Overview
Visual acuity test is an eye examination or test of The eye that how well The eye sees details of letters, symbols and objects from a distinguished distance. This is done with a standard chat especially the Snellen Chart to determine the smallest letter The eye can read from a specify distance of 20 fleets (6 meters) away from the observer undergoing the eye test. Distinguished charts, objects and symbols are used, The Snellen Chart is one of the special tools used for the procedure, some Snellen charts are actually video monitors showing letters or images. Each of The eye is tested separately, the assessment of Visual acuity is important occasionally to monitor and to detect any changes in vision.
Why is visual acuity preformed?
Visual acuity is performed have a baseline record of how effective the eyes is
Visual acuity is performed for diagnostic and examination purposes
To assess refractive errors of the eye
To determine any changes To how the eye functions as regards vision
To determine the success of a surgery and cataract outcomes in patients treated for the disease
For job placement purposes
Equipment used to perform visual acuity
Snellen Chart
E chart
Flash light
Plain occluder, card or tissue
Pinhole occluder
Who perform a visual acuity test?
Visual acuity test is performed by well trained professionals that understands the processes and procedures. It can be:
Optometrist
Technician who was thought about the procedure
A nurse
Ophthalmologist
Optician
Risk associated with visual acuity test
No risks are associated with visual acuity tests, and you don’t need any special preparation.
When do I need to go for a visual acuity test
You may need to go for a visual acuity test if you're feeling uneasy in your eye
When you’re having poor sight that may be due to refractive errors
When you experience a change in your visual capacity
Why it is necessary to do eye test
Early detection is key to avoiding complication and to prevent deterioration of the eyes and worsening the problem.
Procedure for visual acuity test
1. Ensure the lightning of the environment where the test wants to take place is good.
2. Explain the process and procedures to the patient to be able to know what to do as at when due
3. Inform the patient about ethics of the test say what you see and no guessing
4. Position the patient at the appropriate distance of 6meters to the chart or as the case may be and tell the patient to close or block one eye when the Test is been carried out
5. Test each eye separately during the acuity test procedure
6. Use the standard chart recommended for the procedure
7. The chart should have a white background
8. Ask patient to read from the chart when the test begin
9. Ask the patient to read from the top of the chart downward and from left to right.
10. If the patient cannot read the letters due to language difficulties, use an E chart. The patient is asked to point in the direction where the E are facing.
Points to note about visual acuity test
1. The smallest line read is on the chart is expressed as a fraction ( for example 6/18).
2. The upper number on the chart refers to the distance where the chart is positioned to where the patient sit.
3. The lower number is the distance in metres at which a ‘normal’ human eye can read the line as it presents on the chart
4. When reading the chart, Incomplete lines can be added to the last complete line. e.g. 6/12+4, this indicating that the patient read the ‘12’ line at 6 metres
5. When recording the test results for visual acuity, remember to note the Visual acuity for each eye, indicating whether it is with or without correction (spectacles). For example: Right visual acuity is = 6/12 with correction, and the Left eye Visual acuity = 6/18 with correction.
6. If the patient is unable to read the biggest letter on top of the chart move him/her closer to about 1 metre at a time, until the patient can see the top letter.
When this procedure is completed without corrections, then test the patient with a correction spectacle and record your results in each of the eye separately, with the correction used.
If 6/6 which is the normal vision is not achieved, then go a little further by testing one eye at a time at 6 metres using the instrument called pinhole occluder while using any current spectacles. The use of the pinhole reduces the need to focus the light entering the eye of the patient.
State your finding on the test as required.
Types of charts for visual acuity test.
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