​STRUCTURE AND FUNCTION OF THE EYE

The eye consists of several parts that are somewhat similar to a camera
  •   Sclera:  the white material which we normally see as the white of the eye. It is the eye‘s outer protective coat. 
  •   Cornea:  the transparent, curved structure at the front of the eye 
  •   Iris:  through the cornea the iris can be seen, which is that part of the eye which gives it colour – blue, brown, green, grey etc. It is a circular muscle which responds to bright light by contracting, making the pupil smaller. 
  •   Pupil:  in the middle of the iris is the pupil, a transparent aperture which appears black. ​

The pupil constricts in response to bright light and dilates in low levels of light.
  •   Lens:  situated immediately behind the iris and pupil is a transparent disc with both sides being convex. The lens focuses light onto the retina. It divides the eye into two parts – anterior and posterior chambers. 
  •   Anterior Chamber:  a fluid with the consistency of water circulates around this chamber. This fluid is called the aqueous humour. 
  •   Posterior Chamber:  this is filled by the vitreous humour which has the appearance of transparent jelly. 
  •   Retina:  situated at the back of the eye, the retina consists of millions of nerve cells which are divided into two main groups – rods and cones. They are so described because of their appearance under a microscope. 
  •   Cones: concentrated around an area of the retina called the macula. 
  •   Rods: although some are placed near the macula, the majority of rods are spread out to cover the rest of the retina. 
  •   Retinal Pigment Epithelium:  a dark coloured layer of cells underlying the retina responsible for providing oxygen and other nutrients to the rods and cones. 
  •   Choroid:  located behind the retina, it consists of a large network of blood vessels that transport oxygen and other nutrients to the retinal pigment cells. 
  •   Optic Disc: the nerve cell connections from all the rods and cones travel to the optic disc, a small, yellow, oval structure which can be seen through an ophthalmoscope. 
  •   Optic Nerve and beyond:   the optic disc is the front part of the optic nerve which passes from the eye to make connections throughout the brain.​

​THE USHER SYNDROME EYE:
The eye condition those with Usher syndrome suffer with is Retinitis Pigmentosa (RP). RP is caused by a degeneration of the cells at the back of the eye reducing the persons ability to see in dark conditions, along with a narrowing of the field of vision. You can read more about RP in the next section RETINITIS PIGMENTOSA.