As a rapid screening technique for anemia, physicians can pull down the lower eyelid and examine the color of the inside lining of the eyelid, called the palpebral conjunctiva. While a qualitative inspection of the palpebral conjunctiva has been shown to be inaccurate in diagnosing anemia, the palpebral conjunctiva is an excellent access point to measure hemoglobin and other blood constituents when analyzed quantitatively using spectroscopy. Using diffuse reflectance spectroscopy, specifically examining the specific visible light absorbance at the palpebral conjunctiva, our team has shown that total hemoglobin levels can be measured noninvasively in a small initial study. The conjunctiva is illuminated with a low power broadband white light source, the diffusely reflected light is collected, and the reflectance signal is analyzed to calculate hemoglobin concentration. While our proof of concept studies on the accuracy of this technique used a commercial grating based spectrometer, liquid crystal (LC) filter technology, one the core competencies of our team, can be used in conjunction with a single photodiode detector to manufacture an ultra-compact and inexpensive microchip spectrometer. The specific configuration of the liquid crystal material to be used, ferroelectric liquid crystal, has shown a full spectrum tunable notch filter with bandwidth <25nm across this regime. Coupling a white LED as an irradiation source into the microchip spectrometer can allow for the fabrication of a fully functional spectroscopic device used to collect the diffuse reflectance spectra from the conjunctiva, calculate hemoglobin concentration, and reliably diagnose anemia. The simplicity of the examination, explicitly pulling down the lower eyelid to expose the palpebral conjunctiva and holding the sensor up to the exposed area to make a measurement, enable this device to be used by a wide array of healthcare providers in numerous environments. The simplicity of this device can enable hemoglobin concentration screening to become a new vital sign in the same fashion the pulse oximeter enabled oxygen saturation measurement. The proposed project here involves (1) the clinical trial of commercial spectroscopic equipment to demonstrate technique accuracy and (2) the clinical trial of fabricated microspectrometer to demonstrate device operation, accuracy, and repeatability compared to commercial instrumentation and invasive blood testing. ? ? ?
