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Binoculars may have eye relief ranging from a few millimeters to 25 mm or more. Eye relief can be particularly important for eyeglasses wearers. The eye of an eyeglasses wearer is typically farther from the eye piece which necessitates a longer eye relief in order to avoid vignetting and, in the extreme cases, to conserve the entire field of view.
Ophthalmology. In ophthalmology, horror fusionis is a condition in which the eyes have an unsteady deviation, with the extraocular muscles performing spasm-like movements that continuously shift the eyes away from the position in which they would be directed to the same point in space, giving rise to diplopia. Even when the double vision images ...
Five Eyes. The Five Eyes ( FVEY) is an Anglosphere intelligence alliance comprising Australia, Canada, New Zealand, the United Kingdom, and the United States. [1] These countries are parties to the multilateral UK-USA Agreement, a treaty for joint cooperation in signals intelligence. [2] [3] [4] Informally, Five Eyes can refer to the group of ...
The Eye of Horus, also known as left wedjat eye or udjat eye, specular to the Eye of Ra (right wedjat eye), is a concept and symbol in ancient Egyptian religion that represents well-being, healing, and protection. It derives from the mythical conflict between the god Horus with his rival Set, in which Set tore out or destroyed one or both of ...
In young humans, the average visual acuity of a healthy, emmetropic eye (or ametropic eye with correction) is approximately 6/5 to 6/4, so it is inaccurate to refer to 6/6 visual acuity as "perfect" vision. On the contrary, Tscherning writes, "We have found also that the best eyes have a visual acuity which approaches 2, and we can be almost ...
In physics, a fluid is a liquid, gas, or other material that may continuously move and deform ( flow) under an applied shear stress, or external force. [1] They have zero shear modulus, or, in simpler terms, are substances which cannot resist any shear force applied to them. Although the term fluid generally includes both the liquid and gas ...
The effect of this will be that when a vertical beam of light in the distance travels towards the eye, the "minus" cylinder (which is placed with its axis lying horizontally – meaning in line with the patient's horizontal meridian relative to the excessively steep vertical meridian) will cause this vertical beam of light to slightly "diverge ...
Cerebrospinal fluid ( CSF) is a clear, colorless body fluid found within the tissue that surrounds the brain and spinal cord of all vertebrates . CSF is produced by specialised ependymal cells in the choroid plexus of the ventricles of the brain, and absorbed in the arachnoid granulations. In humans, there is about 125 mL of CSF at any one time ...