What Is Visual Acuity?
A visual acuity test is used to measure the vision of the person. It helps to determine the refractive error present in your eyes. Visual acuity tests can be performed at home easily but it is necessary to get eyes checked by a professional. A visual acuity eye test is done using a Snellen chart which is placed 20 feet away from the patient.
The ideal visual acuity is 20/20 which means that you are able to see objects placed 20 feet away from you clearly. If you have a visual acuity of 20/100 it would mean that you need to be at a 20 feet distance to see objects placed at 100 feet. A person with normal eyesight would be able to see objects placed at 100feet easily.
Use of Visual Acuity Test
This measurement of eyesight helps to determine the refractive error present in a person’s eyesight. Other factors like colour vision, focusing ability, eye coordination, depth perception are not determined by the visual acuity test. If your eyesight becomes blurry or you have problems viewing objects placed at a distance or nearby then it is recommended to get an eye test done by a professional ophthalmologist or for reference purposes you can do it at home too.
Visual acuity tests or eye tests can be done from home using the Snellen chart. The chart consists of alphabets which are placed in decreasing order. The Snellen chart helps in determining whether there is any refractive error in your eyes and if you need any corrective lenses or not.
For doing an eye test at home you need to print out Snellen charts available on websites or you can purchase the chart from the market. The chart should contain the biggest letter of size one inch. Tape the chart on the level of your eyes while sitting or standing. Now you should be 10 feet away from the chart. Now cover one of your eyes completely using your palm. Then tell one of your family members to place a stick on the alphabet as you read out with one eye open. Note down the line from which you are not being able to read properly.
Now repeat the process with another eye and record the results accurately. If you wear eyeglasses or contact lenses, make sure you wear them while testing your eyesight to maintain normal vision and then proceed with the eye test. Ensure that you are taking this test in a well-lit room or the chart has enough light on it. The test results vary from age to age and would different for children and adults. This type of home testing would not provide a very accurate result but will give an approximation of the vision.
Test For Presbyopia
For near vision follow the steps of the distance vision testing using a near-eye test card. The eye test card should be held about 14 inches from your eyes and not much closer. And note down the size of the smallest line that you were able to accurately read. If you are not being able to read the smallest line then it may be a sign of presbyopia.
AMSLER Grid Test
AMSLER grid test helps in the detection of macular degeneration. In this test, you need to hold the grid in front of you (14 inches) and try to look at the dot present in the center of the grid. When you are looking at the dot the grid would appear in your peripheral vision and the lines both in horizontal as well as vertical direction would appear straight and unbroken. If these lines appear distorted or broken then mark their location using a pen or pencil. Any distortion in the grid lines indicates macular degeneration and proper medical help should be taken.
Instead of buying or printing Snellen charts for eye tests, you can also download various eye test applications on your phones or laptop to get an idea about how good or bad your vision is. These online eye test applications are only equipped with providing a basic idea about your vision.
If you have any doubt regarding your vision, you should visit an ophthalmologist for the same. Some of the online eye test applications are also equipped with prescription eyeglasses and contact lenses but these are not efficient prescriptions. Some of these online eye tests can check light sensitivity and colour vision too. These tests can’t be used as a substitute for the comprehensive eye test.
Disadvantages of Online Eye Tests
There are certain disadvantages associated with online eye tests. There are chances that you may be misdiagnosed by the eye test. It’s better to get checked by a professional ophthalmologist or optometrist so that they can do a proper comprehensive eye exam and determine the defects in your eyes.
Certain eye conditions like glaucoma and diabetic retinopathy can’t be determined using these online eye tests as in the initial stages of these diseases no to very few symptoms are visible which would not get detected by these eye tests. Such conditions require proper medical attention so that their progression can be stopped as they are sight-threatening conditions.
A false-negative test result generated by the online eye test application may lull you into believing that you do not need to visit a doctor as your eye condition came out to be perfect.
General Eye Test
The general eye test is carried out in the presence of an ophthalmologist or optometrist. In this, a brief discussion about any prior or ongoing health conditions is asked and family history of eye-related disease is also asked. Then you are evaluated for near and distant correction vision using a Snellen chart. After that to correct the vision certain eye lenses are used and you are asked to undergo the test again using those lenses. Evaluation using the best lenses is done and a prescription is given. This is then followed by other tests like a testing alignment of your eyes and eye muscles and pressure exerted on the eyes.
If there are chances of getting greater complications in your vision then a slit lamp test would be used to determine the anterior segment of the eye. There are other tests that determine the health of the retina and optic nerve. Dilation of pupils is also done to determine the health of the inner layers of the eyes. The results from the test will determine further diagnosis and management plan of your eye health.
Eye Test According To Age
It is important to get eye tested regularly and these recommendations vary by age. For children who are aged between 2-5 years should get an eye exam done at least once and children aged between 6-17 years should get an eye exam done annually or as prescribed by the pediatric optometrist.
Young adults who are aged between 18-39 should get an eye exam done after every two years to ensure that they do not have any underlying eye issues. People who have refracted errors should get their eye exam done more frequently. Middle-aged people should also get their eyes tested every two years or as per doctor recommends. Old-aged people need to get their eyes tested more frequently as they might get a medical condition.
The Professional Eye Test Is Important
Eye testing at home can’t be replaced by comprehensive eye evaluation done by a professional ophthalmologist or optometrist. If you feel anxious about your test conducted at home then a visit to a doctor might ease out your tension. You should remember that an online eye test may supplement your eye test with an ophthalmologist but it cannot be substituted for the same.
Skipping routine examination and testing at home will not provide you with proper treatment or keep your prescriptions updated. Eye tests at home can help you understand the problem with your visual acuity and if it progresses you need to seek medical help.