July 2018
Volume 59, Issue 9
Open Access
ARVO Annual Meeting Abstract  |   July 2018
Short-wavelength cone contrast reverses the sign of defocus for emmetropization in chick
Author Affiliations & Notes
  • Frances J Rucker
    Biomedical Science, New England Coll of Optometry, Boston, Massachusetts, United States
  • Christopher Patrick Taylor
    Biomedical Science, New England Coll of Optometry, Boston, Massachusetts, United States
  • Footnotes
    Commercial Relationships   Frances Rucker, None; Christopher Taylor, None
  • Footnotes
    Support  NIH Grant EY023281
Investigative Ophthalmology & Visual Science July 2018, Vol.59, 679. doi:
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      Frances J Rucker, Christopher Patrick Taylor; Short-wavelength cone contrast reverses the sign of defocus for emmetropization in chick. Invest. Ophthalmol. Vis. Sci. 2018;59(9):679.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose :

Chicks respond to wavelength defocus produced by longitudinal chromatic aberration (LCA) with more growth in red monochromatic light than blue monochromatic light. They also respond to a chromatic signal from LCA that predicts reduced growth when red contrast>blue contrast, and increased growth when blue contrast>red contrast. The goal of this experiment was to determine whether contrast, temporal frequency, or blue light content determines which of these signals takes precedence.

Methods :

457 chicks viewed temporal stimuli for three days on an 8/16 hour light/dark cycle. Sinusoidal temporal stimuli (0.2 and 10 Hz) were presented at low (vector length: 30%) and high contrast (vector length: 80%), with seven different cone contrast ratios represented in polar coordinates (0°, 22.5°, 45°, 67.5°, 90°, 120°, 145°; Mean: 650 lux). “White+B” represents white stimuli with long-, middle- and short-wavelength sensitive cone contrast (LM-cone and S-cone). S-cone contrast increased from zero at 0° to a maximum at 90° and vice versa for LM-cone contrast. “White –B”, represents white stimuli (with blue light) but only L- and M-cone contrast. Measurements of the change in ocular components were made with a Lenstar LS 900 and a Hartinger refractometer. The major/ minor axes of the resulting data ellipse were calculated. A difference in axis length indicates sensitivity to relative cone contrast, while ellipse orientation indicates whether detection was of wavelength defocus or a chromatic signal.

Results :

Vitreous chamber growth in low contrast conditions showed sensitivity to relative cone contrast, and was dependent on stimulus orientation, a frequency of 0.2 Hz, and blue light content (F = 3.889; p = 0.002).
With 30% contrast, at 0.2 Hz, in “White +B”, the vitreous changes resulted in a data ellipse, with axes dimensions of 202 and 175 µm, orientated at 135.04°, indicating detection of a signed chromatic signal.
With 30% contrast, at 0.2 Hz, in “White –B”, the vitreous changes resulted in a data ellipse, with axes dimensions of 254 and 172 µm, orientated at 42.31°, indicating detection of a signed wavelength defocus signal.

Conclusions :

Myopia development depends on whether the eye responds to the sign of wavelength defocus or a chromatic signal from LCA, this in turn depends on the presence or absence of a blue light component, low temporal contrast, and low temporal frequency exposure.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.

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