Cataract is the most common non-refractive cause of visual impairment worldwide



In simple terms =  Opacification of the lens.
Not “a skin” growing over the lens as many people think!


  • Main one is AGE!
  • Trauma
  • Smoking (as usual- if in doubt say smoking!)
  • Alcohol use
  • Diabetes
  • Other metabolic disorders eg fabry disease, hypocalcaemia, galactosaemia (you’ll get points for saying these)
  • Uveitis
  • Systemic drugs (eg, corticosteroids)
  • Congenital


  • Painless loss of vision
  • Misting or blurring
  • Glare
  • Change in refractive error
  • (in infants may cause amblyopia)


Diagnosis is best made with a dilated pupil
Examine with a slit lamp/ophthalmoscope- a cataract is seen as black against the red reflex


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- they dissolve the lens 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.


As with every surgery there are complications;
  1. Bleeding – choroidal haemorrhage
  2. Vitreous loss
  3. Endopthalmitis- a very nasty infective complication, but thankfully very rare (0.3%).
  4. Opacification of the capsule- treated by burning holes in the capsule with YAG laser
  5. Glaucoma
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 complications

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