Importance of the Retina

Retina Viewed Through Ophthalmoscope



The Eye with Enlargement of Retina

The retina serves a very important role in the eye as it acts like a computer brain. It converts images from the eye into electrical impulses.  These impulses travel along the optic nerve all the way to the brain where they are interpreted as vision. 

In order to view the retina, a specialized instrument called the ophthalmoscope needs to be used.  Often an optometrist or ophthalmologist uses this instrument to observe the back of a patient’s eye.

 

The retina is nerve tissue in the eye which is light sensitive.  The retina is located in the back two-thirds of the globe and forms a thin lining approximately 0.5mm thick.

The External Retina is made up of two cell layers. 

1.       The first is the Pigmented Epithelium.  These are hexagon shaped cells packed with pigment granules located outside the retina which provide nourishment to the retinal visual cells. They are attached to the Choroid.

2.       The second is the Receptor or Bacillary Layer—This layer is made up of Rods and Cones

A normal retina has 150 million Rods and 6 million Cones

Rods are key in determining our night vision.  They are specialized retinal receptor cells that function in low light.

The Inner Retina consists of three layers.

1.       The Bipolar or Relay cells help to organize impulses from the receptors.  This layer also helps to connect the outer and inner layers of the retina.

2.       Ganglion Cell Layer contains the nuclei of ganglion cells and lies innermost to the retina.

3.       Optic Nerve Fibre Layer continues to process impulses from the receptor fibres which become bundled into the optic nerve.

 There are diseases that can affect the retina which may result in blindness.  I will discuss those on the next post.