Term
|
Definition
Transmission- needs to be transparent
Refraction- Cuvature, length, change in index |
|
|
Term
|
Definition
Anterior: horizontal 12mm, Vertical 11mm
Posterior 11.7 horizontal and vertical (little bit bigger than anterior) |
|
|
Term
|
Definition
Central- 0.53 mm
Peripheral 0.71 |
|
|
Term
| Radius of curvature of cornea |
|
Definition
Anterior 7.8 mm
Posterior 6.5 mm
Steep= shorter radius of curvature. the cornea is steeper at the center and flatter near the periphery. |
|
|
Term
| What is a corneal astigmatism |
|
Definition
| difference in curvature of the eye ball. Cornea is shaped like a football. |
|
|
Term
| Regular corneal astigmatism |
|
Definition
Principle meridians are 90 degrees apart
WTR- vertical meridian is steepest
ATR- horizontal meridian is steepest
Oblique- steepest meridian at 45 or 135 degrees |
|
|
Term
| Can ATR corneal astigmatism and oblique be corrected with spectacles? |
|
Definition
|
|
Term
| Irregular corneal astigmatism |
|
Definition
Principle meridians are not 90 degrees apart
corrected with CL (rigid) not with spectacles
lens can also contribute to astigmatism |
|
|
Term
|
Definition
Bilipid layer- controls molecular entrance and exit
ie drug transport |
|
|
Term
|
Definition
| cytoskeleton-stucture, intercellular transport and communication |
|
|
Term
|
Definition
| Nucleus, ribosomes, ER, golgi apparatus, mitochondria |
|
|
Term
|
Definition
-maintain conc gradient
-diffusion
-facilitated diffusion
-active transport (ATP)
-aquaporins (mvmt H2O)- bidirectional channels |
|
|
Term
|
Definition
|
|
Term
|
Definition
-epithelial tissue attaches to underlying tissue via BM
2 layers:
-Basal lamina- secreted by by epithelial cell
Reticular lamina- secreted by CT layer |
|
|
Term
|
Definition
-mostly with epi tissue
-fx adhesion or communication
Shapes:
-zonular- belt like all the way around the cell
-Macular- round or button like |
|
|
Term
| Adhering intercellular juntion |
|
Definition
-(ZA + MA)
-narrow intercellular space
-transmembrane adehesion molecules
-contributes to cell stability |
|
|
Term
|
Definition
-tight
-ZO + MO
-focal fusion of outer leaflet of plasma membranes
-seals off intercellular space
-no place for ahy substances to pass btwn cells
- epi of cornea- semi permeable, have to pass through cell. |
|
|
Term
|
Definition
|
|
Term
|
Definition
-strong attachment btwn cells
-circular attachment plaque
-filaments extend into cellular cytoplasm
-adhesive mucoprotein fills intercellular space
- not barriers to passage |
|
|
Term
|
Definition
-half
-attachement of basal surface to underlying CT
-strong attachment btwn epi and BM |
|
|
Term
|
Definition
-channel that connects one cell to another
-connexon- tranmembrane channel or pore:
-joins cytoplasm of adjoining cells
-connexon is composed of 6 protein connexinx
-permits passage of small molecules |
|
|
Term
|
Definition
-channel that connects one cell to another
-connexon- tranmembrane channel or pore:
-joins cytoplasm of adjoining cells
-connexon is composed of 6 protein connexinx
-permits passage of small molecules |
|
|
Term
|
Definition
Epithelium
Bowman's layer
Stroma
Descemets membrane
endothelium |
|
|
Term
|
Definition
-stratified squamous
-surface layers is squamous 2-3 cells in thickness and is non keratinized
-microvili, microplicae (on apical side)
-secretes glycocalyx- glycoprotein covering surface of cell
-intercellular junctions:
-Zonular occludens: fx semi permeadbel membreance
- tear film resting on surface but ZO prevent tears from rushing into cornea
-Desmosomes- strong adhesions btwen cells
-Flourescine used to see if damage in ZO layer |
|
|
Term
|
Definition
-Transition layer- surgace cells sloughed off and wing cells replace
-intercellular junctions:
desmosomes
gap junctions
as move up to surface more connection between cells |
|
|
Term
|
Definition
-columnar
-Germinative layer (cell division)
-secretes basal lamina portion of BM
-intercellular junctions:
-desmosomes (fewer than in the wing cell layer)
-gap junctions
-hemidesmosomes:
fibrisl attach to plaques in stroma (strong attachement btwn epi and stroma)
-plaques contain laminin
-attaches basal laer to BM |
|
|
Term
| Reccurent Corneal erosion Cause |
|
Definition
-malfomed hemidesmosomes:
-EBMD epithelial BM dystrophy (condition caused by defective nutrition or metabolism)
-incomplete healing of abrasion |
|
|
Term
| Signs and symptoms of reccurent corneal erosion |
|
Definition
-Areas of sloughed epi (when patient wakes up in moring nerve endings are exposed)
-Pain |
|
|
Term
| Treatment of recurrent corneal erosion |
|
Definition
-bandage CL (soft)
-artificial tears, ointment
-corneal puncture
-stimulates BM adhesion (formation of hemidesmisomes) make pin pricks
-extreme damage and dystrophies |
|
|
Term
|
Definition
-constant replacement
-cell division in basal layer
-basal cells replenished from stem cells in limbus
-barrier function maintained.
-ZO become increasingly more present as cell moves up |
|
|
Term
|
Definition
Dense irregular CT
*Acellular
It is a transition layer- smaller and less regular fibers than stroma
produced prenateally and cannot be regenerated. |
|
|
Term
| What happens to the corneal tissue with a pterygium |
|
Definition
-Conj invades corneal tissue
-bowman's layer is lysed |
|
|
Term
| What is the stroma composed of> |
|
Definition
-Regular dense CT
-collagen fibrils
-cells
-ground substance |
|
|
Term
| Describe the collagen fibrils |
|
Definition
- have lamellae= bundles of fibers
-fibers are parallel to the surface
-fibers extend from limbus to limbus. |
|
|
Term
| which has a higher incidence of crosslinking amoung collagen fiber: posterior or anterior? And why? |
|
Definition
| anterior because crosslinking creates more rigidity whihc helps to maintain the corneal curvature. |
|
|
Term
| What cells are contained in the stroma and what is their function? |
|
Definition
Fibroblasts=keratocytes
produce components of CT
lie between lamellae
contain gap juctions. |
|
|
Term
| What is stromal ground substance made up of? |
|
Definition
Proteoglycans: increase tensile strength and composed of sugar and protein
GAGs: negatively charged side chains, hydrophilic, maintain component spacing.
Ground substance surrounds fibers. A specific amount of water is need to maintain the transparency. |
|
|
Term
|
Definition
Light should pass straight throug the cornea, scattered light causes glare
- fibers arranged in regular lattice pattern
-destructive interference occurs
-light scattering is reduced as long as the distance between different refractive indices is less than 1/2 the wavelength of the light. Get constructive interference is different refractive indexes.
-inverse relationship between destructive interference and light scatter.
-cornea loses transcperency if the spacing is distrupted (can be caused by too much H2O |
|
|
Term
|
Definition
-misshapppened cornea (becomes more like a cone)
-corneal dystrophy (cause is nutritional or metabolic
- intial disruption is in BM or Bowman's
-Eventually involves significant stromal thinning.
-Produces an irregular astigmatism which cannot be correct with spectables.
-RGP CL may slow progression
-Munson's sign- lower lid conforms to conic shap on downgaze.
-Strengthen cornea with collagen? |
|
|
Term
|
Definition
intercellular juntion
Jigsaw puzzles
increases SA
huge # of ionic pumps |
|
|
Term
|
Definition
intercellular junction
quick communication between cells |
|
|
Term
|
Definition
intercellular junction
-slightly leak barrier (incomplete)
-Zo are very closely spaced
-allow material from anterior chamber into strom eaily
-apical surface line anterior chamber |
|
|
Term
|
Definition
-difference in proteins
-attach decsemets to endothelium. |
|
|
Term
|
Definition
-endothelium produces mounds of basement membrane material which are seen as periodic thickenings in descemets membrane that buldge out into the anterior chamber.
called Hassal-henle bodies when in corneal periphery.
Causes endothelial to stretch out and cover, causing increased space btween cells and more fluid in the cornea. Cells can still function.
-increases with age and is very common. |
|
|
Term
|
Definition
Deposits of basement membrane in the central cornea.
Indicative of endothelial dysfunction. Thickening of BM. The endothelium that covers these mounds is thinned and altered. The endothelelial barrier may be compromised. |
|
|
Term
| Are there BV in the cornea? |
|
Definition
| There may be an antiangiogenic agent present- prevent growth of BVs. |
|
|
Term
|
Definition
-Dense sensory innervation- Schwann cell covering lost when enter the epi. Fibers that enter strom lose myelin within 1-2 mm into cornea.
-70-80 bundles enter corneal periphery
-most receptors are nociceptors (pain receptor)
- stromal plexus 900-1200 axons
-subepithelial plexus (bowman's and enterior stroma)
-intraepithelial plexus- Scwhannn cells covering loss as fibers pass through Bowman's
-no nerve endings in descement's and endothelium |
|
|
Term
|
Definition
-Posterior 5/6 of the globe
-Compsed of irregular CT (collagen fibers, fiberblasts, aminoglycans
-avascular
-Continuous with the corneal stroma, but fewer GAGs and less regular pattern of fibers
- White in health, blue when thin or transparent, yellow with fat depositis or liver dysfunction |
|
|
Term
| Anterior Sceleral foramina |
|
Definition
|
|
Term
| Posterior scleral foramina |
|
Definition
-optic nerve
-lamina crirosa- meshwork of scleral fibers |
|
|
Term
|
Definition
| Near limbus: anterior ciliary arteries |
|
|
Term
|
Definition
| Near equator: vortex veins |
|
|
Term
|
Definition
| Around optic nerveL long and short posterior ciliary arteries and nerves. |
|
|
Term
| Why are foramina and aperatures important? |
|
Definition
Openings frm outside to inside tissue
avenue for pathogens and melonoma cells |
|
|
Term
|
Definition
Outer to the scelera
Loose vascular CT |
|
|
Term
|
Definition
| Dense CT capsule outer to episcleral |
|
|
Term
|
Definition
-Outer to tenons capsule
-continuous with palpebral conj at fornices
- stratified non-keratinized columnar epithelium
-contains goblet cells
-stroma is immunologically active
-BVs and lympathics |
|
|
Term
| Ciliary injection vs conjunctival injection |
|
Definition
| The episceleral network becomes congested in ciliary injection, giving the limbus a light purple or rose coloration in serious corneal inflammation or disease of the iris and ciliary body. |
|
|
Term
|
Definition
-annular region surrounding corneal periphery
- 1.5-2 mm width |
|
|
Term
|
Definition
-anterior border- line drawn from termination of Bowman's to termination of Descement's
-Posterior border: line from posterior sclerall spur to conj surface and perpendicular to it. |
|
|
Term
|
Definition
External sceleral sulcus-grove or indentation
-internal scleral sulcus: location of trabecular meshwork and schlems canal.
-Palisades of vogt |
|
|
Term
|
Definition
-grey "pegs"
-regions of thickened epithelium considered niche for corneal and conjunctival stem cells
-contains BVs
-contains melanocytes |
|
|
Term
|
Definition
| Transition of cornea, conjunctival and scleral layers |
|
|
Term
|
Definition
-Transmits light
-absorbs shot wavelength UV
-Refracts lght
-Both require minimal scattering and distortion |
|
|
Term
| How does the cornea transmit light? |
|
Definition
-From UV 310 nm to UR 2500 nm
-cornea scatters less than 1% incident light
-cytoplasm of epi and endo cells contain corneal crystallin, water soluble proteins, that make cytoplasm homogenous and decrease light scattering |
|
|
Term
|
Definition
| Is the reason for photo keratitis- inflammmation caused by absorption of UV Causes-welder's arc, tanning beds, snowblindness cornea epi repairs quickly 70% of the eyes refractive power |
|
|
Term
| How does the cornea refract light? |
|
Definition
-determined by the curvatures of various surfaces
-interfaces between different indices of light
length of pathway throug the structures.
-both require minimal scattering and distorition: no BVs and proper hydration |
|
|
Term
| What helps to maintain maximum transparency |
|
Definition
corneal hydration
relative corneal deturgescene- 78% water |
|
|
Term
| Role of the epithelium in corneal hydration |
|
Definition
| -ZO barrier prevent intercellular water influc from tears -Ions move across both sufaces: - channels allow Na+ to pass into epi from tears and Cl- to pass into tears * cl- and Na+ are major driving forces for water transport -co transporter mechanism moves Na, K and Cl ions - Na+/K+ ATPase pumps located in basolateral membrane actively move ions -aquaporins, water transport channels - present in epi cell membranes, bidirectional flow |
|
|
Term
| what is the importance of ions in the movement of H2O? |
|
Definition
| movement of ions drives movement of H2O. Ions moved across membrane either direction all have acellular function and water moves with them. |
|
|
Term
|
Definition
-GAGs are present in ground substance surrounding collagen fibers
-due to anionic characteristics they bind with water- theres is an inherent tendency to imbibe water and to swell
- water content should be 78%
-Increasing hydration leads to decreasing transperency
-normal water content of sclera is 68% and if falls below 40 or above 80 the scelera becomes lucent (transparent) |
|
|
Term
| why is corneal hydration temperature dependent? |
|
Definition
| swells when cooled, returns to normal at body temperature. |
|
|
Term
| What is the role of endothelium in corneal hydration? |
|
Definition
-high metabolic rate cells (mitochondria and golgi)
-slow leak of fluids and solutes from the aqueous.
-Na/K ATPase pump in the basolateral membrane of the endothelium
-pumps act at a steady rate and the rate of leakage is dependent on pressure gradient.
-cotransporters move NA, K Cl HCO3 across membranes |
|
|
Term
| Coeffcient of Variation CV |
|
Definition
indicates the degrees of uniformity among endo cells
-CV= sd of mean cell area/mean cell area (normal CV= 0.25)
- as CV increases there is an increasin the amound of variation in cell size. |
|
|
Term
|
Definition
Number of cells per unit area
4000-3000 cells/mm^2 in young
2000 cells/mm^2 by age 80
-400-700 cells/mm^2 necessary for normal function |
|
|
Term
|
Definition
|
|
Term
|
Definition
Variation in cell shape
hexagonal is most efficacious shape. |
|
|
Term
| What are the measures of endothelial function |
|
Definition
-coefficient of variation CV
- Cell density
-poly megathism
-pleomorphism |
|
|
Term
| Endothelial stress from CL wear, disease, age, surgery, etc. can lead to what? |
|
Definition
| endothelial remodeling, including change in shape size or both. |
|
|
Term
|
Definition
- as tears evaporate the tear fludi becomes more concentrated
- tear film osmolarity increase realtive to cornea
-hypoertonicity of tear film draws H2O from cornea
-blink response is elicited because hypertonicity causes a slight sting and thus tear flim is restored. |
|
|
Term
| What does the cornea need for cell proliferation |
|
Definition
nutrients including glucose and AA (come from aqueous)
-come glucose goes through the hexose monophosphate shunt providing building blocks for nucleic acid synthesis
-2 ATP per molecule of glucose
-36 ATPs per molecule of glucose.
-O2 from tears when eye are open. from palpebral conj when eyes are closed. |
|
|
Term
| What is necessary for prober corneal cell function? |
|
Definition
appropriate level of hydration is necessary to preserve transpparency
since 90% of the cornea is sstrom, stomal hydration is a major factor |
|
|
Term
| Corneal Edema Manifestation |
|
Definition
- diameter remains the same
-thickness increases- swelling directed posteriorly
-Normally 1% scattering, but with fluid retentionlight scattering increases, cornea becomes cloudy
-buckling of descemets occurs and straie folds are seen
- increase in corneal hydration positively and linearly related to corneal thickness |
|
|
Term
|
Definition
1) epithelial
2) endothelial damage
3) hypoxic conditions
4) High IOP |
|
|
Term
| Clinical manifestations of endothelial damage |
|
Definition
1) formation of guttata
-endothelial cells thin
-apical junctions deteriorate
2) fuchs dystrophy
-results in loss of endothelial function
-guttata form
-reduction of ion movement
-stromal edema
-epithelial microcysts |
|
|
Term
| Hypoxic conditions and corneal edema |
|
Definition
-decreased O2 with poorly fit CL. not getting enough atomospheric air. Cornea will use more anerobic form.
- concentration of lactate increases
-osmotic balance changes
-induces stromal edema
- termed metabolic edema |
|
|
Term
| Epithelial damage and corneal edema |
|
Definition
-loss of ZO
-localized area of swelling and haziness
-caused by abrasion, injury
-transient |
|
|
Term
| Endothelial damage of corneal edema |
|
Definition
- more serious implies loss of active pump mechanism
-caused by disease, surgery, injury
-poorly fit CL may allow stagnation of tears. |
|
|
Term
| very high IOP and corneal edema |
|
Definition
normal range 10-20 mm Hg
borderline 21-25mm Hg
high >25 mm Hg
very high >50 mm Hg
- endo transport overwhelmed
-most be treated quickly |
|
|
Term
| location of corneal edema |
|
Definition
epithelial:
-uncomfortable to painful
-decreases visual acuity
-seperates cells causing surface irregularities
stromal:
-matrix accumulates fluid
- diameter of fiber remains same
-swelling directed posteriorly
-straie folds in Descemet's appear
-usually symptom free |
|
|
Term
|
Definition
-hypoxia affects cullular fx and causes decrease in intracellular pH
-scarring can occur with dysfunction in collagen formation
-neovascularization- body's defense mechanism to provide O2 source |
|
|
Term
|
Definition
Eliminate cause
temporary clearing with hypertonic solution of glycerin instillation |
|
|
Term
| Which molecules are activated when the cornea is damaged? |
|
Definition
Integrins- faciliate and maintain cellular fx
cytokines- facilitate cellular communication
growth factors- mediate proliferation and differentiation |
|
|
Term
| How does the corneal epithelium heal after injury? |
|
Definition
-Mitosis
-Cells at wound edges lose hemidesmosome attachments
-basal cells migrate- epidermal frowth factor is released after injury and enhances cell migration and proliferation
-when defect is covered protein synthesis increases
-mitosis resumes and cell proliferation replaces lost cells
-after wound is healed hemidesmosomes reformed
- cell membrane and BM are linked via and biochemical bond prior to reformation of hemidesmosomes
-epithelium usually heals in 24-48 with hemidesmosomes reformed.
- usually no scarring evident
- if BM injured, normal adehsion may take 12 months to regenerate. |
|
|
Term
| Bowman's layer and corneal wound healing |
|
Definition
-cannot be regenerated
-is replaced by epithelial or stromal tissue
-often scar |
|
|
Term
| Corneal healing and stroma |
|
Definition
-Increase in number of keratocytes
-collagen deposition in stroma:
fiber arrangement not as regular
-diameter of regenerated fibers is freater than normal
-stromal healing not as rapid as epithelial healing
-scar may result
-may take up to 48 months for tensile strength to approach normal |
|
|
Term
| Descemet's membrane and corneal healing |
|
Definition
Is very resistant to injury
will be secreted by the stromal fibroblasts and the endothelium |
|
|
Term
| Endothelium and corneal healing |
|
Definition
-migration to cover area
-cells thin and remodel into hexagonal shape
-pump and barrier functions are reestablished |
|
|
Term
| Corneal neovascularization |
|
Definition
-cause may be disease, inflammation, or lack of oxygen
-new vessels sprout from perilimbal capillariesL
-enzymes degrade BM of capillary
-endothelial cells migrate
-endothelial cells proliferate to form new vessels
-antiangiogenic factors have been identified in the normal cornea
-angiogenic factors are released in some diseases
-vessels do not resorb, but when the situation that produced them is reversed they no longer carry blood and are called ghost vessels |
|
|
Term
|
Definition
-sensory nerves terminate in free nerve endings tightly surrounded by epithelial cells
-nerve ending pattern changes as they retract, reinsert or shift position apparently with epithelial cell turnover
-sensory innervation is 400 times higher than any other epithelial tissue
-sympathetic fibers have been identified in the cornea- may affect Cl ion channels |
|
|
Term
| acetylcholine and acetylchoinesterase in the cornea |
|
Definition
-they may be trasmitters of pain
-they might contribute to tissue reaction that occurs in response to pain
-they might mediate inflammatory response
-they may play role in transport processes and affect cellular permeability
-thye might regulate cell mitosis (perhaps because ACh can stimulate cGMP mitosis |
|
|
Term
| Sensory nerves have a neurotrophic effect ie influence corneal metabolism |
|
Definition
-in animal studies denervation be ablating the ophthalmic division of the trigeminal leads to:
-increased epithelial layer permeability
-decreased cellular adhesion
-impaired wound healing
-reduced mitosis
-reduced cell micreation |
|
|
Term
|
Definition
-primary sensation is pain
-high sensitivity
-CL decrease corneal sesitivity
-clinically measured by blink response using aestheiometer
-temperature sensitivity- registers changes but does not accurately recognize hot and hold |
|
|
Term
|
Definition
-in central corneal damage normal nerve pattern is present by week 4
-in peripheral corneal damage reinnervation takes longer than 60 days and density of pattern is lower than normal |
|
|
Term
|
Definition
-scelera is a dynamic tissue
-progressive myopia:
-collagen degradation
-loss of proteoglycans
-changes in fibroblasts |
|
|
Term
|
Definition
|
|
Term
|
Definition
pupil- diaphragm
miosis and mydriasis |
|
|
Term
|
Definition
Extent:
-Iris root anterior to ciliary body
-pupillary ruff- surrounds pupil
(ruff is anterior to root)
-Two anatomical portions seperated by the collarette |
|
|
Term
| What is the collarette and what are the two anatomical portions? |
|
Definition
-collerette is the attachment site for embryologic membrane:
-pupillary: portion surrounding pupil
-ciliary: from collerte to root |
|
|
Term
|
Definition
composed of CT:
-fibroblasts which branch and interweave
-iris processes extend into anterior chamber in periphery (trab)
-melanocytes blow fibroblasts (melanin within cytoplasm) |
|
|
Term
|
Definition
Composed of loose CT:
-collagen fibers arranged in trabeculae (radial orientation)
-cells:
-pigmented melanocytes and clump cells (likely modified macrophages)
-non pugmented fibroblasts (repair damage) |
|
|
Term
| What are the structures located within the iris stroma |
|
Definition
-BVs:
stromal collagen bundles encircle walls of arterioles and venules
-major circle of the iris is progom pf oris arteries
minor circle of the iris- incomplete circular vessel within iris stroma (remenant of embryological development)
-Sphincter:
Located within the stroma (pupillary portion)
composed of smooth muscle, circular 1 mm in width
constriction miosis |
|
|
Term
|
Definition
-Apical- cuboidal
-basal=dialator (smooth muscle)
-dialator muscle located from root to midpoint below sphincter
-dialation |
|
|
Term
|
Definition
-pigmented columnar
-cell joined by tight junctions |
|
|
Term
| How are the two layers of the epithelium positioned |
|
Definition
apex to apex
joined to each other via desmosomes |
|
|
Term
| What type of innervation does the sphincter have? |
|
Definition
|
|
Term
| What type of innervation does the dialtor have? |
|
Definition
|
|
Term
| Describe the anterior surface of the iris |
|
Definition
-Colllarette ride- raised zig-zag 1mm-.5 from pupil
-crypts-holes in anterior that allow aqueous to get into stroma
-crypts of Fuch (boths sides of collarette)
-peripheral crypts
-circular contraction folds- occur during dialation |
|
|
Term
| Describe the posterior iris surface |
|
Definition
-radial contraction furrows in pupillary zone
-structural furrows in ciliary zone (also radial)
-circular contraction folds |
|
|
Term
| How is iris color determined? |
|
Definition
-the density of melanin in melanocytes(anterior border layer in stroma)
-number of melanocytes fairly constant in various iris colors
-collagen trabeculae are exposed in lighter colored eyes
blue- back scatter of incident light
brown-due to absorption of light by melanocytes
-green and gray- various amounts of absorption and scatter
-in all irises two epithelial layers are highly pigement, but not in albino |
|
|
Term
|
Definition
loss of epithelial pigment evident
see red light reflex shinning through
loss of pigment in posterior epi. |
|
|
Term
|
Definition
-trembling iris
-due to IOL- lens is smaller than human |
|
|
Term
| Pigmentary dispersion syndrome |
|
Definition
| pigment granules are shed from the posterior iris surface and are dispersed into the anterior chamber. They can be depositied on the iris, lens or corneal endothelilim or trab. |
|
|
Term
|
Definition
-adhesions
-Anterior-involves cornea or trab:
-pupil is misshappened due to severe whiplash
-blocks aqueous flow. need to break adhesion via dialation with 2% phenylephrine
-posterior: adhesion posterior and lens |
|
|
Term
|
Definition
-difference on iris color between eyes or wihin an iris
- can be congenital horner's or could indicate uveal inflammation or a tumor |
|
|
Term
| Describe the ciliary body |
|
Definition
-extends from iris root to ora serrata
-triangular in cross section
-base- corner of scleral spur, spans across processes
-apex at ora serrata
-outerside lies the scelera
-inner side lies posterior chamber |
|
|
Term
|
Definition
-contains 70-80 processes
-valleys of Kuhnt |
|
|
Term
|
Definition
-dentate processses
-oral bays |
|
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Term
|
Definition
| transition between ciliary body and choroid |
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Term
|
Definition
- outermost layer of the ciliary body adjacent to the sclera
-loose CT
- allows ciliary body to slide against scelera
-can be dettachment CB and sclera due to blow to head |
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Term
| What are the three muscle layers of the ciliary muscle? |
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Definition
1)longitudinal muscle fibers of Brucke (outer)
-run parallel to scelera
-origin at sclerall spur
-insert at stellate process
2) Radial fibers (middle)
-origin scleral spur
-insertation-stroma of ciliary body
3) mullers annular muscle (inner)
-spinchter action
-located near major circle of iris |
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Term
| What is the fx of the ciliary muscle |
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Definition
| accomodation- changes the shape of lens |
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Term
| How is the ciliary body innervated |
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Definition
parasympathetic- contraction, accomodation
sympathetic- decrease in accomodation |
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Term
| Ciliary stroma location of composition |
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Definition
-extends into processes
-composed of vascular CT
*capillaries in processses are fenestrated and wide lumened
-lymphatic channels have been discovered- possible route for aqueous exit |
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Term
| Ciliary epithelium two layers |
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Definition
-continuation of iris stroma derived from same germ layer
-2 layers apex to apex
-outer is pigmented and continuous iris epi (anteriorly and retinal pigment (posteriorly)
-inner is non pigmented:
-continuous with posterior iris epi (anteriorly)
-continous with neural retina (posteriorly)at orra serrata |
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Term
| Pigmented cillary epithelim |
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Definition
-cuboidal
-intercellular junction: desmosomes and gap junctions
-role in aqueous production |
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Term
| Non-pigmented ciliary epithelium |
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Definition
*ZO
-produces and secretes aqueous humor
-diffusion layer btween blood and aqueous
-metabolically active (mitchondria) |
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Term
| Functions of ciliary body |
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Definition
| -Aqueous production and accomodation |
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Term
| Blood aqueous barrier what is it and three components. |
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Definition
-selectively controlled substance secreted as aqueous (may interfere with vision bc of scatter)
fenestrated CB capillaries permit large molecules to exit blood
-ZO joining cells of the non-pigmented epithelium this is one way to control amount of protein in aqueous (concentration is slight compared to blood)
-non fenestrated iris capillaries prevent large molecules from entering aqueous |
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Term
| Accomdation and ciliary body |
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Definition
-lens is attached to ciliary body via zonules
-ciliary muscle contraction causes reduction in diameter of ciliary body
-tension in zonules is realeased.
-lens thickens and increases in power |
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Term
| Choroid location and extent |
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Definition
-inner to sclera and outer to retina
ara serrata to optic disc |
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Term
| Histology of Chorioid (all the different parts) |
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Definition
suprachoroid
choroidal stroma
choriocapillaris
Bruch's membrane |
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Term
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Definition
Continusous with superciliaris
composed of lamina fucia which allows it to slide against the sclera
potential space (suprachoroidal space)-potential for bleed- long ciliary nerves pass through. |
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Term
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Definition
continous with ciliary body stroma
pigmented vascularized loose CT contaiing melanocytes, lymphocytes, and mast cells.
Contains:
Haller's layer- large lumened vessels
-Sattler's layer- medium lumened vessels
-veins- vortex |
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Term
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Definition
*only located in choroid
-sole blood supply in the mucular area of the retina
-anastomosing
-wide lumened
-fenestrated |
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Term
| Bruch's membrane layers from outer to inner |
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Definition
CT
-BM of choriocapillaris
-outer of collagenous
-elastic layer
-inner collagenous zone
- BM of retinal pigmented epithelium (continuous with BM of pigmented epi of ciliary body) |
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Term
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Definition
-Provides nutrients to and eliminates waste from outer retina
-absorbs excess light |
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Term
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Definition
Accumulation of waste matter which displace retina
yellow white dots, spots in retina |
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Term
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Definition
-degeneration in bruchs in macular area
-normally nutrients pass through Bruch's from choriocapillaris into retina
-waste products fo in the other direction
-with age phospholipids accumulate in Bruch's causing it to become hydrophopic (defective phosphorylation process) |
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Term
| 2 possible consequences of phospholipid accumulation in Bruch's |
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Definition
-fluid accumulates between Bruch's and RPE that may lead to retinal dettachment
-neovascularization from choriocapillaris- leaky vessels-> hemorrhage into retina |
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Term
|
Definition
-genetics
-age
-uv exposure
-light pigmentation |
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Term
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Definition
| wet: neovascularization, 10-20% of pt's, 80% vision loss dry: drusen, more common |
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Term
| Treatment options for AMD |
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Definition
-antioxidant supplements
-laser treatment for neovascularization
-photodynamic therapy
-vascular endothelial growth factor antagonist
-submacular surgery to remove BV network |
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Term
| antioxidant supplements and AMD |
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Definition
-lutein and zeaxanthin
-age related eye disease study AREDS determined that high doses reduced the risk of progression
-current study, AREDS2 some indication that lutein, zeaxnathin plus omega 3 fatty acids can prevent AMD |
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Term
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Definition
-laser purns spot weld leaky spots
-indocyanine green dye injected to better visualize BVs |
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Term
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Definition
-Visuofyne is injected and adheres to abnormal vessel wall
-laser activates substance and closes BV
-targets just one endothelial cell wall. |
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Term
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Definition
-anti VEGF
-recently approved by FDA
-given by intervitreal injection
-decreases formation of new vessels
-must be given periodically over several months |
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Term
| What are the boundaries of the anterior, posterior chambers and periphery |
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Definition
anterior- corneal epitehlium
posterior- anterior iris, pupillary portion of lens
peripheral- tran, ciliary body and iris root |
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Term
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Definition
located in the internal scleral sulcus
junction of cornea and uvea
where aqueous leaves the eye |
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Term
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Definition
located posterior edge of internal scleral sulcus (corneal scleral junction)
anchor for trab
origin of ciliary muscle |
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Term
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Definition
-encircles the circumference of anterior chamber
-triangular in XS apex a scwalbe's line and base at scleral spur |
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Term
| Structure of trab meshwork |
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Definition
-perforated sheets form meshwork
-2 anatomical portionsL
corneoscleral meshwork- outermost attached to sclera
- uveal meashwork- attached to ciliary body tissue
histology: inner core of collage, surrounded by ground substance, covered with endothelium
-aqueous exits through |
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Term
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Definition
-located between sclera and trab
-circular venous channel
-outer wall contains tight junctions
-inner wall contains ZO
-resovoir for collection of aqueous |
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Term
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Definition
also called cribiform layer
-seperates the endothelial cell lining of the canal from the trab meshwork
-contains cells with phagoctyic properties |
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Term
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Definition
-method to view anterior angle structures
-necessary due to total internal reflection
- can overcome internal relflection and contains mirrors
- structures seen: iris root, ciliary body, scleral spur, trab, schlenms canal, schawalbe's line (ring) |
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Term
| If there is blood backed up in schlem's, how will it appear? |
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Definition
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Term
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Definition
-15%-20% of population
-congential hypertrophied schwalbe;s line, projects as a glistening ridge
-is sometimes pigmented |
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Term
| why is it good to check diabetics with gonio |
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Definition
| bc neovascularization of iris (NV of angle) |
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Term
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Definition
-annular (donut shaped) area posterior to iris surrounding lens equator
partitions:
-canal of Hannover- contains zonules
-canal of petit- most posterior zonules to vitral face |
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Term
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Definition
Bathes posterior cornea and anterior lens
provides nutrients (cornea and len both avascular
carries metabolic waste away |
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Term
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Definition
-secreted by ciliary processes into posterior chamber
-moves through pupil into anterior chamber
Exits from anterior chamber via two pathwaysL
1) trab mechwork -> schlemm's canal
2) uveoscleral flow |
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Term
| What is the path of the aqueous through the trab to schelmm's canal |
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Definition
-passive passage through meshwork
active phagocytic process within endothelial cells is theorized to maintian open passageways
-through justacanicular tissue
-passes through giant vaculoes in endothelial cells of schelmm's canal
(temporary vaculoes form and provide eay passage through endothelial canal |
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Term
| How does the aquous move through schelmm's canal to the venous system? |
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Definition
-internal collector channels (of Sondermann)
these are blind pouches (no direct opening)
Exit from Schlemm's:
Schlem's-> external collector channels-> deep scheleral plexus-> intrascleral plexus-> episceleral plexus-> conjunctival veins |
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Term
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Definition
| provide another route from the canal. pass from the outer wall of the canal directly to episcleral veins |
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Term
| What is the convential method of outflow of aqueous? |
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Definition
| Trab meshwork through schelmm's |
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Term
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Definition
-10-20% of outflow goes through this path
0 absorbed into face of ciliary body and then into veins of ciliary body or sclera through uveal meshwork
-unconvential outflow
-just a small amount of aqueous |
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Term
| How much aquous is in the anterior and posterior chambers |
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Definition
anterior- .25 ml
posterior- .06 ml |
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Term
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Definition
optically empty
little or no light scatter
no large molecules
Tyndall phenomenon- look for cells and flare with conical beam. |
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Term
| What must be considered with the IOP |
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Definition
Aqueous is produced by the ciliary body
-must cross epithelial membrane
-concentration gradiant effects
-passage mechanisms |
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Term
| what are the 3 mechanisms by which substances cross epithelial membranes |
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Definition
1)diffusiono down conc gradient
2)ultrafiltration
-flow across epi
-diffusion but movement can be enhanced by increasing hydrostatic driving force
3) active transport
-a pump mechanism
-utilizes ATP when solutes move across concentration gradient |
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Term
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Definition
-molecules exit blood via CB fenestrated caps
-Ions enter PCE via cotransporters, pumps and exhangers from stroma
-pass into NPCE via gap junctions
-ions exit basolateral membrane via channels, cotransporters and pumps
-aqueous is produced as these ions and fluid enter the posterior chamber |
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Term
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Definition
-ascorbate is 20 times higher in aqueous than in plasma (free radical scavenger)
-protein is 200 times greater in plasma than in aqueous (trace amounts in aqueous) |
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Term
| Blood-aqueous barrier affects aquous composition |
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Definition
-fenestrated ciliary body capillaries
-ZO in non-pigmented ciliary epithelim
-non-fenestrated iris capillaries (iris capillaries do not add anything)
-tight junctions in posterior iris epithelium |
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Term
| How is IOp maintained generally? |
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Definition
| -a constant rate of production is balanced by a constant rate of exit. |
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Term
| Aqueous production inflow is dependent on three factors: |
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Definition
1) ultrafiltration from Bv's in ciliary processes which is dependent on hydrodynamic pressure head
(Pcap-IOP)
2) facility of inflow Cin
this takes into account the resistance in the tissue through which the aqueous components pass
measured in microliters/min/mmHg
Cin=1/R
3) metabolic pump S (microliters/min)
located in the ciliary epi
remains constant, in not effected by IOP
can be affected by Drugs |
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Term
| Uveoscleral outflow is dependent on 3 factors: |
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Definition
1) hydrodynamic pressure head
IOP-Pev
2) facility of outflow Cout
takes into account the resistance through the trab mechwork and juxta canalicular tissue
3) uveoscleral outflow U
homesostatic mechanism
U remains constant except at high IOP |
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Term
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Definition
-Holds true at low and moderate IOP
-at high the trabeculae collapse against one another and Schlemm's canal may in fact collapse increases outflow resistance
-when balance is upset usually affects outflow
-a small variation may cause a large change in IOP
- decreased flow through Trab decreases outflow and IOP will increases possibly caused by debris build up in trab
-increase in episcleral venous pressure causes decrease in outflow consequently IOP will increasem however aqueous production will also decrease maintaining homeostasis |
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Term
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Definition
variations in IOP throughout the day, may be due to varying rate in production.
normal change in IOP is 4 |
|
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Term
| what are normal IOP ranges? abnormal? |
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Definition
Normal in teens
between 20-25 watch
.25 high IOP |
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Term
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Definition
-Goldmann-measures the pressure necessary for a prism/probe to applanate specific surface of cornea (indirect measurement of IOP)
-GAT may overestimate IOP with thick cornea
-GAT may underestimate IOP with a thin cornea |
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Term
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Definition
| moderate to high IOP with no ocular damage evident |
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Term
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Definition
-Disease which damage to nerve fiber layer of retina occurs
-it is probable that the intraocular pressure is implicated in reducing the perfusion from the capillaries that supply the nerve fiber layer |
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Term
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Definition
| Normal or even low pressureis capable of causing damage in some individuals |
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Term
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Definition
| Normal or even low pressureis capable of causing damage in some individuals |
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Term
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Definition
-decrease in outflow facility
-accumulation of pigment on trab (pigmentary dispersion syndrome).
-may be of unknown etiology with no blockage evident: colorless plaque build ip in juxtacanalicular tissue or trabb |
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Term
| Drugs that increase outflow |
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Definition
1)Miotic eg pilocarpine (not first choice:
causes contraction of iris sphinter and ciliary muscle
ciliary body attached to scleral spur as in trab
-geometry of trab is changed making it more porous ie resistance through trab is diminished
2) prostaglandins
current tx
increases uveoscleral outflow
opens up spaces between ciliary muscle fibers |
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Term
| Drugs that decrease rate of production |
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Definition
Affect transport mechanisms:
Carbonic anhydrase inhibitors
Beta blocker and alpha adrenergic agonist
oral hypertonic solutions shift fluid out of cells into blood stream |
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Term
| Endoscopic cyclophotocoagulation |
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Definition
| laser ablation of ciliary process pigmented epithelium |
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Term
|
Definition
-peripheral iris pushed into angle and covers trab
-can be acute or chronic problem
-only occurs in person with narrow angle
-exercise caution when dialating |
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