• choroid coat
• ciliary body (ciliary muscle, ciliary process)
• iris

Anterior & Posterior

filled with aqueous humor

Anterior = b/n cornea & iris

Posterior = b/n iris & lens

• renewed continuously
• formed as blood filtrate
• supplies nutrients to lens & cornea

• ring muscle called Ciliary muscle
• Ciliary processes - folds located @ posterior surface of c.b.
• Ciliary Zonule - suspensory ligaments attached around entire circumference of lens

• epithelium secretes aqueous humor
• smooth muscle allows changing in lens shape
• suspensory ligaments position lens so light passing through pupil passes through center of lens

• nourishes cornea (corneal endothelium, stroma, lens, & iris)
• secreted into posterior chamber, flows around iris through pupil to angle b/n cornea & iris

Pars plicata (anterior)

Pars plana (posterior)

• produced by the epithelium of the pars plicata
• secreted into the posterior chamber from ciliary processes

• lined by endothelium with pores & without tight junctions
• very permeable to macromolecules

• Pigmented epi: facing C.B. stroma
• Nonpigmented epi: facing posterior chamber (faces fluid)

the two layers of epi. are joined apex to apex 

• lies w/n "angle" of anterior chamber
• b/n scleral spur & Schwalbe's line (aka end of Descemet's membrane) 

anterior: "nonpigmented"

posterior: "pigmented"; concerned with drainage

• outcropping, thickening of sclera
• rigid with firm attachment to choroid & ciliary muscle & TM chords
• action of longitudinal muscle (C.B.) during accommodation opens TM lessens reistance to aqueous outflow

• drains aqueous
• regulates IOP -(TM is compliant & resilient; responds to functional change)
• filter - (rid of inflammatory cells, pigment, red blood cells)

• central core of type I & III collagen & elastin
• cortical zone of type III, V, & VI collagen, laminin, fibronectin

• no mitosis
• similiar repair process to corneal endothelium
• cells joined by tight junctions & gap junctions

pores

pores in each lamina not "lined up"

1. uveal meshwork
2. corneal scleral portion
3. juxtacanalicular or cribiform meshwork

• inner portion closest to aqueous
• TM cords arise from uveal tract (root of iris & C.B.)
• contains large irregular spaces (100μ) b/n cords

• cords attach to SS
• end near Schwalbe's line
• holes progressively smaller toward Schelmm's canal
• small holes: particles of 1.5-3.0μ can pass

• most significant barrier to flow
• separates fluid filled spaces of TM & canal of Schemm's 
• several layers includes endothelium of TM (tight junctions) & Schemm's canal

• no major outflow resistance here
• most aqueous pass via vacuoles

1. Diffusion - passive; does not need ATP
2. Ulta filtation - passive; does not need ATP
3. Active secretion - needs ATP

• pressure gradient
• filtrate composition*
• area of membrane*
• pore size of the membrane*

* = passive

____ is actively transported into the posterior chamber by the _________________________, 

results in ______ following from the stromal pool into the _________________.

Conventional Outflow &

Unconventional Outflow/Uveoscleral Outflow

• accommodation
• pull scleral spur & stretch Trabecular meshwork; increases outflow 

• sympathetic - aqueous production
• parasympathetic - causes ciliary body muscle movement & drainage 

• Na⁺/K⁺ ATPase
• Carbonic anhydrase

• Epithelial & endothelial blood aqueous barrier (BAB)
• the active transport of organic & inorganic substances by the ciliary epithelium 

• low protein
• high ascorbic acid concentration (protects anterior structures from UV light)
• high lactate
• high Cl^- ions
• high in some amino acids 

• Phthisis bulbi (eye shrinking) if IOP is too low
• Glaucoma when IOP is too high

• ciliary processes 
• non-pigmented epithelium
• inner wall of the canal of Schlemm (endothelium)
• iris vasculature

• Anterior face (non-epithelial)
• stroma

cell types: melanocytes & fibroblasts

collagen, vessels, & nerves

• anterior epithelial (dilator & sphincter muscle)
• posterior pigmented epithelial

• meaning different colors
• bilateral asymmetry
• can either be congenital (benign) or acquired (pathologic)

• Horner's syndrome
• Melanoma (very aggresive cancer)
• drug-induced change in melanin
• vascular change

ptosis (Mueller's muscle; CN III & VII), miosis (pupil constriction); anhydrosis (sweats less) --->

light colored iris b/c sympathetics

• in Caucasians; stroma relatively free of pigment at birth
• if stroma doesn't develop pigment in anterior stromal layers, iris remains blue
• if stroma becomes denser (w/ significant melanosomes); iris appears gray

• radial pattern
• tight endothelial junctions (not leaky)
• long posterior & anterior ciliary arteries merge w/n ciliary body to form circulus vasculosus iridis major

• choroid (ciliary artery that nourishes external part of the retina)
• center retinal artery (nourishes internal retina)

both come from ophthalmic artery; artery can be blocked if there is a clot in your heart

• veins of iris transmit blood back to the vortex veins
• blood vessels compromise bulk of iris stroma & can be found traveling through stroma in a sinusoidal yet radial manner (flexibility for contraction/dilation)

• collarette
• crypts of Fuchs
• contraction folds
• pupillary ruff (frill)

• about 1.5 mm from pupil margin, there is a scalloped line which is the collarette iris
• point at which pupillary membrane is attached during embryonic development
• is formed from the underlying circulus vasculosus iridis minor

• ciliary zone or greater ring of Merkel (peripheral)
• pupillary zone (central)

• from the major arterial circle (w/n the ciliary body)
• to the minor vascular circle (in the collarette)

• channels where the aqueous flow during contraction and dilation of the iris
• allow the stroma & deeper iris tissues to be bathed in aqueous humor 

Ciliary zone also shows _________ lines called

__________ _______ and are made up of folds of iristissue whose _______ form furrows.

Ciliary zone also shows concentric lines called

contraction furrows and are made up of folds of iris tissue whose valleys form furrows.

• embryonic development: pupillary zone is filled w/ pupillary membrane (4 months gestation)
• 8 months: p. membrane regresses due to atrophy of iris tissue resulting from cessation of circulation centrally
• birth: many have remnants of p. membrane
• adult: remnants of p. membrane can be observed under slit lamp observation

• decrease in pupil diameter/contraction: miosis
• increase in pupil diameter/dilation: mydriasis
• controls illuminance; protective (miosis to light0
• depth of focus (miosis w/ accommodation)

• pupil wide open: max light; brightness but very little depth of field
• pupil mostly closed: very dim image, but very large depth of field similar to pinhold; decreases spherical aberration

• assessment of the patient's neurological function, including coma & brain death 
• diameter & movement under different lighting evaluates integrity of anterior visual pathways & autonomic nervous system

• pupillary dilator - sympathetic 
• iris sphincter & ciliary muscle - parasympathetic

• abberations
• color fringes
• extreme photophobia in cases of fixed dilated pupils

• physiologic
• autonomic nerve lesion to iris (unilateral)
• trauma to sphincter
• pharmacological mydriasis or miosis
• sequelae from intraocular inflammation or induced by surgery ("+" shaped) 

1. sensory to the CNS (nasociliary branch of V1) -receives sensations
2. vasomotor to ciliary body & iris (sympathetic) -decreases diameter of blood vessels
3. chromatophores of the iris (sympathetic)         -iris color
4. pupillomotor postganglionic fibers to dilator pupillae (sympathetic)                                     -preganglionic fibers orginate in ciliospinal center of Budge
5. pupillomotor from ciliary ganglion to sphincter pupillae (parasympathetic)                    -preganglionic fibers originate in Edinger-Westphal nucleus w/n mesencephalon

near & light response share common efferent pathway

• Edinger-Westphal nucleus (parasympathetic fibers travel w/ CN III)
• ciliary ganglion synapse
• short ciliary nerves
• sphincter

• superior cervical ganglion in neck
• sympathetic plexus at carotid artery
• ophthalmic division of trigeminal nerve
• long ciliary nerves
• dilator

• afferent (photoreceptors; bipolar; ganglion)
• interneuronal 
• efferent 

• photoreceptors in retina
• to optic nerve & chiasma where nasal fibers cross
• to optic tract
• to midbrain
• to pretectal nucleus (***important!)
• to both right & left Edinger-Westphal (parasympathetic) nuclei bia crossed & uncrossed connections

• Edinger-Westphal nuclei via preganglionic parasympathetic axons along oculomotor nerve to synapse @ ciliary ganglion in each oribt
• to postganglionic parasympathetic fibers that travel in short ciliary nerves
• to sphincter muscle

• cortex to oculomotor nucleus
• to E-W nucleus (bypass the brain stem)

• efferent pathway for the light and near reflex are identical 
• input to the E-W nucleus is different               -light relay in brain stem                                               -near bypass the brain stem 

1. pupil sphincter must relax
2. dilator muscle contracts 

two muscles are antagonistic; impossible to constrict both at the same time

Hering's law

• direct, consensual response to light & near response (any reflex observed on one side of the body when other side has been stimulated)
• light response > near is normal
• near response > light is abnormal 

• useful to monitor health of retina, optic nerve, and to detect disease
• most common clinical test is "swinging flashlight test"                                                 -light alternated b/n eyes & pupil movement in response to light is observed 

• movements similar with alternated light = retinal & optical nerve inputs are matched 
• pupil response to light is attenuated due to diseases that affect retina & optic nerve is referred to as "relative afferent pupillary defect" (RAPD)

• all but 1 layer is dying or dead, but original fibers remain in lens in isolation surrounded by capsule (deprived of contact w/ any other living or dead cell)
• no blood supply or innervation 

• function is cell division & transport processes
• basement membrane secreted on outside
• mitosis of epi. cells forms new fibers
• fibers elongate & migrate to anterior & posterior poles

• secreted by epithelial cells 
• thickest basement membrane of body
• thickest near equator 

• function is to mold lens in response to zonular tension
• elastic - 80% water, 10% GAG (proteoglycan)

• tight fibers, not much extracellular space
• lens grows (inc # of fibers) each year
• fibers elongate, lose nuclei & organelles as pushed to center of lens 

• 84% of lens thickness
• minimal metabolism 

• from basement membrane of ciliary body nonpigmented epithelium (NPE) to lens capsule 
• run along pars plana
• anchor w/ "tension zonules" to valleys of pars plicata (forms fulcrum or sling)
• attach at thickest part of capsule

• 33% protein (gives high refraction index for lens power)                                                     -85% water soluble (mostly crystallins; α, β, & λ)                                                               -15% insoluble (mostly albuminoids in nucleus; increase with age)
• 66% water; most water protein bound & non-diffusable 

1. central - (greatest density); proliferation only in pathological condition
2. proliferative - (germinating); pre-equatorial zone; stem cell population
3. transitional equatorial - (elongate, rotate axis, differentiate, produce crystallin); newly formed cells form pool 

• optical: transparency (crystallins) & refractive
• accomodation: dynamic focal plane
• protective: absorb damaging UV-B & UV-A

• 1/3 total dioptric power of unaccommodated eye                                                                     -requires high protein content; not an air interface
• anterior parabolic curvature (flattens from poles to equator)
• posterior parabolic curvature steeper

• dense packing of fibers gives uniformity in distribution & arrangement
• constructive interference
• protein - spatial organization of crystallins is important

• has complex muscle arrangement so not well understood anatomical or functional division
• 1 muscle subdivided vs. 3 separate muscles; all insert at one end to scleral spur 

• unique smooth muscle that resembles striated
• net movement of C.M. w/ accommodation is inward & forward

longitudinal

circular

radial 

Characteristics of the longitudinal

division of the C.M.:

• aka meridional or Brucke's 
• contains most fibers
• inserts posteriorly into choroid
• fwd shift of anterior choroid, retina
• opens trabecular meshwork (TM)

Characteristics of the Circular

division of the C.M.:

• aka Muller's 
• contains the least fibers
• sphincter action w/ contraction

Characteristics of the Radial

division of the C.M.:

• aka oblique
• all muscle b/n longitudinal & circular, not well defined

afferent - CN II

• parasympathetic - EW nucleus; ciliary ganglion; short ciliary nerve                                    -neural input for accommodation
• sympathetic - mostly to blood vessels

What is the major source of energy for lens epithelium?

a) Sorbital pathway

b) aerobic glycolysis

c) pentose shunt

d) anaerobic glycolysis

• when C.M. is relaxed: choroid acts like a spring pulling on lens via zonule fibers causing lens to become flat
• when C.M. contracts: C.M stretches the choroid, releasing tension on the lens & lens becomes thicker (accommodation)

• cell division
• protein synthesis
• cell differentiation
• cellular homeostasis
• transport
• protection from oxidative damage 

ATP 

78% by anaerobic glycolysis (2 ATP)

(aerobic limited mostly to epithelium)

• can survive in complete anaerobic conditions
• O₂ pressure around lens is 15 mmHg
• no blood supply
• most lactic acid produced diffuse into aqueous

• increase packing of crystallins & protein aggregation
• increase in insoluble protein                                        -youthh has 86-99% soluble protein
• redistribution of H₂O
• inc. intracellular free Ca²⁺

• range of accommodation decreases w/ age
• @ 45 yrs old, only 20% accom. left
• w/ age, lens enlarges & becomes rigid ---> inability to accommodate
• many theories to presbyopia; can be delayed for myopes

• Lenticular theory
• Extra-lenticular theory

• zonule theory - geometrical/mechanical linkage of zonule attachment (shift ant/post with age)
• ciliary muscle
• choroid

• rate of aqueous humor formation
• outflow resistance at the trabecular meshwork
• flow through the uveoscleral path

outflow resistance is often unusually high, resulting in elevated IOP

one of the major risk factors in the development & progression of glaucoma

• direct, intracameral pressure measurement
• only method that is capable of recording true IOP
• invasive - requires entering eye to measure pressure

manometry may be performed in conjunction w/ cataract surgery to calibrate new tonometer technology 

• clinical estimation of IOP
• indirectly measures IOP through walls of eye (cornea or sclera)
• measurements can be influenced by corneal thickness & other biomechanical properties of the eye

• screen for glaucoma
• detect wound leak in post-op & trauma case
• rule out acute glaucoma in red eye cases
• monitor effectiveness of glaucoma therapy

• each method has advantages/disadvantages
• attempts to measure IOP changes it; causes artificial rise in pressure
• influenced by biomechanical properties of coats of eye                                                     -corneal rigidity, thickness, & hysteresis

when flat surface applied to cornea w/ enough force (F) to produce a circular area of flattening exactly 3.06 mm in diameter

the opposing forces of scleral rigidity & tear film surface tension cancel each other out & applied force (F) becomes directly proportional to IOP

• many possible artifacts & sources of error 
• technician error, uncalibrated tonometer

• Diurnal variation, progression of disease
• IOP is dynamic (constantly changing) & each reading is at best a snapshot of IOP of a given eye

mean is 15.5 +/- 2.57 mmHg

15 is average

10-20 is range

22 and above is abnormally high

pressure which does not lead to glaucomatous damage of the optic nerve head

(**high pressure alone does not indicate glaucoma; must be optic nerve damage as well)

the value 22 mm Hg (>2 standard deviations above the mean)

misses up to half of the people with glaucoma

no, no clear level below which IOP can be considered normal/safe & above which IOP can be considered elevated/unsafe

yet elevation of IOP is important risk factor for development of glaucomatous optic nerve damage

• genetics
• age
• sex
• refractive error
• race

• diurnal & postural variation
• exertional influences
• lid & eye movement
• intraocular, systemic, & environmental conditions
• food & drugs

• hereditary control of IOP (polygenic & multifactorial)
• IOP higher in ppl w/ relative that has glaucoma
• IOP higher in ppl w/ larger C/D ratios

• IOP inc. w/ age (western countries); children have lower IOP
• IOP stable 20-40 yrs old, then rises after 40   -due to dec. outflow facility, cardiovascular factors, obesity, etc.
• reduction of outflow facililty of 7-10% per decade in man

• positive correlation with IOP, axial length, & myopia
• increased incidence of POAG in myopes

• IOP lower in full-blooded Native Americans in New Mexico
• African Americans have higher IOP

• inc. corneal thickess --> higher IOP readings w/ applanation tonometry
• dec. corneal thickness --> lower IOP readings w. applanation tonometry
• true IOP not correlated w/ corneal thickness (high reading, but not pressure)

• IOP subject to daily cyclic changes
• amplitude of change usually <5 mmHg (>10 considered pathological)
• time IOP peaks in any person is variable         -in most, IOP rises nocturnally & higher in morning & lower in evening

• IOP inc. from sitting to supine (laying down face up)
• avg. change b/n 0.3-0.6 mmHg
• postural changes greater in glaucoma patient
• mechanism is elevated episcleral venous pressure

• aerobic exercise (running, biking) & brief exercise (knee bends) lowers IOP
• exertional changes greater in glaucoma patients
• valsalva maneuver (forced exhalation when airways closed, as in weight lifting, playing brass instruments, swimming) raises IOP

• blinking can raise IOP up to 10 mmHg
• squeezing eye shut can raise IOP up to 90
• contraction of EOMs inc. IOP
• up gaze inc. IOP (more so in Graves disease)

• IOP affected by many ocular diseases
• many secondary glaucoma mechanisms are intraocular                                                       -pigmentary & neovascular glaucoma
• anterior uveitis & rhegmatogenous retinal detachment lower IOP

• positive correlation b/n short term changes in BP & IOP
• positive correlation w/ obesity, pulse rate, & hemoglobin concentration
• IOP lower in hyperthyroidism & higher in hypothyroidism 

• inc. IOP w/ caffeine (small transient) & tobacco (small transient due to elevation of episcleral venous pressure)
• dec. IOP w/ alcohol (dec. IOP 1-3 mmHg for several hrs) & marijuana (dec. IOP but not clincally useful due to short duration)

group of diseases that have in common a characteristic optic neuropathy (consisting of excavation & undermining of neural & connective tissue elements of optic disc) w/ associated visual function loss

(inc. IOP is only a primary risk factor)

• pathologic changes determined by level of IOP & resistance of optic nerve axons to pressure damage
• IOP can remain in statistically normal range in normal-tension glaucoma patients                         -Baltimore survey says 20% of glaucoma patients never had IOP >21
• IOP presumed too high for proper functioning of optic nerve axons so lowering will stabilize damage

• acts as aperature through which light passes to enter the eye
• size is continually adjusted in response to changes in ambient illumination
• size optimized to provide optimal retinal illumination & minimize optical aberrations

• caused by lesions affecting sympathetic or parasympathetic innervation to iris
• leads to anisocoria (unequal pupil size)

• caused by lesions to retina or optic nerve
• leads to relative afferent pupillary defect

• difference in pupil size of 0.4mm or greater
• may be caused by lesion in symp. or parasym. innervation to iris
• may be normal ("physiologic"); 20% of normal ppl can have it any given time & not due to lesion/abnormality
• may be drug induced (intentional or not; use of dilating drops) 

• parasym. fibers travel to eye via CN III
• lesions affecting oculomotor nerve produce dilated pupil that is not responsive to light or near stimuli
• other findings include strabismus, impaired ocular motility, & ptosis

• intracranial compressive lesions (tumor or aneurysm)                                                       -pupil dilated or fixed; requires neuroimaging (MRI/MRA) to identify lesion
• ischemia (diabetes or hypertension)               -pupil often NORMAL; condition is self-limiting & full recovery is normal 

• symp. fibers travel to eye via convoluted & complex pathway
• lesion anywhere along this pathway is HS
• characterized by miotic (small) pupil that is normally reactive, w/ slight drooping of upper lid (ptosis)
• can also be dec. sweating on affected side of face (anhyrosis)

• lung cancer (Pancoast's tumor)                       -chest MRI/CT scan required to identify lesion
• carotid artery dissection                                          -acute dilation of wall of carotid artery in neck  -vascular imaging required to confirm 
• idiopathic                                                         -most have no identifiable cause & require no treatment

• lesions of optic nerve associated w/ afferent pupillary defect but lesion along anywhere of afferent pathway can produce relative afferent pupillary defect (RAPD)
• RAPD detected clinically using swinging flashlight test

• pupils constrict in proportion to amount of light entering eye & the optic nerve signal of how much light is entering 
• if there is functional difference in # of optic nerve axons carrying impulse from each retina then light shined into eye w/ fewer axons causes less (bilaterally symmetric) pupil constriction than other eye

• humor that fills posterior chamber
• similar to aqueous in composition (amino acids & lactic acid)

• vascular origin - embryonic hyaloid artery
• canal of Cloquet runs from optic nerve to retrolental space of Berger
• lacks collagen fibers 

• begins after 9 weeks gestation
• usually complete, persists in 3% full term & 95% premature infants
• remnants are Mittendorf dot, Bergmeister papilla, & Persistent hyaloid artery

• major portion - lies outside primary vitreous (w/ primary constitutes 80% of globe)
• avascular origin produced by retina (Muller cells) & hyalocytes
• made of 99% water by weight, collagen, & hyaluronic acid

Is there a Tertiary Vitreous?

• anchoring fibrils that are firmly attached to ora serrata & capsule (Weiger's ligament)
• ILM (internal limiting membrane of retina)       -ILM = BM of Muller cells & contains several layers

• influence growth of eye to ideal size
• optical (90% light transmitted)
• support (retina to RPE), cushion/buffer
• nutritional & diffusional barrier

• 80-90% gel as chiild
• 50% gel & 50% liquid (liquefaction) by age 60
• this is a normal aging change

• common by age 65
• some risk of retinal detachment & bleeding
• can be partial or complete
• strong vitreous base attachment remains
• can cause floaters