Anatomy of the eye

Anatomy of the eye
  • A. Sclera

    The sclera

    The sclera is the white part of the eye, its protective outer layer. The optic nerve is attached to the sclera at the back of the eye. With age, the sclera becomes more yellow in colour.

    Related conditions

    Glaucoma

  • B. Choroid

    The choroid

    The choroid is made up of layers of blood vessels that provide oxygen and nourishment to the outer layers of the retina at the back of the eye. It lies between the retina and sclera.

    Related conditions

    Choroideremia

  • C. Retina

    The retina

    The retina is the part of the eye which senses light. It contains cells called photoreceptors which capture light rays and convert them into electrical signals. The signals are sent via nerve cells called retinal ganglion cells (together known as the optic nerve) to the brain. There are two type of photoreceptors: rods and cones. The rods function best in dim light and are responsible for peripheral vision – the side or edges of what is seen. The cones are required to see in bright light and in detail. They are responsible for colour vision.

    Related conditions

    AMD
    Best disease
    Choroideremia
    Diabetic retinopathy
    Glaucoma
    Retinal detachment
    Retinopathy of prematurity
    Retinitis pigmentosa
    Proliferative vitreoretinopathy

  • D. Optic nerve

    The optic nerve

    The optic nerve transmits visual information – what is seen – in the form of electrical impulses from the retina to the brain. The photoreceptor cells of the retina are not present in the optic nerve. This means people have a blind spot in their field of vision at the point on the retina where the optic nerve leads back into the brain. This is not normally noticeable because the vision of one eye overlaps with that of the other.

    Related conditions

    Amblyopia
    Duane retraction syndrome
    Glaucoma
    Leber hereditary optic neuropathy

  • E. Fovea

    The fovea

    The fovea is a small pit near the centre of the macula. It contains cone cells. These help people see colours and see in bright light.

    Related conditions

    Achromatopsia

    Age-related macular degeneration

    Best disease

    Choroideremia

    Diabetic retinopathy

    Leber congenital amaurosis

    Retinitis pigmentosa

    Retinopathy of prematurity

    Stargardt macular dystrophy

  • F. Macula

    The macula

    The macular is found at the centre of the retina. It is responsible for central vision and the ability to see detail. When light comes into the eye, it goes to the macular. It has a diameter of approximately 1.5mm.

    Related conditions

    Age-related macular degeneration
    Best disease
    Diabetic retinopathy
    Stargardt macular dystrophy

  • G. Vitreous gel

    The vitreous gel

    The vitreous gel (also known as the vitreous humour) is a clear, thick, substance that fills the centre of the eye. It is mostly made of water. It makes up approximately 2/3 of the eye's volume and gives it its shape. The vitreous gel helps keep the retina in place.

    Related conditions

    Degenerative vitreous syndrome or floaters

  • H. Lens

    The lens

    The lens is behind the iris. Its job is to focus light on to the retina. The shape of the lens is curved. It is flexible and is controlled by the nerves and muscles around it. The amount the lens curves changes to enable the eye to focus on objects at different distances.

    Related conditions

    Cataract

  • I. Iris

    The iris

    The iris gives the eye its colour. Genes, which people inherit from their parents, determine eye colour. The main function of the iris is to control the amount of light that is let into the eye. In bright light the muscles contract. This causes the opening at the centre of the iris (the pupil) to become smaller. In dim light the muscles dilate. This makes the iris wider and allows more light into the eye.

    Ocular coloboma

  • J. Cornea

    The cornea

    The cornea is the clear surface on the front of the eye. It is about half a millimetre thick. It has two main functions. First, it acts as a barrier preventing germs, dirt and other harmful material from getting into the eye. Secondly, the cornea acts as a lens which controls how light enters the eye. The cornea helps the eye to focus on what is being seen.

    Related conditions

    Acanthamoeba keratitis
    Corneal disease
    Corneal dystrophies
    Fuchs corneal dystrophy
    Keratoconus
    Meesmann corneal dystrophy
    Trachoma

  • K. Pupil

    The pupil

    The pupil is the black dot at the centre of the iris. It is an opening which lets light into the eye. The pupil changes size depending on how light or dark it is.