Introduction
A cataract is a common eye condition where the lens of the eye gradually opacifies i.e. becomes cloudy. This cloudiness makes it more difficult for light to reach the back of the eye (retina), thus causing reduced/blurred vision. Cataracts are the leading cause of curable blindness worldwide.
Classification
Classification
- Nuclear: change lens refractive index, common in old age
- Polar: localized, commonly inherited, lie in the visual axis
- Subcapsular: due to steroid use, just deep to the lens capsule, in the visual axis
- Dot opacities: common in normal lenses, also seen in diabetes and myotonic dystrophy
Epidemiology
- Incidence: 530.00 cases per 100,000 person-years
- Peak incidence: 70+ years
- Sex ratio: 1:1
| <1 | 1-5 | 6+ | 16+ | 30+ | 40+ | 50+ | 60+ | 70+ | 80+ |
Aetiology
Causes
Other possible causes
- Normal ageing process: most common cause
Other possible causes
- Smoking
- Increased alcohol consumption
- Trauma
- Diabetes mellitus
- Long-term corticosteroids
- Radiation exposure
- Myotonic dystrophy
- Metabolic disorders: hypocalcaemia
Clinical features
Patients typically present with a gradual onset of:
Signs:
- Reduced vision
- Faded colour vision: making it more difficult to distinguish different colours
- Glare: lights appear brighter than usual
- Halos around lights
Signs:
- A Defect in the red reflex: the red reflex is essentially the reddish-orange reflection seen through an ophthalmoscope when a light is shone on the retina. Cataracts will prevent light from getting to the retina, hence you see a defect in the red reflex.
Investigations
Investigations:
- Ophthalmoscopy: done after pupil dilation. Findings: normal fundus and optic nerve
- Slit-lamp examination. Findings: visible cataract
Management
Management
- Non-surgical: In the early stages, age-related cataracts can be managed conservatively by prescribing stronger glasses/contact lens, or by encouraging the use of brighter lighting. These options help optimise vision but do not actually slow down the progression of cataracts, therefore surgery will eventually be needed.
- Surgery: Surgery is the only effective treatment for cataracts. This involves removing the cloudy lens and replacing this with an artificial one. NICE suggests that referral for surgery should be dependent upon whether a visual impairment is present, impact on quality of life, and patient choice. Also whether both eyes are affected and the possible risks and benefits of surgery should be taken into account. Prior to cataract surgery, patients should be provided with information on the refractive implications of various types of intraocular lenses. After cataract surgery, patients should be advised on the use of eye drops and eyewear, what to do if vision changes and the management of other ocular problems. Cataract surgery has a high success rate with 85-90% of patients achieving 6/12 corrected vision (on a Snellen chart) postoperatively.
Complications
Complications following surgery
- Posterior capsule opacification: thickening of the lens capsule
- Retinal detachment
- Posterior capsule rupture
- Endophthalmitis: inflammation of aqueous and/or vitreous humour