If you have ever had to go to the optometrist to do a review of your diopters or for any other reason, you may have been surprised to hear that you have very good visual acuity.
Or the opposite could have happened. You do not suffer from myopia, astigmatism, hyperopia or any other visual problem, but they tell you that you do not have 100% visual acuity.
But, wait a minute… Doesn’t visual acuity mean whether you see well or badly? Not exactly. Keep reading and we tell you everything there is to know about visual acuity, how it is measured and the differences with graduation.
What is visual acuity and how is it measured?
Visual acuity is defined as the ability of the visual system to clearly identify different objects and visual stimuli, when there is good lighting, at a certain distance.
Visual acuity is what determines whether you are able to perceive, for example, that two objects located very close to each other are actually separated. Or also, the details of an object that has been placed on a uniform background.
In simpler words, visual acuity determines how clear your vision is, once the necessary diopter correction is applied. If you’ve ever had a visual exam, you’ve had a visual acuity test.
Visual acuity is recorded with two different values: On the one hand, the value without correction and on the other hand the value with the best correction During the visual acuity test, the ability to distinguish a series of letters of different sizes on a white background without carrying any type of correction is first evaluated. You have to cover one eye, try to read the smallest letters that can be distinguished and then repeat with the other eye covered. For people who cannot read, numbers, lines or images are used. These tools that the optometrist uses to make the measurement are called optotypes.
To record visual acuity with the best correction, the lenses with which the person sees most clearly are placed. Again, visual acuity is noted first in one eye and then in the other. There are several ways to write down the result, usually recorded with a decimal value or with a percentage.
What is the visual acuity test for?
This test aims to detect possible abnormalities in the functioning of the visual system.
A reduced visual acuity once the necessary correction has been applied, can indicate other types of pathologies such as cataracts, macular degeneration, amblyopia or lazy eye or diabetic retinopathy.
What factors determine my visual acuity?
A person’s visual acuity depends on three main neurological and physical factors:
- The brain’s ability to interpret stimuli and information coming from the eyes.
- If the lens and cornea focus light on the retina with the necessary precision.
- If the nerves that are located in the retina and in the vision centers have the right sensitivity and work correctly when capturing visual stimuli.
What is the difference between visual acuity and graduation?
The graduation we need is one that allows the light rays that enter the eye to focus on a point on the retina, which will make us have a clear and clear vision of objects.
On the other hand, visual acuity measures the sharpness with which we perceive visual stimuli, once our graduation has been corrected.
In this way, other visual problems can be detected. If your graduation has been completely corrected but your visual acuity is still not as good as it should be, it may be indicative of a visual pathology that needs to be treated.