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Long-term contact lens use can lead to alterations in corneal thickness, stromal thickness, curvature, corneal sensitivity, cell density, and epithelial oxygen uptake, etc. Other changes may include the formation of epithelial vacuoles and microcysts (containing cellular debris) as well as the emergence of polymegethism in the corneal endothelium.
Cold showers may also improve mood and energy or mental alertness, which Dr. Rachelle Reed, an exercise physiologist in Athens, Georgia, has experienced, she said. “You sort of feel a little bit ...
Closed-eye hallucinations and closed-eye visualizations ( CEV) are hallucinations that occur when one's eyes are closed or when one is in a darkened room. They should not be confused with phosphenes, perceived light and shapes when pressure is applied to the eye's retina, or some other non-visual external cause stimulates the eye.
Computer vision syndrome. Computer vision syndrome ( CVS) is a condition resulting from focusing the eyes on a computer or other display device for protracted, uninterrupted periods of time and the eye's muscles being unable to recover from the constant tension required to maintain focus on a close object.
Photokeratitis or ultraviolet keratitis is a painful eye condition caused by exposure of insufficiently protected eyes to the ultraviolet (UV) rays from either natural (e.g. intense direct or reflected sunlight) or artificial (e.g. the electric arc during welding) sources. Photokeratitis is akin to a sunburn of the cornea and conjunctiva.
Abundant visible light to the eyes gives health benefits through its association with the timing of melatonin synthesis, maintenance of normal and robust circadian rhythms, and reduced risk of seasonal affective disorder. [10] On the negative side, UV is a mutagen and carcinogen for skin.
Photopsia is the presence of perceived flashes of light in the field of vision. It is most commonly associated with: [ 4] Vitreous shrinkage or liquefaction, which is the most common cause of photopsia, causes a pull in vitreoretinal attachments, irritating the retina and causing it to discharge electrical impulses.
Flash blindness is an either temporary or permanent visual impairment during and following exposure of a varying length of time to a light flash of extremely high intensity, such as a nuclear explosion, flash photograph, lightning strike, or extremely bright light, i.e. a searchlight, laser pointer, landing lights or ultraviolet light. [ 1]