Night Blindness (Nyctalopia)

What is night blindness?

Night blindness, also known as nyctalopia (pronounced “nik-tah-LOPE-ee-uh”), is when you have trouble seeing in dim or dark settings. It can happen if your eyes have trouble quickly adjusting to changes in brightness or have issues with detecting light.

Night blindness is a symptom of other conditions, not a disease on its own. It’s possible with a wide range of conditions that can affect different parts of your eyes. Some forms develop when you’re a child, while others may not show up until you’re an adult.

How seeing in the dark works

The ability to see in low-light conditions — like in dimly lit rooms or at night — mainly involves two structures in your eyes:

• Retinas. The retinas at the backs of your eyes contain two types of light-detecting (photoreceptor) cells, cones and rods, which get their names from their shape. Cones handle color vision and fine details. Rods mainly handle vision in dim light. Rods make up about 95% of retinal photoreceptors and help your irises adjust how much they widen or narrow.
• Irises. The iris 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 narrow quickly or far enough, too much light can enter your eye and overwhelm the cells in your retinas. This causes light sensitivity and can make it hard to see well in bright light. And if the irises don’t work correctly, making your pupil remain small, they can keep enough light from getting to your retinas. This prevents you from seeing in low-light situations.

But nyctalopia can also happen with conditions that affect how light travels through your eyes. The tissues that make up the forward parts of your eyes need to be clear so light can pass through them. When they aren’t clear or don’t allow light to pass through them correctly, it limits how much light reaches your retinas and can cause difficulties seeing in dim light.

What are the signs of night blindness, or what does it feel/look like?

There are two main ways that night blindness can happen:

• Lack of light making it to your retinas. When this is the case, it can feel like the world you see is darker, blurrier or harder to focus on. It can happen because of issues affecting structures in your eyes that should be clear, conditions that affect your retinas, or when your irises don’t widen as they should in dim light.
• Retinal cells that don’t react to light correctly. Your retinas are light sensors, with cells that sense incoming light and convert the light into electrical signals that go to your brain. Some conditions are like a broken or burned-out sensor, meaning the cells react too weakly or don’t react at all.

What are the most common causes of night blindness?

Conditions that can cause night blindness usually fall into two broad categories: Not enough light getting to your retinas or your retinas not working properly.

Conditions that involve issues with light traveling through your eyes include:

• Cataracts.
• Glaucoma.
• Laser vision correction surgery (like LASIK or similar procedures).

Retina-related causes of night blindness include:

• Rare, genetic retinal diseases like cone-rod dystrophy, retinitis pigmentosa (also called rod-cone dystrophy, similar to but not the same as cone-rod dystrophy) or congenital stationary night blindness (CSNB).
• Vitamin A deficiency (especially in people who have trouble absorbing vitamin A after weight loss surgeries like gastric bypass surgery).

How is night blindness treated?

Treating nyctalopia involves treating the cause. Some conditions are treatable or even curable, like cataracts or vitamin A deficiency.

A few of the conditions that cause night blindness, especially genetic diseases, aren’t treatable. For these conditions, the only option is to try to limit the effects of night blindness or other symptoms.

Because so many different issues can cause or contribute to night blindness, the treatments vary widely. Your eye care specialist is the best person to tell you more about what caused it and the possible treatment approaches.

What are the possible complications or risks of not treating night blindness?

Many conditions that cause night blindness affect your sight in the daytime, too. They can make it harder to see, blur your vision, disrupt how you see colors and more. And because most people rely on their sight so heavily, not being able to see can cause serious or dangerous disruptions.

You might not see well enough to drive at night. Driving at twilight is dangerous if your eyes have trouble adjusting between the darkening landscape and the brighter sky. And driving after dark can be dangerous when your eyes have trouble adjusting between darkness and various light sources like streetlights and headlights of other vehicles.

Can night blindness be prevented?

Some causes of nyctalopia are preventable. An example is taking vitamin A supplements after gastric bypass surgery to avoid a vitamin A deficiency.

When should this symptom be treated by a doctor or healthcare provider?

Night blindness isn’t something you can self-diagnose or self-treat. If you notice it happening, it’s always a reason to see an eye care specialist. While most causes aren’t dangerous, they can still disrupt your eyesight, and early diagnosis and treatment may help avoid bigger issues in the future.

And if you start noticing you’re having trouble seeing in dark settings, you should avoid driving or other potentially dangerous activities until you see an eye care specialist. Until they tell you it’s safe to resume those activities, it’s best not to risk the health and safety of yourself or others.

Is night blindness a disability?

Yes, but the laws and regulations where you live are also a factor. Some places have laws and regulations that recognize night blindness as a vision impairment. Others may not. If you aren’t sure, an eye care specialist can give you a formal diagnosis and offer guidance on what you’ll need to seek disability protections, or refer you to other experts who can help.