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Amy Elizabeth Canham, Ramesh Raskar; A Glasses-Mounted Platform for Optimized Ocular Electrophysiology. Invest. Ophthalmol. Vis. Sci. 2014;55(13):5114.
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The aim of this work is to develop a first prototype for performing electroretinography in a unified interface which can be mounted into a pair of glasses and conducted with minimal training required, to better integrate electrophysiology into routine ophthalmic care and improve outcomes in pediatric patients.
The device incorporates both rigidly affixed electrodes and low-profile stimulator into a modified glasses frame. The electrodes are gold casted discs which are positioned and stabilized by the frame. The stimulator is a DLP projector driven, low-profile dome coupled with a fresnel lens. Analog signal processing and capture via Arduino microprocessor is also mounted within the glasses frame. The function of the 0.3Hz to 300Hz, 1000 V gain filter and amplification circuitry was evaluated by delivering sample signals generated computationally and rendered by a Realtek High Definition Audio sound card. The sample signals consisted of continuous, 30mV peak-to-peak, sine waveforms at 3Hz, 15Hz, 30Hz, 100Hz and 1kHz and decaying, oscillatory impulse signals with total voltage offset from first peak to trough of 30mV. The luminous emittance of the stimulus was measured to calibrate the device against ISCEV standards. Preliminary evaluation of the system was conducted by administering scotopic 3.0 ERG with both our system and a Diagnosys ColorDome ERG system.
The analog filter and amplification stage demonstrated 1000 fold amplification of signals within cutoff frequencies and effectively attenuated the 1kHz waveform. The programmable stimulus system demonstrated the ability to render both full-field and patterned stimuli at multiple wavelengths, with adjustable intensity from 0.1 to 3.0 candela second per meters squared over the surface of the dome. Preliminary evaluation demonstrated comparable results from both our system and the Diagnosys ERG system.
The integration of the system into a glasses-mounted interface simplifies electrode alignment while delivering comparable results and the potential for administering a wide range of tests. Ophthalmic electrophysiology has tremendous potential as an asset in diagnosis and monitoring. Accessible technologies which deliver objective evaluations of retinal function can impact routine ophthalmic practice and large scale screening scenarios.
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