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A cataract is an opacification of the lens of the eye. Cataracts tend to cause gradual loss of visual acuity, with normal pupillary response.

Cataracts are the most common non-refractive cause of visual impairment worldwide. 

They usually occur with age (although can be congenital, or secondary to medication trauma or other conditions). They can be cured with cataract surgery – which in modern times is usually a relatively straightforward procedure.

Patients should be considered for surgery when the cataract is causing visual acuity of <6/18 in one or both eyes.

Photo of a cataract with a dilated pupil
Photo of a cataract with a dilated pupil

Epidemiology and Aetiology

  • Main one is AGE!
  • UV light
    • Regular wearing of sunglasses in sunny climates or those who work outdoors (particularly wrap-around sunglasses) may reduce the risk
  • Trauma
  • Smoking
  • Alcohol
  • Diabetes
  • Other metabolic disorders eg fabry disease, hypocalcaemia, galactosaemia (you’ll get points for saying these)
  • Uveitis
  • Systemic drugs (eg, corticosteroids)
  • Congenital
  • 65% of people over 50 have some sort of opacity
  • 100% of people of 80 have some form of cataracts


In simple terms =  Opacification of the lens.
  • Not “a skin” growing over the lens as many patients think!
The normal proteins that make up the lens of the eye degrade overtime and become opaque. This process is accelerated by many of the risk factors described above.


  • Painless loss of vision
  • Misting or blurring
  • Glare
  • Change in refractive error
  • Often manifests as
    • Difficulty reading
    • Difficulty recognising faces
    • Problems driving – especially at night
    • May have haloes around lights (but beware of glaucoma in these instances)
  • Occasionally an elderly patient may present with sudden loss of vision in one eye. Cataracts are never an acute event, but patients sometimes become acutely aware of it when vision in their other eye becomes obscured for whatever reason.


  • Reduced visual acuity
  • Diagnosis is best made with a dilated pupil
  • Examine with a slit lamp/ophthalmoscope- a cataract is seen as black against the red reflex
  • May have reduced red reflex


Surgery is the only effective treatment. Patients with milder cataracts or who do not wish to undergo surgery may be able to manage their symptoms with simple lifestyle modifications (e.g. not driving at night, correct placement of light source when reading (behind and above the head!), and modifications around the house to the reduce the risk of falling (if bumping into objects).
On the NHS;
  • If the cataract is bad enough to cause sufficient visual symptoms- “reduction in quality of life”
  • Vision worse than 6/12
Most common method of treatment of cataracts is phaecoemulsification- the lens is dissolved with ultrasound and replace it with plastic or silicone lens. This also corrects the refractive error.  This is done as a day case using local anaesthetic with or without sedation. One eye is done at a time. By a skilled surgeon it can take less than 10 minutes! Often there is dramatic improvement of symptoms immediately, but maximum recovery can take 2-3 months.
Recovery period
  • The eye is usually patched for 24 hours
  • Avoid bending and strenuous exercise for several weeks
  • Avoid driving – typically for around 5 days after the procedure
  • Avoid heavy lifting and swimming – typically for 5 days after the procedure
  • Can resume normal activities – e.g. reading, watching TV – straight away
  • Steroids, antibiotics and dilating drops may be prescribed during the recovery period.
Contraindications to surgery


As with every surgery there are complications;
  • Posterior capsule opacification
    • A cloudy layer of scar tissue forms at the posterior of the lens capsule after replacement.
    • Treated by burning holes in the capsule with YAG laser
    • Most common complication
  • Bleeding – choroidal haemorrhage
  • Infection
    • Endopthalmitis – a very nasty infective complication, but thankfully very rare (0.3%).
  • Glaucoma
  • Vitreous loss
  • Visual disturbance
  • Retinal detachment (rare)
Sometimes pre-existing pathology is discovered from removing the cataract- as you can now see the Fundus a lot more clearly on slit lamp examination- e.g. AMD
Key Points
  • Most common cause of visual impairment worldwide
  • Treat if affecting activities of daily living or VA <6/12
  • Treatment is surgery
  • Make patients aware of possible complications



  • Murtagh’s General Practice. 6th Ed. (2015) John Murtagh, Jill Rosenblatt
  • Oxford Handbook of General Practice. 3rd Ed. (2010) Simon, C., Everitt, H., van Drop, F.
  • Beers, MH., Porter RS., Jones, TV., Kaplan JL., Berkwits, M. The Merck Manual of Diagnosis and Therapy

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Dr Tom Leach

Dr Tom Leach MBChB DCH EMCert(ACEM) FRACGP currently works as a GP and an Emergency Department CMO in Australia. He is also a Clinical Associate Lecturer at the Australian National University, and is studying for a Masters of Sports Medicine at the University of Queensland. After graduating from his medical degree at the University of Manchester in 2011, Tom completed his Foundation Training at Bolton Royal Hospital, before moving to Australia in 2013. He started almostadoctor whilst a third year medical student in 2009. Read full bio

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