The Iris Flashcards
Look at objectives… 6 questions
slide 3
True/False: The size of the iris has great effect on the field of view of the eye.
False, has little effect on the field of view of the eye
True/False: The amount of light passing through the iris is proportional to its area.
True
Functions of Iris
Regulates Retinal illumination Regulates glare Regulates Optical Aberrations Regulates Depth of Focus Provides nonverbal communications and social signaling Attraction/ Mate selection
Avg diameter of Iris is what?
12 mm
Pupil center is slightly _____ and _______ to iris center.
nasal
inferior
Abnormally centered pupil is _________.
ectopic
Irregular or ectopic pupils ________ opical quality
degrade
______________ rests on anterior surface of lens.
Pupillary margin
______________ flows from posterior into anterior chamber through the pupil.
Aqueous humor
What are the 4 layers of the Iris?
Anterior Border layer Stroma and sphincter muscle Anterior border layer Stroma and sphincter muscle Anterior epithelium and dilator muscle Posterior epithelium
Which layer of iris is the dilator?
Anterior epithelium
Stroma consists of pigmented and nonpigmented cells, collagen fibrils, and extensive ________________.
ground substance
collagen fibrils are arranged in radial columns
Anterior border layer characteristics?
Not seperate layer from stroma
Fibroblasts and pigmented melanocytes
Can contain oval shaped iris crypts
Anterior iris synechia at iris periphery can adhere to the corneal endothelium or trabecular meshwork.
Sphincter muscle within stroma, what are some characteristics?
Smooth muscle cells joined by tight junctions .75 - 1 mm wide Anchored to stroma Constricts for miosis Innervated by parasympathetic system
Anterior epithelium and dilator muscle has _________ which is pigmented epithelium joined by tight junctions
Apical portion
Anterior epithelium and dilator muscle has _________ which is composed of smooth muscle processes which extend into stroma.
Basal portion
Dilator causes mydriasis and is __________________ innervated.
sympathetically
What is single layered, heavily pigmented, columnar cells joined by tight junctions.
Posterior Epithelium
Where is the major circle of the Iris located?
Ciliary body
they are thick walled blood vessels
Where is the minor circle of the iris?
At junction of ciliary and pupillary portions Inferior to the collarette Located within the iris and stroma Not fenestrated Forms blood-aqueous barrier
You fire a YAG laser shot at the Iris and see pigment coming out of the pupil. What layer caused this?
Posterior epithelium
You fire an infrared diode laser at the iris and notice radial movement from the pupil to the limbus. WHat layer was this?
Anterior epithelium and dilator muscle. Specifically dilator muscle
Iris dilates and constricts approx __ times per sec.
2 times per sec
Rythmic oscillation of Iris is called ________.
Hippus
Pupil size always has an implicit +/- _____
0.2 mm
Absence of hippus can indicate problem with what?
innervation or damage to iris
Where root tears away from the ciliary body.
Iridodialysis
May cause nerve and vessel damage
What does eye color depend on?
Color depends on number and type of melanin granules within melanocytes. (Number of melanocytes are constant)
This effects 6 out of 1,000 eyes.
heterochromia
Anisocoria
Difference in iris
Difference of anything less than 4 mm is normal
