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  2. Progressive lens - Wikipedia

    en.wikipedia.org/wiki/Progressive_lens

    The symmetric design, however, was difficult to accept for patients, because the eyes in general work asymmetrically. When you look to your right, your right eye views distal (i.e. looking through the lens near to the arm of the spectacles) while your left eye views nasal (i.e. looking through the lens near to the bridge). Modern sophisticated ...

  3. Human eye - Wikipedia

    en.wikipedia.org/wiki/Human_eye

    The human eye is a sensory organ in the visual system that reacts to visible light allowing eyesight. Other functions include maintaining the circadian rhythm, and keeping balance . Arizona Eye Model. "A" is accommodation in diopters. The eye can be considered as a living optical device. It is approximately spherical in shape, with its outer ...

  4. Visual acuity - Wikipedia

    en.wikipedia.org/wiki/Visual_acuity

    Between these extremes is the pupil diameter that is generally best for visual acuity in normal, healthy eyes; this tends to be around 3 or 4 mm. If the optics of the eye were otherwise perfect, theoretically, acuity would be limited by pupil diffraction, which would be a diffraction-limited acuity of 0.4 minutes of arc (minarc) or 6/2.6 acuity.

  5. Refractive error - Wikipedia

    en.wikipedia.org/wiki/Refractive_error

    A distant object is defined as an object located beyond 6 meters (20 feet) from the eye. When an object is located close to the eye, the rays of light from this object no longer approach the eye parallel to each other. Consequently, the eye must increase its refractive power to bring those rays of light together on the retina.

  6. Cataract - Wikipedia

    en.wikipedia.org/wiki/Cataract

    Frequency. 60 million (2015) [ 6 ] A cataract is a cloudy area in the lens of the eye that leads to a decrease in vision of the eye. [ 1 ][ 7 ] Cataracts often develop slowly and can affect one or both eyes. [ 1 ] Symptoms may include faded colours, blurry or double vision, halos around light, trouble with bright lights, and difficulty seeing ...

  7. Adaptation (eye) - Wikipedia

    en.wikipedia.org/wiki/Adaptation_(eye)

    In visual physiology, adaptation is the ability of the retina of the eye to adjust to various levels of light. Natural night vision, or scotopic vision, is the ability to see under low-light conditions. In humans, rod cells are exclusively responsible for night vision as cone cells are only able to function at higher illumination levels. [ 1]

  8. Keratoconus - Wikipedia

    en.wikipedia.org/wiki/Keratoconus

    Keratoconus. Keratoconus ( KC) is a disorder of the eye that results in progressive thinning of the cornea. [ 3] This may result in blurry vision, double vision, nearsightedness, irregular astigmatism, [ 4] and light sensitivity leading to poor quality-of-life. [ 3][ 5] Usually both eyes are affected. [ 3] In more severe cases a scarring or a ...

  9. Ocular immune system - Wikipedia

    en.wikipedia.org/wiki/Ocular_immune_system

    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 ...