Korean J Ophthalmol.  2005 Jun;19(2):149-152. 10.3341/kjo.2005.19.2.149.

Development of Pupillography Using Image Processing

• Lee IB
• Choi B
• Park KS
• Kim SS
• Hwang JM

• KMID: 754415
• DOI: http://doi.org/10.3341/kjo.2005.19.2.149

Abstract

PURPOSE
Pupillary examination is an important objective method to diagnose lesions of the anterior visual pathways. However, errors and faults may easily alter the interpretation and value of the test as it is highly dependent on the examiner's skills. Therefore, we tried to develop a pupillography which is independent of the examiner. METHODS: Hardware composed of a binocularly measuring instrument adapted for an infrared charge coupled device (CCD) was developed. Two arrays of infrared light emitting diodes (LED) were supplied in front of each of the subject's eyes. A microcontroller to modulate these LED was developed, as was software to save and analyze the pupil images. The hardware was able to deliver a light to either eye or to both eyes, and to change the time, frequency, and intensity of the stimulus. The software automatically analyzed the pupil size and location by image processing. Pupil size was calculated continuously. After artifact elimination, the response amplitudes of the pupils were determined for the right and left pupils. RESULTS: Pupillary images of size 320 x 240, at 30 frames/second, were saved and processed to evaluate the change of the actual pupil size and the velocity of pupillary response. CONCLUSIONS: A pupillography to measure, save and analyze the pupillary response using image processing was developed. Further detailed clinical studies with a large number of patients will be required to validate this new method.

Keyword

Image processing; Pupillography; Pupillary response

MeSH Terms

Diagnostic Techniques, Ophthalmological/*instrumentation
Equipment Design
Humans
*Image Processing, Computer-Assisted
*Reflex, Pupillary

Figure

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  Fig. 1 Eye tracking system. The eye tracking system is composed of a head-mounted goggle and control box.

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  Fig. 2 Inner part of the goggle. The inner part of the goggle is composed of a CCD camera for image capture, two infrared LEDs for illumination, and four white LEDs for stimulation.

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  Fig. 3 Image analyses with pupil tracking software. A real-time, simultaneous, pupillary image is automatically targeted with a circle and was visible during testing on the computer screen.

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  Fig. 4 Pupillary responses to light stimuli. The X-axis represents the time in seconds and the Y-axis, the size of the pupil in mm. Values for the diameter (pixels) of an each pupil at any given time are recorded as the light alternatively flashes from right eye to left eye (direct and consensual stimulation of the right eye). □: represents the beginning of the pupillary response to light, ○: maximal constriction time, and ◇: 2/3 recovery time.

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