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A person taking the test covers one eye from 6 metres or 20 feet away, and reads aloud the letters of each row, beginning at the top. The smallest row that can be read accurately indicates the visual acuity in that specific eye. The symbols on an acuity chart are formally known as "optotypes". Variation of Snellen chart with another letter ...
Eye color outside of the iris may also be symptomatic of disease. Yellowing of the sclera (the "whites of the eyes") is associated with jaundice, [82] and may be symptomatic of liver diseases such as cirrhosis or hepatitis. [83] A blue coloration of the sclera may also be symptomatic of disease. [82]
An eye chart is a chart used to measure visual acuity comprising lines of optotypes in ranges of sizes. Optotypes are the letters or symbols shown on an eye chart. [ 1 ] Eye charts are often used by health care professionals, such as optometrists , physicians and nurses , to screen persons for vision impairment .
For example, not everyone who takes medications like sildenafil reports cyanopsia, suggesting individual differences in retinal sensitivity or enzyme activity. One theory suggests that cyanopsia may develop due to the sudden unmasking of blue light sensitivity after cataract surgery, as the brain adjusts to the removal of the natural lens. For ...
Perimetry or campimetry is one way to systematically test the visual field. [1] [failed verification] It is the systematic measurement of differential light sensitivity in the visual field by the detection of the presence of test targets on a defined background. Perimetry more carefully maps and quantifies the visual field, especially at the ...
A slit lamp exam allows a detailed inspection of the conjunctiva and sclera and improves the detection of globe injury. Slit lamp exam findings like decreased anterior chamber depth or damage to posterior chamber structures indicate open-globe injury. [3] A seidel test detects more subtle or partially self-sealing open-globe injuries.
Many methods of performing Perls Prussian blue stain for iron have been published, [2] Drury and Wallington (1980) give a protocol that uses a mixture of 1 part 2% hydrochloric acid and 1 part 2% potassium ferrocyanide that is applied to the section for 20–30 minutes followed by a rinse in distilled water and application of a counterstain ...
Central heterochromia, blue with brown. Central heterochromia is also an eye condition where there are two colors in the same iris; but the arrangement is concentric, rather than sectoral. The central (pupillary) zone of the iris is a different color than the mid-peripheral (ciliary) zone.