As Halloween approaches, the days become a little cooler, a little spookier, and little “darker.” From haunted houses and Halloween parties to good old-fashioned trick-or-treating, everything starts taking place at night. Not only does this time of year bring out costumes that require some eye safety measures, but it brings to mind the subject of night vision and what that really means.
Night Vision is defined as the faculty of seeing in very low light, especially after the eyes have become adapted. For some, this may come easy; for others, it may be very difficult. This is why some older individuals, whose eyes have aged, avoid driving at night. This is due to “decreased contrast sensitivity.”
Contrast Sensitivity is a measure of visual function, more so in situations of low light, fog, or glare, when the contrast between objects and their background may be reduced. It’s important to understand the difference between this and “good vision,” as you can have perfect visual acuity (or sharpness) and still struggle with low contrast sensitivity, or poor night vision.
It’s common to hear poor night vision referred to as “night blindness,” implying that a person cannot see at all at night. This isn’t the case. It really just means that a person struggles with seeing in low light – not complete blindness.
In short, the main symptom for poor night vision or “night blindness” is a noticeable difficulty seeing in the dark. As mentioned before, driving at night becomes much harder (and riskier), especially with intermittent brightness from streetlights and headlights. Transitioning from a bright environment to a dimly-lit space is another struggle, as it takes longer to adjust to the darker conditions after being in well-lit surroundings.
There could be several causes of reduced contrast sensitivity, but the main ones are cataracts, lack of vitamin A, not enough zinc, genetic disorders, sunlight exposure, LASIK problems, and diabetes. Cataracts eventually cloud one’s lens, with the first symptom being a problem with night vision, and without vitamin A, a person’s retina becomes unhealthy. Similarly, without zinc, vitamin A is unable to work as it should, which leads to problems seeing at night. Sustained bright light can temporarily hurt a person’s ability to see in low light. Lastly, night vision suffers when a person’s blood sugar damages blood vessels and nerves in the eyes, which may happen in someone with diabetes.
Testing one’s contrast sensitivity is the same as any other eye exam, except the doctor will likely use an additional chart called the Pelli Robson Contrast Sensitivity Chart. This chart looks like any other eye exam chart, other than the fading of the letters as they get further down. This will help the doctor see if a patient is struggling with discerning contrast. If results show that the patient does, in fact, have vision errors that can be corrected with special eyewear or surgery, the doctor will likely suggest specially tinted lenses, which can improve that contrast. Many who need prescription eyeglasses find that an anti-reflective coating also helps a lot in seeing in low light.
Although correcting poor night vision is possible, preventing poor night vision is better. Of course, genetics can make that impossible, but there are things we can do, such as eating right, that can help us strengthen our visual acuity.
Unfortunately, Halloween candy will not help improve night vision. By properly monitoring one’s blood sugar levels and eating a balanced diet, we can make night blindness less likely. Foods rich in antioxidant vitamins and minerals will help prevent conditions like cataracts. Foods to focus on would be those with high levels of vitamin A, which reduce that risk for poor night vision. Examples of these mostly orange-colored foods would be cantaloupes, sweet potatoes, carrots, pumpkins, butternut squash, and mangoes. You can also find this vitamin in spinach, collard greens, milk, and eggs.
If you do in fact struggle with night vision (or low contrast sensitivity), take extra precautions this Halloween. Bring a long flashlight, have someone else drive, and be careful of harmful costume accessories, like costume contacts. Holidays are always much more fun when everyone sees and feels their best.