An astigmatism is a type of refractive error that causes lights at night to have halos or streaks that appear. You’ve probably experienced something similar if you’re looking through a rainy window and you squint your eyes to see the lights all look streaky like in the tweet below.
Astigmatism is most noticeable in dim/nighttime lighting. Bright lights such as street lights or car headlights will appear more blurred, fuzzy, or streaky. This is because of what the dim/night light does to the pupil. As you know, your pupil will dilate or expand in low light scenarios to allow more light to enter the eye. This allows us to see better in environments with less light. However, this also increases the amount of “aberrations” a patient will experience with astigmatism. Aberrations are small optical irregularities that can result in glare, halos, blurred vision, smeared vision, etc. These aberrations and optical imperfections are more noticeable with a larger pupil, and thus are more noticeable at night.
Astigmatism is when the cornea is slightly curved rather than completely round..
With astigmatism, light focuses on several points of the retina rather just one point. This is what people with Astigmatisms vs without. pic.twitter.com/RXWWayFBRJ
— Unusual Facts (@UnusualFacts6) March 25, 2019
Astigmatism occurs when the front surface of your eye, the cornea, is misshapen. Instead of the eye being perfectly spherical like a soccer ball, the eye is shaped more like a rugby ball with two separate curvatures. This difference in curvatures forces light to focus at two separate locations on the back of the eye, the retina. Because the light is not focused on one specific area of the retina, this causes a patient to see a blurred image.
Many patients with uncorrected astigmatism complain of blur, smeared images, ghosting or a shadowing of images, or double images. These symptoms will worsen in certain lighting conditions such as dim lighting, or nighttime.
How does astigmatism affect your vision at night or in low light?
Uncorrected astigmatism is most noticeable in dim/night time lighting. This is because of what the dim/night light does to the pupil. Your pupil will dilate, or expand, in low light scenarios which allows more light to enter the eye. This, in turn, will increase the amount of “aberrations” a patient will experience with astigmatism. Aberrations are small optical irregularities that can result in glare, halos, blurred vision, smeared vision, etc. These aberrations and optical imperfections are more noticeable with a larger pupil, thus are more noticeable at night.
Many patients with uncorrected astigmatism will be more symptomatic and notice blurred, imperfect vision at night time. If you notice glare, halos, streaky vision, blurred vision, smeared images, or doubled images while looking at lights at night, schedule an appointment with your eyecare provider to see if you need an updated astigmatism prescription.
Do blue light glasses help astigmatism?
Blue light glasses will not help with astigmatism. Blue light glasses may help reduce eye strain and fatigue, but they will not do anything to help focus the light and correct for astigmatism. A pair of prescription eyeglasses or contact lenses will be able to help refocus light properly on the back surface of the eye, the retina, which will allow a clear image to occur.
Can astigmatism be corrected?
Astigmatism can be corrected by glasses, contacts, or refractive surgeries.
Contact lenses can also correct for astigmatism. These lenses will also have a “cyl” correction and can be labeled as toric contact lenses. Astigmatism contacts are becoming extremely popular and there are tons of different options. The best contacts for astigmatism are all comfortable so that you can wear them for a full day of work. They even make progressive contacts for astigmatism, so they will correct for presbyopia as well.
Patients who have an astigmatism will have something called a cylinder “cyl” correction incorporated into their glasses prescription. The “cyl” in the glasses prescription will tell you how much astigmatism you have, while the “axis” of the prescription will tell you where the astigmatism is located. You can have an astigmatism while also being nearsighted, farsighted, or presbyopic. A glasses prescription can help correct all of these refractive errors.
Another way to correct for astigmatism is with different types of refractive surgeries such as PRK/LASIK/LASEK etc. These surgeries can only be performed on patients who have a certain amount of astigmatism and who will be a good candidate. An eye doctor will be able to tell you if refractive surgery for your astigmatism is an option for you.
How do people with astigmatism see lights in the dark?
Many patients with uncorrected astigmatism will notice their imperfect vision most while looking at lights at night. The lighting conditions at night cause people to be more symptomatic, especially when looking at bright headlights or street lights. If you notice glare, halos, streaky vision, blurred vision, smeared images, or doubled images while looking at lights at night, schedule an appointment with your eyecare provider to see if you need an updated astigmatism prescription.
What can I do to help with lights at night while I am driving?
If you are frequently symptomatic for glare, halos, blurred vision etc. while night time driving, then you will want to schedule an appointment with your eyecare provider to see if uncorrected astigmatism is the cause of your symptoms.
Not all glare/blurred vision with night time driving is related to astigmatism, however. This could be due to other eye conditions such as cataracts, dry eye, post LASIK complications, hooded eyes, etc. That is why a full comprehensive eye examination is required to rule out all causes.
It is also important to make sure that your glasses are cleaned regularly, as this can be a simple cause for blurred, smeared vision. Dirty mirrors, headlights and windshields can also make driving at night more difficult, so make sure to keep them all cleaned regularly.
You should also make sure that your headlights aren’t foggy so that everything in front of you is illuminated properly. Doing these things will help lessen the effects because you’ll see things more brightly.
Do I need glasses to drive at night if I have an astigmatism?
A patient’s visual acuity is the clinical way to determine whether or not they should be wearing correction to aid with night time driving. The legal visual driving requirements depend on the laws in your state and the severity of your unaided visual acuity. If you feel like your vision is not adequate for night driving, you may want to make an appointment with your eye doctor to see if your vision can be improved with either glasses or contacts to help with nighttime driving.
Why is astigmatism worse at night?
Astigmatism is worse at night and in low light conditions because of what happens to the pupil in these lighting scenarios. When the lighting is dim your pupil will dilate, or grow larger, which allows more light to enter the eye. With the increased amount of light entering the eye, this also allows for more glare, halos, blur, and distorted vision to occur.
Therefore many people who walk around without any issues during the day now notice their astigmatism vision at night because of the lighting difference and increase in symptoms. This is why lights at night appear more smeared and distorted than during the day.
What are night driving glasses? Do they work?
Night driving glasses are essentially just a pair of glasses that a patient can wear at night to sharpen their distance vision for night time driving. They are different depending on whether they were prescribed by a doctor, or purchased online.
Night driving glasses prescribed by a doctor will likely have a prescription in them. These glasses will be specifically made for a patient depending on what their current visual routine entails. For example, if a patient has a small amount of astigmatism, but is not wearing astigmatism/toric contact lenses, this pair of glasses can contain their astigmatism prescription and help sharpen up their distance vision at night. These glasses will be worn over top of the contacts and do not need to be worn all the time. However, they can help give the patient a boost of sharper vision when needed in difficult visual scenarios like nighttime driving.
Another example would be if a patient is wearing multifocal/progressive or monovision contact lenses. Oftentimes these patients will be purposefully undercorrected in these lenses so that their up-close vision is better, however, this can create problems for distance vision in difficult circumstances like night driving. A pair of driving glasses can be worn over top the contact lenses to fully correct for the distance vision and help crispen things while driving at night.
Night driving glasses purchased online will likely not have a prescription in them, but will include a tint that might help with the glare induced from night time driving. These tints can vary in color, but most will be yellow/orange/amber. Don’t forget to see if you have vision insurance benefits to help cover the cost!
The best color tinted lenses vary for each patient as everyone’s color vision and the way we perceive color and glare can vary. A tint evaluation can be performed by your optometrist to evaluate what exact color of tinted lenses might work best for you. This is different from color contacts, which change the physical appearance of your eye color.
Dr. Olivia Burger, O.D. is an optometrist who graduated from the Pennsylvania College of Optometry. She is pursuing a 1-year residency at the UC Berkeley School of Optometry in Vision Science in Primary Care / Contact Lens. Her optometric areas of interest include private practice, contact lenses, and optometric service organizations such as VOSH. In her free time, she enjoys live music and is a freelance concert photographer.