Lets learn about the eye.
Our eyes allow us to see the beauty of the world around us.
Lets take a closer look at how the eye works.
There are 6 eye muscles.
These include the superior rectus inferior rectus medial rectus and lateral rectus which
is cut in this picture.
There is also a superior oblique and inferior oblique.
The structure of the eye can be described in 3 layers.
The outer or fibrous tunic consists of the transparent cornea and opaque sclera.
The middle or vascular tunic consists of the iris, ciliary body and choroid.
The inner tunic includes the retina which contains light receptors or photoreceptors.
The anterior portion of the eye contains the anterior cavity.
The lens and ciliary body divide the eye into anterior and posterior cavities.
The iris divides the anterior cavity into anterior and posterior chambers.
The anterior cavity is filled with a fluid called aqueous humor.
The posterior cavity contains the vitreous body and vitreous humor.
Aqueous humor is secreted by the ciliary body which also holds the lens in place by suspensory
ligaments.
The fluid flows around the iris and drains via the scleral venous sinus or canal of Schlemm.
Light passing directly into the eye will follow the visual axis.
Light will pass through the cornea, aqueous humor, pupil, lens, vitreous body and end
up on the retina at an area known as the fovea centralis.
The fovea centralis contains a central area called the macula.
The macula contains the largest concentration of photoreceptors.
The area of sharpest vision occurs here.
The optic nerve (cranial nerve II) attaches at the back of the eye at an area called the
optic disc.
The optic disc contains no photoreceptors �so it produces a blind spot.
Two muscles work to dilate and constrict the pupil these are called dilators and constrictors
and respond to light intensity and autonomic nervous system stimulation.
The retina contains photoreceptors that respond to light.
There are 2 types of photoreceptors.rods and cones.
Rods do not sense colors so they help us see in dimly lit conditions.
Rods contains rhodopsin or visual purple.
Rhodopsin contains opsin (a protein) and retinal which is synthesized from Vit A.
Cones contain different kinds of opsins.
There are cones for the 3 primary colors blue, green and red.
Color blindness results from absent or non-functional cones.
We hope you have learned something about the eye and see you next time.