A 58-year-old man from rural India presents with gradual, painless vision loss over 2 years. He works as a farmer and spends 8–10 hours daily in bright sunlight without protective eyewear. On slit-lamp examination, the cataract begins at the periphery of the lens and progresses centripetally, with a characteristic brown discoloration at the nucleus. Visual acuity is 6/36 in both eyes. Which type of cataract is most likely responsible for his presentation?

Explanation

## Clinical Diagnosis: Cortical Cataract **Key Point:** Cortical cataracts are characterized by opacification that begins at the lens periphery (cortex) and progresses centripetally toward the nucleus. They are the most common type of age-related cataract and are strongly associated with chronic ultraviolet (UV) light exposure. ### Epidemiology & Risk Factors - Most common type of senile cataract globally - Strong association with prolonged UV-B exposure (outdoor workers, tropical climates) - Develops over years to decades - Bilateral and symmetric in most cases ### Clinical Features of Cortical Cataract | Feature | Cortical Cataract | | --- | --- | | **Onset** | Gradual, painless | | **Location** | Peripheral cortex → central nucleus | | **Appearance** | Radial striations, "spokes" pattern; white opacification | | **Color** | Initially clear, progresses to white; nucleus may appear brown | | **Vision loss** | Glare and monocular diplopia (early); progressive blurring | | **Progression** | Slow (months to years) | | **Associated symptoms** | Glare in bright light (cortical fibers scatter light) | ### Why Cortical Cataract Fits This Case 1. **Peripheral-to-central progression** — classic cortical pattern 2. **Chronic UV exposure** — farmer working 8–10 hours daily in sunlight 3. **Brown nucleus** — indicates nuclear involvement as cortical opacity advances 4. **Bilateral presentation** — typical of UV-related cataracts 5. **Gradual onset over 2 years** — consistent with age-related cortical cataract **Clinical Pearl:** Cortical cataracts cause **early glare** and **monocular diplopia** because the peripheral opacities scatter light rays. Patients often report worse vision in bright sunlight than in dim light—opposite to posterior subcapsular cataracts. **High-Yield:** UV-B protection (sunglasses, hats) is the single most effective preventive measure for cortical cataracts in at-risk populations. This is a key public health message for NEET PG. ### Differential Diagnosis at a Glance | Type | Onset | Location | Appearance | Risk Factor | | --- | --- | --- | --- | --- | | **Cortical** | Gradual | Periphery → center | Radial spokes, white | UV exposure | | **Nuclear** | Gradual | Central nucleus | Brown/amber nucleus | Age, smoking | | **Posterior subcapsular** | Rapid | Posterior pole | Granular, vacuoles | Steroids, trauma, diabetes | | **Traumatic** | Acute/subacute | Variable | Rosette pattern (if punctate) | Mechanical injury | **Mnemonic: CORTICAL = Centripetal Opacification, Radial Trauma-Independent, Cortex-Initiated, Anterior Location**