A 68-year-old Indian man presents to the ophthalmology clinic with progressive painless blurring of vision in both eyes over 3 years. He reports difficulty reading newspapers and watching television. On examination, visual acuity is 6/24 in both eyes. Slit-lamp examination reveals a brown-coloured opacity in the nucleus of both lenses with a characteristic radial brown discolouration. The patient denies trauma, prolonged corticosteroid use, or metabolic disease. What is the most likely diagnosis?

Explanation

## Diagnosis: Nuclear Sclerotic Cataract ### Clinical Presentation **Key Point:** Nuclear sclerotic cataracts are the most common type of age-related cataract, typically presenting in patients over 60 years with insidious onset of blurred vision. ### Characteristic Features | Feature | Nuclear Sclerotic | Cortical | Posterior Subcapsular | |---------|-------------------|----------|----------------------| | **Colour** | Brown/amber | White/milky | Granular, vacuoles | | **Location** | Central nucleus | Cortical fibres | Posterior lens surface | | **Onset** | Gradual (years) | Variable | Often rapid | | **Symptoms** | Blurred vision, reduced contrast | Glare, monocular diplopia | Glare, difficulty reading | | **Progression** | Slow, predictable | Variable | Can be rapid | ### Pathophysiology **High-Yield:** Nuclear sclerosis occurs due to: 1. Compression of lens fibres from new fibre formation at the lens equator 2. Cross-linking of lens proteins (α-crystallins) 3. Accumulation of brown pigment (lipofuscin) from oxidative damage 4. Increased refractive index of the nucleus ### Clinical Pearl **Myopic shift:** Patients often report temporary improvement in near vision ("second sight") early in the disease due to increased refractive power of the hardened nucleus, which may delay seeking treatment. ### Why This Case Fits Nuclear Sclerotic Cataract - **Age:** 68 years (typical age group) - **Duration:** 3 years of gradual progression (characteristic slow onset) - **Appearance:** Brown nucleus with radial discolouration (pathognomonic) - **Bilateral:** Common in age-related cataracts - **No risk factors:** No trauma, steroids, or metabolic disease (rules out secondary causes) **Mnemonic: BROWN NUCLEUS = Nuclear sclerotic** — Think of the hardened, compacted nucleus turning brown from oxidative damage over decades. [cite:Khurana 6e Ch 8]