Eye structure

Eye structure

Tashkent Medical Academy

Urganch branch Faculty of treatment

Davletova Madina

Eye structure

• Eye is a complicated organ.
• It consists of three layers: inner, outer and middle.

Optic tracts These are the pathways of the optic nerves

• Posterior to the optic chiasmaEach tract consists of the nasal fibres of the opposite retina and the temporal fibres of the same side retina.Pass through the cerebrum to synapse with nerve cells of the lateral geniculate bodies of the thalamus. Thence the fibres pass as optic radiations to terminate int the visual area of the cerebral cortex in the occipital lobe of the cerebrum.Other neurones originating in the lateral geniculate bodies convey impulses from the eyes to the cerebellum where together with impulses from the smicircular canals, and from the skeletal muscles and joints, they contribute to the maintenance of the balance.

Outer layer

• Outer layer consists of sclera and cornea.
• Sclera is a white layer. It protects the eye from damage.
• Cornea is a transparent layer.

• Rhodopsin (visual purple) - degraded or bleached when exposed to light – regeneration requires vitamin A.The time taken for the regeneration of rhodopsin is called dark-adaptationOther pigments present in cones respond to different wavelengths of visible ligt and are responsible for colour vision.0.5 cm to the nasal side of the macula lutea all the nerve fibres of the retina converge to form the optic nerve which passes through the sphenoid bone  cerebral cortex in the occipital lobe of the cerebrum.Optic disc or the blind spot – optic nerve leaves the eye.

Middle layer

• Middle layer consists of three parts: iris, ciliary body and choroid.
• Ciliary body holds the lens in the eye.
• Lens focuses incoming light.
• Iris has eye coloring pigments. In the middle of the iris there is an opening called pupil. Light enter through this opening.
• Choroid has blood vessels. They bring nutrients for the eye.

Inner layer

• Inner layer is a retina. It has cells called receptors. They receive information from outside and transfer it to our brain by optic nerve.

Extraocular muscles of the eye

•  Six extrinsic musclesAttached to the eye ball at one end and to the walls of the orbital cavity at the other end.4 straight muscles and 2 oblique muscles :Medial rectus – rotates inwardsLateral rectus – rotates outwardsSuperior rectus – rotates upwardsInferior rectus - rotates downwardsSuperior oblique – downwards and outwardsInferior oblique – upwards and outwardsVoluntary muscles – needed for convergence and accommodation

Facts

• Newborns don’t produce tears. They make crying sounds, but the tears don’t start flowing until they are about 4-13 weeks old.
• Ophthalmologist is a medically trained doctor who is an expert in diagnosing, treating and preventing eye diseases.

• https://www.youtube.com/watch?v=LxI30P64Sfk