🏘 Pathophysiology and epidemiology
Cataracts refers to opacification of the lens. It occurs due to denaturing of crystallin proteins. This opacification impairs light passage onto the retina → reduced vision or blurred vision. It is the leading cause of curable blindness.
The lens serves to refract light onto the the retina and help focus our vision
75% of patients over the age of 65 have some form of cataracts, with about 30% of these patients having an impairing cataract in either of their eyes.
⚠️ Risk factors
- Diabetes mellitus
- Increasing age
- Smoking
- Alcohol consumption
- Corticosteroids
- Dehydration
- Malnutrition
- UV exposure
- Previous eye surgery
- Hypocalcaemia
- Trauma
- Female gender
😷 Presentation
It tends to be a gradual onset and patients report:
- Reduced vision generally (both centrally and peripherally).
- Blurred vision
- Faded colours and colours start to seem browner/yellower.
- Glare (lights seeming brighter than usual)
- Halos around lights
Cataracts cause generalised reduction of vision.
Glaucoma cases peripheral vision loss.
Macular degeneration causes central vision loss.
🔍 Investigations
- Lack of/reduced red reflex
- Cloudy/grey/white lens
- Ophthalmoscopy - done after using a mydriatic such as atropine. It will show a normal fundus and optic nerve.
- 🏆 Slit-lamp examination - will show visible cataracts.
🔢 Classification
- ⭐️ Nuclear - affect the centre of the lens. Lens becomes less flexible and thus accommodation is affected.
- Polar - inherited form of cataracts.
- Subcapsular/posterior - opacification lies in the posterior portion of the lens. It occurs often due to chronic steroid use as well as allopurinol use.
- Blue dot/Cerulean - these are characterised by blue and white opacifications. Seen in normal lenses and also in diabetics and patients with myotonic dystrophy.
🧰 Management
- Prescription of stronger glasses or contact lenses.
- Encourage brighter lightening and optimise the vision that they currently have.
- If unstable diabetes, wait until the patient’s diabetes is under control first.
Phaecoemulsification with intraocular lens implant is the only treatment that is curative. It has a good success rate at about 85-90% success of 6/12 corrected vision
During the surgery, the cloudy lens is removed and replaced with an artificial lens. It is a day case procedure done under LA.
Referral for surgery depends on if the impairment affects quality of life as well as patient choice. NICE guidance states that cataract surgery should not be rationed on the basis of visual acuity. To delay surgery is a false economy. Even a slight reduction in visual acuity increases the risk of falls and other complications, such that cataract surgery is one of the most cost-effective operations on the NHS.
🚨 Complications
- Posterior capsule opacification - a “secondary cataract”.
- Posterior capsule rupture
- Retinal detachment
- Endophthalmitis - rare but serious complication of the surgery. It is inflammation of the aqueous and/or vitreous humour. It is usually due to infection and can be treated with intravitreal antibiotics. It is serious as it can cause loss of vision permanently and even loss of the eye itself.
