Cataracts and Types

Study Notes

Cataracts

A cataract is an opacification or clouding of the lens, the most common cause of blindness worldwide.
There are three main types of cataracts, classified according to the part of the lens affected.

Types of Cataracts

Nuclear cataracts:
- Caused by sclerosis of the lens nucleus.
- Common in old age.
- Symptoms include myopia (short-sightedness) and colors appearing dull.
- Patients may experience a decrease in need for reading glasses.
Cortical cataracts:
- Caused by opacifications of the lens cortex.
- On ophthalmoscopy, the opacifications look like the spokes of a wheel around the edge of the lens.
- Vision is often unaffected.
Posterior subcapsular cataracts:
- Caused by opacifications in the posterior aspect of the lens capsule.
- Typically affect younger patients and individuals taking steroids.
- Patients complain of glare when looking at lights (e.g., when driving at night).
- Progress more rapidly than other types of cataracts.
Congenital cataracts:
- Present from birth.
- Associated with infection (e.g., congenital rubella syndrome) and genetic predisposition.
- Often diagnosed during the newborn examination due to the absence of the fundal reflex.
- Urgent referral to ophthalmology is required, as surgical management may be necessary in the first 6 weeks of life to prevent amblyopia.

Causes of Cataracts

Age-related changes.
Diabetes.
Steroid use.
UV exposure.
Smoking.
Ocular trauma.
Genetic predisposition.
Galactosemia.
Wilson disease.
Myotonic dystrophy.

Clinical Features

History:
- Progressive blurring of vision.
- Glare when looking at lights.
- Colors appearing dull.
Clinical examination:
- Reduced red reflex.
- Clouded lens.
- Mature cataracts with loss of red reflex.

Investigations

Clinical diagnosis made following history and clinical examination.
Slit-lamp examination with dilated pupils can support the diagnosis.

Management

Conservative management:
- Control risk factors such as diabetes, smoking, steroid use, and UV exposure to slow down cataract development.
- NICE recommends refraining from surgical management until symptoms affect lifestyle.
Surgical management:
- Phacoemulsification with an intraocular lens implant is the most common cataract surgery.
- Ocular biometry is conducted to measure the corneal curvature and shape of the eye before surgery.
- Complications of unmanaged cataracts include loss of vision.

Description

Learn about cataracts, the most common cause of blindness worldwide, and its three main types, classified according to the part of the lens affected. Understand the causes, symptoms, and effects of nuclear and cortical cataracts.