Looking at the Christmas tree could help diagnose a common vision problem.
If the lights look more like streaks or rays than distinct points, this could indicate astigmatism, which is extremely common: About 33 percent of Americans have it.
Symptoms of the condition include blurred vision, headaches, and eye strain, especially after prolonged periods of concentration, such as computer use.
Astigmatism occurs when the clear lens around the eyeball becomes an irregular oval shape instead of the typical perfect roundness.
The football-like shape causes light to focus unevenly on the retina, causing blurred or distorted vision.
A perfectly round shape helps focus light rays sharply on the retina so you can see clearly.
In cases of astigmatism, light is not bent evenly as it enters the eye, causing it to focus in multiple locations rather than directly on the retina. This causes blurred vision both near and far.
Dr. Jennifer Stone, an optometrist in Baltimore, told Health magazine that the glare from Christmas lights “can interfere with the sharp details of your vision and can affect near and distant objects.”
A perfectly round lens or cornea shape helps focus light rays sharply on the retina so you can see clearly.
An oval-shaped lens or cornea depends largely on genetics.
Astigmatism usually runs in families. If one or both parents have astigmatism, their children are also more likely to develop it.
But in some cases, astigmatism can develop later in life due to injury, illness, or age.
There are several tests you can perform at home that could suggest the presence of astigmatism.
For example, the astigmatism chart test, also known as the “astigmatism fan” test, is a simple, at-home method to detect possible signs of astigmatism.
First, print an astigmatism chart, which typically features lines or circles radiating from a central point.
Hold the chart at a comfortable distance and cover one eye at a time.
As you focus on the lines, take note of any lines that appear lighter or darker than others, or if any lines appear blurry or distorted.
If you notice these irregularities, it may indicate the presence of astigmatism, but it is important to remember that this is not a definitive diagnosis. That must be determined by a doctor.
In cases of astigmatism, light is not bent evenly as it enters the eye, causing it to focus in multiple locations rather than directly on the retina.
Astigmatism is measured in diopters, such as -1.00 or -2.00, to show how uneven the curve of the eye is. The higher the number, the more correction you will need to focus the light correctly.
Dr. Jennifer Tsai, an ophthalmologist in New York City, demonstrated in a video how a person with different levels of astigmatism would see when looking at their Christmas tree.
The lights become increasingly blurry and lightning-like as the numbers increase, from -1.00 onwards.
The higher the number, the blurrier uncorrected vision becomes because the irregular curve of the eye is more severe.
Astigmatism is measured in diopters, such as -1.00, -2.00, -3.00, and more, to show how uneven the curve of the eye is. The higher the number, the more correction you will need to focus the light correctly.
And astigmatism is especially dangerous when driving at night.
Like the lights on a Christmas tree, the lights of oncoming cars stretch and blur to the point that they nearly blind the driver from seeing other cars, enveloping them in a halo of light.
Driving can be dangerous for reasons other than lights on. For example, people driving on streets illuminated with lights and yard decorations can make it difficult to see traffic lights and signs.
Wet roads can make this worse by creating reflections, distorting vision, and intensifying glare.
Some people may experience the symptoms of astigmatism without realizing they have it.
Common signs include eye fatigue or discomfort, eye pain, blurred or distorted vision, headaches, fatigue, difficulty seeing at night, and frequent squinting to see clearly.
If you notice these symptoms, visiting an ophthalmologist could help diagnose and address the problem.
The condition can be managed with glasses, contact lenses, or laser surgery in some cases.