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Lennert W. Lock, Jesper G. Peterse, Jacobus J. Beerepoot, Nooshinossadat Mortazavi, Sander Schutte, Nicole M. Bakker, Huibert J. Simonsz; Optimal Pursuit Velocity To Assess Red-eye Reflex For Objective Calibration Of Eye Position With DAISY. Invest. Ophthalmol. Vis. Sci. 2011;52(14):6373.
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© ARVO (1962-2015); The Authors (2016-present)
The Delft Assessment Instrument for Strabismus in Young children (DAISY) should measure angles of strabismus in young children in 1-2 minutes. Objective calibration of eye position with the red-eye reflex should, hence, take less than 20s. We determined the optimal pursuit velocity to minimize influence of confounders.
Orthotropic subjects (22-26 yrs) with 1.0 vision followed a yellow 7.2’ dot projected by a beamer (EPSON EMP30) on an infrared-translucent, reflecting plate at 1.00m, in the dark. Their eyes were illuminated by a 5mm, 870nm, 240mW LED at 0.14m behind the plate, that was coaxially placed with a Proscilica GC2450 camera at 1.17m viewing distance, using a small aluminum coated mirror. The fixation dot moved sinusoidally from 7.35° left to 7.35° right at 0.08, 0.16, 0.24, 0.32 and 0.48Hz. Five images were made per second. Luminance was assessed as the average grayscale of each pupil in the images measured in automatically segmented images. Horizontal eye position was assessed as position of the first Purkinje image withing the pupil and converted into degrees (±0.3° accuracy).
The relation between luminance and horizontal eye position showed a V-shaped luminance profile. The fixation object was followed most accurately at 0.24Hz. The differences between the luminance profiles obtained at different speeds were small, but vertical eye movements, an important confounder, were minimal at 0.24Hz: The SDs at 0.08, 0.16, 0.24, 0.32 and 0.48Hz were 0.60°, 0.49°, 0.43°, 1.27° and 0.74° for left eyes and 0.57°, 0.58°, 0.4°, 1.02° and 0.53° for right eyes.
Vertical eye movement was minimal when the fixation dot moved sinusoidally from 7.35° left to 7.35° right at 0.24Hz, but the influence of this confounder could not be verified in different variation in the V-shaped luminance profiles.
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