Cataract

Cataracts are a common eye condition characterised by clouding of the lens, leading to a decrease in vision. They develop slowly and can affect one or both eyes. Symptoms include faded colours, blurry or double vision, halos around light, trouble with bright lights, and difficulty seeing at night.

This condition can hinder daily activities such as driving, reading, and recognising faces, and it significantly increases the risk of falls and depression. Cataracts account for 51% of all cases of blindness and 33% of visual impairment worldwide.

Causes and Risk Factors

Cataracts are primarily caused by ageing, but other factors include trauma, radiation exposure, genetic predisposition, and post-eye surgery changes. Risk factors include diabetes, prolonged use of corticosteroids, smoking, prolonged exposure to sunlight, and alcohol consumption. The underlying mechanism involves the accumulation of protein clumps or yellow-brown pigment in the lens, reducing light transmission to the retina.

Signs and Symptoms

Symptoms of cataracts vary based on the type but often include visual impairment. Nuclear cataracts affect distance vision more than near vision, while posterior subcapsular cataracts primarily cause glare. Other signs include frequent changes in glasses prescription and coloured halos due to lens hydration. Congenital cataracts, if untreated, can lead to amblyopia.

An example of normal vision versus vision with cataracts.

Diagnosis

Diagnosis primarily involves a visual acuity test and a comprehensive eye examination. Cataracts can be classified histologically into nuclear sclerosis, cortical, and posterior subcapsular types. These types can be further classified based on severity using the Lens Opacities Classification System (LOCS III).

Prevention

Although no definitive prevention methods exist, certain lifestyle changes may reduce the risk or slow the progression. Wearing sunglasses that block ultraviolet light, maintaining a proper diet rich in vitamins A, C, and E, and avoiding smoking are recommended. The evidence for vitamin supplements is mixed but suggests some potential benefits.

Treatment

Non-Surgical

In the early stages, visual symptoms may be managed with glasses. However, this is often insufficient in advanced cases.

Surgical

Surgery is the only effective treatment when cataracts significantly impair vision. The most common procedure is phacoemulsification, where an ultrasonic probe breaks up the lens, which is then removed and replaced with an artificial intraocular lens. This surgery is typically performed on an outpatient basis under local anaesthesia with a high success rate, restoring vision to 20/40 or better in most cases.

Postoperative care involves avoiding strenuous activities and using protective measures like an eye shield. Complications are rare but can include retinal detachment and endophthalmitis. Posterior capsular opacification is a common condition managed with Nd:YAG laser capsulotomy.

Epidemiology

Cataracts are a leading cause of blindness globally, affecting over 20 million people. In the United States, cataracts are prevalent in 68% of those over 80 years old, with significant medical costs associated with treatment.

Research

Emerging treatments include N-Acetylcarnosine eye drops and femtosecond laser-assisted cataract surgery, which offer promising alternatives to traditional methods. Stem cell research is also looking at lens regeneration, particularly in children with congenital cataracts.

---

Self-assessment MCQs (single best answer)

What is the primary cause of cataracts?

Which of the following is NOT a symptom of cataracts?

Which type of cataract primarily causes glare?

Which lifestyle change is NOT recommended to reduce the risk of cataracts?

What is the most common surgical procedure to treat cataracts?

What percentage of blindness cases worldwide are due to cataracts?

What is a common complication that may occur a few months after cataract surgery?

In which age group in the United States are cataracts prevalent in 68% of individuals?

Which of the following is a promising emerging treatment for cataracts?

What does the Lens Opacities Classification System (LOCS III) classify?