10 Questions
What is the name of the condition where the pupil is dilated?
Mydriasis
What is the effect of muscarinic antagonists and alpha-adrenoceptor agonists on the ciliary muscle?
They cause paralysis of the ciliary muscle, leading to loss of accommodation for far vision.
What is the primary function of the aqueous humor?
To provide nutrients and drugs to the nonvascular eye tissues.
Which of the following can cause cataracts?
Glucocorticosteroids, chlorpromazine, amiodarone, and phenytoin.
What is the normal range of intraocular pressure (IOP)?
10-20 mmHg
Which of the following is NOT a component of the anterior part of the eye?
Retina
What is the function of the iris?
To regulate the amount of light entering the eye
Which of the following statements about the cornea is correct?
It is the outermost layer of the eye
Which of the following substances would cause constriction of the pupil?
A muscarinic agonist
What separates the aqueous humour from the vitreous humour?
The lens
Study Notes
The Eye Structure
- The eyeball consists of two fluid-filled compartments: the aqueous humour and the vitreous humour, separated by a translucent lens.
- The eye has four layers of supporting tissue: cornea and sclera, pigment epithelium, uveal tract, and retina (neural tissue containing photoreceptors).
Light Pathway
- Light enters the eye through the cornea and is focused by the lens onto the retina.
- The signal from the retina reaches the brain via the optic nerve.
Eye Regions
- The eye has two main regions: the anterior (front) part and the posterior (internal) part.
- The anterior component consists of the iris, pupil, cornea, sclera, and conjunctiva.
- The internal component consists of the lens, retina, optic nerve, aqueous humour, and vitreous humour.
Iris and Pupil
- The iris has a sphincter muscle that receives parasympathetic nerve fibres, causing constriction of the pupil.
- Muscarinic agonist and α-adrenoceptor antagonist cause constriction (miosis) of the pupil.
- Muscarinic antagonist and alpha-adrenoceptor agonist cause dilatation (mydriasis) of the pupil.
Lens and Accommodation
- Contraction of the innervated ciliary muscle allows the lens to become thicker for near vision.
- Muscarinic antagonist and alpha adrenoceptor agonist paralyze the ciliary muscle, leading to loss of accommodation for far vision.
- The lens provides refractive power for the adjustable part of the eye.
Cataracts and Retina
- Opacity of the lens is called cataract, and can be caused by certain drugs.
- The retina is part of the CNS and is relatively unaffected by drugs due to the blood-retinal barrier.
- The retina can be damaged by drugs or high oxygen tension in newborn babies.
Aqueous Humour Formation and IOP
- The ciliary body produces the aqueous humour, which flows through the anterior segment of the eye and provides nutrients and drugs to non-vascular eye tissues.
- The normal intraocular pressure (IOP) is about 15mmHg, maintained by a balance of aqueous humour formation and outflow.
Corneal Damage and Inflammation
- Fluorescein dye is used to reveal damage to the corneal epithelium.
- Inflammation from allergy or chemical burn can be treated with topical anti-inflammatory agents.
- Infections require treatment with anti-inflammatory agents together with effective chemotherapeutic agents.
Test your knowledge on the anatomy of the human eye, including its structures like the cornea, iris, and retina. Learn about the components that make up the eyeball and their functions.
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