A 68-year-old man presents with progressive painless vision loss over 2 years. Slit-lamp examination reveals opacity starting at the periphery and gradually advancing toward the center, with a characteristic brown discoloration. What is the most common type of cataract in this patient?

Explanation

## Diagnosis: Cortical Cataract **Key Point:** The clinical presentation of peripheral opacity advancing centripetally with a characteristic "spoke-like" or "bread-crumb" appearance is pathognomonic for cortical cataract. ### Epidemiology and Prevalence **High-Yield:** Cortical cataracts are the **most common type** of age-related cataract, accounting for approximately 40–50% of all senile cataracts in population-based studies. ### Clinical Features of Cortical Cataract | Feature | Cortical | Nuclear | Posterior Subcapsular | |---------|----------|---------|----------------------| | **Location** | Cortex (periphery → center) | Nucleus | Posterior lens capsule | | **Onset** | Gradual, peripheral | Gradual, central | Rapid, posterior | | **Color** | White, chalky, "bread-crumb" | Brown, amber | Granular, vacuoles | | **Vision impact** | Glare, monocular diplopia | Myopic shift, dim vision | Severe glare, near vision loss | | **Age of onset** | 60–70 years (most common) | 70+ years | 50–60 years (variable) | ### Pathophysiology 1. **Water influx** into cortical lens fibers due to osmotic gradient (loss of Na^+^/K^+^ ATPase function) 2. **Fiber swelling** and disruption of organized lens architecture 3. **Light scattering** from irregular refractive interfaces 4. **Centripetal progression** as the process extends from periphery inward **Clinical Pearl:** Cortical cataracts often cause **monocular diplopia** and **glare** (especially in bright light) because the opacity is peripheral and allows light rays to refract irregularly through the clear central nucleus. ### Why This Case Is Cortical - **2-year gradual progression** → typical for age-related cortical cataract - **Peripheral opacity advancing centrally** → classic cortical pattern - **Brown discoloration** → indicates oxidative changes in cortical proteins (though cortical cataracts are typically white; the brown may reflect concurrent nuclear changes, but the primary morphology described is cortical) - **Age 68 years** → peak incidence for cortical cataract **Mnemonic:** **CORTICAL** = **C**enter-sparing, **O**pacity at periphery, **R**adial/spoke-like, **T**ransparent nucleus initially, **I**nflux of water, **C**omplains of glare, **A**ge 60–70, **L**oss of lens fiber organization