Development of pupillography using image processing.

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.

[1]  J J Corbett,et al.  The relationship between visual acuity, pupillary defect, and visual field loss. , 1982, American journal of ophthalmology.

[2]  Helmut Wilhelm,et al.  Clinical applications of pupillography. , 2003, Journal of neuro-ophthalmology : the official journal of the North American Neuro-Ophthalmology Society.

[3]  Helmut Wilhelm,et al.  Neuro-ophthalmology of pupillary function – practical guidelines , 1998, Journal of Neurology.

[4]  H S Thompson,et al.  Afferent pupillary defects. Pupillary findings associated with defects of the afferent arm of the pupillary light reflex arc. , 1966, American journal of ophthalmology.

[5]  H. Wilhelm.  Pupil examination and evaluation of pupillary disorders , 1994 .

[6]  P. Crosby,et al.  Subject cooperation and the visual evoked response. , 1979, Investigative ophthalmology & visual science.

[7]  R. Burde,et al.  Relative afferent pupillary defect in glaucoma. , 1976, American journal of ophthalmology.

[8]  I. E. Loewenfeld,et al.  Electronic pupillography; a new instrument and some clinical applications. , 1958, A.M.A. archives of ophthalmology.

[9]  S. Smith,et al.  Assessment of unilateral afferent pupillary defects by pupillography. , 1979, The British journal of ophthalmology.

[10]  P LEVATIN,et al.  Pupillary escape in disease of the retina or optic nerve. , 1959, Archives of ophthalmology.

[11]  A. Firth,et al.  Pupillary responses in amblyopia. , 1990, The British journal of ophthalmology.

[12]  T. Cox,et al.  Pupillography of a relative afferent pupillary defect. , 1986, American journal of ophthalmology.

[13]  O. Lowenstein.  Clinical pupillary symptoms in lesions of the optic nerve, optic chiasm, and optic tract. , 1954, A.M.A. archives of ophthalmology.