So it’s your third time this week tripping on the sidewalk at night just because you couldn’t see the little step? Well, we’ve all been there, except you’ve been there a couple of times more.
You are blaming it on your carelessness as you’ve recently had an eye test and there can’t be anything possibly wrong with your eyesight. But, how would you feel if I tell you that having 20/20 visual acuity doesn’t mean that you can see perfectly clear under every environmental condition?
If you don’t know what I am talking about, let me tell you about visual contrast sensitivity. It is one of the most important aspects of your overall vision that determines how well your eyes can perceive contrast. Curious to know more? Let’s do it!
What is Visual Contrast Sensitivity?
To put it simply, visual contrast sensitivity refers to the ability of the eye to distinguish between an object and its background.
But, that’s not all. It specifically defines how well you can see low contrast images and identify slight increments of light versus dark. For instance, if the road signs are visible to you at night, then you may have good contrast sensitivity.
A normal eye test is only meant to test your visual acuity with an eye chart. But it only determines how well a person can see high contrast images with black-on-white letters.
An eye test does not assess your visual performance, especially in low light conditions and glare when the contrast between the image and its background is quite low.
Even if you have 6/6 visual acuity, you may experience trouble seeing in dim lights which means that you have low contrast sensitivity. Sometimes, it could be a symptom of other vision-related problems such as amblyopia, cataracts or macular degeneration.
What does Visual Contrast Sensitivity do?
For starters, it helps you tell the foreground and background apart. It is an important factor in your visual function, especially in low light situations.
Seeing clearly through fog or high glare could only be done if you have good contrast sensitivity. Common circumstances where CS will help are:
- Driving at night when visibility is low
- Seeing objects clearly when they are placed against a similar coloured backdrop. For example, finding a black pen in a black drawer
- Reading low print quality such as a newspaper
- Distinguishing between different facial features
- Seeing steps in the dark
It is important to note here that contrast sensitivity is a measure to describe your real-world vision. People with perfect vision may feel that they are not seeing things clearly in low contrast situations.
Symptoms of Low Visual Contrast Sensitivity
Most of the signs of low CS are not uncomfortable or painful. So, you may think it’s normal and don’t pay heed to them. But, they could lead to danger in certain events. Everyday examples where it could lead to problems are:
- Driving at night, in the early morning or in rain
- Increase your chances of falling when walking up or down the stairs
- Eyes getting tired when reading a newspaper or watching television
However, it is not a sign of low visual acuity. If you feel like you are having trouble discerning contrast, you should talk to an eye doctor. Regular vision exams won’t detect the problem. So the optometrist will most probably use the Pelli Robson contrast sensitivity chart.
In normal situations, this problem could be corrected by using the right prescription glasses. Talk to your optometrist to identify the best glasses for your problem.
What is a Visual Contrast Sensitivity Test?
A routine eye exam won’t assess your contrast sensitivity. But, if your doctor suspects that you have this problem, they will most probably use a Pelli Robson contrast sensitivity chart.
The chart contains horizontal lines of capital letters and the contrast decreases as you go from left to right. The letters will seem as if they are fading against the white background.
The patient will start from the top of the chart and read until they are no longer able to read the letters. If you wear prescription glasses or contacts, you will be allowed to use them when taking the test.
You can get a visual contrast sensitivity test online but it is better if you take it in the presence of an optometrist. They will know your problem better and suggest you the right treatment option. In most cases, you will be recommended to use tinted glasses with yellow lenses.
What Reduces Visual Contrast Sensitivity?
If you’ve had Lasik or any refractive surgery, it will affect how well your eyes perceive contrast. Other than that, the following things may lead to a loss of visual contrast:
1. Cataracts - It is an age-related eye condition where the crystalline lens in your eye becomes cloudy. Many cataract patients complain of not being able to see clearly at night. This indicates that cataracts lead to a decline in contrast sensitivity.
2. Glaucoma - Glaucoma damages your optic nerves. These nerves transmit signals to the brain including crucial information such as colour, contrast and brightness. Thus, any kind of damage to your optic nerves will have an impact on your CS.
3. Macular Degeneration - Macula is a vision problem most commonly found in old people. It leads to a loss of vision affecting everything from your visual acuity to contrast sensitivity.
4. Amblyopia - Amblyopia or lazy eye refers to the problem when the connection between your brain and one eye is off. Thus, you will have low visual contrast with the affected eye.
5. Diabetic Retinopathy - It refers to the problem when the tiny blood vessels in your retina start to leak. Patients with this eye condition may experience a mild or significant decline in their eye’s ability to discern contrast.
What can you do about poor visual contrast sensitivity?
Your visual contrast sensitivity test results will help the optometrist determine if you have underlying vision errors that could be corrected with special eyewear.
If you have this problem, your optician will most probably ask you to use yellow-tinted glasses. These glasses are able to reduce short-wavelength light that is responsible for reducing the contrast.
Moreover, the yellow lens will enhance your vision when viewing objects against a blue background. However, you must not use tinted glasses when driving at night as they will only reduce visibility and make the situation more dangerous.
But on the other hand, driving with low visual contrast sensitivity is also dangerous. In this case, you can use anti-reflective glasses that will block headlights glare and improve glare.
If you use eyeglasses for vision correction, you will find that having an anti-reflective coating on the lenses helps you see better in low light conditions.
Even if you can take a visual contrast online test for free, you must have it under the supervision of an eye doctor. Ask them about the right type of lenses for your vision problem. If you want, you can take a free eye test from us and get advice from our experienced optical staff. Schedule the test online or visit our stores and have an on-site eye test.