Flashcards in B10 Deck (242):
The pupil that is seen is actually a _____ image of the ____ pupil
Magnified virtual image of the real object pupil
Name the 7 functions of the iris
-improve visual clarity (regulates optical aberrations
-non verbal communication
-increase the depth of focus
The iris separates the
Anterior and posterior chambers of the eye
The iris is surrounded by what fluid?
T/f: the iris is the most anterior portion of the uveal tract
The iris rests lightly upon the ___
What is the average diameter of the iris?
The pupil center is slightly __ and ___ to the iris center
Slightly nasal and inferior
An abnormally decentered pupil
What does irregular or ectopic pupils do to optical quality
They degrade it
The pupillary margin rests on the ___ surface of the lens
How does aqueous humor flow
It flows from the posterior-->anterior through the pupil
T/F: Temporal iris in humans broader than nasal iris
The posterior portion of the iris is derived from?
The dilator muscle is derived from the
The sphincter muscle is derived from the
The posterior pigmented epithelium is derived from the
The anterior portion of the iris is derived from
The iris stroma is derived from
The iris vessels is derived from
The iris nerves are derived from
The chromatophores are derived from
What are the 4 layers of the iris?
-anterior border layer
-stroma and sphincter muscle
-anterior epithelium and dilator muscle
What layer contains both mesoderm and ectoderm
Stroma and sphincter muscle
The reduction in optical aberrations and depth of focus is optimal at
2mm or less
What are the only elements in the iris that is capable of initiating movement
What occurs in miosis (constriction if pupils)
the pupillary portion of iris gathers into pleats while the ciliary portion smooths out.
What occurs in mydriasis (dilation)
the stroma in the pupillary zone pulls flat while
contraction furrows appear in the ciliary area.
T/F: blow flow is impeded by wither miosis or mydriasis
False. It is not impeded
T/F: in the past, it was believed that the stroma and blood vessels were responsible for iris movements, via elastic expansion, changes in hydration, and/or engorgement.
T/F: the stroma and iris vessels are elastic
False. They are not elastic
is a loose but orderly meshwork of collagen fibers with aqueous fluid and scissor like angles for folding
Thin-walled layer of endothelium with an outer
covering of collagen fibrils.
The thickest portion of the iris
What are the 4 functions of the stroma
-provides an anchor for structures
-protects the nerves and vessels from stretching and kinking
-adapts to constant movement
-folds and unfolds with minimal resistance to minimize energy expenditure
The stroma provides an anchor for what 4 structures?
Structure that is more densely than deeper stroma
Anterior border layer
Dark brown spots that are compact masses of rounded cells filled with melanin
T/F: the anterior border layer is more solid and dense with more layers in darkly pigmented eyes.
What kind of cells does the ABL have
Fibroblasts interlaced with melanocytes
T/F: In the ABL the iris is porous (no anterior limiting layer)
What gives us a blue iris
Light scatter in uniform space across stromal tissue
Why do most newborns start out with blue eyes then turn dark?
Because they haven't developed pigment yet
What causes dark irises?
Development of anterior stromal melanocytes and production of pigment
Blood flow of the iris is derived from
ophthalmic artery from two long posterior ciliary arteries and anterior ciliary arteries.
The anterior ciliary arteries run along the
T/F: the iris doe not bleed when its cut
There are 2 anterior ciliary arteries in each rectus muscles except for
Lateral rectus (it only has 1)
Allows for little distension and folding of vessels during constant movement of iris
Perivascular collagen sheaths
T/F: Perivascular collagen sheaths are unique to iris vessels
T/F" Humans react to light stimulation of the retina rather than the iris.
Light reflex is an important test to discover the integrity of the
The entire stimulus response function resembles a ___curve
The latency time becomes ____ with dimmer light stimuli
In scotopic and photopic conditions, the pupil_____with variability in light
Doesnt really change all that much
In mesopic conditions, the pupil_____with variability in light
Changes a lot
In the dark adapted state, the threshold light of intensity needed to produce a pupil contraction becomes ___ as rods are brought into play
T/F: Rods in the dark adapted state do not produce as much increase in pupil contraction in response to increases in stimulus intensity
In dark-adapted eyes, pupillary reactions occur at intensities
Below photopic range
In dark adapted eyes the parafovea and peripheral are ____ sensitive than the fovea
In normal light adapted eyes, pupillary threshold is
In normal light adapted eyes, the fovea is ___reactive than the periphery
T/F: the pupil has a max speed to contract
True. Not matter the intensity of light the pupil will contract at the same speed
What is the max speed of pupil contraction?
T/F: The pupil has to be able to see a stimulus long enough for it to react
With longer duration of a stimulus, the pupil contracts___, there is a ___latency time, and the contraction lasts ___
-shorter latency times
-contraction lasts longer
The pupil is more constricted when the light covers a ____ area and when light is ____bright
Covers a greater area and light is equally bright
T/F: Pupils sums afferent impulses regardless of spatial distribution, both rods and cones.
Under dark adaptation, the fovea shows ___ sensitivity compared to surrounding retinal areas because of the lack of rods
In mesopic and photopic adaptations the pupil responds greatest in the ___ field
T/F: the temporal field response is usually greater than the nasal field response
The peak sensitivity under photopic conditions is
The peak sensitivity under scotopic conditions is
The greater the spatial frequency, the ___ the pupil contracts
20/20 has a ___ spatial frequency
T/F: The pupil responds to motion even when the light level stays the same
Some people think that myopes have ___ pupils and hyperopes have ___ pupils
Myopes: larger pupils
Hyperopes: smaller pupils
Larger pupils can result in what 2 things
If the pupils are too small (<2mm) what 2 things can effect visual performance
What is the optimal pupil size?
Does pupil size increase of decrease with age?
The pupil diameter can vary between?
What is the near vision triad?
Convergence, miosis, and accommodation
What is the 3rd nerve nucleus?
Amplitude for young people is ___ to contraction from bright light
Is iris sphincter and dilator muscle is derived from
The iris sphincter is predominately innervated by
The parasympathetic system
The iris dilator is predominately innervated by?
The sympathetic system
T/F: the sphincter and dilator muscle are equally strong
When are the pupils smaller?
During sleep and death
When are the pupils bigger?
During waking hours and when frightened
What 3 things can elicit a pupillary dilation?
If something is less arousing how will this effect a pupillary reaction?
There will be less of a pupillary response
If you are infuriated, will you have a greater or lesser pupillary reaction?
What are some findings of pupil size in adults
-they can still respond fully to mydriatic drugs
-pupils are still round and smooth
-light reflex remain brisk
-reduction is size is a linear process
-no change in thickness of dilator muscle with age
-decreasing pupil size begin in healthy eyes with strong levels or accommodation and brisk reactive pupils
If someone has horners syndrome what happens to the pupil when you put cocaine in their eye?
The horners pupil dilates less than the normal pupil
What does cocaine do to the eye?
blocks the reuptake of post-ganglionic norepi
resulting in the dilation of a normal pupil from retention of norepi in the synapse.
What can high levels of infrared do to the eye?
It can burn any ocular structure and have very deep penetration
What layer of the iris absorbs heat?
The black pigment of the posterior iris layer
When stimulated directly by heat, what happens to the iris sphincter?
If the iris ensues, what may occur?
T/F: the ciliary body contains the minor arterial circle of the iris
What is the most posterior structure when looking doing gonio?
What is the most anterior structure when doing gonio?
Name the order from anterior to posterior when doing gonio
Schwalbes line--> trabecular meshwork --> scleral spur --> ciliary body
Name the 4 functions of the ciliary body?
-indirectly causes iris contraction
What does aqueous production do?
Supplies nutrients to the lens and cornea
What does aqueous outflow do?
-removes waste products
What are the 3 main process to produce/secretary aqueous humor?
The stroma within the ciliary processes contains a dense network of ____ capillaries, and the number and shape of the processes provides a large ____ for secretion into the posterior chamber.
-large surface area
Active secretion accounts for ___ of aqueous production
What is the most significant factor in aqueous production?
What facilitates water movement
-coordination of ion pumps, channels
-cotransporters in the 2 epithelial
What primarily drives secretion in the posterior chamber?
Movement of Na+ and Cl-
What has an indirect role in moderating the Cl flux
What is the rate of aqueous production?
2.5 ul per minute
This substance is a metabolic waste produce of glycolysis of the lens and cornea and is in high concentrations in the aqueous
Ascorbate concentration is ___ higher in the aqueous than in blood plasma
If aqueous produced more during the day or night?
Day. Decreased 50% at night
T/F: Dilating and constricting blood vessels can influence aqueous blood vessels by increasing and decreasing blood volume.
Diameter of zonular fibers
Elastic fibers that stabilize the lens and allows fluid to flow from the posterior chamber to the vitreous. And attaches to the lens
When is accommodation lost?
Contraction of the longitudinal fibers of the ciliary muscle pulls the choroid forward, and contraction of the circular fibers draws the CB closer to the lens, decreasing the diameter of the ring formed by the CB. This releases tension on the zonule fibers and allows the lens capsule
to adopt a more spherical shape.
During accommodation the lens ____ ,the anterior surface curve ____, zonular fibers ____, the lens capsules becomes a more ___shape, and _____ refractive power
The lens thickens
The anterior curve increases
Zonular fibers relax
Lens capsule becomes more spherical shape
Increases refractive power
When looking at a distance, the ciliary muscle is ___ and the zonular fibers are ___
The ciliary muscle is relaxed
The zonules are pullin on the lens capsule
Pilocarpine cases ciliary muscle ____
Does accommodative amplitude decrease or increase with age
What stimulates miosis
Accommodation and convergence
Subjective measurements of accommodation rely on
Perception of clarity
Objective measurements of accommodation can be obtained with an
Autorefractor or aberrometer
T/F: dynamic measurements are better than static measurements
What really effects presbyopic eye movement?
The lens becoming thicker and stiffer
T/F: reduced near vision is caused by significant reduction in strength of ciliary muscle
False. It is not caused by it
What are some structural changes in the aging eye that could lead to reduced contractile force?
-thickening of tendons
-reduced muscle mass
-increased connective tissue
T/F: Measurements of contractile strength of ciliary muscle strips with stimulation show no reduction with increasing age.
In presbyopes are there changes in M receptor numbers, binding affinity, or ACh activity?
Loss of the ability to accommodate
Ciliary muscle contractive power ___ up until age that
Are there changes in zonular length with age?
What is the limiting factor for accommodation
The movement and shape of the lens
Why can ciliary muscle contraction change the configuration of the TM?
And what does this do?
Because some of the longitudinal fibers are attached to the TM sheets
Facilitates aqueous movement through the anterior chamber angle structures
What is the max reductions of IOP when dealing with accommodation?
The ciliary muscle is derived from
Describe the Tyndall phenomenon
-When breakdown of blood-aqueous barrier occurs, cells and flare become visible.
-Often immune factors, leucocytes.
-Can form hypopyon
What is hyphema?
-Trauma to head or injury such as whiplash can tear/ break the iris
-This can break the iris blood vessels entering from the major circle of
-Blood settles inferiorly.
A clear, colorless fluid that fills the anterior
and posterior chamber of the eye
What are the 4 functions of the AH?
-Supplies nutrients and oxygen to and remove metabolic wastes from the anterior intraocular tissues such as cornea, lens and TM
-Inflates the eye globe and creates an IOP for normal optical functioning of the eye
-Transports ascorbic acid(AA) into anterior segment where it
serves as an antioxidative agent
-Facilitates the local immune responses during inflammation and
What is the primary site of AH formation?
Which layer of the CE is necessary for AH formation?
What is the major mechanism of solutes across CE?
What drugs reduce aqueous humor formation?
CAI and alpha 2 agonists
Which one has a higher concentration of protein? (Blood plasma or aqueous humor)
Which one has a higher concentration of ascorbic acid? (Blood plasma or aqueous humor)
Beta 2 agonist ___aqueous humor formation
Is AH average rate of formation greater or less during the daytime?
Greater (2.75 ul/min)
What is the pathway (5 steps) of the blood to the AH?
1.) Blood flow-->vascular bed of ciliary stroma
2.) Loading of solute from the ciliary stroma blood into the PE cells
3.) Translocation of solute through the gap junction into the NPE
4.) Exclusion of solute from the NPE cells to the posterior
chamber (driven by an electrochemical gradient and/or by
5.) The osmotic gradient established by the solutes facilitates the
passive flow of water into the posterior chamber by osmosis
What are the 3 mechanisms of solutes across the CF?
Defined as the passive movement of solutes across the CE in response to a concentration gradient
defined as the passive movement of water and water soluble substances across cell membranes as a result of the hydrostatic and oncotic pressure between the ciliary stroma and the AH
an energy-consuming process involving the movement of solutes across the CE against their concentrations gradients
Will people who smoke marijuana have increased or decreased IOP?
What causes this?
Is IOP constant throughout the day?
Why don't we want a lot of protein in the AH?
Because we want to keep transparency
What is the major part of the blood aqueous barrier?
Tight junctions between NPCE cells
What 2 things are allowed to pass to the posterior chamber?
Ions and water
What is a part of the primary vitreous
What are the 3 conditions with remnants of the hyaloid artery?
What is the outermost zone of the vitreous?
Vitreous cortex also called hyaloid surface
What is the center zone of the vitreous called?
Cloquets Canal (hyaloid canal)
What is the intermediate zone of the vitreous?
Inner to the cortex and surrounds the center canal
Where does AH come from?
Barrier to the movement of intermediate- and high-
molecular weight substances such as protein.
Blood aqueous barrier
Barrier protecting the eye from entry of toxic substances and maintaining the homeostatic control
Blood aqueous barrier
Barrier that explains why drugs administered orally
or IV can hardly reach therapeutic levels in
Blood aqueous barrier
Tight junctions are present in the ____ ciliary epithelium
Non-pigmented ciliary epithelium (NPCE)
Other than NPCE where are tight junctions also present?
- in the iridial vascular endothelium
-between the iris epithelial
Endothelial of the inner wall of _____ are tight joined to prevent retrograde movement of solutes and fluid from the canal lumen into the AC
Tight junctions between NPCE cells constitute an effective barrier to intermediate and high molecular weight substances such as ____
What happens to the aqueous when there is a breakdown of the BAB?
And what cells may also be present?
Aqueous becomes cloudy due to leakage of plasma proteins into the posterior chamber (PC) and anterior chamber (AC).
Inflammatory cells may also be present.
In anterior uveitis what 2 things will you see?
Cells and flares (proteins)
Breakdown of the BAB can cause what 2 eye conditions?
- Anterior uveitis
Blood in the anterior segment due to trauma
What are 4 ocular injuries that causes or is caused by BAB breakdown
-Surgical and non-surgical traumas
-Intraocular inflammation (such as uveitis)
-Vascular and systemic disorders (such as diabetes)
- Intraocular tumor
is usually defined as an IOP of 5 mm Hg or less (extremely low pressures)
When there is ocular inflammation what 2 things are releases?
Clear gel which occupies the posterior compartment of the eye.
The vitreous is located between the ___ and the ___
Retina and lens
The vitreous occupies ___ of the volume of the eye
Light initially entering the eye through the
cornea, pupil and lens, is transmitted through the
____ to the ____
Vitreous --> retina
3-4 gestational stage of the vitreous
6th gestational week of vitreous
Zonular fibers are in the ___ vitreous
Is secreted by NPCE of pars plana and persists in the
adult as the suspensory ligament of the lens
Zonular fibers (tertiary vitreous)
Optic cup filed by a system of fibrillar material, presumably secreted by embryonic retina cells is during what stage of vitreous development?
VEGF released by lens induces vasculogenesis; Hyaloid artery penetration is a part of what vitreous developmental stage?
Vitreous stage where Anti-angiogenesis factor present, Hyaloid vessels retract, Vitreous gel body formed
arises from the center of the optic disc, consists of a small tuft of fibrous tissue and represents a remnant of the fetal hyaloid artery.
small, circular opacity on the posterior lens capsule, classically nasal in location, which represents the anterior attachment of the hyaloid artery.
a tubular structure containing remnants of the primary vitreous, located between the posterior aspect of the lens and the retina in the vicinity of the optic disk
Cloquets canal (hyaloid canal)
The pigmented and nonpigmented CE are connected by
Apex to apex
The middle layer of the eye
What are the 3 regions of the uvea?
The choriod extends from the ___ to the ___
Ora serrata to the optic nerve
The choroid is located between the ___ and the ___
Sclera and retina
Layer of the choroid that is thin, pigmented, connective tissue
Pigmented, vascularized, loose connective tissue that contains melanocytes, fibroblasts, macrophages, lymphocytes, mast cells
Large and medium vessels
A later of the choroid that is a single layer of fenestrated capillaries
This layer of the choroid fuses with the retina multilaminated sheet
____choriod absorbs excess light
Provides nutrients to and remove the waste products from outer retina
Sole blood supply to the fovea
Provides a pathway for the posterior vessels that supply the anterior segment
A branch of the ophthalmic artery
What are the 2 branches of the ciliary artery
Short posterior ciliary artery and long posterior ciliary arteries
Long ciliary nerves carries ___ and ___ fibers
Sensory and sympathetic fibers
Short ciliary nerves carry ___ and ___fibers
Sympathetic and parasympathetic
Provides a pathway for the nerves that supply the anterior segment
Suprachoroidal space of choroid
If someone has a hyperopic defocus the choroid will be ___ and the growth is ______
Thin choroid and growth increased
If someone has a myopic defocus the choroid will be ___ and the growth is ______
Thick choroid and growth decreased
The choroid can ___ modulates its thickness, varying the position of the retina and the state of focus of the eye
What are the 4 functions of the choroid?
-Provide nutrients and remove the waste products from outer retina
-Passage of nerves and vessels
-Absorption of excess light
-Regulate emmetropization (study in chicken)
What are the 3 changes in the iris?
-loss of pigmentation
-dilator muscle becomes atrophic
-sphincter muscle becomes sclerotic
What are the 2 aging changes in the ciliary body
-elasticity decreased due to the amount of connective tissue increased within the layer of the CB
-formation of aqeuous humor decreases with aging
What are the 3 aging changes in the choroid?
- choriocapillaries decrease in density and diameter-->choroidal blood flow decreases
- bruchs membrane increases in thickness
-various substance and particles accumulates in bruchs membrane
Nutrients from the choriocapillaries and waste product from the retina pass through what structure?
Name the 5 layers of the bruchs membrane
1.) interrupted basement membrane
2.) outer collagenous zone
3.) elastic layer
4.) inner collagenous zone
5.) basement membrane of RPE cells
Calcification and the yellow deposits in the inner collagenous layer of Bruch’s membrane. Made of the remaining damaged cells (called lipofuscin) from the oxidative stress.
yellow-brown pigment granules composed of lipid-containing residues form oxidative stress
Does the accumulation of drusen make Bruchs hydrophobic or hydrophilic?
T/F: the accumulate of drusen inhibits the passage of metabolites
Accumulation of water between RPE and bruchs membrane causes _____
Stage of ARMD where the choroid still functions
What layer of the choroid is multilaminated sheet and fuses with RPE?
What provides blood to the fovea region?
What part of the retina receives blood supply from choroid?
Which layer of the choroid proves a pathway for the vessels and nerves that supply the anterior segment?
Which layer of Bruchs membrane does drusen deposit?
Inner collagenous zone
Bruchs membrane thickness ___ with aging
With pupil constriction you have a ____depth of field
Low concentration of proteins in aqueous helps prevent ___