[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [General pathology](https://durgical.com/en/general-pathology/) › [Eye](https://durgical.com/en/general-pathology/areas/eye/) › Cataract

# Cataract

- Lesion

A cataract is a cloudy lens; it is the leading cause of blindness in the world and is cured by surgery.

Updated Nov 12, 2026

## Key points

- Nuclear sclerosis: yellow-brown hardening of the centre with age, often causing near-sightedness.
- Cortical cataract: spoke-like opacities from fibre swelling and liquefaction (Morgagnian globules).
- Posterior subcapsular cataract: epithelial cells migrate behind (bladder cells); steroids, diabetes, radiation, uveitis.
- Congenital cataract: rubella, galactosemia, chromosomal disorders, inherited mutations; must be treated early to prevent amblyopia.
- Phacolytic glaucoma: proteins leak from a mature cataract and macrophages full of lens material block the trabecular meshwork.

## What it is

The lens is a capsule of epithelium and long fibres packed with crystallin proteins that must stay clear. With age, ultraviolet light, diabetes, steroids, radiation, trauma, inflammation or inherited and congenital causes, crystallins aggregate, fibres swell and break, and light scatters. Cataracts are named by where the opacity lies. A very mature cataract can leak lens proteins, provoking inflammation or blocking the outflow channels and causing glaucoma.

## Step by step

- Lens fibres live for life with no turnover of their crystallin proteins.
- Oxidation, glycation and ultraviolet damage alter crystallins.
- Altered proteins aggregate and fibres lose their regular packing.
- Light scatters and the lens yellows; vision blurs and glare increases.
- Very mature lenses liquefy and leak proteins that can inflame the eye or block drainage.

## Types of cataract

| Type | Location | Main causes |
| --- | --- | --- |
| [Nuclear](https://durgical.com/en/conditions/cataract/) | Centre of the lens | Ageing, ultraviolet, smoking |
| Cortical | Outer fibres, spoke-like | Ageing, diabetes |
| Posterior subcapsular | Just inside the back capsule | Corticosteroids, diabetes, radiation, uveitis |
| [Congenital or infantile](https://durgical.com/en/conditions/congenital-and-childhood-cataract/) | Variable | Rubella, galactosemia, trisomies, inherited |
| Traumatic | Variable, often rosette-shaped | Blunt or penetrating injury |

## Clinical notes

- Cataract surgery with an intraocular lens is one of the most effective procedures; cataract remains a leading cause of avoidable blindness in Colombia.
- In diabetes, sorbitol from the polyol pathway draws water into the lens.

## Memory aid

A lifelong lens never recycles: years of light and sugar fog the window from the centre, the spokes or the back.

## Test yourself

Think of the answer, then tap the question to see it.

## Which type of cataract is typical of long-term corticosteroid use?

Posterior subcapsular cataract.

## What causes phacolytic glaucoma?

Lens proteins leaking from a hypermature cataract, with macrophages that clog the trabecular meshwork.

## Which congenital infection classically causes cataract?

Rubella (congenital rubella syndrome).

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## Elsewhere in DurgiPedia

- [The lens and zonules through life](https://durgical.com/en/ophthalmology/the-lens-and-zonules-through-life/)
- [Steroid eye drops: glaucoma, cataract and infection](https://durgical.com/en/ophthalmology/steroid-eye-drops-glaucoma-cataract-and-infection/)
- [Coloboma, congenital cataract and congenital glaucoma](https://durgical.com/en/embryology/coloboma-congenital-cataract-and-congenital-glaucoma/)

## Connections

## Related 4

- [Glaucoma and the optic nerve](https://durgical.com/en/general-pathology/glaucoma-and-the-optic-nerve/)
- [Intraocular inflammation: uveitis and endophthalmitis](https://durgical.com/en/general-pathology/intraocular-inflammation-uveitis-and-endophthalmitis/)
- [Ionizing radiation injury](https://durgical.com/en/general-pathology/ionizing-radiation-injury/)
- [Diabetes: chronic lesions](https://durgical.com/en/general-pathology/diabetes-chronic-lesions/)

## Related conditions 6

- [Cataract](https://durgical.com/en/conditions/cataract/)
- [Congenital and childhood cataract](https://durgical.com/en/conditions/congenital-and-childhood-cataract/)
- [Type 2 diabetes mellitus](https://durgical.com/en/conditions/type-2-diabetes-mellitus/)
- [Classic galactosaemia](https://durgical.com/en/conditions/classic-galactosaemia/)
- [Rubella and congenital rubella syndrome](https://durgical.com/en/conditions/rubella-and-congenital-rubella-syndrome/)
- [Congenital (TORCH) infections: syphilis, toxoplasmosis, CMV and Zika](https://durgical.com/en/conditions/congenital-infections-syphilis-toxoplasmosis-cmv-and-zika/)

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Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: [Cataract](https://www.ncbi.nlm.nih.gov/books/NBK539699/) (StatPearls (NCBI Bookshelf), 2026).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/general-pathology/cataract/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/cataract/