nCPMs showed capillaries in exquisite detail on the limbal region and the limbal region appeared as a random distribution of branching, overlapping, and crossing vessels (Fig. 1A). The velocity of blood flow (Fig. 1B) in conjunctival arteries was 0.71 ± 0.09 (mean ± SD, mm/s) and 0.80 ± 0.11 mm/s, for normal and dry eye patients, respectively (p < 0.05). The blood flow velocities in conjunctival veins were 0.69 ± 0.08 mm/s and 0.81 ± 0.16 mm/s, for normal and dry eye patients, respectively (p < 0.05). There were no significant differences in blood flow velocities between arteries and veins in each group (P > 0.05).
This pilot study demonstrated for the first time that blood flow velocity of the conjunctiva may be altered in dry eye patients, which might be a possible biomarker for evaluating dry eye severity and treatment efficacy. This potential biomarker may also provide a window into dry eye causes and pave the way for more specific tracking methods of dry eye endpoints in humans for the purpose of new drug approval.
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