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Boris I Gramatikov, Ivan Gramatikov, Kurt Simons, David L Guyton; A shutter glasses controller for visual stimulation. Invest. Ophthalmol. Vis. Sci. 2017;58(8):2355.
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© ARVO (1962-2015); The Authors (2016-present)
In recent years, new methods for treating amblyopia have emerged, based on liquid crystal (LC) shutter glasses that intermittently occlude the better eye, or alternately occlude the two eyes, thus stimulating vision in the “lazy” eye. As yet there is no technology that allows easy and efficient optimization of the shuttering characteristics for a given patient. Our goal was to develop an inexpensive, computer-based system to perform LC shuttering in laboratory and clinical settings to help “wake up” the suppressed eye in amblyopic patients, and to help optimize the individual shuttering parameters such as wave shape, level of transparency/opacity, frequency, and duty cycle of the shuttering.
We developed a LC glasses controller connected by USB cable to a PC computer. It generates the voltage waveforms going to the glasses, and has potentiometer knobs for interactive adjustments by the patient. We direct-wired a pair of Xpand X103-M Active Shutter 3D Glasses. Such LC shutter glasses can be controlled with monopolar or bipolar electrical pulses of amplitudes in the order of several volts, depending on the type of the LC and the level of occlusion desired. Further, it is highly desirable to provide feedback from the patient, indicating which shuttering frequency, duty cycle, and voltage amplitude are found to be optimal. This was achieved by including three potentiometers, providing analog signals. We used an inexpensive input/output module, NI USB-6009, from National Instruments, providing two analog outputs and eight analog inputs. The outputs were used to control the shuttering voltage, while the inputs were reading the potentiometers. In order to achieve good timing performance in this bidirectional system, we used multithreading programming techniques.
The hardware and software developed were assessed experimentally. We achieved an accuracy of ±1 Hz for the frequency, and ±2% for the duty cycle of the occlusion pulses. We consider these values to be satisfactory for the purpose of optimizing the visual stimulation by means of shutter glasses.
We believe that a computer-based system to perform LC shuttering is the appropriate way to go when optimizing shuttering characteristics for each patient. Our system can be used by clinicians, for training sessions in clinical settings, or even at home, aimed at stimulating vision in the “lazy” eye.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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