This is the front window of the eye.

In camera terms: lens cover

In fact light is focused (bent) the most here.

It is extremely sensitive, so dust in the eye feels like glass.

To see clearly it needs to remain transparent.

The cornea has different layers:


  • front protective skin
  • the main thickness of the cornea


  • inside lining cells

If the eye is scratched, the cornea loses its epithelium, this uncovers nerves in the stroma which feel pain. The epithelium quickly heals within hours or a few days. The tears have an antibiotic effect so scratches don't often get infected. If it does the scratch develops into an ulcer.

The cells of the endothelium prevent aqueous (inner eye fluid) from water logging the cornea, but if there aren't enough cells to cover the back of the cornea or If the eye is sick and the eye pressure increases it can force inner eye fluid into the cornea and so make it cloudy. (corneal oedema), Severe oedema is called bullous keratopathy.

If the cornea doesn't focus the light properly then vision will be poor. This happens if it is misshapen (keratoconus), scarred from injury or ulcers, or if it is constantly waterlogged and painful. Then it is possible to change the window of the eye with a corneal graft.

Bullous Keratopathy

Corneal Graft Surgery

Back to Eye Parts

This information site has been provided by varied UK and US eye doctors for patients with eye problems.

Once your eye doctor has made a diagnosis or recommended an investigation or treatment, then you will be able to find further explanation on this site.

It is not a self diagnosis centre. It should not be relied upon without taking professional advice.