Spectral bandwidth and ocular accommodation.

Schnurmacher Institute for Vision Research, State College of Optometry, State University of New York, New York 10010.
Journal of the Optical Society of America A (Impact Factor: 1.67). 04/1995; 12(3):450-5. DOI: 10.1364/JOSAA.12.000450
Source: PubMed

ABSTRACT Previous studies have suggested that targets illuminated by monochromatic (narrow-band) light are less effective in stimulating the eye to change its focus than are black-white (broadband) targets. The present study investigates the influence of target spectral bandwidth on the dynamic accommodation response in eight subjects. The fixation target was a 3.5-cycle/deg square-wave grating illuminated by midspectral light of various bandwidths [10, 40, and 80 nm and white (CIE Illuminant B)]. The target was moved sinusoidally toward and away from the eye, and accommodation responses were recorded and Fourier analyzed. Accommodative gain increases, and phase lag decreases, with increasing spectral bandwidth. Thus the eye focuses more accurately on targets of wider spectral bandwidth. The visual system appears to have the ability to analyze polychromatic blur to determine the state of focus of the eye for the purpose of guiding the accommodation response.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Longitudinal chromatic aberration (LCA) provides a cue to accommodation with small pupils. However, large pupils increase monochromatic aberrations, which may obscure chromatic blur. In this study, we examined the effect of pupil size and LCA on accommodation. Accommodation was recorded by infrared optometer while observers (nine normal trichromats) viewed a sinusoidally moving Maltese cross target in a Badal stimulus system. There were two illumination conditions: white (3000 K; 20 cd/m) and monochromatic (550 nm with 10 nm bandwidth; 20 cd/m) and two artificial pupil conditions (3 and 5.7 mm). Separately, static measurements of wavefront aberration were made with the eye accommodating to targets between 0 and 4 D (COAS, Wavefront Sciences). Large individual differences in accommodation to wavefront vergence and to LCA are a hallmark of accommodation. LCA continues to provide a signal at large pupil sizes despite higher levels of monochromatic aberrations. Monochromatic aberrations may defend against chromatic blur at high spatial frequencies, but accommodation responds best to optical vergence and to LCA at 3 c/deg where blur from higher order aberrations is less.
    Optometry and vision science: official publication of the American Academy of Optometry 05/2011; 88(5):593-600. · 1.53 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: At birth most, but not all eyes, are hyperopic. Over the course of the first few years of life the refraction gradually becomes close to zero through a process called emmetropisation. This process is not thought to require accommodation, though a lag of accommodation has been implicated in myopia development, suggesting that the accuracy of accommodation is an important factor. This review will cover research on accommodation and emmetropisation that relates to the ability of the eye to use colour and luminance cues to guide the responses. There are three ways in which changes in luminance and colour contrast could provide cues: (1) The eye could maximize luminance contrast. Monochromatic light experiments have shown that the human eye can accommodate and animal eyes can emmetropise using changes in luminance contrast alone. However, by reducing the effectiveness of luminance cues in monochromatic and white light by introducing astigmatism, or by reducing light intensity, investigators have revealed that the eye also uses colour cues in emmetropisation. (2) The eye could compare relative cone contrast to derive the sign of defocus information from colour cues. Experiments involving simulations of the retinal image with defocus have shown that relative cone contrast can provide colour cues for defocus in accommodation and emmetropisation. In the myopic simulation the contrast of the red component of a sinusoidal grating was higher than that of the green and blue component and this caused relaxation of accommodation and reduced eye growth. In the hyperopic simulation the contrast of the blue component was higher than that of the green and red components and this caused increased accommodation and increased eye growth. (3) The eye could compare the change in luminance and colour contrast as the eye changes focus. An experiment has shown that changes in colour or luminance contrast can provide cues for defocus in emmetropisation. When the eye is exposed to colour flicker the eye grows almost twice as much, and becomes more myopic, compared to when the eye is exposed to luminance flicker. Neural responses of the luminance and colour mechanisms direct accommodation and emmetropisation mechanisms to different focal planes. Therefore, it is likely that the set point of refraction and accommodation is dependent on the sensitivity of the eye to changes in spatial and temporal, colour and luminance contrast.
    Ophthalmic and Physiological Optics 05/2013; 33(3):196-214. · 1.74 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The aim of this study was to evaluate the accommodation response under both mono- and polychromatic light while varying the amount of spherical aberration. It is thought that chromatic and spherical aberrations are directional cues for the accommodative system and could affect response time, velocity or lag. Spherical aberration is often eliminated in modern contact lenses in order to enhance image quality in the unaccommodated eye. This study was divided into two parts. The first part was done to evaluate the amount of spherical and other Zernike aberrations in the unaccommodated eye when uncorrected and with two types of correction (trial lens and spherical-aberration controlled contact lens) and the second part evaluated the dynamic accommodation responses obtained when wearing each of the corrections under polychromatic and monochromatic conditions. Measurements of accommodation showed no significant differences in time, velocity and lag of accommodation after decreasing the spherical aberration with a contact lens, neither in monochromatic nor polychromatic light. It is unlikely that small to normal changes of spherical aberration in white light or monochromatic mid-spectral light affect directional cues for the accommodative system, not in white light or mid-spectral monochromatic light, since the accommodative response did not show any change.
    Journal of Modern Optics 01/2011; 58(19-20):1696-1720. · 1.16 Impact Factor

Full-text (2 Sources)

Available from
Jun 10, 2014