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Leaves change color in the fall because their chromophores (chlorophyll molecules) break down and stop absorbing red and blue light. [1] A chromophore is a molecule which absorbs light at a particular wavelength and reflects color as a result. Chromophores are commonly referred to as colored molecules for this reason.
This results in an image of the light being focused on the periphery of the retina. Light from this spot then casts shadows of the blood vessels (which lie on top of the retina) onto unadapted portions of the retina. Normally the image of the retinal blood vessels is invisible because of adaptation. Unless the light moves, the image disappears ...
Ophthalmogram showing blood vessels in front of the retina. Their shadow is the cause of the blue field entoptic phenomenon. The dots are white blood cells moving in the capillaries in front of the retina of the eye. [5] Blue light (optimal wavelength: 430 nm) is absorbed by the red blood cells that fill the capillaries.
The blood–ocular barrier is a barrier created by endothelium of capillaries of the retina and iris, ciliary epithelium and retinal pigment epithelium. [1] It is a physical barrier between the local blood vessels and most parts of the eye itself, and stops many substances including drugs from traveling across it. [2]
The optical mechanisms by which the nonpigmented stromal components influence eye color are complex, and many erroneous statements exist in the literature. Simple selective absorption and reflection by biological molecules (hemoglobin in the blood vessels, collagen in the vessel and stroma) is the most important element.
Chlorophyll does not reflect light but chlorophyll-containing tissues appear green because green light is diffusively reflected by structures like cell walls. [4] This photosynthetic pigment is essential for photosynthesis in eukaryotes, cyanobacteria and prochlorophytes because of its role as primary electron donor in the electron transport ...
The macula responsible for central vision and the anterior part of the optic nerve are dependent on choroidal blood supply. [4] The structure of choroidal vessels can be revealed by optical coherence tomography, and blood flow can be revealed by Indocyanine green angiography, and laser Doppler imaging. [5]
Humans have only one class of pigment cell, the mammalian equivalent of melanophores, to generate skin, hair, and eye colour. For this reason, and because the large number and contrasting colour of the cells usually make them very easy to visualise, melanophores are by far the most widely studied chromatophore.