Session 6 Flashcards
(17 cards)
Describe the bones that make up the boundaries of the orbit
Pyramidal shaped; Apex - optic canal
Superior - frontal and sphenoid
Inferior - zygomatic and maxillary (weakest part - blow out fracture - can caus inferior rectus to be stuck)
Medial - Maxillary, ethmoid, lacrimal and sphenoid
Lateral - zygomatic and sphenoid
What are the three layers of the eyeball and what are their function?
Sclera (outer) - continuous anteriorly as the transparent cornea. Provides attachments for extraocular muscles. Continuous with the dural sheath at the back of the eye over the optic nerve
Choroid - very vascular (middle layer also contains iris and ciliary body)
Retina - optic and non-visual parts
Describe the distribution of the conjunctivae
Extends up to the edge of the cornea and is reflected up onto the inner surface of the eyelid.
Where are the three chambers of the eye and what are they filled with?
Anterior - between cornea and iris. Aqueous humous
Posterior - between iris and lens. Aqueous humour
Vitreous - between lens and retina. Vitreous humour
Where is aqueous humour produced and drained and what is the clinical significance?
Produced by ciliary body
Drained via trabecular meshwork in anterior chamber in idro-corneal angle (between iris and cornea)
Failure to drain can lead to glaucoma
What are the muscles of the iris?
Sphincter and dilator pupilae
What causes cataracts?
Degradation of proteins in the lens as we age - becomes cloudy
What is presbyopia?
Inability to accommodate and focus on nearby objects
What does the lacrimal apparatus consist of?
Lacrimal gland (in a fossa in the superolateral part of orbit), lacrimal duct and lacrimal canaliculi
What are the muscles in the eyelid and what innervates them?
Obicularis oculi closes eyelid - CNVII
Levator palpabrae superioris opens eyelid - CNIII and some sympathetic
Describe the blood supply to the eye
Ophthalmic artery (gives off central retinal artery) and vein. Runs through optic canal
What are the ocular muscles and what nerves innervate them?
LR6 SO4
Lateral rectus - CNVI
Superior oblique - CNIV
Medial, superior and inferior rectus and inferior oblique -CNIII
Where do the extra-ocular muscles originate from?
Recti - tendinous ring surrounding the optic canal
Oblique - wall of the orbit
Describe the actions of the oblique muscles
Superior - depresses (especially when eye is pointing inwards), abducts and medially rotates eyeball
Inferior - elevates, abducts and laterally rotates the eyeball
When looking at the retina which lies most laterally- the optic disc or the macula?
Macula
List the points that need to be considered when examining the eye
Look - general, sclera, conjunctive, eyelids
Visual acuity - snellen chart
Visual fields - one eye at a time
Pupils - accommodation and light reflex (direct and consensual to test afferent and efferent limbs)
Movements of the eye
Fundoscopy
Describe the light reflex pathway
Afferent limb - optic nerve
Efferent limb - occulomotor nerve (parasympathetic fibres)
