Posterior subcapsular cataract: what it is, how it is found and how it is treated

The lens sits just behind the pupil and focuses light onto the retina at the back of the eye. A cataract is a clouding, or opacity, of that lens. Moorfields Eye Hospital describes the effect as a picture that becomes dull and fuzzy because light rays can no longer pass cleanly through to the retina.

Doctors classify cataracts by where in the lens the cloudiness forms. NICE Clinical Knowledge Summaries list nuclear (the centre of the lens), cortical (the outer layers) and posterior sub-capsular as the most common types. A posterior subcapsular cataract is the one that forms at the back of the lens, just beneath the thin capsule that surrounds it. Other, rarer types are named in the same summary, including anterior sub-capsular.

The labels matter mainly for clinicians, who use them to describe what they see on examination. For a patient the practical question is usually how much the cataract is interfering with daily life, and that is what NICE says the decision about surgery should rest on.

The UK pages used for this guide describe the symptoms of cataract in general rather than listing a separate symptom set for each type. NICE notes that each type has its own typical symptoms, so an optometrist or eye specialist is the right person to say what applies to you. It would be wrong to assume that every symptom below is present in every person.

According to the NHS, symptoms of cataracts usually develop slowly, you will often have cataracts in both eyes, and the symptoms may be different in each eye. NICE adds that the main symptom in adults is a gradual and painless reduction in sharpness of vision, which can show up as difficulty reading, recognising faces or watching television, and that glare may dominate early on.

• Blurred or misty vision that glasses no longer fully correct.

• Difficulty seeing at night, and difficulty driving when headlights come towards you.

• Glare and discomfort in bright light or sunshine.

• Seeing glowing rings (halos) around lights, or double vision in one eye.

• Colours that look faded, especially blue.

• Needing a change of glasses prescription more often than usual.

The NHS advises seeing an optician if you have symptoms of cataracts. If the optician thinks you have cataracts they will refer you to an eye specialist for more tests or treatment. Moorfields Eye Hospital explains that the first step is usually to update your glasses, and that once an optician cannot improve your vision any further with glasses or contact lenses you are referred to a cataract clinic to be considered for surgery.

A cataract that develops slowly is not an emergency. Sudden changes are different. The NHS cataract surgery page says to get help from NHS 111 if floaters suddenly appear or increase, you get flashes of light, a dark curtain or shadow moves across your vision, or your vision gets suddenly blurred, because these could be signs of a detached retina. That advice is written for people after cataract surgery, but the same symptoms need prompt assessment at any time.

Most cataracts are related to ageing. NICE says most cataracts occur as a result of ageing and are most common in people aged over 60, and that they can form in one or both eyes. Moorfields says age-related cataract can occur at any time after the age of 40.

The NHS says you may be more likely to get cataracts if you are aged 60 or over, have had an eye injury or eye surgery, have another eye condition such as uveitis or being very short-sighted, have taken steroid medicines for long periods, smoke, have a parent, brother or sister who has had cataracts, are a woman, or have had regular unprotected exposure to a lot of sunlight. Type 2 diabetes, severe dermatitis and high blood pressure are listed as long-term conditions that can increase the risk.

NICE also names hypertension, corticosteroid treatment, smoking and prolonged exposure to ultraviolet B light among the risk factors, and lists trauma, chronic anterior uveitis, high myopia and diabetes among the other contributors. Moorfields notes drug-induced (steroids) cataracts as a recognised category. If you take steroid medicine for a long-term condition, do not stop it on your own because of this information; raise it with the prescriber and keep up regular eye tests.

NICE recommends that an adult with a cataract is encouraged to have an eye examination by an optometrist, both to assess visual acuity accurately, with and without glasses or contact lenses, and to exclude other causes of poor vision. With an ophthalmoscope the clouded area can be seen in the lens.

Moorfields says cataract is often diagnosed in primary care by an optician or GP during a routine eye examination. Before surgery, the NHS says you will have an appointment with a specialist who will examine and measure your eye so that the right artificial lens can be chosen.

NICE says referral for surgery should follow a discussion about how the cataract affects your vision and quality of life, whether one or both eyes are affected, what surgery involves including risks and benefits, how your quality of life may be affected if you choose not to have surgery, and whether you want surgery at all.

The NHS says cataracts do not usually need treatment straight away. Stronger glasses and brighter light for reading may help for a while, but over time cataracts get worse and surgery is the way to improve sight. Whether to go ahead depends on how much the cataract affects daily life and whether one or both eyes are involved.

Cataract surgery replaces the cloudy lens with an artificial one. The NHS describes it as done in hospital under local anaesthetic, so you are awake but should not feel pain. A small opening is made at the front of the eye, the old lens is broken up with ultrasound and removed by suction, and a clear plastic lens is placed in the lens capsule. The operation usually takes between 20 and 45 minutes, stitches are usually not needed, and you should be able to go home the same day. If both eyes need surgery, they are done on separate days.

Moorfields explains that the standard NHS lens has a single focal power, so most people still need glasses for either distance or reading afterwards, and that specialised lenses for astigmatism may be available on the NHS when the astigmatism is above a stated threshold at its sites. Other lens types are available privately. Anyone weighing lens choices should ask their surgeon what applies locally.

The NHS says most people recover quickly. Vision may be blurry for a few hours, the eye may hurt for a few days, a plastic shield may be advised at night, and it may take several days for vision to improve. Eye drops are usually needed for about 4 weeks. You should not rub the eye, drive until your vision is back to normal, do heavy lifting, swim or get water in the eye while it heals.

Moorfields says serious complications are uncommon: about 1 in 1,000 people have a problem that significantly or permanently reduces vision, 1 in 100 may need further surgery, and for 1 in 10 people the lens capsule can become hazy over time, which a simple laser procedure treats. The NHS also notes this haziness, called posterior capsule opacification, can make vision cloudy months or years after surgery.

On driving, the NHS says you may still be able to drive if your vision is good enough, and you must let the DVLA know if your eyesight does not meet the minimum standards. An optician can advise if you are not sure.

On the NHS the route normally runs from an optician to a hospital cataract clinic and then to surgery, and the NHS says there may be a wait. Some people choose private treatment to shorten that wait or to pay for lens types that are not routinely provided on the NHS. Moorfields notes that if you move to private care you should cancel your NHS appointment and that it is not possible to top up the NHS lens with a private one during an NHS operation.

The operation itself and its risks are the same in both settings. Whichever route you take, ask who will be doing the surgery, which lens is planned and what follow-up is included.