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A distant object is defined as an object located beyond 6 meters (20 feet) from the eye. [citation needed] 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.
Using the World Health Organization's (WHO; Geneva, Switzerland) blindness definition,1 45 million people worldwide are bilaterally blind, of which 6 to 8 million are blind due to corneal disease. In some African areas, nearly 90% of the total blindness is due to corneal pathology.
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. The smallest cone cells in the fovea have sizes corresponding to 0.4 minarc of the visual field, which also places a lower limit on acuity.
System: Eye and visual system: Significant diseases: Cataract, retinal disease (including diabetic retinopathy and other types of retinopathy), glaucoma, corneal disease, eyelid and orbital disorders, uveitis, strabismus and disorders of the ocular muscles, ocular neoplasms (malignancies, or cancers, and benign eye tumors), neuro-ophthalmologic disorders (including disorders of the optic nerve)
A number of alternative therapies have been claimed to improve myopia, including vision therapy, "behavioural optometry", various eye exercises and relaxation techniques, and the Bates method. [122] Scientific reviews have concluded that there was "no clear scientific evidence" that eye exercises are effective in treating myopia [ 123 ] and as ...
Anosmia is the inability to perceive odor, or in other words a lack of functioning olfaction.Many patients may experience unilateral or bilateral anosmia. A temporary loss of smell can be caused by a blocked nose or infection. In contrast, a permanent loss of smell may be caused by death of olfactory receptor neurons in the nose or by brain injury in which there is damage to the
Near visual acuity or near vision is a measure of how clearly a person can see nearby small objects or letters.Visual acuity in general usually refers clarity of distance vision, and is measured using eye charts like Snellen chart, LogMAR chart etc. Near vision is usually measured and recorded using a printed hand-held card containing different sized paragraphs, words, letters or symbols.
An illustration depicting primary tumor (in the form of tumor microenvironment) and the circulating tumor cells. A circulating tumor cell (CTC) is a cancer cell from a primary tumor that has shed into the blood of the circulatory system, or the lymph of the lymphatic system. [1]