Photopic condition

Takahashi Not really. It is too narrow. There are some really old action spectra from the Karolinska Institute that were done in rats. Under photopic conditions the action spectrum is much narrower than any opsin nomogram. This is common in rodents it is because of the contribution of multiple pigments at high light intensities. This is what the hamster action spectrum looks like it peaks near 500 nm, but it is narrower than an opsin nomogram. 

In the primitive nervous system, sensory cells evolved from general epithelial cells. Primitive nervous systems of modern echinoderms and lower deuterostomes are still composed of three cell types that include the primary sensory cells, the neurons that connect the sensory cells to distal targets, and a supporting cell that serves the special physiological needs of such a system (Lacalli, 2001). The basic structural plan of the retina is comparable to such a primitive nervous system. In the course of evolution, the photoreceptive system developed specialized photoreceptor cells (rods and cones), intra-retinal second-order neurons (bipolar cells), and tertiary output neurons (ganglion cells). This evolution perhaps took place in photopic conditions therefore early photoreceptor cells were more like cones. 

Ocular effects the barbiturates affect both ERGs and VEPs. Knave and Persson and NoelU found that a low dose of pentobarbital enhanced "a and b wave amplitude this effect was greatest under moderate photopic conditions and least during complete dark adaptation when long duration stimuli were used. A high dose of pentobarbital increased the latency, decreased the slope and reduced the amplitude of the b wave. 

Vision results from signals transmitted to the brain by about 125 million sensors located in the retina. These photoreceptors are of two types, called cones and rods. Cones work under intense light - that is, during daylight hours - and this mode of vision is called photopic vision. Rods work under dim lighting conditions, and this is called scotopic vision. 

The cones are used for color vision in bright light conditions (photopic vision), whereas the rods are used when very little light is available (scotopic vision). 

The International Commission on Illumination (CIE) has defined a standard observer to be used for accurate color reproduction (International Commission on Illumination 1983, 1990, 1996). In Chapter 2 we have seen that the rods mediate vision when very little light is available. This type of vision is called scotopic vision. The cones mediate high acuity vision in bright light conditions. This type of vision is called photopic vision. The sensitivities for a standard observer as defined by the CIE for scotopic and photopic vision are shown in Figure 4.3. The scotopic function is denoted by V (k). The photopic... 

Figure 8 ERG B-wave amplitude ratios (drug device implanted eye/fellow eye) in normal rabbit eyes with a cyclosporin A/dexamethasone sustained-release device in one eye. There was a significant depression in B-wave ratios from weeks 1 to 11 (P < 0.05). Maximum depression occurred at four weeks when photopic ERGs showed a 35% reduction in B-wave ratio while scotopic ERGs showed a 42% reduction. Both photopic and scotopic ERGs returned to normal by week 12. The B-wave latencies under both photopic and scotopic conditions were normal throughout the course of the study. Abbreviation ERG, electroretinography.

Photopic Vision Vision under bright-light conditions. 

Figure 7-12. Age related deterioration (a) in static acuity under optimal (photopic), low illumination (Mesopic), and glare conditions, and (b) in dynamic visual acuity, ability to detect motion across the visual field (Central Angular Motion - CAM), and forward motion (Central Movement in Depth - CMD) (from Shinar and Schieber, 1991, data from Shinar, 1977).

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