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W. Teetz, M. S. Eckmiller, R. E. Eckmiller; Cooperation Between the Visual Feedback Loops for Human Cone Photoreceptor Alignment and Lens Accommodation. Invest. Ophthalmol. Vis. Sci. 2007;48(13):3808. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To develop a sensorimotor eye simulator (SMES) in software and to use it to study the interaction between the local feedback systems for the alignment of individual human foveal cone photoreceptors (as a function of chromatic aberration, retinal eccentricity, spectral and directional sensitivities) and the feedback system for lens accommodation in response to optical patterns (OPs).
A: The geometry of the human eye was simplified to have rotational symmetry about the visual axis through the foveal center.B: Spectral sensitivity characteristics of the outer segments were defined with maxima for M cones at M= 535 nm and for L cones at L= 565 nm.C: M and L cones were homogeneously distributed with decreasing packing density (60 cones/deg in foveal center) up to retinal eccentricities of 10 deg.D: In accordance with the Stiles-Crawford effect, each cone was simulated with a directional characteristic and a feedback system for radial alignment of its longitudinal axis by bending of the motile inner segment (M. S. Eckmiller, ARVO 2007).E: The accommodation range for OPs (with wavelength distributions of 400-750 nm) was defined for object distances of 20-500 cm.F: The contribution of the separate input signals from M and L cones to the accommodation feedback system depended on the individual alignment angles and retinal eccentricities of the cones.
(1) For rotationally symmetrical OPs, the SMES algorithms were processed on a standard PC in real time while OP, corresponding retinal image (RI) in color, and various signal time courses and parameters were visualized on a monitor.(2) The RI was simulated by a dynamic set of cone output signals as a function of changes in cone alignment and accommodation.(3) The dynamic properties of the feedback systems for individual cone alignment and for lens accommodation could be modified and monitored as time courses in real time.(4) The time courses of key signals [e.g., distance between location of the intraocular image plane of OP (for a given ) and retina, or cone alignment angle as a function of changes in distribution versus OP distance] could be analysed.
A. The SMES demonstrates that high RI quality (hence visual acuity) is significantly dependent on effective cooperation between the feedback systems for foveal cone alignment and lens accommodation.B. Pathological changes in the cone alignment systems that influence either their direction-specific inputs or their motor properties are expected to cause severe visual dysfunction.
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