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This can be seen when the eyes are closed and looking at the back of the eyelids. In a bright room, a dark red can be seen, owing to a small amount of light penetrating the eyelids and taking on the color of the blood it has passed through. In a dark room, blackness can be seen or the object can be more colourful.
Entoptic phenomena (from Ancient Greek ἐντός (entós) 'within' and ὀπτικός (optikós) 'visual') are visual effects whose source is within the human eye itself. (Occasionally, these are called entopic phenomena, which is probably a typographical mistake.) In Helmholtz 's words: "Under suitable conditions light falling on the eye ...
The ocular immune system protects the eye from infection and regulates healing processes following injuries. The interior of the eye lacks lymph vessels but is highly vascularized, and many immune cells reside in the uvea, including mostly macrophages, dendritic cells, and mast cells. [ 1] These cells fight off intraocular infections, and ...
Rheum from a cat's eyes. Rheum (/ r uː m /; from Greek: ῥεῦμα rheuma 'a flowing, rheum') is a thin mucus naturally discharged from the eyes, nose, or mouth, often during sleep (contrast with mucopurulent discharge). [1] [2] [3] Rheum dries and gathers as a crust in the corners of the eyes or the mouth, on the eyelids, or under the nose. [3]
A subconjunctival hemorrhage can often occur without any obvious cause or harm to the eye. A strong enough sneeze or cough can cause a blood vessel in the eye to burst. Hyphema is a result of blunt or penetrating trauma to the orbit that increases intraocular pressure, causing tears in the vessels of the ciliary body and iris.
The best way to prevent headaches behind your eyes is to narrow down what's causing them, for which you'll need a doctor's help. If your vision is to blame, wearing corrective lenses and having ...
Red-eye effect seen on a teenager. The red-eye effect in photography is the common appearance of red pupils in color photographs of the eyes of humans and several other animals. It occurs when using a photographic flash that is very close to the camera lens (as with most compact cameras) in ambient low light.
The blood–retinal barrier, or the BRB, is part of the blood–ocular barrier that consists of cells that are joined tightly together to prevent certain substances from entering the tissue of the retina. [1] It consists of non-fenestrated capillaries of the retinal circulation and tight-junctions between retinal epithelial cells preventing ...