The Lens

Question 1

what are lens sutures?

Answer 1

where mature lens fibers attach end-to-end

Question 2

what does the lens separate?

Answer 2

anterior from posterior segment

Question 3

what is aphakic crescent?

Answer 3

space between pupil and lens equator

Question 4

what are contraindications for pupil dilation?

Answer 4

glaucoma
lens instability

Question 5

how can you assess for lens clarity?

Answer 5

direct illumination
retroillumination

Question 6

what does parallax help with?

Answer 6

determining anterior vs posterior lesions

Question 7

what is nuclear sclerosis?

Answer 7

aging change
increased lens fiber density scatters light
lens fibers are normal but there are more of them

Question 8

what can cataracts be due to?

Answer 8

increases in water content
changes in protein content
altered nutrition
altered metabolism
oxidative stress

Question 9

do cats develop diabetes mellitus cataracts?

Answer 9

no

Question 10

what is a morgagian cataract like?

Answer 10

cortex liquefies faster than nucleus
regains tapetal reflection

Question 11

has any medication or supplement been shown to reverse cataracts?

Answer 11

no

Question 12

what are treatments for anterior lens luxation?

Answer 12

lens removal
trans-corneal lens repositioning
enucleation

Question 13

what are potential consequences of posterior luxation/subluxation in a dog?

Answer 13

glaucoma
retinal detachment

Question 14

how can you treat Encephalitozoon cuniculi?

Answer 14

fenbendazole
anti-inflammatories
cataract surgery
enucleation

Question 15

how much of the focusing power does the lens provide?

Answer 15

25%

Question 16

where are newer cells of the lens as it grows throughout life?

Answer 16

newer on outside
older on inside

Question 17

how does glucose get to cells in the lens?

Answer 17

diffuses in from aqueous humor

Question 18

what extends 360 degrees from ciliary body to lens capsule?

Answer 18

lens zonules

Question 19

what is normal when using a slit beam to evaluate anterior chamber depth?

Answer 19

parallel lines with some space between

Question 20

what is direct illumination?

Answer 20

uses light to illuminate lesion of interest

Question 21

what is indirect illumination?

Answer 21

uses tapetal reflection to illuminate lesion of interest

Question 22

what is parallax?

Answer 22

axis of rotation: anterior vs posterior lesions

Question 23

how can you identify nuclear sclerosis?

Answer 23

pearly/hazy nucleus but clear cortex of lens
retroillumination to differentiate from cataract

Question 24

what is a cataract?

Answer 24

any opacity that blocks light passage in the lens

Question 25

what commonly causes cataracts in dogs?

Answer 25

diabetes juvenile/inherited retinal degeneration uveitis

Question 26

what normally metabolizes glucose in the lens?

Answer 26

hexokinase enzyme

Question 27

what does increased glucose in the aqueous humor cause?

Answer 27

aldose reductase enzyme shunts towards sorbitol pathway sorbitol accumulates and increases osmotic pressure

Question 28

what happens in intumescent cataract?

Answer 28

diabetes or rapidly progressive juvenile cataract lens swelling, shallow anterior chamber lens sutures pull apart

Question 29

what are equatorial vacuoles indicative of?

Answer 29

impending cataract formation

Question 30

how is lens induced uveitis managed?

Answer 30

topical NSAIDs, steroids atropine oral NSAIDs, steroids (no oral steroids if diabetes mellitus)

Question 31

what screening should you do prior to cataract surgery?

Answer 31

schirmer tear test intraocular pressure electroretinogram ocular ultrasound

Question 32

which breeds are predisposed to primary lens luxation?

Answer 32

terriers australian cattle dog chinese crested shar pei

Question 33

what drug should you avoid with anterior lens luxation in a dog?

Answer 33

latanoprost

Question 34

what is posterior luxation like in a dog?

Answer 34

often asymptomatic medical management with miotics to prevent anterior movement

Question 35

why do cats tolerate anterior luxation better than dogs?

Answer 35

bigger anterior chamber

Question 36

what is Encephalitozoon cuniculi?

Answer 36

protozoan parasite found inside lens capsule

Question 37

what is feline ocular post-traumatic sarcoma like?

Answer 37

multiple histologic variants very aggressive locally