Coordinated movement of ocular muscles Distributes tears over the cornea and conjunctiva Protects eye from potential danger

Ocular Anatomy Flashcards by Alexis Partee

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Coordinatedmovementofocularmuscles
Distributestearsoverthecorneaandconjunctiva
Protectseyefrompotentialdanger

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ANATOMYOFTHEEYELIDS:

Externalsurface‐coveredbyathinlayerofskin

Internalsurface‐linedwiththepalpebralportionofthe
conjunctiva,whichisavascularizedmucousmembranecontinuouswith thebulbarconjunctiva

Fornix:Spacewherethepalpebralandbulbarconjunctivaemeet

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Where is the fornix located?

Locatedsuperiorlyandinferiorlybehindtheupperandlowereyelids, respectively.

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TorF: Topicalmedicationsusuallyareplacedintheinferiorfornix,also
knownastheinferiorconjunctivalsac

True

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The lacrimal system consists of:

secretoryglandsandexcretory(nasolacrimal)ducts

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Thesecretorysystemincludes:

Lacrimalglandslocatedinthetemporalouterportionoftheorbit
Innervatedbytheautonomicnervoussystem

*Accessoryglands(alsoknownasKrauseandWolfringglands)
locatedintheconjunctiva

Meibomianglandslocatedposterior&inferiortotheeyelashes
Orificesofglandsposteriortoeyelashes -Secreteoilsthatretardevaporationofthetearfilm

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What are the 3 layers of tears?

ANTERIOR *lipid layer by meibomian glands

MIDDLE *aqueous layer by lacrimal glands and accessory lacrimal glands(Krause and Wolfring)

POSTERIOR * mucus layer by globlet cells

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TorF: the cornea is a multilayered hydrophilic epithelialbarriertoforeign matter,includingdrugs

False: MultilayedHYDROPHOBICepithelialbarriertoforeign matter,includingdrugs

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The limbus of the eye is the transitional zonebetweenthe:

Cornea and sclera

Consistsofseveralstructures,includingconjunctival
epithelium,Schlemm’sCanalandthetrabecularmeshwork

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TorF: The aqueous humor is formed in the anterior chamber

FALSE . Posterior chamber

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ANTERIORCHAMBER(AC)

cornea forms the roof of the chamber, Iris forms the base of the AC
Theanteriorchamberangleisformedbytheintersectionofthecorneaandiris
Holdsabout250µLofaqueoushumor(AH)

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The posterior chamber

Theposteriorsurfaceoftheirisformstheroof;anteriorsurfaceofthe lensandtheciliaryprocesses formthebase
Holdsapproximately50µLofaqueoushumor

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The uvea consists of

theirisandciliarybodyintheanteriorsegment

thechoroidintheposteriorsegment

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The iris

Separatesanteriorandposteriorchambers

Providescoloroftheeye

Muscular,circularstructureresponsibleforcontrollingthediameterandsizeofpupil,thusregulatingthe amountoflightpassingintotheeye

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CILIARYBODY

Consistsofciliarymusclesand,anteriorly,ciliaryprocesses

Ciliaryepithelialcellslineciliaryprocessesandformaqueoushumor whichfillstheposteriorandanteriorchambers

Ciliarymuscleschangetheshapeofthelenswhentheeyefocusesonanobject(accommodation)

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What is the conventional pathway: describe it

AH secreted by the capillaryplasmaintheciliaryepithelialcellsandreleasedintothe posteriorchamber(AHinflow)

•Passesthroughpupilintoanteriorchamber •Flowsthroughtrabecularmeshwork(TM)intotheCanalof Schlemm,eventuallyreturningtothesystemiccirculation

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Uveoscleral Pathway

AHdrainsfromthebaseoftheciliarymusclethroughtissuesin&aroundtheuvea,ultimatelypassingintothe sclera

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ROLEOFAQUEOUSHUMOR

• Helpsmaintainintraocularpressure(IOP)andthe
eye’sshape

• Servesasarefractivemedium

• Providesmetabolicsubstratestoavascular
structuresoftheeye(lens,cornea)

Carriesawaymetabolicwastes
Facilitatesthedistributionofsomedrugs

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ElevatedIOPisusuallyduetoincreasedresistanceto

outflow(Trabecular meshworkdysfunction)

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Innervatestheciliarybody,ciliarybloodvessels
andirisdilatormuscle

INCREASESAHPRODUCTIONbyciliaryepithelium
ThedilatormusclescauseMYDRIASIS(dilationofpupils)

SYMPATHETICNERVOUSSYSTEM

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Where are lacrimal glands located?

Study These Flashcards

inthetemporalouterportionoftheorbit

Where are accessory glands located?

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locatedintheconjunctiva

Where are Meibomian glands located?

Study These Flashcards

locatedposterior&inferiortotheeyelashes

Abnormalities in _________ cangreatlyaffecttearfilmfunction

Study These Flashcards

Abnormalitiesinglandfunctioncangreatlyaffecttearfilmfunction
(examples:acnerosaceaandmeibomitis)

The trabecular meshwork drains the AH from the anterior chamber into the: '

Schlemm’s Canal

The PNS Innervates the sphincter pupillae and ciliary muscles which causes:

* the ciliary and sphincter muscle to CONTRACT leading to * relaxation of the zonules suspending the lens allowing lens to be more convex and facilitate(ACCOMMODATE) near vision * reduces IOP by decreasing resistance to conventional AH flow (pulls TM open to increase AH outflow) * MIOSIS

VITREOUS HUMOR:

*Transparent gelatinous medium that fills the posterior segment * Maintains eye shape * Transparency facilitates passage of light to the retina * Functions in metabolic exchanges * May serve as a protective cushion for the retina

The OPTIC NERVE

Myelinated nerve that conducts retinal sensory output to the visual centers in the brain

TorF: the choroid contains the photoreceptors (Rods and cones)

False: The RETINA contains photoreceptors (rods and cones)

TorF: the retina Forms the light sensitive outermost layer of tissue in the posterior segment for vision perception

False: Forms the light‐sensitive INNERMOST layer of tissue in the posterior segment for vision perception

Highly vascular middle layer which supplies nutrients to interior structures of the eye and removes metabolic waste

Choroid

Tough, fibrous tissue forming the outermost layer of the eye, extending from the cornea in the anterior segment to the optic nerve at the back of the eye.

Sclera

single layer of cells underlying the retina that provides nutrients and maintains the photoreceptors

Retinal pigment epithelium (RPE)

multilayered membrane; separates the RPE and retina from the choroid

Bruch's membrane

capillaries that form inner layer of the choroid

Choriocapillaris

The retina is comprised of:

• Photoreceptors (rods and cones) • Integrators (bipolar, horizontal, amacrine, ganglion cells) * Output pathway (nerve fiber layer) * Support cells (Muller cells)

Of the 10 layers of the eye, The 3 layers that predominantly contain nuclei are:

outer nuclear layer, inner nuclear layer and the ganglion cell layer

The 2 layers that contain-synaptic connections are

outer plexiform layer and inner plexiform layer

Extra cellular space acting as scaffolding for neural and vascular elements:

Muller cells

TorF:Optic nerve fibers traverse the retinal surface and unite at the optic disc.

True

TorF: Rods and cones are present at the optic disc

False. Rods and cones are absent at the optic disc

What is responsible for the sharp, detailed central vision such as reading

Macula lutea

Fovea centralis

shallow depression in the middle of the yellow spot.

TorF: Most topical ophthalmic medications are poorly absorbed

True. Only ~5% of dose given as an eye drop is absorbed | intraocularly (Poorly bioavailable)

What factors affect ocular bioavailability?

• Administration (proper technique; nasolacrimal drainage) • Medication formulation (e.g., ointment, suspension, solution) * Dosage * Route of administration (e.g., topical, injectable)

Factors Affecting Absorption and Distribution of Ocular Drugs:

* Route of administration * Drug solubility * Molecular weight of drug * Concentration of drug * Intraocular diffusion barriers * Pigmentation of the uvea * Anatomical and functional factors * Physiological and biochemical factors * Influence of the drug carrier (vehicle)

• OTHER ROUTES OF ADMINISTRATION: OCULAR INJECTIONS

* Sub‐conjunctival injection * Retrobulbar injection * Peribulbar injection * Intracameral injection ‐ into the anterior segment * Intravitreal injection ‐ into the vitreous * Invasive routes used only in special situations * High drug concentration needed * Non‐compliant patients * Ocular surgeries * Endophthalmitis

• FACTORS AFFECTING OCULAR PK OF DRUGS: PIGMENTATION OF | UVEA

• Uveal pigments bind certain drugs, forming an inactive depot Example: Mydriatics bind to melanin pigments • Dark iris has more melanin than light iris - Onset of action of mydriatics may be delayed - Duration of action prolonged

FACTORS AFFECTING OCULAR PK OF DRUGS:

PIGMENTATION OF UVEA METABOLISM EXCRETION

FACTORS AFFECTING OCULAR PK OF DRUGS: METABOLISM

• Enzymatic biotransformation of ocular drugs may be significant: -Esterases, oxidoreductases, lysosomal enzymes, peptidases, glucuronide and sulfate transferases, glutathione‐conjugating enzymes, catechol‐O‐methyl‐transferase, monoamine oxidase, and 11 ‐hydroxysteroid dehydrogenase •Esterases are of particular interest because of the development of prodrugs for enhanced corneal permeability. For example, latanoprost is a prodrug for prostaglandin F2alpha used for treating glaucoma.

FACTORS AFFECTING OCULAR PK OF DRUGS: EXCRETION

Drugs administered into the eye are eliminated by the liver and kidney after systemic absorption Some portion of topically applied formulations are washed out in tears or through nasal secretions (via nasolacrimal drainage)

Ocular Anatomy Flashcards

(51 cards)