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Block 4: Musculoskeletal > Orbit/Glaucoma (Week 1--Melega) > Flashcards

Orbit/Glaucoma (Week 1--Melega) Flashcards

1
Q

What goes through the optic canal?

A

Optic Nerve (CN II)

Ophthalmic artery

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2
Q

What goes through the superior orbital fissure?

A

Occulomotor nerve (CN III)

Trochlear nerve (CN IV)

Ophthalmic nerve (CN V1)

Abducent nerve (CN VI)

Superior ophthalmic vein

Inferior ophthalmic vein (one part)

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3
Q

What goes through the inferior orbital fissure?

A

Maxillary nerve branches (CN V2)

Maxillary artery branches

Inferior ophthalmic vein (one part)

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4
Q

Walls of orbit shared with paranasal sinuses

A

Orbital plate of frontal bone with frontal sinus

Thin plate of ethmoid bone with ethmoid sinus

Orbital plate of maxillary bone with maxillary sinus (infraorbital nerve in wall)

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5
Q

Fascial sheath

A

Forms socket for eyeball

Pierced by tendons of extraocular muscles

Forms check ligaments (medial check ligament, lateral check ligament, suspensory ligament) that make sure you can’t turn your eyeballs too far in one direction

Orbital fat provides cushion

Periosteum is called periorbita (lines bone of the orbit)

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6
Q

7 extraocular muscles

A

1) Levator palpebrae superioris (CN III superior): elevate upper eyelid
2) Superior oblique muscle (CN IV): rotate in/intortion
3) Inferior oblique muscle (CN III inferior): rotate out/extortion
4) Superior rectus muscle (CN III superior): look up/elevation
5) Inferior rectus muscle (CN III inferior): look down/depression
6) Medial rectus muscle (CN III inferior): look in/adduction
7) Lateral rectus muscle (CN VI): look out/abduction

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7
Q

3 somatic motor nerves

A

1) Occulomotor nerve (CN III)
2) Trochlear nerve (CN IV)
3) Abducent nerve (CN VI)

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8
Q

Occulomotor nerve (CN III)

A

Superior division: innervates levator palpebrae superioris muscle, superior rectus muscle

Inferior division: innervates medial rectus muscle, inferior rectus muscle, inferior oblique muscle

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9
Q

Trochlear nerve (CN IV)

A

Innervates superior oblique muscle

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10
Q

Abducent nerve (CN VI)

A

Innervates lateral rectus muscle

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11
Q

3 coats of wall of eyeball

A

Fibrous coat

Uvea

Retina

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12
Q

Fibrous coat

A

Cornea: anterior 1/6; avascular; somatic sensory (CN V1)

Sclera: posterior 5/6; pierced by optic nerve and ophthalmic vessels; attachment point for extraocular muscles

Limbus: corneoscleral junction

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13
Q

Uvea

A

Vascular pigmented coat

Choroid: highly vascular

Ciliary body: ciliary muscle (smooth muscle, parasympathetic), ciliary processes become zonules that attach to lens, capillaries (vitreous humor production)

Iris: sphincter pupillae muscle (smooth muscle, paraympathetic, circular muscle?), dilator pupillae muscle (smooth muscle, sympathetic)

Pupil

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14
Q

Retina

A

Retinal pigment epithelium

Neurosensory retina

Optic disc forms optic nerve that penetrates lamina cribrosa of sclera; central retinal artery/vein also passes through

Optic chiasm

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15
Q

Eyeball interior

A

Lens (elastic qualities)

Vitreous chamber with vitreous body (proteoglycans/hyaluronan)

Aqueous humor fills anterior part, which has 2 chambers (posterior chamber and anterior chamber)

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16
Q

What happens to the vitreous chamber at 40 - 70 years of age?

A

Vitreous becomes more liquid and can detach from retina (vitreous detachment) which causes flaskes of light/floaters

If fluid gets into retina get retinal detachment (serious visual problem)

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17
Q

What is the flow of aqueous humor?

A

Aqueous humor produced by epithelium lining ciliary process of ciliary body –> into posterior chamber –> through pupil –> into anterior chamber –> into trabecular meshwork –> into canal of Schlemm –> scleral veins

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18
Q

What is aqueous humor?

A

Produced by epithelium lining ciliary processes of ciliary body

Protein-free ultrafiltrate of blood plasma

Maintains shape of anterior eyeball

Nourishes cornea and lens

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19
Q

Ophthalmic nerve (CN V1)

A

Lacrimal nerve to lacrimal gland

Frontal nerve to upper eyelid and forehead (supraorbital nerve and supratrochlear nerve)

Nasociliary nerve (ciliary ganglion branches pass through ciliary ganglion and become short ciliary branches for sensory to iris and cornea; long ciliary branches are to iris and cornea; ethmoid branches to nasal cavity; infratrochlear branches to medial eyelid)

20
Q

Ciliary ganglion roots

A

Parasymp pre fibers from oculomotor nerve (CN III) symapse in ganglion

Somatic sensory fibers from ophthalmic nerve (CN V1) pass through

Sympathetic fibers from surface of internal carotid artery (superior cervical ganglion) pass through

21
Q

Short ciliary nerves

A

Branches off ciliary ganglion

Parasymp post fibers to ciliary muscle and to sphincter pupillae muscle

Somatic sensory fibers from ophthalmic nerve (CN V1) FROM cornea and iris

Sympathetic fibers to blood vessels in choroid

22
Q

Sympathetic fibers of the orbit

A

Symp pre cell bodies in T1 - 4 –> symp post cell bodies in superior cervical ganglion –> symp post fibers course on surface of internal carotid artery

23
Q

2 courses of sympathetic fibers

A

Ciliary ganglion (no synapse) –> short ciliary nerves –> blood vessels in choroid

Long ciliary nerves (branches of ophthalmic nerve-nasociliary) –> dilator pupillae muscle in iris

24
Q

Ophthalmic artery

A

Central artery of retina

Ciliary arteries supply choroid

Lacrimal artery

Supraorbital and supratrochlear arteries

Anterior and posterior ethmoid arteries

Muscular branches

25
Q

Ophthalmic veins

A

Superior ophthalmic vein –> superior orbital fissure –> cavernous sinus

Inferior ophthalmic vein branch –> superior orbital fissure –> cavernous sinus

Inferior ophthalmic vein branch –> inferior orbital fissure –> pterygoid venous plexus

26
Q

Optic disc

A

Small white area where there are no photoreceptors

Optic nerve (CN II) passes through

Entrance of ventral artery of retina (branches don’t anastomose with each other = end artery)

Exit of central vein of retina

27
Q

Sympathetic innervation of the eye

A

NE –> alpha 1 receptors –> contract radial smooth muscle of iris (dilator pupillae) –> mydriasis (bigger pupil)

28
Q

Parasympathetic innervation of the eye

A

1) ACh –> muscarinic receptor –> contract sphincter smooth muscle of iris (constrictor pupillae) –> miosis (smaller pupil)
2) ACh –> muscarinic receptor –> contract ciliary body –> accommodation

29
Q

Accommodation

A

Light from single point of distant object and light from single point of near object being brought to a focus by changing curvature of the lens

Ciliary body muscle contracts and moves anteriorly –> relaxes tension on suspensory ligaments that support lens –> lens becomes more convex (rounds up in shape) –> eye focuses on nearby object

30
Q

Accommodation development and age-dependence

A

Effective by age 4 months

Remains adequate until onset of presbyopia at 40 years old

31
Q

Presbyopia

A

Condition in which lens of eye loses some ability to focus which makes it difficult to see objects up close

Also continuing appositional growth of lens fibers and age-related changes in lens capsule causes elasticity of lens to diminsh ??

32
Q

Cycloplegia

A

Paralysis of ciliary muscle of eye
results in loss of accommodation

Due to devervation or pharmacologic action (ACh antagonist like atropine)

33
Q

Relationship between mydriasis and accommodation

A

Mydriasis can occur without loss of accommodation (alpha 1 agonist)

If have loss of accommodation, then will have mydriasis (muscarinic antagonist)

Alpha 1 only at pupillary dilator smooth muscle

ACh at both ciliary muscle and pupillary sphincter smooth muscle

34
Q

Mydriatic agents (increase pupil size)

A

Sympathomimetics (alpha 1 agonists): phenylephrine

Parasympatholytics (muscarinic antagonists): atropine

35
Q

Miotic agents (decrease pupil size)

A

Parasympathomimetics (cholinergic agonists)

Sympatholytics (alpha 1 antagonists)

Opioids

36
Q

How do opioids cause miosis?

A

Opioid inhibitory interneurons maintain inhibitory tone on Edinger-Westphal cell bodies (para pre that regulate para contraction of pupillary sphincter smooth muscle of iris) –> opiods bind receptors on these interneurons and cause them to have less inhibition of E-W pre neurons so they fire more rapidly and lead to more activation of para post neurons –> contraction of pupillary sphincter smooth muscle of the iris –> miosis

37
Q

Aqueous humor production and outflow

A

Produced by ciliary body and derived from plasma capillary network

Secretion of Na+ and HCO3- into aqueous humor draws water in osmotically

Drained mostly through trabecular meshwork to Canal of Schlemm; also via uveoscleral pathway (<10% of total)

38
Q

Glaucoma

A

Group of diseases that can damage optic nerve and cause vision loss/blindness

Obstruction of aqueous drainage –> elevated intraocular pressure –> damage to optic nerve (more than 1 million fibers connecting retina to brain)

39
Q

Open-angle glaucoma

A

Angle between peripheral iris and cornea is normal

Drainage of aqueous humor affected due to clogging of trabecular meshwork

Increased IOP, degeneration of optic head, restricted visual field all typify primary open-angle glaucoma

Symptoms: generally field of vision narrowed so cannot see clearly

40
Q

Closed-angle glaucoma

A

Angle between iris and cornea narrows which blocks drainage of aqueous humor

Rarer, but severe, acute form of disease can cause blindness if not treated in 24 - 48 hours

Sudden increase in pressure inside eye causes intense pain and blurred vision

Symptoms: nausea, vomiting, headaches, intense pain in eyes, bloodshot eyes and increased sensitivity, medium dilatation of pupil, blurred vision, coloured circles surrounded by light

41
Q

What is the aim of pharmacotherapy for glaucoma?

A

Reduce intraocular pressure (IOP) to prevent damage to nerve fibers and prevent visual defects

1) Decrease aqueous production by ciliary body
2) Increase aqueous outflow through trabecular meshwork and uveal outflow paths

42
Q

Drugs used to manage chronic glaucoma

A

Beta blockers

Alpha 2 agonists

Carbonic anhydrase inhibitors

Prostaglandin agonists

Parasympathomimetics

43
Q

Drugs for emergency condition–closed angle glaucoma

A

Hyperosmotics

Note: can also use laser to puncture iris and allow outflow of aqueous humor from posterior chamber!

44
Q

Drugs that inhibit aqueous humor inflow

A

Beta blockers (timolol (topical administraction)): block beta receptors on ciliary epithelium so Na/K ATPase can’t let Na+ into aqueous humor and thus no water osmotically moves in either

Alpha 2 agonists (brimonidine, apraclonidine (topical administration)): act presynaptically at alpha 2 receptors to inhibit NE release and also block Na/K ATPase from letting Na+ into aqueous humor and thus no water osmotically moves in either

Carbonic anhydrase inhibitors (acetazolamide (systemic) and dorzolamide (topical)): reduce HCO3- production (enzymatic process) and secretion into aqueous humor and thus no water osmotically moves in either

45
Q

Drugs that increase aqueous humor outflow

A

Parasympathomimetics (pilocarpine, AChE inhibitors): contract ciliary muscle to increase tone and alignment of trabecular network and facilitate aqueous humor outflow via trabecular meshwork

F2alpha prostaglandin agonists (lantanoprost): increase uveoscleral outflow (aqueous humor goes between ciliary bundles and into episcleral tissues to be reabsorbed into orbital blood vessels and drained via conjunctival vessels)

46
Q

Hyperosmotics

A

Mannitol (20% IV solution) or glycerol (50% oral solution)

Increase serum osmolarity to reduce intraocular water content by drawing water out of the eye

Use caution in congestive heart failure; avoid glycerol in diabetics

Used only in management of acute elevations of IOP as seen in closed angle glaucoma and occasionally after surgery

47
Q

Optic cupping

A

Cuppng of optic nerve is appearance of optic nerve viewed through pupil–empty space in middle of optic nerve surrounded by nerve fibers

Glaucoma causes loss of nerve fibers and cup becomes larger (larger C/D ratio means more damage) because less space occupied by remaining nerve fibers

Block 4: Musculoskeletal (37 decks)

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