Test 2: lecture 29 lens Flashcards
The transparent structure inside the eye that focuses light rays onto the retina.
lens
phako-
lens
what side of the lens will have epithelial cells
anterior
during gestation cells are pushed forward
congenital cataracts are located where in the eye?
nucleus/center
secondary lens fibers form at the — and move —
equator
inward- new layers are formed around primary fibers (onion)
lens is held in place by
zonular fibers attached to ciliary body processes
lie in patella fossa of the vitreous
epithelial cells — on the lens are the thickest
anterior
cells elongate and loose nucleus and organelles at equator
epithelial cells form a Y at what part of the lens
anterior
will have inverted Y at posterior of lens
the lens is surrounded by —
elastic acellular capsule
new layers of lens fiber are formed at the —
equator
older fibers are pushed toward the center
equator: is a frquent site for aquired cataracts
what part of the lens can you see with split lamp
capsule(anterior lens)
nucleus
lens is made of soluble proteins (—) and insoluble proteins (—-)
cyrstallins (85%)
decreases with age
albuminoid (15%)
increases with age
34% of lens is protein, 65% is water
what type of protein in the eye will decrease with age?
soluble (cyrstallin)- can leak out over time
how does lens get energy
anearobic glycolysis
nuclear sclerosis of lens will cause —
blue-whitish- but can still see through it
normal aging process
caused by change in protein composition and packing of lens fibers
issue with lens
nuclear sclerosis
blue-whitish- but can still see through it
normal aging process
caused by change in protein composition and packing of lens fibers
Any opacity of the lens or its capsule
cataract
3 type of age of onset cataracts
Congenital: present at birth
Juvenile (developmental): from birth to middle age (dog:~ 6 years)
Senile (age-related): (dog > 6 years)
inverted Y= back of eye
posterior polar/subcapsular cataract
what type of catarct
incipient
small- less then 10-15% of lens
do not impair vision
can still see back of eye
mat be located at the equator- easier to see if you dilate pupil
incipient catarct take up — % of the eye and — vision
10-15%
do not impair vision
can still see back of eye
can be found at equator- easier to see if you dilate eye
— cataract is Any degree of lens opacity that is more than incipient but less than complete
immature/incomplete
can impair some vision, but not total blindness
can still see back of eye
mature/complete catarct
complete opacity- total blindness- can not see back of eye
mature cataract do what to the eye
complete opacity of lens
total blindness- can not see back of eye
hypermature/resorbing cataract
what happens to lens with hypermature cataract
becomes smaller as lens is liquefied
anterior lens capsule becomes wrinkled
can see tapetal reflection
can cause uveitis
total resorption can lead to dissapearance of opacities
hypermature cataract will cause the — to become wrinkled and can cause lens-induced —
anterior lens capsule
uvelitis (phacolytic uveitis)
hypermature cataract will cause resorption that will do what to opacities?
appear crystallized and then over time will dissolve/liquify opacities
morgangnian cataract is a form of — cataract in which the nucleus —
hypermature
sinks ventrally in a fluid cilled capsular bag
often associated with len-induced uveitis
what type of cataract
morgagnian
A form of hypermature cataract in which the nucleus sinks ventrally in a fluid-filled capsular bag.
Often associated with lens-induced uveitis.
what are the two major causes of cataracts
most are genetic
metabolic (DM)
how does Diabetes cause cataract
excess glucose can not be broken down by hexokinase
lens will use aldose reductase to create sorbitol which will cause water to enter lens
can occur in 24hrs!
cararact caused by
diabetes
excess glucose broken down by aldose reductase to form sorbital which pulls water into the lens and swells fibers
intumescent cataract- can occur in 24 hrs!
besides genetics and DM what else can cause cataract
secondary to other ocular disorder: uveitis, glaucoma
trauma: lens perforation
age related: UV exposure, decrease in antiocydant activity in the lens
nutritional: low arginine
toxic: DMSO
how to treat cataracts
medical: antioxydants, anti-inflammatory, mydriatic drugs
surgical: Extracapsular cataract extraction (ECCE), Phacoemulsification
two surgical treatments of cartaracts
Extracapsular cataract extraction (ECCE)
Phacoemulsification
tremor of the lens
phacodonesis
tremor of iris
iriododonesis
clinical signs of lens luxation
- tremor of lens and iris (phacodonesis, iridodonesis)
- increased or decreased anterior chamber depth, depends of how lens moves
- increased IOP
- aphakic crescent
- corneal edema
- uveitis
- vitreous syneresis (liquefaction)
primary cause of lens luxation
defect in zonules
ADAMST17 mutation- terriers, spaniels, sharpeis
secondary causes of lens luxation
glaucoma, uveitis, intraocular tumor, trauma
— lens luxation is an ocular emergency because it —
anterior
risk of acute glaucoma- within 24 hrs can increase IOP
intracapsular lens extraction
how to treat anterior lens luxation
intracapsular lens extraction
