Eye Histology Flashcards
divisions of eye
two compartments - anterior and posterior
-divided by lens, suspensory ligaments, ciliary body
anterior compartment
aqueous humor, anterior and posterior chambers
posterior compartment
vitreous humor (jelly like, proteins, hyaluronic acid, specialized cell types)
three tissue types in eye
exterior > interior corneo-scleral (fibrous tunic) uveal layer (vascular tunic) retinal layer (neural tunic)
sclera
white of eye posterior 5/6 of eye
-made of corneo-scleral layer
uveal layer
vascular layer
- choroid - posterior of 5/6 eye
- anterior - ciliary body and iris
retinal layer
anterior - pigmented epithelium
posterior - neuronal
accessory structures of eye
conjunctiva
lacrimal gland
eyelid
conjunctiva
glands
tarsal gland and lacrimal gland
continuous with the sclera
ends corneo-scleral lymbus
sclera
collagen and elastin
-nearly avascular, except scleral horn
cornea
transparent in anterior 1/6 of eye
avascular but highly innervated
5 layers of cornea
outer epithelium bowmans membrane substantia propria descemets membrane corneal endothelium
outer epithelium of cornea
non-keratinized squamous
bowmans membrane
thin basal lamina
substantia propria
dense collagen tissue with sparse keratinocytes
descemets membrane
thick basal lamina
corneal endothelium
responsible for active transport of fluid out of SP and allowing diffusion of metabolites from aqueous humor
cornea
myelinated due to schwann cells
-become unmyelinated in corneal epithelium
corneal epithelium stem cells
at corneal-scleral lymbus
- can multiple to heal the cornea
- tissues underneath - don’t have ability to regenerate
myopia
nearsightedness
- focused in front of retina
- cornea too curved, lens too powerful
hyperopia
farsightedness
- focused behind retina
- lens and cornea too weak
lasik
laser assisted in situ keratomileusis
for both myopia and hyperopia
corneal flap raised - ablation of corneal stroma
- flap irrigated and replaced
- no sutures applied
- corneal epithelial cells are replaced by mitotic cells found in periphery, which migrate into wound
uveal layer
back of eye - choroid
choroid
blood supply to outer layers of retina
- photoreceptor cells
- loose CT, fibroblasts, melanocyte
- bruchs membrane
- choriocapillaris
bruch membrane
separate choroid from retina
-controls movement of metabolites
choriocapillaris
next to retina, rich in capillaries
drusen
deposited between retina and bruchs membrane
-often later in life
sign of macular degeneration
impede flow and exchange of metabolites
-cannot support photoreceptors
ciliary body
anterior uveal layer
- wedge shaped - between iris and vitreous body
- loose CT, smooth m., pigmented / nonpigmented epithelium, zonule fibers
zonule fibers
radiate from ciliary processes to lens
function of ciliary body
production of aqueous humor
accomodation
change shape of lens to view something closer/farther
- with help of ciliary muscles in ciliary body
- three bundles
- one opens canal of schlemm, two stretch ciliary body
close vision
ciliary muscle contracts
distant vision
-lax zonule fibers
ciliary muscle relaxed
-tense zonule fibers
suspensory ligaments??
look at notes
pigmented ciliary epithelial cell
outside layer
nonpigmented ciliary epithelial cell
inside layer
fenestrated capillaries
open to pigmented ciliary epithelial layer
- goes to ciliary channel
- non-pigmented layer for active transport
circulation of aqueous humor
important for intraocular pressure
- fluid flows posterior chamber to anterior chamber
- to trabecular meshwork
- to canal of schlemm (circular canal)
- drains to episcleral veins
corneal irideal angle
area between descemets membrane of cornea and anteiror surface of iris
canal of schlemm forms complete circle here
glaucoma
group of Dx characterized by optic neuropathy
-loss of vision due to death of retinal ganglion cells (back of eye)
risk factor for glaucoma
increased intraocular pressure
clinician looking for glaucoma
size of cup of optic nerve
open angle glaucoma
most common corneal irideal angle is open -increased IOP -optic nerve cupping -Tx: prostaglandins, beta blockers, alpha adrenergic agonists, trabeculectomy or trabecloplasty
angle closure glaucoma
corneal-irideal angle is obstructed
- aqueous outflow impeded
- primary anatomic cause or secondary cause
Pt may show characteristic conjunctival redness
iris
colored anterior extension of ciliary body
- controls pupil
- separates anterior and posterior chambers
- two concentric ring
anterior iris
does not have epithleium
pigmented melanocyetes - determine color
stroma of iris
vascularized loose CT with radial vessels
contractile of iris
dilator pupillae muscle (sympathetic)
sphincter pupillae muscle (parasympathetic)
posterior surface of iris
pigmented epithelium, continuous with ciliary body
lens
transparent, biconvex, avascular
-supported by zonule fibers
three components of lens
lens capsule lens epithelium (only anterior and lateral surface) lens fibers - elongated flattened
types of lens fibers
cortical lens fibers
nuclear lens fibers
crystalline protein
makes lens clear
solubility of these proteins is important
-must be hydrated
insoluble crystalline protein
precipitate out - form cataracts
cataracts
leading cause of blindness worldwide
- mechanism unknown
- as lens cells become fibers, never shed
- continue to compact nucleus of eye
- damage is accumulated to these cells
believe cause is photo/oxidative injury
Tx of cataract
surgical replacement of synthetic intraocular lens
- emulsify lens and remove it
- put in new synthetic lens
