OPTHALMOLOGY 7 Flashcards
what are the 4 layers of the lens
capsule
epithelium
cortex
nucleus
is lens cpsule thicker at the anterior or posterior edge?
anterior
which side of the lens has an epithelial layer?
anterior
what are suture lines? [theyre in the cortex]
shape where the cortex fibres meet
Y in front, λ at back
What is the function of lens zonules?
collagenous fibres that suspend lens behind pupil
from ciliary body muscle to lens capsule
function of ciliary body muscle?
which CN controls it?
accomodation
CN III
what are 2 broad categories of diseases of the lens
oapcities
abnormal positon
what is the difference in APPEARANCE betweennuclear sclerosis & cataract?
sclerosis: transperant ring on distant direct opthalmoscopy
nuclear sclerosis has what effect on vision?
not much. normal ageing change
the condition with opacity of the lens is called
cataracts
what are two structural changes of the lens due to cataracts
disruption of fibre arrangement
accumulation of insoluble protiens
Nuclear sclerosis vs cataracts: which si typically in older animals?
sclerosis
Nuclear sclerosis vs cataracts: which can be located anywhere in the lens?
cataracts
Nuclear sclerosis vs cataracts: which one blocks tapetal reflection?
cataracts
Nuclear sclerosis vs cataracts: which one requires treatment?
cataracts
What are the 4 stages of cataracts
incipeint
immature
mature
hypermature
how are incipient and immature cataracts classified?
by affected alyer
An incipient cataract affects what % of the lens?
is tx indicated?
<15%
no
An immature cataract affects what % of the lens?
is tx indicated?
15-80%
if severe end & vision is poor
a mature cataract filld the entire lens. is taeptal reflection visible?
is sx indicated?
no
yes
what causes a hypermature cataract
is sx indicates?
cataract liquefacation and resorption
lens shrinks in volume, creating wrinkles
sx is risky
5 causes of cataracts
- congenital
- hereditary
- diabetes mellitus
- secondary
*senile/sponaneous
what is the physiological cause of a diabetic cataract?
hyperglycaemia –> XS glucose metabolised to sorbitol –> sorbitol cannot diffuse through lens capsule –>draws water into lens
what is the apearance of a diabetic cataract?
intumescent cataract
(swollen lens due to fluid accumalation. risk rupture!)
secondary cataracts can often be due to atrophy of what other part of the eye?
retina
what is the name of a cataract sx?
what does it do? (briefly)
phacoemulsification
removes opaque lens and replaces with artificial lens
2 types of lens luxation?
anterior & posterior
(also aetiolgoy is primary and secondar)
anterior lens luxation is an emergency because it can lead to _____
glaucoma
also its painful
posterior lens luxation takes place due to degeneration of the _________
vitreous
tx of anterior lens luxation
surgical:
non-surgical:
A: surgical extraction of lens
NS: transcorneal reduction/couching
a patient with lens luxation will need which lifetime medication? why?
prostaglandin analogue drop to maintain pupillary constriction
