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# Cornea and sclera: keratitis, dystrophies and scleritis

- Lesion

The clear cornea can be infected, scarred, thinned or clouded with fluid; the white sclera can be inflamed in autoimmune disease.

Updated Nov 12, 2026

## Key points

- Bacterial keratitis: contact lens wear (Pseudomonas), trauma; stromal ulcer with neutrophils, can perforate.
- Herpes simplex keratitis: dendritic epithelial ulcer, later stromal inflammation with granulomatous reaction to Descemet membrane and scarring.
- Acanthamoeba: contact lens with tap water, painful ring infiltrate, cysts in stroma; fungal keratitis after plant trauma.
- Band keratopathy: calcium in the Bowman layer, with chronic uveitis or hypercalcemia; actinic band keratopathy from ultraviolet.
- Keratoconus: thinning with breaks in the Bowman layer, cone-shaped cornea, irregular astigmatism; acute hydrops when Descemet membrane ruptures.
- Fuchs dystrophy: endothelial loss with guttae on a thick Descemet membrane, stromal edema and bullous keratopathy; a main reason for corneal transplant.

## What it is

The cornea is clear because it is avascular, regularly organised and kept dry by its endothelium. Infection (bacteria, herpes, fungi, Acanthamoeba) causes keratitis and ulcers that scar or perforate. Degenerations deposit material such as calcium (band keratopathy), and dystrophies are inherited, usually bilateral disorders, of which Fuchs endothelial dystrophy is the most common. Keratoconus is a progressive thinning and bulging of the cornea. The sclera can be inflamed in rheumatoid arthritis and vasculitis, sometimes to the point of necrosis.

## Step by step

- The corneal endothelium pumps water out of the stroma to keep it clear.
- In Fuchs dystrophy endothelial cells are lost and lay down excrescences (guttae).
- Pump capacity falls and the stroma swells.
- Fluid reaches the epithelium, which forms painful blisters (bullous keratopathy).
- Vision blurs, worst in the morning; transplant of the endothelium restores clarity.

## Corneal and scleral disorders

| Disorder | Layer | Hallmark | Cause or association |
| --- | --- | --- | --- |
| [Bacterial keratitis](https://durgical.com/en/conditions/keratitis-and-corneal-ulcer/) | Epithelium and stroma | Ulcer with neutrophils | Contact lenses, Pseudomonas, Staphylococcus |
| [Herpetic keratitis](https://durgical.com/en/conditions/herpes-zoster-ophthalmicus/) | Epithelium, then stroma | Dendritic ulcer; stromal scarring | HSV-1, herpes zoster |
| Acanthamoeba keratitis | Stroma | Ring infiltrate, cysts | Contact lenses and tap water |
| Band keratopathy | Bowman layer | Calcium band across the fissure | Chronic uveitis, hypercalcemia |
| [Keratoconus](https://durgical.com/en/conditions/keratoconus/) | Stroma and Bowman layer | Thinning, cone, Bowman breaks | Eye rubbing, atopy, Down syndrome |
| Fuchs endothelial dystrophy | Endothelium and Descemet | Guttae, stromal edema | Inherited (TCF4 repeat), older women |
| [Necrotising scleritis](https://durgical.com/en/conditions/scleritis-and-episcleritis/) | Sclera | Granulomatous inflammation with necrosis | Rheumatoid arthritis, granulomatosis with polyangiitis |

## Clinical notes

- Painful red eye with an ulcer in a contact lens wearer is an emergency.
- Necrotising scleritis signals active systemic vasculitis or rheumatoid disease and can thin the sclera (scleromalacia).

## Memory aid

Calcium sits in Bowman's band, the cone breaks Bowman's line, and Fuchs drowns the cornea from behind.

## Test yourself

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

## In which corneal layer is calcium deposited in band keratopathy?

The Bowman layer, usually in the exposed band across the lid fissure.

## What are guttae?

Drop-like excrescences of abnormal basement membrane on Descemet membrane, made by failing endothelial cells in Fuchs dystrophy.

## What is acute hydrops in keratoconus?

Sudden corneal swelling when Descemet membrane ruptures and aqueous enters the thinned stroma.

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## Elsewhere in DurgiPedia

- [The cornea: clarity, nerves and healing](https://durgical.com/en/ophthalmology/the-cornea-clarity-nerves-and-healing/)
- [Red eye in a contact lens wearer](https://durgical.com/en/ophthalmology/red-eye-in-a-contact-lens-wearer/)
- [The eye wall: cornea, sclera, uvea and lens](https://durgical.com/en/histology/the-eye-wall-cornea-sclera-uvea-and-lens/)

## Connections

## Related 4

- [Conjunctiva: conjunctivitis, trachoma and pterygium](https://durgical.com/en/general-pathology/conjunctiva-conjunctivitis-trachoma-and-pterygium/)
- [Intraocular inflammation: uveitis and endophthalmitis](https://durgical.com/en/general-pathology/intraocular-inflammation-uveitis-and-endophthalmitis/)
- [Pathologic calcification: dystrophic vs metastatic](https://durgical.com/en/general-pathology/pathologic-calcification-dystrophic-vs-metastatic/)
- [ANCA-associated vasculitis](https://durgical.com/en/general-pathology/anca-associated-vasculitis/)

## Related conditions 8

- [Keratitis and corneal ulcer](https://durgical.com/en/conditions/keratitis-and-corneal-ulcer/)
- [Keratoconus](https://durgical.com/en/conditions/keratoconus/)
- [Scleritis and episcleritis](https://durgical.com/en/conditions/scleritis-and-episcleritis/)
- [Herpes zoster ophthalmicus](https://durgical.com/en/conditions/herpes-zoster-ophthalmicus/)
- [Rheumatoid arthritis](https://durgical.com/en/conditions/rheumatoid-arthritis/)
- [Granulomatosis with polyangiitis](https://durgical.com/en/conditions/granulomatosis-with-polyangiitis/)
- [Corneal abrasion and ocular foreign body](https://durgical.com/en/conditions/corneal-abrasion-and-ocular-foreign-body/)
- [Hypercalcaemia](https://durgical.com/en/conditions/hypercalcaemia/)

## Microorganisms 4

- [Herpes simplex virus 1](https://durgical.com/en/microbiology/herpes-simplex-virus-1/)
- [Pseudomonas aeruginosa](https://durgical.com/en/microbiology/pseudomonas-aeruginosa/)
- [Acanthamoeba spp.](https://durgical.com/en/microbiology/acanthamoeba-spp/)
- [Staphylococcus aureus](https://durgical.com/en/microbiology/staphylococcus-aureus/)

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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: [Corneal Disease | Cornea | MedlinePlus](https://medlineplus.gov/cornealdisorders.html) (MedlinePlus, US National Library of Medicine, 2026).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/general-pathology/cornea-and-sclera-keratitis-dystrophies-and-scleritis/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/cornea-and-sclera-keratitis-dystrophies-and-scleritis/