Chart for Vision Rehabilitation
#258000

Lea symbols developed by Lea Hyvärinen, M.D.

The LEA Symbols Chart for Vision Rehabilitation (#258000) is designed for examination of severely visually impaired children and adults. The largest symbols are 50M in size corresponding to 1/50 (20/1000, 6/300, 0.02) and the smallest symbols are 1M in size corresponding 1/1 (20/20, 6/6, 1.0) at a distance of one meter. The test comes with a one meter cord to maintain the proper testing distance.

Instructions

• When examining young children, introduce the distance chart to the child after near testing by saying, "Let's look at the same pictures a little further away."

  Ask what is the first symbol in each line in descending order when testing binocularly.
  (Pointing is no more allowed because it may improve the visual acuity http://whqlibdoc.who.int/hq/2003/WHO_PBL_03.91.pdf .)

  Move down until the child hesitates or misidentifies a symbol.

  Move back up one line and ask the child to identify all the symbols on that line.

  If the child identifies all symbols correctly go to the next line with smaller symbols and ask the child to identify all symbols on that line.

  If the child skips a symbol ask the child to try again while briefly pointing to that symbol.

  A child with fixation problems may skip symbols within a line of symbols.

  Visual acuity is recorded as the last line on which at least 3 of the 5 symbols are identified correctly. The visual acuity value is found in the margin adjacent to that line.

  After obtaining good responses with binocular testing, proceed by testing each eye separately.

  When testing monocularly, use the first symbol of each line or every second line for one eye and the last symbol of each line for the other eye to determine on which line to start testing close to the threshold value.

• If the child has profound low vision, the lowest rows of the test can be used as a near vision test. The distance of 25cm is the most practical distance because calculation of the visual acuity values is simple. They are ¼ of the value printed next to the last line read. (To calculate ¼ of a Snellen value, you multiply the denominator by 4.)

M-unit, metric unit is the distance in meters at which the reference optotype C is seen at a visual angle of 5'.