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VISUAL ACUITY 1200px-Snellen_chart.svg, Advantages of LogMAR chart:
Can…
VISUAL ACUITY 
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Tumbling E chart
An E chart (also known as a tumbling E chart) is an ophthalmological chart that is used to assess a patient's vision. The chart is especially useful for patients who are unable to read the alphabet – for example, small children and also in cases where patients don't speak English.
The tumbling E eye chart is typically used to test individuals who are unable to properly communicate or identify letters of the alphabet. This may include young children who do not know their alphabet, people who are illiterate or perhaps individuals who suffer from a handicap. This test provides doctors an easy and effective means to test the visual acuity of individuals who fall into any of these categories. In fact, studies have shown that the results of this test are as accurate as the standard Snellen eye chart.
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2.Have the person cover one eye (without applying pressure to it) so that their vision is completely blocked.
3.Start with the first line at the top of the chart and have the person point with their fingers the direction the "fingers" on the E are pointing.
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5.When the person fails to correctly identify the orientation of at least 50 percent of the Es on a line stop the test and note the previous line they were able to correctly identify at least 50% of the tumbling E's.
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Disadvantages
This eye chart only measures a person's visual acuity and cannot be used to determine other vision issues such as color blindness, depth perception or disorders such as glaucoma.
Landlolt C chart
The Landolt C is a test object used for measuring visual acuity consisting of an incomplete ring resembling the letter C
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Pros and Cons
There are several advantages to the Landolt C test, including equal difficulty of all targets (unlike letters that vary in degree of difficulty), sensitivity to astigmatic refractive error, and suitability for use with illiterate subjects.
However, the Landolt C test is not widely used because it has a guessing rate of 25%, so an alternative is to standardize another optotype set by comparing acuities obtained with it to Landolt C test acuities.
The broken ring symbol is made with a "C" like figure, which subtends 5 minutes of arc in the 20/20 optotype and has an opening (oriented in the top, bottom, right, or left) measuring 1 minute of arc.
The Landolt C chart is a way to check vision for age group of 3 to 6 yrs who cannot recognize letters or mute patients.
The patient has to indicate where the break is located, the break being positioned in any direction.
(up, down, left, right by finger)
The optotypes are usually oriented in four or eight directions.
Advantages of LogMAR chart:
- Can measure low visual acuity score accurately
- Progression of optotype size from one line to another in geometric format
- Horizontal and vertical crowding effect gives better estimate of visual acuity.
- LogMAR chart more accurate compare to other chart
- Letter size from line to line varies logarithmically
Zero LogMAR (0.0) indicates standard vision
Positive value indicates poor vision
Negative value indicates good vision
0.0 = 20/20
-0.1= 20/15
0.3 = 20/40
Best corrected VA worse than 0.5 LogMAR but equal or better than 1.3 LogMAR is defined as low vision.
Blindness is defined as best corrected VA worse than 1.3
How to use a LogMAR cbart?
- Ask patient to read down chart with one eye covered.
- Note how many letters are read coreectly
- Read off vision score
- Repeat with pinhole if vision worse than 0.2
- If LogMAR vision worse than 1.0, retest at 2m or 1m
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