Lens and Cataract

Question 1

primary function of the lens

Answer 1

accommodation

Question 2

mechanisms of lens transparency

Answer 2

nonpigmented
avascular
precise organization of fibers
few organelles
relatively dehydrated
precise crystalloid protein ratios

Question 3

Y suture?

Answer 3

can see with cataracts. each suture extends 1/3 the way around the lens so a Y is formed in the center of the lens (usually too clear to see)

Question 4

lens fibers are produced …..

Fibers are compacted in the center of the lens (lens nucleus) This density becomes apparent as _____ ______.

Answer 4

continually throughout life!

Nuclear Sclerosis

Question 5

Nuclear sclerosis is
\_\_\_\_\_
\_\_\_\_\_
\_\_\_\_\_
where Cataract is not.

Answer 5

bilateral/symmetric
in the center always
doesn’t block tapedum or vision

Question 6

It can be difficult to correctly diagnose lens disease without ______.

Answer 6

mydriasis

Question 7

How does cataract affect the pupillary light reflex?

Answer 7

it doesnt

Question 8

microphakia

Answer 8

• congenitally small lens
• can visualize lens equator and zonules
• most common disease of lens
• does NOT need treatment

Question 9

What part of the lens should you never be able to see?

Answer 9

equator

Question 10

must differentiate a subluxated lens with a ?

Answer 10

microphakia (small lens)

Question 11

spherophakia

frequently accompanies ____?

Answer 11

congenitally round lens

microphakia

Question 12

coloboma

Answer 12

flattened area of lens equator

-just needs monitoring

Question 13

what is a cataract?

Answer 13

any opacity of the lens
(loss of transparency secondary to disruption of lens fiber cells and their precise anatomic relationship to one another)
(ex/ Protein ratio’s disrupted)
does not always progress

Question 14

Incipient cataract

Answer 14

<10% of total lens volume

Question 15

immature cataract

Answer 15

11-99% of total lens volume

Question 16

Mature cataract

Answer 16

100% of lens is cataractous

Question 17

Hypermature cataract

Answer 17

resorption of lens material

Question 18

Morgagnian cataract

Answer 18

(variant of hypermature) all cortical material has been resorbed leaving behind nucleus (which floats to bottom)
(dont worry about this one)

Question 19

Areas cataract can be located?

Answer 19

anterior/posterior subcapsular
anterior/posterior cortical
equatorial 
llamellar/perinuclear
Nuclear
Axial

Question 20

causes of cataracts

Answer 20

hereditary *most common*
senile
systemic disease (DM most common)
....
Trauma (especially penetrating injuries)
Toxins
Electric shock 
Secondary to ocular disease (uveitis **most common cause in cats***
retinal atrophy
persistent pupillary membranes)
Radiation (treating periocular neoplasia)

Question 21

Pathophysiology of Diabetic cataracts?

Answer 21

Normal glucose is overwhelmed and shunted to the sorbitol pathway, in which the rate limiting step (Aldose reductase) can’t keep up (especially bc dogs don’t have a lot of AR) resulting in a swollen broken, cataractous lens full of sorbitol

Question 22

what percent of DM dogs get cataracts?

How bad the diabetes is?

Answer 22

85% within 2 yrs

INDEPENDENT of degree of diabetic regulation

Question 23

Vacuoles indicate

Answer 23

active cataract formation

Question 24

cataract treatment

Answer 24

surgery only

phacoemulsification US Energy used to break up lens, then implant a new one

Question 25

All cataracts are associated with some degree of ____

(all cataracts bigger than incipient have clinically significant __^___.

Answer 25

lens induced uveitis (phacolytic uveitis)
*during cataract formation , lens proteins leak across lens capsule causing inflammation, a quicker developing cataract causes more uveitis

Question 26

Evil PIFVM?

Answer 26

Pre-Iridal Fibrovascular Membrane and Glaucoma
(happens with inflammation, so give anti-inflammatories fooorreevveerr)
No epithelial membrane, all plugged up.

Question 27

All cataracts larger than insipient need to be treated with?

Answer 27

topical anti-inflammatory for life to prevent phacolytic uveitis

Question 28

Phacoclastic uveitis

Answer 28

traumatic disruption of lens capsule -> liberation of lens proteins -> overwhelming uveitis leading to vision loss (50%)
-treatment is controversial

Question 29

Primary lens luxation

Answer 29

TERRIERS

loss of zonules, often associated with glaucoma

Question 30

secondary lens luxation

Answer 30

glaucoma, chronic uveitis (cats and horses), intraocular neoplasia, trauma
-treatment is unrewarding

Question 31

when lens luxates partially through pupil ->

Answer 31

glaucoma,

thats the worst way to luxate

Question 32

Can use _________ therapy to prevent anterior lens luxation of the second eye after first lens luxates and is removed.

Answer 32

long term miotic therapy

Question 33

diagnosing lens subluxation

Answer 33

vitreous in anterior chamber
aphakic crescent
Iridodensesis - iris fluttering
phacodenesis - lens wiggle
abnormal anterior chamber depth
visualized lens equator

Question 34

treatment for lens luxation?

Answer 34

miotic therapy to trap lens behind iris
lensectomy and glaucoma tx
tx for underlying cause

Question 35

lens is formed from ____ ______ that is placed in position by infolding

Answer 35

surface ectoderm

Question 36

the lens capsule is much thicker ____ than _____

Answer 36

anteriorly than posteriorly

Question 37

in cataractous eye, there is an increase in ____ proteins and a decrease in ____ proteins

Answer 37

increase in insoluble proteins and a decrease in soluble proteins

Question 38

what does it mean when we can see vacuoles within lens?

Answer 38

signs that cataract is being actively produced

Question 39

what is the normal rate limiting enzyme for glycolysis of the lens ?

Answer 39

hexokinase

Question 40

what are some consequences of untreated lens inflammation

Answer 40

• glaucoma
• retinal detachment
• posterior synechiae
• keratitis

Question 41

primary _____ lens luxation is very painful and lens should be removed, while primary ____ lens luxation is not painful and should be treated with miotic agents

Answer 41

anterior is painful, posterior is not