Comparison of pupil responses to luminance and colour in severe optic neuritis.
OBJECTIVE
The pupil response to light flux increments is abnormal in severe optic neuritis, but little is known about the effects of this condition on the pupil colour response. The aim of this study was to examine how optic neuritis affects pupil responses to light flux and colour modulation and the extent to which such pupil responses mirror the loss and recovery of vision.


METHODS
A new pupil examination technique that makes use of sinusoidal modulation of either luminance contrast or chromatic saturation was employed. This technique enables the automatic extraction of both pupil response amplitude and latency and achieves a high signal to noise ratio with fewer averages.


RESULTS
The study reveals a greater loss of pupil response amplitude and significantly longer latencies to chromatic modulation (i.e. approximately 80 ms). Stimulation of the unaffected eye in the optic neuritis group results in smaller response amplitudes when compared to the normal group for both light flux and colour modulation.


CONCLUSIONS
Pupil response components can be affected differently in optic neuritis. These findings suggest that the pupil colour response, in particular, may provide a useful, objective estimator to judge the extent of damage and recovery in diseases of the optic nerve.
Barbur
J L
JL
The Henry Wellcome Laboratories for Vision Sciences, Applied Vision Research Centre, City University, Northampton Square, London EC1V 0HB, UK. johnb@city.ac.uk
Moro
S
S
Harlow
J A
JA
Lam
B L
BL
Liu
M
M
D000328:Adult; D003116:Color; D006801:Humans; D008027:Light; D009902:Optic Neuritis / Q000503:physiopathology*; D010775:Photic Stimulation; D011680:Pupil / Q000528:radiation effects*; D011930:Reaction Time; D020127:Recovery of Function; D012025:Reflex, Pupillary / Q000528:radiation effects; D014785:Vision, Ocular; D014792:Visual Acuity