C: Eye Flashcards
What 4 structures does light have to pass through before reaching the retinal photoreceptors in the eye?
1) Cornea
2) Aqueous humour (Anterior and posterior chambers)
3) Lens
4) Vitreous body
Retinal photoreceptors
What and where is the conjunctiva?
Epithelium which covers the exposed part of the sclera and inner surface of the eye lids
What is the function of the conjunctiva?
secretes mucous which contributes to the protective layer on the exposed surface of the eye and allows the lids to move more freely over the eyes
What is the function of the sclera?
Tough protection from injury, supports eye and provides attachment for the extraoccular muscles which move the eye
What is the function of the iris?
Contains the dilater pupillae and sphincter pupillae muscles - acts as an adjustable diaphragm which regulates the amount of light reaching the retina
What is the nerve supply to the circular muscle of the iris ie. the sphincter pupillae muscle?
Parasympathetic nerves via the ciliary ganglion
Presynaptic - occulomotor nerve CN3
Post synaptic - V1 (ophthalmic)
What is the nerve supply to the ciliary muscle contained within the ciliary body?
Parasympathetic fibres via the ciliary ganglion
Presynaptic = oculomotor CN3
Post synaptic = V1 (ophthalmic)
What effect does contraction of the ciliary body have upon the lens?
Muscle contracts - tension on the suspensory ligament is reduced, so the lens assumes a more convex position
What are cataracts?
Abnormal opacification of the lens leading to loss of visal acuity and when severe, blindness
Other than its involvement in controlling the shape of the lens, what is the other function of the ciliary body?
Production of aqueous humour which fills the anterior compartment of the eye
What is the function of the aqueaous humour which fills the anterior compartment of the eye?
Pressure of this fluid helps to maintain the shape of the cornea and thus the refractive properties of the eyes
Through what structures is aqueous humor absrobed back into blood stream?
Through the canal of schlemm at the irido-corneal angle
Problems with drainage of aqueous humour can lead to what?
Glaucoma
What is glaucoma?
Increased intra-ocular pressure due to obstruction to the drainage of aqueous humour whilst the ciliary body continues to secrete it.
if untreated it can cause damage to the neural retina and can cause blindness
Give 2 functions of the choroid layer of the eyeball?
1) Provides support to retina
2) Heavily pigmented thus absorbing light which passes through the retina