Table of Contents
Overview – Cataracts
Cataracts are a leading cause of reversible vision loss worldwide. They refer to an opacity or clouding of the eye’s crystalline lens, resulting in progressive blurring of vision. Although often age-related, cataracts can also occur secondary to systemic diseases, trauma, medications, or environmental exposures. As such, they are both a public health concern and a core clinical topic for final-year medical students.
Definition
- Cataract = Opacification of the crystalline lens of the eye
- Interferes with light passing through to the retina → blurred or impaired vision
Aetiology
- Metabolic Disease: Diabetes mellitus (↑ sorbitol accumulation in the lens)
- UV Light Exposure: Solar radiation contributes to protein denaturation in the lens
- Smoking: Increases oxidative stress
- Ocular Disease: Eg. Glaucoma, uveitis
- Dermatological Conditions: Eg. Atopic dermatitis
- Medications: Long-term corticosteroid use
- Ageing: Idiopathic age-related lens degeneration – most common cause
Pathophysiology
- Crystalline lens proteins denature and aggregate with age or stress
- Leads to increased light scatter and reduced clarity of lens transmission
- Result = gradual, painless loss of vision, especially for near or dim light
Clinical Features
- Painless, progressive visual blurring
- Difficulty reading or seeing in low light
- Glare sensitivity (especially at night)
- Reduced colour discrimination (colours appear faded or yellowed)
- Halos around lights
- Visual acuity improved with pinhole testing
Investigations
- Ophthalmoscopy: Opacified lens, may obscure fundal view
- Slit-lamp Examination: Confirms lens changes
- Visual Acuity Testing
- Pinhole Test: Improvement in acuity = refractive cause like cataract
Management
- Preventative Measures:
- Adequate nutrition (esp. antioxidant-rich diet)
- UV protection – sunglasses with UV-A/UV-B filters
- Good glycaemic control in diabetics
- Medical: No proven pharmacological treatment
- Surgical (definitive):
- Phacoemulsification with intraocular lens (IOL) implantation
- Safe, day-case procedure with excellent outcomes
- Reserved for functionally significant cataracts (affecting daily activities)
Complications
- Delayed surgery → further visual decline, risk of falls
- Rare surgical risks: posterior capsule rupture, endophthalmitis, retinal detachment
Summary – Cataracts
Cataracts are a common, progressive lens opacity that leads to painless visual impairment. Although often age-related, metabolic, environmental, and drug-related causes are also implicated. Surgical lens extraction with intraocular lens replacement remains the gold-standard treatment. For related content, visit our Nervous System Overview page.