Vision Flashcards
What makes up the outer layer of the globe?
- sclera
- Limbus
- Cornea
What makes up the middle layer of the globe?
- choroid, ciliary body, iris stroma
- melanocytes
What makes up the inner layer of the globe?
- retinal pigmented epithelium
- Neural retina
- Ora serrata
- anterior ciliary processes
- posterior iris
What is an open globe injury?
-a full thickness laceration or perforation of the cornea, limbus, or cornea
**opthalmic emergency
What are the three smooth muscles in the eye?
- constrictor muscle
- Dilator muscle
- circumferential muscle (in ciliary body)
What is the Near Synkinesis reflex made up of?
- Accomodation
- Convergence
- Miosis
Which nerve controls the levator palbebrae superioris?
CNIII
Which nerve controls the circumferential ciliary body muscle?
-CNIII
Which nerve controls the Iris constrictor muscle?
CNIII
In which portion of the eye is ocular melanoma most common?
-Choroid
What types of neurons are in the retina?
- photoreceptors
- bipolar cells
- ganglion cells
- interneurons (horizontal & amacrine cells)
What is the blood supply to the retina?
- inner 2/3 = central retinal artery
- outer 1/3 = choroidal vasculature
What is the ora serrata?
serrated junction between the retina and the ciliary body
What are the signs that can lead to a diagnosis of an open globe injury?
- seidel positive testing
- peaked pupil
- low intraocular pressure
What is Nystagmus?
- when eye shakes back and forth very quickly
- common in albinism
What are the interneurons of the retina?
- horizontal cells
- amacrine cells
What suspends the lens to the ciliary body?
Zonules
What collagen is most prominent in the lens?
Type IV collagen
What is a cataract?
a crystalline lens that has lost its transparency
What are the 5 layers of the cornea?
- stratified squamous epithelium
- Bowman’s layer (Type I)
- Stroma (Type I)
- Descemet’s layer (Type IV)
- Endothelium
What is Keratoconus? Which layer causes it?
a degenerative disaease of the cornea that leads to protrusion of the cornea into a cone shape
-bowman’e layer loses integrity
What is Fuchs Dystrophy?
- progressive corneal dystrophy involving loss of endothelial cells
- common in older women
What drains through the angle of the eye?
Aqueous humor
Where is aqueous humor synthesized?
two layers of epithelial cells on the ciliary proccesses
Describe the inflow of Aqueous humor.
Ciliary processes > posterior chamber > through pupil > anterior chamber
What is the difference between Trabecular outflow and uveoscleral outflow?
Trabecular: Pressure dependent. Trabecular meshwork > Schlemm’s Canal > Venous system
Uveoscleral: Pressure independent. Anterior Chamber > Ciliary muscle > subraciliary/suprachoroidal spaces > exit via intact sclera or along its nerves/vessels
What is the laminar portion of the optic nerve?
- thought to be damaged in glaucoma
- continuous with sclera
- provides main support for the optic nerve as it exits the eye
What is primary open-angle glaucoma?
- trabecular meshwork can become dysfunctional leading to increased outflow resistance
- can cause death of CNII fibers
**pts experience painless, slow, progressive loss of vision, starting in periphery
What are the 5 ways to lower the intraocular pressure?
- modify ANS to slow down blood flow in ciliary body
- Induce parasympathetic miosis and accomodation to open up trabecular meshwork
- Show down production of aqueous
- Mechanically open trabecular meshwork to increase fluid drainage
- Create artificial conduit to drain directly into venous system
What adrenergic receptors are on the ciliary body, and how do they influence aqueous humor production when activated?
B1/2 = increase production
a1/2 = decrease production
Which of these drugs is NOT useful in treating glaucoma?
- Beta 1 blocker
- Carbonic anhydrase inhibitor
- Cholinergic agonist
- Alpha 2 antagonist
- Acetylcholine esterase inhibitor
- Marijuana
- Alpha 2 antagonist
Which of the following drugs will dilate pupil and
also prevent accommodation?
- Tyramine
- Echothiophate
- Curare
- Atropine
- Muscarine
- Atropine
What is the innervation tot he dilator muscle of the eye?
-Sympathetics from the tcarotid plexus (synapsed at superior cervical ganglion)
What is the innervation of the constructor muscle of the eye?
-parasympathetics from CNIII
Describe accomodation.
- lens is fatter
- constriction of the circumferential muscle in the ciliary body
- zonular fibers are relaxed
What is presbyopia
- patients need reading glasses
- normal part of aging
- lens loses elasticity, so even though ciliary body contracts, the lens does not get fatter (no accomodation)
What nerve controls the near synkinesis reflex?
-CN III
Between what two layers does a retinal tear occur?
-Peeling of the photoreceptors from the RPE
What is a colorful sign of the congenital form of horner’s syndrome?
- Heterochromia
* melanocytes from neural crest
Why does the lens continue to thicken as we age?
- lens epithelial cells on the anterior of the lens continuously make basement membrane which migrates posteriorly
- anterior capsule continues to thicken while posterior capsule remains 4 um thick
What is luekocoria?
-white pupil that is a result of cataracts
What is the function of the endotheium of the cornea?
- secrete a basement membrane (Descemet’s layer)
- house ATP H2O pumps that remove water out of the stromal matrix to preserve structure & Clarity
