Anatomy of the Eye

What is the function of the eye lid?

- Protects the eye

- Provides the blink reflex

- Lubricates eye with tear fluid

What is the function of the sclera?

Protection

What is the function of the pupil?

Regulates the amount of light entering the eye

What is the function of conjunctiva?

Thin membrane which covers the front of the eye which protects the eye.

What is the function of the cornea?

Refracts light as it enters the eye.

What is the function of the anterior chamber and the aqueous humour?

- Filled with the aqueous humour which provides nutrients and oxygen to the cornea.

- Also maintains intraocular pressure in the eye.

- Secreted by ciliary body, then out of the pupil to the canal of schlemm.

What is the function of the lens?

Focuses light onto the retina

What is the function of suspensory ligaments?

Hold the lens in place and to transmit tension from the ciliary muscles to lens, which causes it to change shape

What is vitrious humour?

- Viscous fluid which protects delicate structures such as the neural retina.

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What is the function of the retina?

- Contain the neural retina and the retinal pigment epithelium.

- Neural retina is light sensitive.

What is the function of the fovea?

Responsible for sharp central vision via light being focussed onto the fovea.

What is the function of choroid?

- Pigmented layer which is highly vascular and provides blood to the retina.

- Pigmentation allows absorption of light.

What is the function of the optic disk?

- Axons from the retina go out pf the eye and form the optic nerve.

- This takes visual information to the brain.

- Blood vessels come in and out at this point which also supply the inner retina with blood.

- No light sensitive cells in this area producing the blind spot.

What are the two types of smooth muscle in the iris?

- Circular muscle

- Radial muscle

Describe circular muscle in the iris.

- Fibres are in a circular position around the pupil.

- This allows for pupil to get smaller when they contract.

- Innervated by parasympathetic nervous system

Describe radial muscle in the iris.

- Fibres run radially across the iris.

- This causes pupils to dilate by pulling the pupil wider.

- Innervated by sympathetic nervous system.

What is the first point of focussing light?

- Greatest degree of refraction of light.

- Must be very smooth in order to refract light correctly.

- Uneven surface causes astigmatism.

Describe accommodation of the eye for far vision.

- Ciliary muscle is relaxed.

- This causes lens to be pulled flat and thin due to intraocular pressure.

- This allows far vision.

- Mediated by sympathetic nervous system.

Describe accommodation of the eye for near vision.

- Ciliary muscles contract.

- Lens now has a higher curvature and rounded allowing near vision.

- This is mediated by parasympathetic nervous system.

What is presbyopia?

- Lens is less flexible so can no longer become rounded.

- Prevents focusing on near objects.

What is shortsightedness (myopia)?

- Eyeball is too long.

- Parallel light is focussed in front of retina.

What is longsightedness (hyperopia)?

- Eyeball is too short.

- Near objects are brought to focus behind the retina.