Vision tests

A variety of examinations used to determine how well a person can see. Vision tests are often combined with a physical examination of the eye. Vision tests check for visual acuity (the sharpness of vision), refraction (which determines the correct prescription for glasses or contact lenses), blind spots, color perception, and visual field (the total area a person can see when looking straight ahead).


Most vision tests examine a person’s sharpness of vision (visual acuity) and often of the field of vision. Refraction tests assess whether a person has an error that can be corrected with glasses such as astigmatism, hypermetropia or myopia. Visual acuity is tested using a Snellen chart, when the patient tries to read letters of differing standard sizes from 6 metres away. The optician will prescribe lenses to correct any defects detected by such vision tests.


The segment of an eye exam that assesses a decline in visual acuity.


Examinations for visual sharpness, or acuity, often involve the use of a Snellen chart for evaluating distance vision, and near-vision test cards to gauge one’s ability to see objects up close.


Refraction exams evaluate how well the eye focuses light directly onto the retina through the cornea and lens. These tests are helpful in identifying conditions like longsightedness (hypermetropia), shortsightedness (myopia), and abnormal eye curvature (astigmatism). By studying how light reflects off the eye when using various lenses, optometrists can objectively determine the prescription needed for glasses or contact lenses to correct the vision issue. Subsequent visual acuity tests confirm that the newly prescribed lenses allow the patient to see clearly, with minor adjustments made as necessary.


Visual field tests may be conducted to evaluate eye conditions like glaucoma, which involves elevated fluid pressure in the eyeball, or neurological issues such as a stroke.


 


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