The eye works like a camera. Light passes through the clear front window (cornea) and a focusing lens, and forms an image on the light-sensitive film at the back (retina). The optic nerve then carries the picture to the brain, which makes sense of what you see.
Parts of the eye and common problems
| Part | What it does | Common problems |
|---|---|---|
| Eyelids and tears | Protect the eye and keep it moist | Dry eye, blepharitis, stye, chalazion, drooping lids |
| Conjunctiva | Thin clear skin over the white of the eye | Conjunctivitis, pterygium, subconjunctival haemorrhage |
| Cornea | The clear front window; does most of the focusing | Scratches, infections, keratoconus, scars |
| Iris and pupil | The coloured part, which controls how much light enters through the pupil | Uveitis (iritis) |
| Lens | Fine-tunes focus for near and far | Cataract, presbyopia (needing reading glasses) |
| Drainage angle | Where fluid drains out to keep pressure normal | Glaucoma |
| Vitreous | Clear jelly filling the eye | Floaters, vitreous haemorrhage |
| Retina and macula | Light-sensitive layer; the macula gives sharp central vision | Diabetic retinopathy, macular degeneration, retinal detachment |
| Optic nerve | Carries signals to the brain | Glaucoma, optic neuritis |
Why we need two eyes
The brain combines slightly different pictures from each eye to judge depth (3-D vision). Six small muscles on each eye move them together; when they are out of balance, a squint results.
Frequently asked questions
Which part of the eye is affected in cataract?
The lens, which becomes cloudy.
What is the macula?
A small central area of the retina responsible for sharp reading and face-recognition vision.
Why does glaucoma affect side vision first?
Glaucoma damages optic nerve fibres that usually carry side vision first, so central vision is often kept until late.
Can the eye be transplanted?
The whole eye cannot, but the cornea can be transplanted from a donor.
Related: Your Eye Check-up, Eye & Related Diseases, Interesting Eye Facts.
This leaflet gives general information and does not replace advice from your own eye doctor. Reviewed by Dr. Dhaval Patel, MD (Ophthalmology, AIIMS New Delhi), November 2026.
Questions about this?
Sadbhaav Eye & Dental Clinic, Motera, Ahmedabad. Dr. Dhaval Patel, MD (AIIMS New Delhi). Monday to Saturday, 10 am to 1 pm and 5 pm to 8 pm. For a serious eye injury outside clinic hours, go to the nearest eye hospital or emergency department.