Investigative Ophthalmology and Visual Science (supp), vol 38, No. 4, p. 338

Bước tới: chuyển hướng, tìm kiếm
 Tạp chí Investigative Ophthalmology and Visual Science 1997 ; 4 (38):338
 Tác giả   A. Siegel, B. Dumery, Vo Van Toi
 Nơi thực hiện   Department of Biomedical Engineering, Bioengineering Center,Tufts University, 4 Colby Street, Medford, MA 02155
 Từ khóa   BLINK RATE,
  DOI   URL  [ PDF]


Purpose. To develop a portable device which can record the blink rate without coming in contact with the subject. The recorded data can be retrieved and processed by an IBM compatible personal computer (PC).

Method. The system consists of a miniature optical sensor and a portable datalogging unit (DLU) and powered by a 9 volt battery. The sensor, which consists of a narrow-beam 910nm LED and a silicon photodetector, functions on the light reflected back fro m the surface of the eye. The LED current is modulated at 20KHz to isolate the sensor from environmental noise. The DLU mainly contains an 8Kbyte electrically programmable memory (EEPROM) with timing and other logic circuits. It connects to the compute r through a programmable peripheral interface 8255 card. Analog signals received from the sensor are converted into digital pulses and accumulated for a certain period of time (e.g., 1 min.). At the end of that time, the count is latched into the memory , the accumulator is cleared for the next count and the counter address is incremented. A software program written in QuickBasic retrieves the data from the DLU which can be processed and plotted, and clears the DLU’s memory for the next experiment.

Results. A prototype was built. The DLU consists of a 17x12x3 cm case with a display indicating the recording elapsed time (up to 34 hours). A removable audible device facilitates the fitting process. When the sensor is appropriately positio ned on the subject, each blink triggers an audible signal which is muted during the recording. The sensor is incorporated in a miniature articulated arm which can be mounted on the subject eyeglass, aims toward the temporal corner of the subject’s eye an d does not obstruct the subject central visual field. Comparative tests using our device and a video camera were performed. The difference of the blink rates between the two systems was not statistically significant. It indicates that our device is rel iable. Blink rates of several subjects were recorded. The average values were in agreement with reported data. Further, our device provided a dynamic profile of the subject blinking; e.g., when the task was not visually demanding the blink rate fluctua ted drastically; in the opposite situation the blink rate was much lower but more stable.

Conclusion. As our device is portable, reliable, non contact and non obstructive, it constitutes an important tool for investigating the relationship between the blink rate and visual functions.

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