ted i ercise you will con inve t gate visual perception. Except where it is othe
ID: 63940 • Letter: T
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ted i ercise you will con inve t gate visual perception. Except where it is otherwise l rods for black and white instructor tells you ferently, always remove glasses or corrective lenses thefore mak NEAR POINT Your near point is the r of a centimeter scale against your cheek just below your right eye. Hav eye with an index card. Hold a pin against the scale and move it along the scale until you fid the minimum distance at which you can keep the pin point focused. Record this as the near point for your right near point with glasses, right eye-- cm : left eye cm. near point is the minimum distarce at which you can focus on as object, Place e someone cover your eye, cm. Repeat for the left eye crm. If you wear glasses, determine your VISUAL ACUITY The amount of detai the eve can distinguish is its visual acuity. The Snellen chart uses in ters of successively si aler size to nseasure visual acuity. A normal eve has a visuai as measured on the S ellen chart The Snellen chart uses lines ot s acuity o : 20 The subject stand 6.1 m (20 ft) from the Snellen chart and covers the left eye card. The observer p nts to the top line of the chart and pauses while the subject calls out the let ter. The observer the points to the second line aned patuses until the letters are treard. This continues until a line is reachod vhich the subject cannot read correctly or until all lines are read. To the left of eact Ine is a value for visual acuity. The observer should record this value for the Determine visual acuity for the lef1 eyt last line correctly ree . Visual acuity, right eye If the subis t wears glasses, repeat the test with the glasses on. Vistal acuity, right e (glasses) . Visi, ii acuity, left eye glasses) ACCOMMODATION your It you normally vwar glasses, leave them on. Mark a large cital " on the batk t finger. Stand 6.1 m (20 1) from the Snellen Chart. Hold up your ndex lne at a l at the top of the chartwith both w-ot tert in focus? the top ot the chart. With buth eyes u eyes op, look n, "E"on your finger appears beside the large "E Now iook at the ''E., on the on your finger. Is the E" on the chart in focus? Is the "E on yous tinger in s the ..E.. on your t chart. How many images of the"E" on vour finger do you see? ! ocus Then ciose your left eve and open it. What happens to the images ot the "E" on your finger? 7 While continuing to look at the .E" on the chart. close your right re nd open . Shitt your gaze from the "E on the chart to the "E on your finger and back several times This is accomodatio the automatic adjustment of the eye for viewing objects at different dis tances If the cornea or the ns is unequally curved, not all light rays will focus at the same point, and nart of the visual field w 1 be blurred. Stand in front of and about 1.5 to 3 m (4 to 8 It) trom te matism chart, cover r e eye with an index card and look at the center of the chort Al tthe ratial lines appear to have h: same darkness to the nermal eye: however, the astigmati eve ell lines in shatp focus,king them appear darker than the ines that are out of tocus Reuset u ASTIGMATISM In your lett ev with the other eve.you !..rve as tigrilatisin vour ruht eve? If you have astigmat an and wear glasses, repeat the test you have astigmat n and wear glasses, repeat the test with your giasses on. Do the glasses correct your astigmatism?Explanation / Answer
Visual acuity:
Snellen’s eye test is useful for testing the sharpness of one’s vision or otherwise called as visual acuity. It this test, a white chart having letters in different sizes is placed on a board, at certain distance from the person. The distance at which the person reads letters normally (emmotropic vision) is printed at the end of that line.
The visual acuity is normal, if one can read the line of letters on the chart from 20 feet away, that is generally seen by a person with normal vision (i.e., 20/20 vision).
In Snellen’s test, both eyes are tested separately, because both eyes do not have same vision, as two eyes have two individual sets of processes for vision. The vision of one eye could be different from the other one.
In Snellen’s eye test, 20/40 vision means, the individual can read a line of letters from 40 feet distant from the letter chart, which a normal person could have read them from 20 feet distance from the chart. So, in this case, the vision of the individual is having less visual acuity (myopic vision).
In Snellen’s eye test, 20/10 vision means, the individual can read a line of letters from 10 feet distant from the letter chart, which a normal person could have read them from 20 feet distance from the chart. In this case, the individual is having better than normal visual acuity.
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