Anatomy of the eye 1
What are the primary depressor and elevator extraocular eye muscles?
- depressor = inferior rectus
- elevator = superior rectus
What are cataracts?
Opacification(clouding) of the lens caused by
compaction and protein deposition
Name 3 drug classes which can be used to treat glaucoma
- Beta blockers
- Alpha2-adrenoceptor agonists
- Carbonic anhydrase inhibitors
- Prostaglandin analogues
- Miotics (muscarinic agonists)
what are the primary abductor and adductor eye muscles?
- abductor = lateral rectus
- adductor = medial rectus
parasympathetic
Which extraocular muscle is innervated by cranial nerve IV (trochlear nerve)?
superior oblique
Name 3 risk factors for cataracts
- aging
- trauma
- diabetes
- smoking
- Radiation exposure (UVB light)
- genetics
What is tropicamide used for and how does it work?
- used for pupil dilation/mydriasis
- It is a non-selective muscarinic antagonist.
- By binding to muscarinic receptors, tropicamide relaxes the pupillary sphincter muscle and causes pupil dilation
what is the primary role of the superior oblique?
intorsion
Which histological layer of the retina contains rod and cone cells?
Photoreceptor layer
What is the accommodation reflex?
Purpose: to focus on near objects
Parasympathetic control
Three components:
• Pupil constriction
• Lens accommodation
• Convergence
Name 3 risk factors for glaucoma
- Raised intraocular pressure
- High blood pressure
- Long-term corticosteroid use
- Severe myopia (nearsightedness)
- Secondary to eye injury/surgery
How do beta blockers work in the eyes?
treat glaucoma by lowering high intraocular pressure by reducing the production of aqueous humour
which extraocular muscle is innervated by cranial nerve VI (abducens nerve)?
lateral rectus
- Rods: Scotopic (night-time) vision – very sensitive to light
- Cones: Photopic (daytime) vision – less sensitive, but signals from different cone types are compared to differentiate colours
which extraocular muscles are innervated by Cranial nerve III (oculomotor nerve)?
- medial rectus
- superior rectus
- inferior rectus
- inferior oblique
How is open-angle glaucoma caused?
clogging of trabecular meshwork
How does mannitol work in treatment of glaucoma?
mannitol elevates blood plasma osmolarity, resulting in enhanced flow of water from the eye into plasma and a consequent reduction in intraocular pressure.
Name 4 differences between miosis and mydriasis
Miosis:
- Pupil constriction
- Iris sphincter active
- Iris dilator relaxed
- Response to light increase
- Parasympathetic control
- Relaxed state
- Also helps focus (accommodation)
Mydriasis:
- Pupil dilation
- Iris sphincter relaxed
- Iris dilator active
- Response to light decrease
- Sympathetic control
- Elevated emotional/aroused state
- Lets in more light
What is the role of the autonomic nervous system in the eye?
- pupil size regulation
- accommodation
- ocular blood flow
- intraocular pressure regulation
- tear production
what are the 2 types of gaze stabilisation movements?
- vestibulo-ocular - initiated by vestibular mechanisms during brief/rapid head movement
- optokinetic - initiated by visual mechanisms during slow head movement
How is acute angle-closure glaucoma caused?
Iris bulges forward and seals off the trabecular meshwork from the anterior chamber, preventing aqueous humour from draining.
How do carbonic anhydrase inhibitors work in the eyes?
- carbonic anhydrase inhibitors reduce the production of aqueous humour by the epithelium of the ciliary body
- they do this by reducing the production of bicarbonate ions and reducing fluid flow.
- The reduction in aqueous humour production lowers the intraocular pressure, helping treat glaucoma
- saccade - directs eyes toward visual target
- smooth pursuit - follows moving visual target
- vergence - adjusts eyes for different viewing distance (depth)
What epithelial cell type makes up the retinal pigmented epithelium? (outermost layer)
cuboidal