Colour vision

R. Fletcher and J. Yoke, defective Colour Vision, Hilger, Bristol, UK, 1985. 

W. S. Stiles, Mechanisms of Colour Vision, Academic Press, Inc., New York, 1978. 

Cardiac glycosides have a small ratio of toxic to therapeutic concentration. Possible adverse effects are nausea, vomiting, abdominal pain, diarrhoea, fatigue, headache, drowsiness, colour vision disturbances, sinus bradycardia, premature ventricular complexes, AV-block, bigeminy, atrial tachycardia with AV-Block, ventricular fibrillation. There are several mechanisms relevant for their toxic action (Table 2). 

Anstis, S. M. and P. Cavanagh (1983). A minimum motion technique forjudging equiluminance. In Colour Vision Psychophysics and Physiology, J. D. Mollon and L. T. Sharpe (eds.). London Academic Press, pp. 66-77. 

Brindley, G. S. et al. (1966). The flicker fusion frequency of the blue-sensitive mechanism of colour vision. Journal of Physiology (London) 183 497-500. 

Rodriguez-Carmona, M. et al. (2006). The effects of supplementation with lutein and/or zeaxanthin on human macular pigment density and colour vision. Ophthalmic and Physiological Optics 26 137-147. 

The experimental values for. /V = 9 —> 15, compare extremely well with calculated spectra [74], The method is sufficiently accurate to elucidate the mechanism of colour vision in terms of the calculated spectrum of the related chromophore, retinal [76]. 

In colour vision there are three specific types of cone cell corresponding to red, green and blue receptors. The chromophore is the same for all three colours, being 11-cis-retinal bound to a protein which is structurally similar to opsin. Colour selectivity is achieved by positioning specific amino acid side chains along the chromophore so as to perturb the absorption spectrum of the chromophore. 

At the heart of much of this book is the fact that human beings are able to see colour by the interaction of light with the receptors in the retina of the eye. Any fault in this mechanism, such as red-green colour blindness, is a distinct hindrance in a world constructed around normal colour vision. 

Adverse effects include dose related gastrointestinal disturbances, hypotension particularly after rapid IV administration and transient disturbance in colour vision rarely. 

Colour vision relies on three pigments of different absorption spectra, B, G and R. Wavelength A in nm/100... 

CORDX usually begins within the first two decades of life and is progressive. Clinical features of the disorder include reduced visual acuity, poor colour vision, fundus abnormalities, central scotomas in the visual field, photophobia, myopia and low b-waves in ERG recordings (Jacobson et al., 1989 Brown et al., 2000). A single... 

Figure 8.14 Neural architecture of Usui and Nakauchi (1997). The architecture consists of four layers denoted by A, B, C, and D. The input image is fed into the architecture at the input layer. Layer D is the output layer. (Redrawn from Figure 8.4.1 (page 477) Usui S and Nakauchi S 1997 A neurocomputational model for colour constancy. In (eds. Dickinson C, Murray I and Carded D), John Dalton s Colour Vision Legacy. Selected Proceedings of the International Conference, Taylor Francis, London, pp. 475-482, by permission from Taylor Francis Books, UK.)...

Land EH 1974 The retinex theory of colour vision. Proceedings of the Royal Institution of Great Britain 47, 23-58. 

Linnell KJ and Foster DH 1997 Space-average scene colour used to extract illuminant information In John Dalton s Colour Vision Legacy. Selected Proceedings of the International Conference (eds. Dickinson C, Murray I and Carden D), pp. 501-509. Taylor Francis, London. 

Neumeyer, C. Arnold, K. (1989) Tetrachromatic colour vision in goldfish Vision Res. vol. 29, pg. 1719-27... 

Neumeyer, C. Arnold, K. (1989) Tetrachromatic colour vision in goldfish and turtle. Xxx pp 617-630 Douglas, R. Bowmaker, J. Kunz, Y. (1987) Ultraviolet vision in fish. In Kulikowski, J. Diskinson, C. Murray, I. ed. Seeing Contour and Colour. NY Pergamon Press, pp 601-616... 

In theory, it should be possible to further augment the effect of sildenafil with nitrate drugs, shouldn t it However, this cannot be recommended - it has been tried and resulted in heart attacks. Sildenafil may also cause disturbances of colour vision this is due to the role of cGMP-gated channels in the excitation of the sensory cells of the retina. 

Vertebrates have two types of light-responsive photoreceptor cells the rods and the cones. The photoreceptor cells convert light into nerve impulses. Cones are responsible for colour vision and function only in bright light, whereas rods also function in dim light. The retina in the human eye contains about 3 million cones and 100 million rods. 

Comeal deposits of chloroquine may be asymptomatic or may cause halos around lights or photophobia. These are not a threat to vision and reverse when the dmg is stopped. Retinal toxicity is more serious, however, and may be irreversible. In the early stage it takes the form of visual field defects late retinopathy classically gives the picture of macular pigmentation surrounded by a ring of pigment (the bull s-eye macula). The functional defect can take the form of scotomas, photophobia, defective colour vision and decreased visual acuity resulting, in the extreme case, in blindness. 

Adverse effects are short-lived, dose-related, and comprise headache, flushing, nasal congestion and dyspepsia. High doses can inhibit PDE6 which is needed for phototransduction in the retina, and some patients report transient colour vision disturbance. (The more recently developed PDE5 inhibitors, cialis and vardenafil, appear less likely to cause visual upset.) Priapism has been reported. 

A deficiency of this fat-soluble vitamin may result in total blindness. Found in spinach, carrots, sweet potatoes, and cantaloupe, it is responsible for maintaining good colour vision and night vision. 

Duff GR, Fraser AG. Impairment of colour vision associated with amiodarone keratopathy. Acta Ophthalmol (Copenh) 1987 65(l) 48-52. 

Lawrenson JG, Kelly C, Lawrenson AL, Birch J. Acquired colour vision deficiency in patients receiving digoxin maintenance therapy. Br J Ophthalmol 2002 86(11) 1259-61. 

Cavalleri A, Belotti L, Gobba F, et al. 1995. Colour vision loss in workers exposed to elemental mercury vapour. Toxicol Lett 77 351-356. 

MS is a multifocal disease frequently starting with ocular symptoms like diplopia when it becomes established in the brain stem, or a reduction of visual acuity, or disturbances in colour vision and pain when established as optic nerve neuritis. The typical plaques are initial sites of demyelination, whereas inflammatory elements... 

The retina of the eye contains innumerable nerve ends which can be differentiated into two categories known, because of their shapes, as the rod and cone types. The rods function when the illumination is of low intensity and do not appear to play much part in colour vision. This is demonstrated by the fact that objects appear colourless in a dim light. It... 

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