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Flashcards in Anatomy Deck (12)

Which muscles of the eye does CNIII supply?

Oculomotor nerve supplies 5 muscles: Superior rectus, inferior rectus, medial rectus, levator, & inferior oblique.
NB: NOT lateral rectus!


Which ocular muscle is supplied by CNVI?

Abducens nerve supplies the lateral rectus muscle.
A palsy here will cause convergent deviation.


Which ocular muscle does CN IV supply?

Trochlear nerve supplies the superior oblique muscle. Pulley just behind superonasal rim.


What is the retinal pigment epithelium (RPE)?

The RPE is a specialised cellular monolayer between the neurosensory retina and the choroid.

It has many functions including phagocytosis of debris, and maintenance of normal physiology of rods and cones.
In disease of the choroid and retina, RPE cells replicate and migrate. The ophthalmic signs of such processes are atrophy (loss of pigmentation) and hyperpigmentation.
Age-related macular degeneration ("normal") is where RPE unable to maintain normal function of macular rods and cones: loss of central vision results.


Ora serrata

The serrated junction between the retina and the ciliary body.


What are the six bones which make up the orbit?

Four Mean Zebras Liked Stomping Emus:
Frontal, maxillary, zygomatic, lacrimal, sphenoid, ethmoid.


Which two structures does the optic foramen/optic canal convey?

1. The optic nerve backwards to the intracranial optic chiasm
2. The opthalmic artery forward into the orbit


What five main structures does the superior orbital fissure convey?

The superior orbital fissure provides passage for the third, fourth and sixth cranial nerves; the superior ophthalmic vein (passing backwards to the cavernous sinus); and V1 of the fifth cranial nerve (the lacrimal, frontal and nasociliary nerves).


What two structures does the inferior orbital fissure convey?

The inferior orbital fissure permits the exit of the inferior opthalmic vein from the orbit, and the entry of the maxillary division (V2) of the fifth cranial nerve - thus a fracture of the floor of the orbit can cause abnormal sensation in the cheek.


What are the three optical components of the eye, and which is the most powerful focusing element?

1. The cornea
2. The lens
3. The length of the eyeball

Of these, the cornea is the most powerful focusing element, but only the lens is naturally adjustable. All three components change during childhood as the eye grows.


What type of additional lens is required to correct for hypermetropia?

An additional CONCAVE lens is required in long-sightedness, as the refractive power of the eye is inadequate so that light from distant objects is focused 'behind' the eye (falls 'long' of the retina).
Think about narrowing the light down so that it hits the retina, needs a concave lens (increase the refractive power of the lens).


What type of additional lens is required to correct for myopia?

In short-sightedness, distant targets are focused in front of the retina (ie. focused image falls short of the retina). This is corrected by a CONVEX lens.
However, objects close to the myopic eye may be focused directly onto the retina (because light from near object is divergent): hence the term 'short-sightedness'. See p. 78 for refractive error diagrams.