![]() ![]() The high concentrations of yellow pigments within the human central macula result in a reduction of up to 80% of high-energy visible light reaching the photoreceptor outer segments 10. It is generally thought that low concentrations of macular pigment predispose to eye disease, particularly age-related macular degeneration 6– 9. Additional vision-related functions include the reduction of chromatic aberration 4 and light scatter 5. Macular pigments are thought to protect against the damaging effects of high-energy visible wavelengths (380–500 nm) by acting as violet/blue light filters and free-radical scavengers 1– 3. Centred on the visual axis of the eye, it derives its name ( macula lutea = yellow spot) from its high concentration of plant-derived xanthophyll carotenoid pigments (i.e. The human macula is the retinal area anatomically and functionally optimised for high visual acuity. We conclude: (i) MS and HB both result from differential light absorption through a radial diattenuator, compatible with the arrangement of macular pigments in Henle fibres (ii) the morphology of MS is dependent on the degree of linear polarization (iii) perceptual differences between MS and HB result from different states of neural adaptation. ![]() These findings support a common origin of each phenomenon, and are relevant to the clinical use of polarization stimuli in detecting and monitoring human eye disorders, including macular degeneration. Predictions were tested psychophysically in human observers, whose measured differences in the diameters of each entoptic phenomenon generated with depolarized and linearly polarized light were consistent with the model simulations. The model also predicted a correlation between the observed diameters of MS and HB. The model predicted that polarized light modifies the appearance of MS leading to the perception of a novel phenomenon. ![]() To simulate MS and HB, an existing computational model of polarization-dependent properties of the human macula was extended by incorporating neuronal adaptation to stabilized retinal images. Under specific conditions of illumination and polarization, differential absorption of light by macular pigments is perceived as the entoptic phenomena of Maxwell’s spot (MS) or Haidinger’s brushes (HB). ![]()
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