ABSTRACT
When its spatial frequency is high enough, a grid of grey horizontal strips presented on a coloured background may change its neutral colour. It was found that some background colours induce a strong illusion and some no illusion at all. The effect of the background colour on the illusion was studied for the spatial frequencies of 0.5, 2.5, 4, and 8 c/deg. Thirty chromaticities (evenly distributed across the colour gamut triangle) of the backgrounds in the equiluminant plane, and 24 in the ML plane (where S-contrast was zero), were tested. Five matches were made for each frequency and each background chromaticity. Viewing was binocular. For the low (0.5 c/deg) frequency strips, the backgrounds were found to induce the colour, if any, approximately complimentary to that of the background (i.e., chromatic simultaneous contrast). For the high (8 c/deg) frequency, most backgrounds induced only illusory colours close to unique hues (yellow, blue, and green), with a few backgrounds inducing a mixture of green with blue. Then, the method of adjustment was used to determine the unique hues for the same three observers. A remarkable similarity was found between unique hues and illusory loci, suggesting that the illusion is due to a difference in the spatial resolution of the post-receptor channels producing the unique hues.
Subject(s)
Color Perception , Illusions , Color Perception/physiology , Contrast Sensitivity/physiology , Female , Humans , Illusions/physiology , Illusions/psychology , Photic Stimulation/methods , Photoreceptor Cells, Vertebrate/physiology , Psychophysics , Vision, Binocular/physiologyABSTRACT
Luminance contrast was found to affect high-spatial-frequency tritanopia despite the S-cone coordinates of the stimuli being kept constant. This proves that a traditional account of artificial tritanopias based on the spatial resolution differences between the S-cone channel and the M- and L-cone channels is not applicable here. We suggest that the lack of spatial resolution in one of the post-receptor (rather than receptor) spatio-chromatic channels could be a cause of high-spatial-frequency tritanopia.
Subject(s)
Color Vision Defects/physiopathology , Contrast Sensitivity , Retinal Cone Photoreceptor Cells/physiopathology , Color Vision Defects/psychology , Humans , Models, Neurological , Models, Psychological , Optical Illusions , Pattern Recognition, Visual , Photic Stimulation/methods , Psychophysics , Space PerceptionABSTRACT
Contrary to the general belief that the yellow-blue mechanism has lower spatial resolution than the red-green mechanism, it has been recently claimed that both mechanisms have similar spatial sensitivity (McKeefry et al, 2001 Vision Research 41 245-255). Studying high-spatial-frequency tritanopia (a colour illusion based on spatio-chromatic interactions in human vision), we found strong evidence for the existence of two blue mechanisms-with low and high spatial-frequency resolution. If confirmed, this may resolve the apparent paradox concerning spatial resolution of the yellow-blue mechanism.
Subject(s)
Color Perception/physiology , Optical Illusions , Color Perception Tests , Female , Humans , Psychophysics , Space Perception/physiologyABSTRACT
PURPOSE: To evaluate phacoemulsification combined with silicone oil removal through the posterior capsulorhexis tear. METHOD: The records of 20 patients with cataract after silicone oil repair of retinal detachment with giant retinal tear or complicated by proliferative vitreoretinopathy were reviewed. All eyes underwent phacoemulsification, posterior capsulorhexis, aspiration of silicone oil with an irrigation-aspiration hand piece, and intraocular lens implantation into the capsular bag. Lens calculation was based on the fellow eye. The mean follow-up period after cataract surgery was 15.4 months. RESULTS: There were three recurrences of retinal detachment (15%). Transient corneal edema was noted in two eyes. Unpredictable refraction was the main problem, but the myopic refractive error was <4.5 diopters in all cases. CONCLUSION: Cataract extraction combined with silicone oil removal is an effective technique.