Orbit CC

Question 0

Orbital fractures can cause

Answer 0

Intraorbital bleeding which can cause protrusion of the eyeball (exophthalmos)

Question 1

Define Orbital fractures, which walls are most thin, blowout fracture?

Answer 1

Usually form at the sutures between the bones forming the orbital margin
Medial and inferior walls are most thin
Blowout fracture - indirect traumatic injury that displaces the orbital walls

Question 2

**preseptal (periorbital) cellulitis

Answer 2

Inflammation due to an infection is located anterior to the orbital septum
Fever, swollen eyelids, blurry vision, medication

Question 3

**orbital cellulitis

Answer 3

Inflammation due to an infection is located posterior to the orbital septum
Life threatening
Sudden loss of vision, pain when moving the eye, proptosis of the eye, or swelling of the eyelid. Prompt administration of intravenous antibiotics in a hospital must be given. An abscess may have to be removed surgically.

Question 4

Inflammation of palpebral glands

Ciliary glands vs Tarsal glands

Answer 4

Ducts of the ciliary glands become obstructed, a painful red suppurative swelling develops on the eyelid (sty)

Cysts of the tarsal glands (sebaceous glands) may form and are called chalazia.

Question 5

Retinal detachment

Answer 5

May follow a blow to the eye causing seepage of fluid between the neural and pigmented layers of the retina.
Flashes or light or specks floating in front of their eye.

Question 6

Papilledema

Answer 6

Increase in CSF pressure slows venous return from the retina, causing edema of the retina (fluid accumulation)
Swelling of the optic disk

Question 7

Presbyopia

Answer 7

As people age, their lenses become harder and more flattened. These changes gradually reduce the focusing power of the lenses.

Question 8

Cataracts, extracapsular cataract extraction vs intracapsular lens extraction

Answer 8

Clouding of the lens.
Cataract extraction combined with an intra-ocular lens implant
Extracapsular cataract extraction involves removing the lens but leaving the capsule of the lens intact to receive a synthetic intra-ocular lens
Intracapsular lens extraction involves removing the lens and lens capsule and implanting a synthetic intra-ocular lens in the anterior chamber

Question 9

Glaucoma

Answer 9

Outflow of aqueous humor through the scleral venous sinus into the blood circulation must occur at the same rate at which the aqueous is produced.

If the outflow decreases significantly because the outflow pathway is blocked, pressure builds up in the anterior and posterior chambers of the eye, a condition known as glaucoma.

Blindness can result from compression of the retina and retinal arteries

Question 10

Open angle vs closed angle glaucoma?

Answer 10

Open angle or primary open angle (most common): the drainage angle formed by the cornea and the iris remains open but the drainage canals in the angle are partially blocked causing the fluid to drain out of the eye too slowly.
Closed angle or angle-closure: occurs when the iris bulges anteriorly to narrow or block the drainage angle formed by the cornea and the iris.

Question 11

In full aBduction, the superior/inferior rectus do what?

Answer 11

Super rectus elevates

Inferior rectus depresses

Question 12

In full adDduction, the superior/inferior oblique do what?

Answer 12

Inferior oblique elevates the eye

Superior oblique depresses the eye

Question 13

Central retinal artery occlusions

Answer 13

any obstruction by embolus causes instant blindness

older people, unilateral

Question 14

Central retinal artery occlusion

Answer 14

Thrombophlebitis in the cavernous sinus can result in the passage of a thrombus into the central retinal vein which lead to smaller retinal veins
If one becomes included it will result in slow and painLESS loss of vision

Question 15

Partial CN III palsy
What 3 things can cause compression of CN III?
Internal vs External Ophthalmoplegia

Answer 15

1 Rapidly increasing ICP due to epidural or subdural hematoma will often compress CN III against the petrous portion of the temporal bone.
Para fibers are superficial and affected first = internal ophthalmoplegia.
External ophthalmoplegia = somatic motor fibers.
2 Injuries to the lateral wall of the cavernous sinus may affect CN III.
3 An aneurysm involving the superior cerebellar or posterior cerebral artery may exert pressure on CN III because it passes between these vessels.

Question 16

Complete CN III palsy

5 symptoms?

Answer 16

Ptosis of upper eyelid caused by paralysis of the levator palpebrae superioris.
No pupillary (light) reflex in the affected eye.
Dilation of the pupil, resulting from the interruption of parasympathetic fibers to the sphincter pupillae, leaving the dilator pupillae unopposed.
No accommodation of the lens because of paralysis of the ciliary muscle.
Eyeball down and out because of unopposed actions of the lateral rectus & superior oblique muscles.

Question 17

CN IV injury

What happens and how do patients compensate?

Answer 17

The characteristic sign = diplopia (double vision) when looking down.
Hypertropia is a type of strabismus where there is a vertical misalignment of the eyes. Although there are many causes of vertical strabismus, one of the most common is superior oblique palsy.
Patients may tilt their head away from the affected side to correct for extorsion. A chin tuck while looking upward is also present and this corrects for hypertropia.

Question 18

CN VI palsy

What happens and why

Answer 18

CN VI has a long course and it is often stretched when ICP increases. This is partly because of the sharp bend it makes over the crest of the petrous portion of the temporal bone after entering the dura mater.
A space occupying lesion such as a brain tumor may compress CN VI and cause paralysis of the lateral rectus muscle.
Complete CN VI Palsy: causes medial deviation of the affected eye – that is, it is fully adducted at rest and does not fully abduct owing to the unopposed action of the medial rectus muscle, leaving the person unable to abduct the eye.

Question 19

Pupillary light reflex
What CNs does it test?
Describe the reflex
Whats the first sign of CN III compression?

Answer 19

Afferent limb (CN II) and an efferent limb (CN III)

When light enters one eye, both pupils constrict because each retina sends fibers into the optic tracts of both sides. The sphincter pupillae muscle is innervated by parasympathetic fibers of CN III; consequently, interruption of these fibers causes dilation of the pupil because of the unopposed action of the sympathetically innervated dilator pupillae muscle.
*The first sign of compression of the CN III is ipsilateral slowness of the pupillary response to light.

Question 20

Corneal reflex, what is it?
Which nerves cause the loss of this reflex?
Afferent and efferent limbs?

Answer 20

Either ophthalmic nerve (V1) or (CN VII) is lesioned.
A bilateral blinking response should result.

Touch cornea (afferent limb) via opthalmic nerve (V1) to spinal nucleus of trigeminal nerve (efferent limb) to motor nucleus of CN VII creates contraction of orbicularis oculi