Function of the Iris Flashcards
Cornea _______ the iris
magnifies
Diameter of Iris
12mm
Thickness of Iris
500 microns at thinnest point
Abnormally decentered pupil
ectopic
Posterior portion of iris originates from….
neuroepithelium
Parts of posterior portion of iris
dilator m
sphincter m
post pigmented epithelium
Anterior Portion of iris originates from…..
mesoderm
Parts of anterior portion of iris
iris stroma
iris vessels
iris nerves
chromatophores
Optimal Pupil Size
2mm
Functions of Iris
regulates retinal illumination, glare, optical aberrations, depth of focus
nonverbal communication and social signaling
attraction/ mate selection
Miosis
Constriction
pupillary portion pleats, ciliary portion smooths out
Mydriasis
Dilation
stroma in pupillary portion goes flat, ciliary portion pleats
T/F Stroma and iris are elastic
false
Iris Stroma
thickest part
made of collagen
Function of Stroma
anchor for sphincter m, nerves and vessels
protects nerves and vessels from stretching and kinking
Anterior Border Layer
pigment- melanocytes
thicker in darker eyes
Iris Vessels come from….
ophthalmic artery- long post ciliary aa + ant ciliary arteries (next to rectus mm)
T/F Iris does not bleed when cut
T
Myopes/ Hyperopes have larger pupils?
myopes
greater corneal power and deeper anterior chambers
Affects vision if pupil size is smaller than 2 mm
diffraction limit
reduced illumination
Pupil size ______ with age
decreases
Near Vision Triad
convergence, miosis, accommodation
Iris sphincter and dilator originate….
neural ectoderm
Iris Sphincter innervated by…
parasympathetic
Iris Dilator innervated by…
sympathetic
Which iris muscle is stronger?
they are equal
Iris and Aging
no change to dilator m or light reflex
pupil size reduced
Horner’s Pupil
dilates less than normal when given cocaine
Cocaine
blocks reuptake of post-ganglionic NE causing dilation
Apraclonidine
increased mydriasis in Horner eye
Part of iris absorbing heat
pigment of posterior iris
causes sphincter to contract- possible iritis w/ miosis
