Night vision problems: causes, what to check and when to see an optician

RNIB explains that the retina contains two kinds of light-sensitive cells. Cone cells in the central retina work best in bright light and give us colour and fine detail. The peripheral retina is made mostly of rod cells, which allow us to see in dim light, such as at night, and help us detect movement and see what is around us.

Poor night vision therefore points to a problem with the rods or with the way light reaches them. That may mean something that is clouding the lens, such as a cataract, or a disorder of the retina itself. It can also reflect a change in glasses prescription, which is why an optician is the usual first stop.

The NHS lists difficulty seeing at night as a feature of cataracts, in which the lens becomes cloudy, and also as part of general vision loss. The NHS vision-loss page also lists other conditions with their own typical symptoms.

• Cataracts. The NHS says symptoms include blurred vision, difficulty seeing at night, sensitivity to light and glare, double vision, halos around lights and faded colours, and that they usually develop slowly.

• Retinitis pigmentosa and other inherited retinal dystrophies. RNIB lists night blindness, loss of peripheral vision, progressive change in vision, increased light sensitivity, delayed adaptation moving between light and dark, and sometimes flashing lights and colours.

• Changes in your glasses prescription. The NHS notes that if you wear glasses you may need to change your prescription more often with cataracts.

• Other eye conditions that the NHS lists as causes of vision loss, including glaucoma, age-related macular degeneration and diabetic retinopathy.

RNIB describes an inherited retinal dystrophy (IRD) as a genetic eye condition in which the light-sensitive cells of the retina stop working and are lost over time. Retinitis pigmentosa is the most common, and the genes involved affect the rod cells first. The age at which symptoms start varies: some people notice them in early childhood, others between adolescence and early adulthood and some not until later in life.

RNIB says most IRDs cause ongoing and permanent changes that reduce vision, usually slowly over years. Different inheritance patterns exist (autosomal dominant, autosomal recessive and X-linked), so a genetics assessment can be helpful. It says a gene therapy treatment is available on the NHS for one IRD (Leber congenital amaurosis, linked to the RPE65 gene), but apart from this there is still no treatment or cure for IRDs, although research is ongoing. Support, low-vision services and registration as sight impaired are available through eye clinics and local authorities.

The NHS says to see an optician if you think you have vision loss or have symptoms of cataracts, and that if they think you have a condition you will usually be referred to an eye specialist (ophthalmologist) for further tests. An assessment is likely to include questions about when the problem started and whether it affects one or both eyes, a check of your vision and glasses prescription, and an examination of the front and back of the eye.

Where a retinal problem is suspected, specialist tests are used, and RNIB advises discussing any new symptoms with your ophthalmologist or optometrist as soon as you notice them. If symptoms point to a possible general health cause, the optician or GP may suggest other checks.

The NHS says to ask for an urgent GP appointment or get help from NHS 111 if you have changes in your vision such as blurred vision, double vision or seeing flashing lights or shapes, a dark shadow moving across your vision, pain in one or both eyes, a red and painful eye or eyes that feel painful in bright light. It says to go to A&E or call 999 if you suddenly cannot see from one or both eyes or suddenly have severe eye pain.

A gradual loss of night vision is less dramatic but should still be assessed, and it is worth being cautious about driving after dark until you have been checked.

Treatment depends on the cause. For cataracts, the NHS says they do not usually need treatment straight away, that stronger glasses and brighter light for reading may help for a while, and that cataract surgery is done under local anaesthetic with the cloudy lens replaced by an artificial one, usually as a day case. For most people surgery improves vision, recovery is quick and serious complications are rare.

For conditions without a cure, the NHS says support can include advice on adapting your home, low vision aids and assistive technology, help with travelling, benefits advice and talking therapies. The NHS also says you must let the DVLA know if your eyesight does not meet the minimum standard for driving.