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Animals renowned for their outstanding night vision include owls, cats, tarsiers (a tiny primate in Southeast Asia) — and even the dung beetle.

But humans? Not so much.

Over time, many people suffer from night blindness, also known as nyctalopia. This condition makes seeing in dim or dark settings difficult because your eyes cannot adjust to changes in brightness or detect light.

What are the dangers for those experiencing night blindness?

Night blindness is especially problematic and dangerous when driving. Your eyes cannot adjust between darkness and the headlights of oncoming vehicles, other cars may appear out of focus, and your depth perception becomes impaired, which makes it difficult to judge distances.

Night blindness also may affect your sight at home by making it hard for your vision to quickly adjust to a dark room after turning off the lights. “This can cause people to bump into furniture or trip and suffer an injury,” says Dr. Isabel Deakins, an optometrist with Harvard-affiliated Massachusetts Eye and Ear.

What happens in the eye to create night blindness?

The ability to see in low-light conditions involves two structures in the eye: the retina and the iris.

The retina, located in the back of the eye, contains two types of light-detecting cells called cones and rods. The cones handle color vision and fine details while the rods manage vision in dim light.

The iris is the colored part of your eye. It contains muscles that widen or narrow the opening of your pupil to adjust how much light can enter your eyes.

If your irises don’t properly react, the pupils can dilate and let in too much light, which causes light sensitivity and makes it hard to see in bright light. Or your pupils may remain too small and not allow in enough light, making it tough to see in low light.

What causes night blindness?

Night blindness is not a disease but a symptom of other conditions. “It’s like having a bruise on your body. Something else causes it,” says Dr. Deakins.

Several conditions can cause night blindness. For instance, medications, such as antidepressants, antihistamines, and antipsychotics, can affect pupil size and how much light enters the eye.

Eye conditions that can cause night blindness include:

• glaucoma, a disease that damages the eye’s optic nerves and blood vessels
• cataracts, cloudy areas in the lens that distort or block the passage of light through the lens
• dry eye syndrome.

However, one issue that raises the risk of night blindness that you can’t control is age. “Our eyes react more slowly to light changes as we age, and vision naturally declines over time,” says Dr. Deakins.  “The number of rods in our eyes diminish, pupils get smaller, and the muscles of the irises weaken.”

What helps if you have night blindness?

If you notice any signs of night blindness, avoid driving and get checked by an eye care specialist like an optometrist or ophthalmologist. An eye exam can determine if your eyeglass prescription needs to be updated.

“Often, a prescription change is enough to reduce glare when driving at night," says Dr. Deakins. “You may even need separate glasses with a stronger eye prescription that you wear only when driving at night.”

Adding an anti-reflective coating to your lens may help to cut down on the glare of the headlights of an oncoming car. However, skip the over-the-counter polarized driving glasses sold at many drug stores. "These may help cut down on glare, but they don't address the causes of night blindness," says Dr. Deakins.

An eye exam also will identify glaucoma or cataracts, which can be treated. Glaucoma treatments include eyedrops, laser treatment, or surgery. Cataracts are corrected with surgery to replace the clouded lens with an artificial one. Your eye care specialist can also help identify dry eye and recommend treatment.

Ask your primary care clinician or a pharmacist if any medications that you take may cause night blindness. If so, it may be possible to adjust the dose or switch to another drug.

Three more ways to make night driving safer

You also can take steps to make night driving safer. For example:

• Wash the lenses of your glasses regularly. And take them to an optician to buff out minor scratches.
• Keep both sides of your front and rear car windshields clean so that you can see as clearly as possible.
• Dim your dashboard lights, which cause glare, and use the night setting on your rearview mirror.

About the Author

Matthew Solan, Executive Editor, Harvard Men's Health Watch

Matthew Solan is the executive editor of Harvard Men’s Health Watch. He previously served as executive editor for UCLA Health’s Healthy Years and as a contributor to Duke Medicine’s Health News and Weill Cornell Medical College’s … See Full Bio View all posts by Matthew Solan

About the Reviewer

Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing

Dr. Howard LeWine is a practicing internist at Brigham and Women’s Hospital in Boston, Chief Medical Editor at Harvard Health Publishing, and editor in chief of Harvard Men’s Health Watch. See Full Bio View all posts by Howard E. LeWine, MD

Nantucket, a beautiful, 14-mile-long island off the coast of Massachusetts, has a 40-point resiliency plan to help withstand the buffeting seas surrounding it as climate change takes a toll. Perhaps we can all benefit from creating individual resilience plans to help handle the big and small issues that erode our sense of well-being. But what is resilience and how do you cultivate it?

What is resilience?

Resilience is a psychological response that helps you adapt to life’s difficulties and seek a path forward through challenges.

“It’s a flexible mindset that helps you adapt, think critically, and stay focused on your values and what matters most,” says Luana Marques, an associate professor of psychiatry at Harvard Medical School.

While everyone has the ability to be resilient, your capacity for resilience can take a beating over time from chronic stress, perhaps from financial instability or staying in a job you dislike. The longer you’re in that situation, the harder it becomes to cope with it.

Fortunately, it’s possible to cultivate resilience. To do so, it helps to exercise resiliency skills as often as possible, even for minor stressors. Marques recommends the following strategies.

Shift your thoughts

In stressful situations, try to balance out your thoughts by adopting a broader perspective. “This will help you stop using the emotional part of your brain and start using the thinking part of your brain. For example, if you’re asking for a raise and your brain says you won’t get it, think about the things you’ve done in your job that are worthy of a raise. You’ll slow down the emotional response and shift your mindset from anxious to action,” Marques says.

Approach what you want

“When you’re anxious, stressed, or burned out, you tend to avoid things that make you uncomfortable. That can make you feel stuck,” Marques says. “What you need to do is get out of your comfort zone and take a step toward the thing you want, in spite of fear.”

For example: If you’re afraid of giving a presentation, create a PowerPoint and practice it with colleagues. If you’re having conflict at home, don’t walk away from your partner — schedule time to talk about what’s making you upset.

Align actions with your values

“Stress happens when your actions are not aligned with your values — the things that matter most to you or bring you joy. For example, you might feel stressed if you care most about your family but can’t be there for dinner, or care most about your health but drink a lot,” Marques says.

She suggests that you identify your top three values and make sure your daily actions align with them. If being with family is one of the three, make your time with them a priority — perhaps find a way to join them for a daily meal. If you get joy from a clean house, make daily tidying a priority.

Tips for success

Practice the shift, approach, and align strategies throughout the week. “One trick I use is looking at my calendar on Sunday and checking if my actions for the week are aligned with my values. If they aren’t, I try to change things around,” Marques says.

It’s also important to live as healthy a lifestyle as possible, which will help keep your brain functioning at its best.

Healthy lifestyle habits include:

• getting seven to nine hours of sleep per night
• following a healthy diet, such as a Mediterranean-style diet
• aiming for at least 150 minutes of moderate-intensity activities (such as brisk walking) each week — and adding on strength training at least twice a week
• if you drink alcohol, limiting yourself to no more than one drink per day for women and two drinks per day for men
• not smoking
• staying socially connected, whether in person, by phone or video calls, social media, or even text messages.

Need resilience training?

Even the best athletes have coaches, and you might benefit from resilience training.

Consider taking an online course, such as this one developed by Luana Marques. Or maybe turn to a therapist online or in person for help. Look for someone who specializes in cognitive behavioral therapy, which guides you to redirect negative thoughts to positive or productive ones.

Just don’t put off building resilience. Practicing as you face day-to-day stresses will help you learn skills to help navigate when dark clouds roll in and seas get rough.

About the Author

Heidi Godman, Executive Editor, Harvard Health Letter

Heidi Godman is the executive editor of the Harvard Health Letter. Before coming to the Health Letter, she was an award-winning television news anchor and medical reporter for 25 years. Heidi was named a journalism fellow … See Full Bio View all posts by Heidi Godman

About the Reviewer

Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing

Dr. Howard LeWine is a practicing internist at Brigham and Women’s Hospital in Boston, Chief Medical Editor at Harvard Health Publishing, and editor in chief of Harvard Men’s Health Watch. See Full Bio View all posts by Howard E. LeWine, MD