Ocular Anatomy Flashcards
BLINKING:
- Coordinatedmovementofocularmuscles
- Distributestearsoverthecorneaandconjunctiva
- Protectseyefrompotentialdanger
ANATOMYOFTHEEYELIDS:
Externalsurface‐coveredbyathinlayerofskin
Internalsurface‐linedwiththepalpebralportionofthe
conjunctiva,whichisavascularizedmucousmembranecontinuouswith thebulbarconjunctiva
Fornix:Spacewherethepalpebralandbulbarconjunctivaemeet
Where is the fornix located?
Locatedsuperiorlyandinferiorlybehindtheupperandlowereyelids, respectively.
TorF: Topicalmedicationsusuallyareplacedintheinferiorfornix,also
knownastheinferiorconjunctivalsac
True
The lacrimal system consists of:
secretoryglandsandexcretory(nasolacrimal)ducts
Thesecretorysystemincludes:
- Lacrimalglandslocatedinthetemporalouterportionoftheorbit
- Innervatedbytheautonomicnervoussystem
*Accessoryglands(alsoknownasKrauseandWolfringglands)
locatedintheconjunctiva
- Meibomianglandslocatedposterior&inferiortotheeyelashes
- Orificesofglandsposteriortoeyelashes -Secreteoilsthatretardevaporationofthetearfilm
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
TorF: the cornea is a multilayered hydrophilic epithelialbarriertoforeign matter,includingdrugs
False: MultilayedHYDROPHOBICepithelialbarriertoforeign matter,includingdrugs
The limbus of the eye is the transitional zonebetweenthe:
Cornea and sclera
- Consistsofseveralstructures,includingconjunctival
epithelium,Schlemm’sCanalandthetrabecularmeshwork
TorF: The aqueous humor is formed in the anterior chamber
FALSE . Posterior chamber
ANTERIORCHAMBER(AC)
- cornea forms the roof of the chamber, Iris forms the base of the AC
- Theanteriorchamberangleisformedbytheintersectionofthecorneaandiris
- Holdsabout250µLofaqueoushumor(AH)
The posterior chamber
- Theposteriorsurfaceoftheirisformstheroof;anteriorsurfaceofthe lensandtheciliaryprocesses formthebase
- Holdsapproximately50µLofaqueoushumor
The uvea consists of
theirisandciliarybodyintheanteriorsegment
thechoroidintheposteriorsegment
The iris
Separatesanteriorandposteriorchambers
Providescoloroftheeye
Muscular,circularstructureresponsibleforcontrollingthediameterandsizeofpupil,thusregulatingthe amountoflightpassingintotheeye
CILIARYBODY
Consistsofciliarymusclesand,anteriorly,ciliaryprocesses
Ciliaryepithelialcellslineciliaryprocessesandformaqueoushumor whichfillstheposteriorandanteriorchambers
Ciliarymuscleschangetheshapeofthelenswhentheeyefocusesonanobject(accommodation)
What is the conventional pathway: describe it
AH secreted by the capillaryplasmaintheciliaryepithelialcellsandreleasedintothe posteriorchamber(AHinflow)
•Passesthroughpupilintoanteriorchamber •Flowsthroughtrabecularmeshwork(TM)intotheCanalof Schlemm,eventuallyreturningtothesystemiccirculation
Uveoscleral Pathway
AHdrainsfromthebaseoftheciliarymusclethroughtissuesin&aroundtheuvea,ultimatelypassingintothe sclera
ROLEOFAQUEOUSHUMOR
• Helpsmaintainintraocularpressure(IOP)andthe
eye’sshape
• Servesasarefractivemedium
• Providesmetabolicsubstratestoavascular
structuresoftheeye(lens,cornea)
- Carriesawaymetabolicwastes
- Facilitatesthedistributionofsomedrugs
ElevatedIOPisusuallyduetoincreasedresistanceto
outflow(Trabecular meshworkdysfunction)
Innervatestheciliarybody,ciliarybloodvessels
andirisdilatormuscle
- INCREASESAHPRODUCTIONbyciliaryepithelium
- ThedilatormusclescauseMYDRIASIS(dilationofpupils)
SYMPATHETICNERVOUSSYSTEM
Where are lacrimal glands located?
inthetemporalouterportionoftheorbit
Where are accessory glands located?
locatedintheconjunctiva
Where are Meibomian glands located?
locatedposterior&inferiortotheeyelashes
Abnormalities in _________ cangreatlyaffecttearfilmfunction
Abnormalitiesinglandfunctioncangreatlyaffecttearfilmfunction
(examples:acnerosaceaandmeibomitis)
The trabecular meshwork drains the AH from the anteriorchamberinto the:
‘
Schlemm’sCanal
The PNS Innervatesthesphincterpupillaeandciliarymuscles which causes:
- theciliaryandsphinctermuscletoCONTRACT leading to
- relaxationofthezonulessuspendingthelens allowing lens to be more convex and facilitate(ACCOMMODATE) near vision
- reducesIOPbydecreasingresistancetoconventionalAHflow(pullsTMopentoincreaseAHoutflow)
- MIOSIS
VITREOUSHUMOR:
*Transparentgelatinousmediumthatfillstheposteriorsegment
- Maintainseyeshape
- Transparencyfacilitatespassageoflighttotheretina
- Functionsinmetabolicexchanges
- Mayserveasaprotectivecushionfortheretina
The OPTICNERVE
Myelinatednervethatconductsretinalsensoryoutputtothe
visualcentersinthebrain
TorF: the choroid contains the photoreceptors (Rods and cones)
False: The RETINA containsphotoreceptors(rodsandcones)
TorF: the retina Formsthelight sensitiveoutermostlayeroftissueintheposteriorsegmentfor
visionperception
False: Formsthelight‐sensitiveINNERMOSTlayeroftissueintheposteriorsegmentfor
visionperception
Highlyvascularmiddlelayerwhichsuppliesnutrientstointeriorstructuresoftheeyeandremovesmetabolicwaste
Choroid
Tough,fibroustissueformingtheoutermostlayeroftheeye,extendingfromthecorneaintheanteriorsegmenttotheopticnerveatthebackoftheeye.
Sclera
singlelayerofcellsunderlyingtheretinathatprovidesnutrientsandmaintainsthephotoreceptors
Retinalpigmentepithelium(RPE)
multilayeredmembrane;separatestheRPEandretina fromthechoroid
Bruch’smembrane
capillariesthatforminnerlayerofthechoroid
Choriocapillaris
The retina is comprised of:
• Photoreceptors(rodsandcones)
• Integrators(bipolar,horizontal,amacrine,ganglion
cells)
- Outputpathway(nervefiberlayer)
- Supportcells(Mullercells)
Of the 10 layers of the eye, The 3 layers that predominantlycontain nuclei are:
outernuclearlayer,innernuclearlayerandtheganglioncelllayer
The 2 layers that contain-synaptic connections are
outerplexiformlayerandinnerplexiformlayer
Extra cellular space acting as scaffoldingforneuralandvascularelements:
Mullercells
TorF:Opticnervefiberstraversetheretinalsurfaceanduniteattheopticdisc.
True
TorF: Rodsandconesarepresent attheopticdisc
False. Rodsandconesareabsentattheopticdisc
What is responsible for the sharp,detailedcentralvision such as reading
Macula lutea
Foveacentralis
shallowdepressioninthemiddleoftheyellowspot.
TorF: Most topical ophthalmic medications are poorly absorbed
True. Only~5%ofdosegivenasaneyedropisabsorbed
intraocularly(Poorlybioavailable)
What factors affect ocular bioavailability?
• Administration(propertechnique;nasolacrimal
drainage)
• Medicationformulation(e.g.,ointment,suspension,
solution)
- Dosage
- Routeofadministration(e.g.,topical,injectable)
FactorsAffectingAbsorptionandDistributionofOcularDrugs:
- Routeofadministration
- Drugsolubility
- Molecularweightofdrug
- Concentrationofdrug
- Intraoculardiffusionbarriers
- Pigmentationoftheuvea
- Anatomicalandfunctionalfactors
- Physiologicalandbiochemicalfactors
- Influenceofthedrugcarrier(vehicle)
• OTHERROUTESOFADMINISTRATION:OCULARINJECTIONS
- Sub‐conjunctivalinjection
- Retrobulbarinjection
- Peribulbarinjection
- Intracameralinjection‐intotheanteriorsegment
- Intravitrealinjection‐intothevitreous
- Invasiveroutesusedonlyinspecialsituations
- Highdrugconcentrationneeded
- Non‐compliantpatients
- Ocularsurgeries
- Endophthalmitis
• FACTORSAFFECTINGOCULARPKOFDRUGS:PIGMENTATIONOF
UVEA
• Uvealpigmentsbindcertaindrugs,forminganinactive
depot Example:Mydriaticsbindtomelaninpigments
• Darkirishasmoremelaninthanlightiris
- Onsetofactionofmydriaticsmaybedelayed
- Durationofactionprolonged
FACTORSAFFECTINGOCULARPKOFDRUGS:
PIGMENTATIONOFUVEA
METABOLISM
EXCRETION
FACTORSAFFECTINGOCULARPKOFDRUGS:METABOLISM
• Enzymaticbiotransformationofoculardrugsmaybesignificant:
-Esterases,oxidoreductases,lysosomalenzymes,peptidases,
glucuronideandsulfatetransferases,glutathione‐conjugating enzymes,catechol‐O‐methyl‐transferase,monoamineoxidase, and11‐hydroxysteroiddehydrogenase
•Esterasesareofparticularinterestbecauseofthedevelopmentofprodrugsforenhancedcornealpermeability.Forexample, latanoprostisaprodrugforprostaglandinF2alphausedfortreating glaucoma.
FACTORSAFFECTINGOCULARPKOFDRUGS:EXCRETION
Drugsadministeredintotheeyeareeliminatedby
theliverandkidneyaftersystemicabsorption
Someportionoftopicallyappliedformulationsare
washedoutintearsorthroughnasalsecretions(via
nasolacrimaldrainage)
