Ocular Anatomy / Physiology Flashcards
a CN X lesion will have what effect in the mouth? How does this compare to a CN XII lesion?
CN X: Uvula will pull away from side of lesion
CN XII: Tongue pushes towards the side of lesion
What are the three possible destinations for a ganglion nerve fiber coursing through the optic nerve? What do these destinations control?
LGN: Primary visual cortex
Superior Colliculus: Saccades
Pretectal Nucleus: Pupils
What does CN I control?
Smell
What does CN II control?
Vision
What does CN III control?
EOMS (superior rectus, inferior rectus, inferior oblique, medial rectus)
Pupil Size
Accommodation
What does CN IV control?
Superior Oblique
What does CN V control?
Facial sensation
Mastication
What does CN VI control?
Lateral Rectus
What does CN VII control?
Facial Expression
Anterior 2/3 taste
Salivation (Submaxillary, Submandibular)
Lacrimation
What does CN VIII control?
Hearing
Balance
What does CN IX control?
Swallowing
Salivation (Parotid)
Posterior 1/3 taste
Monitor carotid sinus
What does CN X control?
Taste (epiglottis)
Palate elevation
Talking
Thoracoabdominal viscera
What does CN XI control?
Shoulder movement
What does CN XII control?
Tongue movement
The medial longitudinal fasciculus connects what four cranial nerves?
CN III, CN IV, CN VI, CN VIII
What sub-nucleus of CN III decussates to innervate the contralateral muscle?
Superior Rectus
Sub-nuclei for IR, IO, and MR go to ipsilateral muscle
What is unique about the levator sub-nucleus?
There is only ONE sub-nucleus for BOTH levators
What are the divisions of the CN III?
Superior - Superior Rectus and Levator, Sympathetic fibers (Muller’s muscle)
Inferior - Inferior Rectus, Inferior Oblique, Medial Rectus
What structures do the fibers of CN III travel with as they course from the sub-nuclei to their respective muscles?
Sub-nuclei in Brainstem -> PCOM Artery -> Cavernous Sinus -> Superior Orbital Fissure
Where do sympathetic fibers join CN III? Where do they come from? What division of CN III do they join?
Superior division of CN III receives sympathetic fibers from the ICA in the cavernous sinus
Where do parasympathetic fibers join CN III? Where do they come from? What division of CN III do they join?
Inferior division of CN III receives parasympathetic fibers from the EW nucleus
What would happen to the eye in a complete CN III palsy?
Severe ptosis. Eye would be DOWN and OUT.
Pupil involved CN III palsy is most likely due to ______. Pupil-sparing CN III palsy is most likely due to ______.
Pupil-involving CN III palsy -> PCOM and ICA junction (tumor / aneurysm)
Pupil-spring CN III palsy -> Microvascular ischemia (DM / HTN)
What is unique about the course of CN IV?
Exits DORSALLY from the midbrain (at the level of the inferior colliculus) and decussates to innervate the CONTRA superior oblique
The ______ connects the sub-nucleus of CN IV to the visual cortex through the _________
The tectobulbar tract connects the sub-nucleus of CN IV to the visual cortex through the superior colliculus
Damage to the LEFT CN IV sub-nucleus will cause a _____ superior oblique palsy and _____ head tilt
Damage to the LEFT CN IV sub-nucleus will cause a RIGHT superior oblique palsy and LEFT head tilt
The anatomical origin of the superior oblique is the _______, the physiological origin is the _______
Anatomical origin - lesser wing of sphenoid
Physiological origin - trochlea
What is the Arden Ratio? What value is considered normal?
EOG measurement of the differences in the RPE response under light and dark conditions
normal Arden Value = Greater than 1.80
What do the waves of an ERG correspond to?
A-wave?
B-wave?
C-wave?
A-wave: Photoreceptors
B-wave: Bipolar and Amacrine cells
C-wave: RPE
How fast will a healthy visual cortex respond to visual stimuli in a healthy patient?
Less than 100 msec
Henle’s nerve fiber layer in the Macula is another name for what layer in the retina?
Outer Plexiform Layer
The synaptic endings of rods are called ______ while the synaptic endings of cones are called ______
Rods - Spherules (smaller are more “sphere”-like)
Cones - Pedicles (larger and flatter like a “pedestal”)
How long does it take for a demarcation line to become present after a retinal detachment stabilizes?
3 months
What is the patellar fossa?
Depression of the vitreous which abuts the posterior surface of the lens
What is the name of the additional retinal layer that many nocturnal vertebrate animals posses that functions to enhance visual sensitivity at low light levels?
Tapetum Lucidum
Cone photoreceptors are neatly organized in what type of arrangements in the macula?
Hexagonal
What are the three photopigment in cones? What are their peak wavelength absorbency?
Erythrolabe - 565 nm
Chlorolabe - 535 nm
Cyanolabe - 430 nm
What branch of the nasociliary nerve carries sympathetic fibers to the dilator muscle of the iris?
Long Posterior Ciliary Nerves
Increase intracranial pressure will most likely affect which cranial nerve first?
CN VI
Where is the lacrimal artery, lacrimal nerve, and ciliary ganglion in relation to CN VI in the orbit?
Lacrimal nerve and artery - superior to CN VI
Ciliary ganglion - medial to CN VI
Why does a CN VI palsy with ipsilateral horner’s localize to the cavernous sinus?
ICA aneurysm in the cavernous sinus will compress CN VI and sympathetic fibers
What is the difference between the facial manifestations of Bell’s Palsy and a stroke?
Bell’s Palsy - IPSI LMN lesion -> entire side of face is affected
Stroke - CONTRA UMN lesion -> only lower side of face is affected
What nerve carries the final parasympathetic innervation to the pupillary sphincter muscle and ciliary body?
What nerve carries the final sympathetic innervation to the pupillary dilator muscle?
SPCN - Pupillary sphincter and ciliary body
LPCN - Pupillary dilator
Wha is the Canal of Hannover?
Between anterior and posterior lens zonules over the equator. Contains equatorial zonules.
What is the Canal of Petit?
Between posterior zonules and anterior hyaloid membrane and ciliary body
Iris cysts can develop if there is a separation between what two layers?
Anterior and posterior pigmented iris epithelium. Typically they are joined apex to apex by desmosomes and microvilli.
What layer of the ciliary body secretes aqueous humor?
Non-pigmented ciliary body of the pars plicata
What are the valley of Kuhnt?
Heavily pigmented areas located between the ciliary processes
What produces lens zonules?
Pars Plana
_____ produces zonules, which travel through _____ before inserting on the _______
Pars plana NPCE produces zonules, which travel through the Valley of Kuhnt and insert onto the lens capsule
What is the Supraciliaris?
Potential space! Outermost layer of the ciliary body that is loosely attached to the underlying sclera
What structures must nerves and blood vessels travel through to get from the choroid to the anterior portion of the eye?
Choroid -> Suprachoroid -> Supraciliaris -> Anterior portion of eye
*Suprachoroid is continuous with supraciliaris at the ora serrata
Where does fluid accumulate in a ciliary body detachment?
Supraciliaris
What is the largest intrinsic muscle of the eye?
Ciliary muscle
The ciliary muscle is anchored anteriorly by what structure?
Scleral spur
What are the Longitudinal muscle fibers of the ciliary muscle also known as?
Longitudinal muscle fibers of Brucke
What comprise the largest proportion of CM fibers?
Longitudinal muscle fibers (of Brucke)
What is Muller’s annular muscle?
Most medial portion of the ciliary muscle. Has a similar action as pupillary sphincter of iris.
What are the two routes aqueous can take once it reaches schlemm’s canal?
SC -> short efferents -> deep scleral venous plexus -> intrascleral venous plexus -> episcleral venous plexus
OR
SC -> veins of Ascher -> episcleral venous plexus
Schwalbe’s line represents the termination of what structure?
Descemet’s Membrane
Name the structures seen on gonioscopy from most posterior to most anterior
"I Can't See This Stupid Shit, Seriously" Iris Ciliary Body Band Trabecular Meshwork Scleral Spur Schwalbe's Line Sampolesi's Line
What is the internal scleral sulcus?
Fancy name for the angle: the cornea-slcera junction
What is the Becker-Shaffer grading system?
Grade 0 - No structures visible Grade 1 - Anterior aspect of TM Grade 2 - 1/2 to 1/3 of TM Grade 3 - Scleral Spur Grade 4 - Ciliary body
What are the only two parts of the sclera that contain elastin?
Scleral Spur
Lamina Cribosa
The TM is triangular in shape, with the base of the triangle abutting the _____ and the apex pointing towards the _____
The TM is triangular in shape, with the base of the triangle abutting the scleral spur and the apex pointing towards the cornea
What portion of the angle typically has the greatest amount of pigment?
Inferior TM
Aqueous is transported from the JXT to schlemm’s canals through ______
Giant vacuoles?
Schlemm’s canal often contains multiple channels formed by CTT septae that increase the surface area for aqueous filtration. These channels are known as _______
internal collector channels
Posterior Embryotoxin represents an anteriorly displaced _______
Schwalbe’s line
The pupil is not in the center of the iris. How is it displaced?
Inferior and nasal to center
What are Schwalbe’s contraction furrows?
Variations in the thickness of the posterior pigmented iris epithelium
Where is the iris thickest?
Collarette
What are the Crypts of Fuchs?
Depressions / openings near the collarette of iris
What zone of the iris is expected to have radial streaks? What are these radial streaks? What color are they?
The ciliary zone of the iris has radial streaks that are white and represent collagen traveling along iris vessels
Which is bigger…. The anterior iris stromal leaf or the posterior iris stromal leaf?
Posterior Iris Stroma Leaf
Is Aniridia bilateral or unilateral? What condition is it mostly associated with? What other conditions is it associated with?
Bilateral
Associated with Glaucoma
Also a/w foveal hypoplasia, nystagmus microcornea, lens subluxation, optic nerve hypoplasia
What makes an eye blue?
Thin anterior border layer
Melanocytes contain a small amount of melanin
What is the only condition characterized by a lack of pigment within the iris epithelial layers?
Oculocutaneous albinism
The non-pigmented CB epithelium is continuous with what layer of the iris?
The non-pigmented CB epithelium is continuous with the posterior pigmented iris epithelium
Keratic Precipitates are made of what two types of cells?
Macrophages
Epithelioid Cells
The ciliary body is triangular in shape and its apex points towards the _______
ora seratta
What is Vossius’s Ring? What can cause this?
Annular ring of iris pigment on the anterior lens capsule.
Trauma, Posterior Synechiae
What is the difference between Dalen-Fuchs, Busacca, Koeppe, and Berlin Nodules?
Koeppe Nodules - Pupillary border
Busacca Nodules - Mid-Iris border
Berlin Nodules - Anterior Angle
Dalen-Fuchs Nodules - Chorioretinal lesions
What vitamin interferes with vitamin A absorption?
Vitamin E
What is Salus’s sign? Bonnet Sign? Gunn Sign? What are they all indicative of? What grade do they represent?
Salus’s sign - venule changes course due to arteriolar hardening. Grade 2.
Bonnet sign - banking of the venule around the arteriole. Grade 3.
Gunn sign - tapering of the venule around a hardened artery. Grade 3.
What is HYPERfluorescent on FFA?
Neovascularization (retinal, CNVM), CME, Central Serous, PED, RPE dropout
What is the classic “triad” of Retinitis Pigmentosa?
Arteriolar Attenuation, Waxy ONH pallor, Bone-Spicule Pigmentation
What is the most likely place that a Hollenhorst plaque comes from?
ICA
Order Carotid-Doppler ultrasound
What layers of the LGN contain Magno fibers? What layers contain Parvo fibers?
Layers 1 and 2 = MAGNO
Layers 3, 4, 5, 6 = PARVO
The cornea gets the majority of its glucose from ______
Aqueous
What bone of the orbit is the thinnest? What bone is the weakest?
Thinnest - ethmoid
Weakest - maxillary
