Contrast Sensitivity and Eye Health
Contrast sensitivity is a very sensitive measure of visual function that can be easily administered by an eye doctor who has the right equipment. This test is different from the standard “Big E chart” in that it tests how patients see in the real world under typical low-contrast and low-light conditions.
Below is an example of the Big E Chart, formally known as The Snellen Chart. The chart tests only black-on-white letters.
While the Big E Chart measures only black on white, contrast sensitivity measures how well you can see shades of gray in the real world. Below are two pictures of the same real-world scene, one in high contrast and one in low contrast. Many people can read the black on white letters of the Big E Chart, but have trouble seeing the little girl in the street under low contrast.
Contrast Sensitivity and Eye Health
Contrast sensitivity is a very accurate and sensitive measure of eye health and can detect eye diseases, including macular degeneration, before other tests. This test can also measure improvements in vision after treatment with Lumega-Z. Improvements in contrast sensitivity can occur as early as 2 to 3 months after patients start taking Lumega-Z. The Big E chart cannot measure these improvements until many months later, if at all.
Contrast Sensitivity and Carotenoids
The secret to Lumega-Z’s ability to improve contrast sensitivity lies in its special and unique formula. Lumega-Z is the only Medical Food that contains all three macular carotenoids, as well as a full complement of antioxidant and anti-inflammatory ingredients. Further, Lumega-Z is the only Medical Food designed directly to treat the macular pigment, the area in the center part of your eye responsible for protecting and enhancing your central vision. Many patients with macular degeneration have a reduced macular pigment. These patients also have reduced contrast sensitivity. After taking Lumega-Z, macular health improves and contrast sensitivity increases. Many patients report that they can see better in the real world under low-contrast conditions, like driving at night, finding items in a darkened garage or stepping over a curb at dusk.
Research Shows Carotenoids Improve Contrast Sensitivity
Numerous studies show that patients’ contrast sensitivity improves after taking carotenoids. This research has shown these improvements occur, not only in patients with eye diseases like macular degeneration, but also in patients without eye disease, such as athletes.
The graph below shows how contrast sensitivity is plotted for the patient. The solid blue area shows the normal range for a patient’s age group. If the graph is below the gray area, it means the patient has abnormally low contrast sensitivity (which means objects have to be higher contrast for the patient to be able to see them). In many cases, these patients can still read the letters on the Big E Chart. The dotted and solid lines show the results for each eye. (OD means right eye and OS means left eye in eye doctor language.) This patient has early macular degeneration (AMD) and their contrast sensitivity is low; the curve is below the solid blue area.
This graph also shows what happens after the patient has been treated with the vision-specific Medical Food, Lumega-Z. The contrast sensitivity improves and the curve shifts up into the normal range – the solid blue area.
How Do You Measure Contrast Sensitivity?
The most scientific and accurate way to measure contrast sensitivity is to use a type of bar pattern, called a sine-wave grating, in a test that uses a calibrated light source which holds testing light level extremely consistent. During the test, different size gratings are presented to the patient at different levels of contrast. The patient simply says when they can or cannot see the gratings.
Some eye doctors use lower quality types of contrast tests that present gray letters instead of the scientifically-proven grating bar patterns. These letter tests are less sensitive and the FDA does not recommend letter contrast tests for use in their clinical trials.
Below are examples of the different size bar patterns that are scientifically proven to be best for contrast sensitivity testing and for evaluating ocular health.
How is the Contrast Test Administered?
The image below provides an example of how the test is administered. On the left, a sample grating is shown at very high contrast under the letter “B.” Then the patient is asked to look across the row, and under each number, identify which grating has the bars. Are the bars in the top circle or the bottom circle under each number?
For this example above, the patient should respond:
- Number 1 – Bottom
- Number 2 – Bottom
- Number 3 – Top
- Number 4 –Top
- Number 5 – Bottom
- Number 6 -Bottom
If a patient is able to see all six of these grating patterns, then a new set of gratings is shown at lower contrast levels. As the test progresses, the gratings become harder to see. This process goes on until the contrast is so low, the patient cannot see any bars.
Your Contrast Sensitivity Improves with Lumega-Z
The image below shows the typical results for a patients who has early AMD and then is treated with Lumega-Z. Before treatment, the patient could see only the 2nd level of contrast. Then 3 months after taking Lumega-Z, the patient could see much better contrast levels. The patient could see all the way down to the 5th level of contrast.
You Should Have Your Contrast Sensitivity Tested Regularly
Contrast sensitivity is a very important measure of vision. You should have it tested regularly. In the United States, this test is not covered by insurance, although it is in many other countries. Make sure you ask for a test that uses the special scientifically proven gratings, as shown in the examples above, and one that ensures the test is conducted under conditions where the test lighting is standardized to the level recommended by the FDA and National Academy of Sciences.