ACCOMMODATION WITHOUT FEEDBACK SUGGESTS DIRECTIONAL SIGNALS SPECIFY OCULAR FOCUS

Accommodation was monitored continuously under open-loop conditions wh ile subjects viewed a sinusoidally oscillating sine-wave grating (0,2 Hz; +/-1 D; 2.7 c/d; 0.56 contrast) in a Badal optometer, The target w as illuminated by monochromatic light (590 mm) or white light (3000 K) with longitudinal chromatic aberration (LCA) normal, doubled, neutral ized and reversed, Subjects (12) accommodated well in white light with LCA normal and doubled (mean gains = 0.85 and 0.94), gain was reduced in the neutralized condition (0.54), in monochromatic light (0.43), a nd especially when LCA was reversed (0.30). The results suggest that a ccommodation responds to changes in the relative contrast of spectral components of the retinal image and perhaps to the vergence of light. (C) 1997 Elsevier Science Ltd.