final content/learning not covered

trace the arterial supply pathway from the heart to the ophthalmic artery.

aortic arch → common carotid artery → internal carotid artery → carotid canal → cavernous sinus → ophthalmic artery (enters orbit through the optic canal, inferolateral to cn ii)

what are the ocular and orbital branches of the ophthalmic artery

ocular is central retinal artery, spca, lpca and orbital is muscular branches, lacrimal artery, supraorbital, supratrochlear, ethmoidal

what are the ocular and orbital branches of the ophthalmic artery

ocular is central retinal artery, spca, lpca and orbital is muscular branches, lacrimal artery, supraorbital, supratrochlear, ethmoidal

what does the ocular (central retinal artery, spca, lpca) of the ophthalmic artery supply

inner retina, choroid for outer retina and optic nerve head via circle of zinn-haller, ciliary body and iris through major arterial circle of iris

what does the orbital branches (muscular branches, lacrimal artery, supraorbital, supratrochlear, ethmoidal) of the ophthalmic artery supply

anterior ciliary arteries, lacrimal gland and lateral lids, forehead nose ethmoid sinuses

why is the venous drainage of the eye and orbit clinically dangerous

veins are valveless, so blood and infection can flow in either direction (e.g., facial infections spreading intracranially)

trace the venous drainage leaving the cavernous sinus

cavernous sinus → superior and inferior petrosal sinuses → sigmoid sinus → internal jugular vein

what are the 3 layers of the meninges and their functions

dura mater tough, fibrous outer layer providing mechanical protection and forming dural venous sinuses. arachnoid middle avascular web-like layer housing the subarachnoid space containing csf and major cerebral vessels and arachnoid granulations for csf reabsorption. pia delicate, vascular inner layer adhering directly to the brain/spinal cord surface, following gyri and providing metabolic support

trace the production and ventricular circulation of csf

choroid plexus (mainly in lateral ventricles) → lateral ventricles → interventricular foramina of monro → third ventricle → cerebral aqueduct through midbrain → fourth ventricle (behind pons and medulla)

trace the subarachnoid circulation and absorption of csf

fourth ventricle → median (magendie) and lateral (luschka) apertures → subarachnoid space (around brain, spinal cord, and optic nerves) → arachnoid granulations → superior sagittal sinus → internal jugular vein

what are the 3 tear film layers and their anatomical sources

outer lipid from meibomian and glands of zeis, middle aqueous from lacrimal and accessory glands of krause and wolfring (basal tearing), inner mucin from goblet cells and corneal/conjunctival epithelial glycoalyx

what are the functions and failure consequences of the lipid tear layer

retards evaporation, smooths the anterior optical surface, seals the lid margin during sleep. meibomian gland dysfunction causing evaporative dry eye

what are the functions and failure consequences of the aqueous tear layer

oxygen and nutrient transport to avascular cornea, antimicrobial defense, flushes debris. lacrimal deficiency causing aqueous-deficient dry eye.

what are the functions and failure consequences of the mucin tear layer

converts the hydrophobic corneal epithelium into a hydrophilic (wettable) surface, traps and removes debris. goblet cell loss causing poor wetting and rapid tear break-up time (tbut)

describe the location and structure of the cavernous sinus

paired dural venous sinuses located on either side of the sella turcica and sphenoid body, extending from the superior orbital fissure to the petrous temporal bone. it is a trabeculated venous network lined by endothelium

what is the blood supply and drainage structures of cavernous sinus

superior/inferior ophthalmic veins, central retinal vein, sphenoparietal sinus, superficial middle cerebral vein draining to superior/inferior petrosal sinuses and pterygoid plexus

blood–brain barrier (bbb) structure

tight junctions between capillary endothelial cells, supported by astrocyte end-feet and pericytes

inner blood–retinal barrier (ibrb) structure

tight junctions between retinal capillary endothelial cells, supported by astrocytes and müller cell processes

outer blood–retinal barrier (obrb) structure

tight junctions between retinal pigment epithelial (rpe) cells

blood–aqueous barrier structure

tight junctions in the non-pigmented ciliary epithelium (npce) and non-fenestrated iris vessels

what are the visual/oculomotor functions of the superior colliculus

saccades, smooth pursuit, vergence

what are the visual/oculomotor functions of the pretectal nucleus

pupillary light reflex, smooth pursuit, accommodation reflex

what are the visual/oculomotor functions of the cn iii oculomotor nucleus

innervates all extraocular muscles except so (cn iv) and lr (cn vi), plus levator palpebrae superioris

what are the visual/oculomotor functions of the edinger–westphal nucleus

parasympathetic nucleus driving the accommodation reflex and pupillary constriction via ciliary muscle and sphincter pupillae

trace the afferent pathways of the corneal (blink) reflex

touch cornea → long ciliary nerves → nasociliary nerve (v1) → trigeminal ganglion → spinal trigeminal nucleus (pons/medulla)

trace the efferent pathways of the corneal (blink) reflex

interneurons project bilaterally to both facial nuclei (pons) → cn vii on both sides → palpebral orbicularis oculi → both eyes blink (direct and consensual)

how do you localize a lesion in the corneal blink reflex (right v1 vs right vii)

in right v1 lesion touching right cornea cause no blink in either eye but touching left cornea cause both eyes blink. in right vii lesion touching either cornea cause only the left eye blinks (right eye cannot close)

what are the anatomical features and fiber types of the long ciliary nerves

branches of nasociliary nerve, pierces sclera near optic nerve and contains sensory fibers from cornea, conjunctiva,limbus, and anterior sclera, postganglionic sympathetic fibers "hitchhiking" to the dilator pupillae (has no autonomic fibers of its own)

what are the anatomical features and fiber types of the short ciliary nerves

emerge from ciliary ganglion, pierces sclera around the optic nerve and contains sensory fibers from iris, ciliary body, and choroid, postganglionic parasympathetic fibers to ciliary muscle and sphincter pupillae, sympathetic fibers passing through to choroidal blood vessels

trace the parasympathetic pathway for pupil constriction and accommodation

edinger–westphal nucleus (midbrain) → cn iii (inferior division → nerve to inferior oblique) → ciliary ganglion (synapse) → short ciliary nerves → sphincter pupillae (miosis) and ciliary muscle (accommodation)

trace the parasympathetic secretomotor pathway for reflex tearing

superior salivatory nucleus (pons) → cn vii (nervus intermedius) → greater petrosal nerve → nerve of the pterygoid canal → pterygopalatine ganglion (synapse) → zygomatic nerve (v2) → lacrimal nerve (v1) → lacrimal gland

trace the 3-neuron sympathetic pathway to the eye and list its 4 target effectors

1st order: hypothalamus → descends brainstem/cervical cord → ciliospinal centre of budge (c8–t2, synapse). 2nd order: exits at t1, crosses lung apex, ascends sympathetic chain → superior cervical ganglion (synapse). 3rd order:ascends on ica → cavernous sinus → joins v1 (nasociliary) → long ciliary nerves. targets dilator pupillae, superior tarsal / müller’s muscle, sweat glands of face (via external carotid), orbital blood vessels (vasoconstriction)

list all ocular structures derived from surface ectoderm

lens, corneal epithelium, conjunctival epithelium,eyelid epidermis and its glands (meibomian, zeis, moll), lacrimal gland, and the entire lacrimal drainage apparatus

list all ocular structures derived from neuroectoderm (optic vesicle and cup).

neural retina, retinal pigment epithelium (rpe), optic nerve axons and glia, both layers of the ciliary epithelium (pigmented and non-pigmented), both layers of the iris epithelium, and the sphincter and dilator pupillae muscles

list all ocular structures derived from neural crest (mesectoderm)

corneal stroma and endothelium,trabecular meshwork, most of the sclera, choroidal stroma and melanocytes, ciliary muscle, iris stroma and melanocytes, optic nerve meninges, and most orbital connective tissue and bone

list all ocular structures derived from mesoderm and endoderm

extraocular muscles, all vascular endothelium (including hyaloid system), endothelium of schlemm’s canal, temporal sclera contribution, vitreous contribution. nothing for endoderm

discuss conventional aqueous outflow

80–90% share, trabecular meshwork → juxtacanalicular tissue (main resistance) → schlemm's canal → collector channels → aqueous/episcleral veins, pressure-dependent, ciliary muscle contraction pulls scleral spur to open meshwork and increase outflow

discuss unconventional aqueous outflow

10–20% share (declines with age), between ciliary muscle bundles (main resistance) → supraciliary/suprachoroidal spaces → across sclera to orbital vessels, pressure-independent, ciliary muscle contraction closes spaces and decreases outflow

what is the composition of the vitreous and its 3 main attachment sites

~99% water with collagen fibrils and hyaluronan. attached at the vitreous base (strongest), margin of the optic nerve head, and the fovea/macula

why can a posterior vitreous detachment (pvd) cause a retinal tear

as the vitreous liquefies and pulls forward, traction at its firm adhesion sites (especially the vitreous base) can tear the neurosensory retina

what are the 4 parts of the optic nerve and their key features

intraocular (optic nerve head) containing unmyelinated axons through lamina cribrosa, no meninges. intraorbital s-shaped and slack within muscle cone, covered by dura, arachnoid, and pia. intracanalicular dura fused to canal periosteum, fixed and vulnerable to trauma, travels with ophthalmic artery. intracranial covered by pia only, runs to chiasm above sella turcica (vulnerable to pituitary/circle of willis lesions)

trace the visual pathway from the optic chiasm to the primary visual cortex

nasal retinal fibers decussate (cross) at the chiasm while temporal fibers stay uncrossed, optic tract, synapse at lateral geniculate nucleus (lgn), optic radiations, primary visual cortex (v1) in the occipital lobe

what are the 3 tunics of the globe and what structures belong to each

outer fibrous tunic cornea and sclera, middle vascular tunic (uveal tract) iris, ciliary body an choroid, inner nervous tunic retina (rpe and neurosensory retina)

what are the main axes and dimensions of the globe

optical axis poles of cornea and lens, visual axis fixation point to fovea, pupillary axis perpendicular through pupil center, undergoes rapid growth from birth to puberty

what is the pathway and response of the near triad

stimulus (blur/disparity), visual cortex, near-response center. convergence (medial recti contract via cn iii), accommodation (ciliary muscle contracts, zonules slacken, lens rounds up), miosis (sphincter pupillae contracts for pinhole effect)

compare the afferent and central pathways of the pupillary light reflex vs near reflex

in light reflex afferent via retina/optic nerve/tract to pretectal nucleus (bypassing lgn), producing a bilateral consensual response. near reflex, cortical input (v1/association areas) to edinger-westphal and medial rectus subnuclei, driving the full near triad

what is light–near dissociation and what are its main causes

loss of the pupillary light reflex with preserved near constriction response causes include argyll robertson pupil (neurosyphilis), adie's tonic pupil, and dorsal midbrain syndrome

how do you differentiate horner's syndrome, cn iii palsy, adie's pupil, and rapd

horner's is sympathetic lesion causing miosis (worse in dark), ptosis, anhidrosis. cn iii palsy is parasympathetic/motor lesion causing fixed dilated pupil, severe ptosis, "down and out" eye. adie's tonic pupil is ciliary ganglion damage causing large slow-reacting pupil, hypersensitive to dilute pilocarpine. rapd is optic nerve/retinal lesion causing reduced direct constriction compared to consensual

compare the sphincter pupillae and dilator pupillae muscles (innervation, receptor,pharmacology)

sphincter pupillae has circular fibers, parasympathetic (cn iii), muscarinic receptors, constricted by pilocarpine, dilated by tropicamide/atropine. dilator pupillae has radial fibers, sympathetic (long ciliary nerves), a1-adrenergic receptors, dilated by phenylephrine

what are the regions of the ciliary body and the 3 ciliary muscle fiber groups

pars plicata (anterior with ciliary processes) and pars plana (posterior flat zone) and longitudinal (meridional), radial (oblique) and circular

why does accommodation fail with age (presbyopia)

progressive hardening and sclerosis of the crystalline lens and capsule, causing it to lose elasticity and fail to round up despite normal ciliary muscle contraction

what determines intraocular pressure (iop) and how do main glaucoma drug classes work

iop depends on aqueous production rate, outflow facility and episcleral venous pressure. prostaglandin analogues increase uveoscleral outflow, beta-blockers & alpha-2 agonists decrease aqueous production, carbonic anhydrase inhibitors reduce aqueous secretion, miotics/rho-kinase inhibitors increase conventional trabecular outflow

how is the lateral geniculate nucleus (lgn) structured and how does it segregate visual input

6-layered structure with temporal fibers go to layers 2, 3, 5 and nasal fibers go to layers 1, 4, 6 to create a precise point-to-point retinotopic map

compare magnocellular vs parvocellular lgn layers

magno (layers 1–2) have large receptive fields, low resolution, motion, luminance, rod vision. parvo (layers 3–6) have small receptive fields, high resolution,color (l/m cones), form, visual acuity

what are the optic radiations and how do superior vs inferior visual fields project

axons from lgn to v1. inferior visual field fibers travel through the parietal lobe and superior visual field fibers loop anteriorly through the temporal lobe (meyer's loop)

what are the structural and functional features of the primary visual cortex (v1)

located in the occipital lobe around the calcarine sulcus, ~2 mm thick with 6 layers (lgn inputs end in layer 4c). organized into retinotopic maps, cortical magnification (macula takes up half), ocular dominance columns, orientation columns, cytochrome-oxidase blobs, and hypercolumns