Lawrence R. Stark

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The eye's longitudinal chromatic aberration (LCA) is known to drive 'reflex' accommodation to moving objects, but the evidence is not as clear for stationary objects. The present study examined whether accommodation can be driven by static simulations of the effects of defocus and LCA. Accommodation was recorded continuously while each of 12 subjects viewed(More)
We wished to determine how pupil size and mean accommodation response level interact to influence the fluctuations of accommodation. A dynamic infra-red optometer was used to record accommodation responses while subjects viewed a steady target at two stimulus levels (1.5 and 3 D) through four pupils (1, 2, 4 and 6 mm). It was found for most subjects that(More)
PURPOSE The authors investigated the potential of subject instructions to alter the static accommodative stimulus-response function. They also investigated whether the reduced cue environment of the Badal optical system leads to accommodative responses different from those that occur for targets presented in real space. METHODS Static accommodative(More)
The properties of small monochromatic targets as accommodative stimuli are not well understood. We used a dynamic optometer to record accommodation responses to monochromatic disc targets (1.0-27.3 min arc) and to a Maltese cross. Accommodation responded adequately to points as small as 13.6 min arc. The response to these small targets is relevant to the(More)
Previous studies have demonstrated that accommodation will respond to sine gratings in which the relative modulations of red, green and blue image components have been altered to simulate the effects of defocus and longitudinal chromatic aberration. The present study aimed to determine the tolerance of the accommodative system to relative phase shifts in(More)
We investigate the potential for the third-order aberrations coma and trefoil to provide a signed cue to accommodation. It is first demonstrated theoretically (with some assumptions) that the point spread function is insensitive to the sign of spherical defocus in the presence of odd-order aberrations. In an experimental investigation, the accommodation(More)
PURPOSE When the targets or the background in a display are different colors, longitudinal chromatic aberration ensures that there is no single correct accommodative response. The purpose of the present study was to determine whether the response becomes more variable when viewing certain multicolor displays. METHODS Accommodative responses of five young(More)
The purpose of this study is to determine if cues within the blurred retinal image due to the Stiles-Crawford (SC) effect and the eye's monochromatic aberrations can drive accommodation with a small pupil (3 mm) that is typical of bright photopic conditions.The foveal, psychophysical SC function (17 min arc) and ocular monochromatic aberrations were(More)
PURPOSE To compare visual acuity measures obtained with the M&S Technologies Smart System II (SSII) and the revised Early Treatment of Diabetic Retinopathy Study (ETDRS) charts in terms of accuracy and test-retest repeatability. METHODS Monocular visual acuities were taken in 57 young, visually normal adults on two separate visits in which both the SSII(More)
PURPOSE To investigate the accuracy and stability of the monocular accommodation response when attention is directed toward a totally occluded distant object. METHODS A static infrared optometer was used to measure the monocular accommodative response in 16 participants while they viewed a distant letter target in the presence or absence of an intervening(More)