7: the lens - pearce Flashcards Preview

IP 11 Ophthalmology > 7: the lens - pearce > Flashcards

Flashcards in 7: the lens - pearce Deck (93):
1

what are the components of the lens?

where are they located relative to each other?

capsule, anterior epithelium, cortex, nucleus, equator

nucleus is the center, cortex is around the nucleus and capsule is thin outer coating

2

where is the lens located?

in the patellar fossa

3

what structure suspends the lens in its location?

zonular fibers - run from ciliary body to lens

4

what occurs to the lens when zonular fibers break down?

lens luxation

5

what are "Y-sutures"?

under what circumstances are they more visible?

fibers produced by epithelial cells located at the equator - elongate from the equator and go all the way around the lens and connect to each other on the suture lines

become more visible with cataracts

6

where are "Y-sutures" located?

and upside down "Y-sutures" ?

Y sutures are anterior and upside down Y sutures are peace signs

7

why do many other species have larger lenses than humans?

humans have high corneal refraction - vs other spp which depend on lens for refraction more than we do

8

what shape lens do water animals have?

and land animals?

water -> spherical

land -> ellipsoid

9

t/f

the lens is very vascular

false

the lens is AVASCULAR after birth

10

where does the lens derive its nutrition from?

the aqueous humor

[NOTE: this is why things wrong with the aqueous humor can be reflected in the lens]

11

what is the 1* metabolic pathway utilized by the lens?

hexokinase pathway

12

what molecule does the lens utilize for energy?

glucose -> metabolized into lactic acid [I think]

13

how does glucose enter the lens?

active transport and diffusion

14

when aerobic glycolysis is utilized in the lens, what pathway?

citric acid cycle

15

how does lens physiology change in diabetic patients?

inc blood glucose -> hexokinase pathway saturated -> shunt glucose towards alternative pathway -> aldose reductase enzyme -> sorbotol is produced

16

what alternative pathway is glucose shunted to in diabetic patients who have a saturated hexokinase pathway?

what is produced as a result?

aldose reductase enzyme

sorbotol is produced

17

how does sorbotol in the lens lead to cataracts?

sorbotol diffuses poorly across the lens

it has higher osmotic pressure so leads to intense lens swelling

aqueous humor is imbibed

18

t/f

the occurrence of cataracts is approximately equal in dogs and cats

why or why not

false

MC in dogs b/c they have the aldose enzyme reductase

cats do NOT have the enzyme so they do not really get cataracts

19

t/f

nuclear sclerosis is a form of cataracts

false

nuc sclerosis is an aging change, NOT a true lens opacity but a translucency

a cataract is a true lens opacity

20

how does nuclear sclerosis develop?

lens fibers continue to grow throughout life -> become more numerous and compress the nucleus of the lens -> nucleus becomes firm/hard b/c of compression from additional lens fibers forming -> dec in accommodation

21

what is the presentation and appearance of nuclear sclerosis?

bilateral
pearl like nuclear density
spherical
translucent
fundus detail visible
NOT a cataract

22

what is microphakia?

a congenital abnormality

small lens
* if you can see the edges of the lens, it is too small or luxated

often seen with other ocular mal formations

23

what is lenticonus?

etiology?

anterior or posterior protrusion of the lens

will see pointed profile / angle to the lens when it should be smooth

congenital

24

what is PHPV?
PHTVL?

persistend hyperplastic primary vitreous?

persistent hyperplastic tunica vasculosa lentis

the persistence of the primary vitreous vessel after birth

*normal: lens if vascularized in the embryo - the 1* vitreous is a large vessel that has a net of vessels, the tunica vasculosas - giving the lens a red color

25

what does a cataract look like?

focal or diffuse lens opacity

26

what is the prevalence of cataracts in dogs?

2.42%

27

t/f

dilation is important in order to dx cataract?

true - dilation allows more complete exam and should be done

28

t/f

cataracts can be diagnosed with either retro illumination or direct illumination?

true

29

under direct illumination, what is the appearance of nuclear sclerosis vs cataract?

nuc sclerosis appears hazy or translucent

cataracts appear white

30

under retro illumination, what do cataracts look like compared to nuclear sclerosis?

cataracts appear black
nuclear sclerosis appears clear

31

during a fundus exam, if cataracts are present, what will you see?

you will see a shadow on the retina/fundus

32

in what ways are cataracts classified?

stage of development
position
age of development
etiology
consistency

33

what are 4 classifications of cataracts based on stage of development?

incipient
immature
mature
hypermature

34

which stages of cataracts have a smokey appearance?

incipient, immature, mature

35

what stage of cataracts has a sparkly appearance?

hypermature

36

what stages of cataracts have a smooth capsule?

incipient, immature, mature

37

what is the texture of the capsule if a hypermature cataract?

wrinkled

38

what % of the lens is affected by incipient cataracts?

0-15%

39

what % of the lens is affected by immature cataracts?

15-98%

40

what % of the lens is affected by mature cataracts?

90-100%

41

what % of the lens is affected by hypermature cataracts?

OVER 100

42

what does intumescent mean?

swollen

43

what category of cataract typically has an intumescent appearance?

mature

44

what stage of cataracts has areas of re-absorption?

hypermature

45

what does a lens with a Morgagnian appearance have?

slightly suspended and dropped down - hyper mature - nuc becomes more liquid and NOT held up in the middle as well

46

how can cataracts be classified according to position?

capsular
sub capsular
cortical
equatorial
nuclear
perinuclear
anterior
posterior

47

how can cataracts be classified based on age of development?

congenital
developmenta
juvenile
senile
acquired

48

what are 2 main classifications of etiology / pathogenesis for cataracts?

1*
2*

49

what is the nature of 1* cataracts?

inherited

50

what are some things that lead to 2* cataracts?

traumatic
uveitis
nutritional
radiation
diabetic
toxic
congenital
senile

51

what is MC cause of cataracts in dogs?

1* - inherited

52

what is 2nd MC cause of cataracts in dogs?

2* to diabetes

53

what is MC cause of cataracts in cats and horses?

2* to uveitis

54

what dz does cataracts predispose patients to?

lens-induced uveitis

55

what are the 2 types of lens induced uveitis?

phacoCLASTIC

phacoLYTIC

56

what is the progression of lens induced uveitis?

leakage occurs and mounts an Aby response => proteins deposit in eye d/t the reaction

57

what is phacoclastic vs phacolytic lens induced uveitis?

phacoclastic is "catastrophic" - ruptured lens capsule and severe immune reaction as a result

phacolytic is a gradual leakage that occurs during the progression of cataracts => capsule remains intact and a mild to moderate immune reaction occurs

58

what is the likely result if cataracts are neglected to be treated?

100% failure => enucleation

59

what are medical options to treat cataracts?

anti cataract drugs
anti inflammatory drugs

60

how effective are anti cataract drugs?

ineffective => typically delay professional care

61

what type of treatment is the only cure for cataracts?

surgery

62

what are 3 types of surgery of the lens?

- extra capsular extraction
- intra capsular extraction
- phacoemulsification

63

which 2 types of surgery of the lens are a large incision?

extra capsular extraction
intra capsular extraction

64

how is an extra capsular extraction performed?

what is incised and what stays?

- capsule is incised, lens extracted via manual extraction; large incision

- capsule stays

65

how is intra capsular extraction performed?

- the lens is removed with the entire lens capsule via manual extraction; large incision

66

how is phaco emulsification performed?

capsule is incised, automated extraction via irrigation / aspiration
small incision
capsule stays behind

67

at what point should a cataract be referred to specialist?

at initial diagnosis

68

what does the ophthalmologist evaluation consist of?

vision deficit
progression of the cataract
amenable patient
patient health - general anesthesia
client commitment - financial and time

absence of pathologic processes - minimum ophthalmic database
glaucoma risk - gonioscopy
retinal function - ERG (electroretinogram)
retinal attachment - ocular u/s

69

what is a major key to post operative success for cataract surgery?

eyedrops

70

what are common complications of cataract surgery?

uveitis
glaucoma
retinal detachment

less common:
persistent corneal edema
synechiae
intraocular hemorrhage
corneal ulceration
suture failure

71

what meds are used before cataract surgery?

anti inflammatory
dilation
abx

72

what meds are used after cataract surgery?

anti inflammatory
abx
dilation maybe
anti glaucoma maybe
e collar (4-6 weeks)

73

what is pseudophakia?

a prosthetic lens

74

what is aphakia?

absence of lens

75

what is the appearance of an anterior lens luxation?

- ID lens in anterior chamber
- pupil margin obscured
- shallow / absent anterior chamber
- aphakic crescent

76

what breeds are prone to anterior lens luxation?

- jack russell
- other terrier breeds
- chinese crested
- shar-pei

77

what is etiology of primary etiology?

hereditary

common in terrier breeds

78

what are some common causes of 2* lens luxation?

- glaucoma [buphthalmos]
- uveitis [cats] - break down of lens fibers (zonular degeneartion)
- intraocular tumors
- cataracts
- blunt trauma

79

t/f

chronic or 2* luxation is a surgical emergency

false

NOT a surgical emergency

80

acute and 1* lens luxation leads to what condition?

2* glaucoma

81

t/f

acute primary luxation is a surgical emergency

true

82

t/f

acute 1* lens luxation is painful

false

83

what is vitreous presentation of an eye?

common in lens luxations

gel comes forward if the lens is not holding it in place - viterous sneaks around lens and into the pupil

84

what are 3 surgical options for anterior lens luxation?

- intracapsular lens extraction
- enucleation
- evisceration w prosthesis

85

what is the goal / prognosis associated w enucleation procedure?

comfort preservation only

86

when is intracapsular lens extraction performed to repair anterior lens luxation?

prognosis?

- visual animal with acute vision loss
- referral Sx: remove capsule and entire lens

- 50% chance for long-term vision and comfort

87

what is the prognosis of evisceration with prosthesis to repair anterior lens luxation?

comfort preservation only

88

what is the only anterior lens luxation surgery that has a chance for long term vision and comfort?

intra capsular lens extraction

89

what are 2 goals of medical management of anterior lens luxation?

*NOTE: these are done prior to referral

- lower IOP
- dec inflammation

90

what drugs are used to dec IOP to Tx anterior lens luxation?

- Mannitol [2mg/kg IV]
- carbonic anhydrase inhibitors

91

what are 2 carbonic anhydrase inhibitors used to Tx anterior lens luxation?

- topical dorzolamide
- oral methazolamide

92

what drugs are used to dec inflammation to Tx anterior lens luxation?

also what method of administration?

- prednisone acetate - topically

- other anti inflammatories - orally

93

when is lens trapping done to Tx anterior lens luxation?

what drugs do this?

ONLY if posterior lens luxation

synthetic PGs