What is Night Blindness (Nyctalopia) ?

Night blindness (nyctalopia) is the inability to see well at night or in poor lighting conditions. It’s not a condition in itself, but happens as a result of a range of underlying eye conditions.

What causes night blindness (nyctalopia)?

Night blindness is a catch-all term for various eye conditions that make it very difficult to see at night or in low light environments. Here are some of the more common causes:

Glaucoma

Glaucoma develops when there is damage to the optic nerve and the nerve fibres from the retina, this is usually because of high pressure within the eye.

Because glaucoma affects the sensitivity of vision in general, night vision also becomes an issue. Both day and night are affected as nerve fibres become damaged.

Glaucoma medications that constrict the pupil can also make it harder to see in the dark because ordinarily the pupil would be wide to let in as much light as possible in.

Cataracts

Cataracts occur when cloudy patches develop in the clear lens inside your eyes, stopping light from reaching the back of the eye and causing blurred or cloudy vision. As a result, people with cataracts might find it especially difficult to see clearly in low light conditions, and they may see blurry halos around bright lights (such as street lamps or car headlights) when driving at night.

Retinitis pigmentosa

Retinitis pigmentosa (also known as RP) develops as a result of certain genetic disorders which cause the breakdown of cells in the retina. Once these photoreceptor cells in the retina begin to degenerate, people with RP will notice a gradual decline in their vision, such as struggling to see at night and losing their peripheral vision.

In most cases, it takes our eyes about 20 minutes to fully adapt to low-light conditions, but with RP, it can take much longer or not happen at all. Eventually you may be diagnosed with night blindness which will likely restrict your ability to drive to the daytime only.

Diabetic retinopathy

If you have diabetes, you’re at risk of developing an eye condition known as diabetic retinopathy, a complication of diabetes that damages the light-sensitive retina. As with many other retinal conditions, any damage to the retina would usually make it harder to see at night.

Keratoconus

Keratoconus occurs when the cornea (the round, clear front part of the eye) starts to weaken and thin at its centre, causing it to become irregular (or coned) in shape. Eventually this prevents the eye from focusing properly, which causes poor vision. This poor vision will be exacerbated in low light. Any damage or distortion to the cornea would usually make it harder to see at night.

Night blindness symptoms

Everyone will find it harder to see detail in low light levels, but if you have night blindness, you might also experience the following symptoms, depending on the underlying condition that’s causing it:

• Difficulty focusing in dim light
• Blurry or cloudy vision
• Discomfort when moving from a bright environment to a darker one
• Poor peripheral vision
• Difficulty seeing into the distance
• Problems adapting to sudden bright lights (for example, car headlights of street lights) which can make driving at night difficult
• Headaches and nausea
• Sensitivity to light (also known as photophobia)