Dzs of the lens (Whitley)

Question 1

Normal lense placement

responsibilities

Answer 1

• behind iris, in front of vitreous
• patella fossa
• held in place by zonules
• responsibilities
  
  • refraction
  • accomodation

Question 2

Lens anatomy

Answer 2

• Capsule
  
  • basement membrane surrounding lens
• Anterior epithelium
• Lens fibers
  
  • interdigitating layers
  • form Y sutures
    
    • upright anterior Y
    • inverted postierior Y
  • Cortex
  • Nucleus

Question 3

Clinical anatomy of lens

Answer 3

• second most imp refractive structure
  
  • cornea is number 1
• transparent
• no innervation
• no vascular structures
• lens epithelium
  
  • present at equator
  • lines anterior cortex
• three major regions
  
  • cortex
  • nucleus
  • capsule

Question 4

Lens formation

embryology

Answer 4

• basement membrane becomes lens capsule
• anterior lense capsule get thicker and thicker
• posterior doesn’t

Question 5

Lens fibers

Answer 5

• Fibers continuously produced
  
  • compacted towards center of lens
• lens becomes more dens/sclerotic with age
  
  • nuclear sclerosis
  • central nucleus gets hard

Question 6

Dzs of lens

Answer 6

• Cataract
  
  • opacity of lens or lens capsule
• Subluxation
• luxation
• congenital abnormalities
  
  • microphakia
  • aphakia
  • lenticonus

Question 7

Nuclear sclerosis vs cataract

Answer 7

• Nuclear sclerosis
  
  • lens within a lens
  • bilateral
  • symmetric
  • center of lens
  • doesn’t interfere with fundus exam
  • can visualize tapetal reflex through sclerosis
  • no clinical interference with vision

Question 8

Answer 8

• Left: Cataract
• Right: Nuclear sclerosis

Question 9

Answer 9

Nuclear Sclerosis and Cataract

Question 10

Classifying cataracts

Location

Answer 10

• Structure of lens
  
  • capsular
  • subcapsular
  • cortical
  • nuclear
• Direction
  
  • anterior
  • posterior
  • equatorial
  • polar
  • axial

Question 11

Leukocoria

Answer 11

• White pupil
  
  • usually means a cataract

Question 12

Cataract classification

Schemes

Answer 12

• stage of development
• maturity
• size
• location of opacity within lens
• age of development of cataract
• consistency
  
  • fluid
  • soft
  • hard
  • sticky
• etiology

Question 13

Cataract

stages of maturity (amount of lens involved)

Answer 13

• Incipient
  
  • ,15% total lens volume
• Immature
  
  • early
  • late
  • 16-99%
• Mature
  
  • 100% lense is cataractous
• Hypermature
  
  • lens resorption
    
    • lens cortex liquifies
    • may result in return of sight in young dogs
  • morgagnian
    
    • lens nucleus sinks ventrally in liquified cortex
    • all cortical material has been resorbed leaving behind nucleus

Question 14

Incipient cataract

Answer 14

• early focal opacity of lens
• appearance
  
  • punctate
  • linear “spoke-like”
  • vacuoles
• vision usually not affected

Question 15

Immature cataract

Answer 15

• Opacity is more expansive than incipient
• reduced transparency
• some tapedal reflection remaines
• decreased vision
• optimum time to surgically remove

Question 16

Mature cataract

Answer 16

• Lens totally opaque
• No tapedal reflection present
• Eye functionally blind
• Fundus cannot be examined ophthalmoscopically

Question 17

Hypermature cataract

Answer 17

• Cataract begins to liquefy
• Wrinkles in anterior lens capsule are visible
• Crystals
  
  • glistening particles
  • often present in anterior cortex
• Lens resorption
• Morgagnian cataract: sandwich bag with milk and marble
• Possible sequelae
  
  • return of vision
  • uveitis
  • retinal detachments

Question 18

Lens-induced uveitis

LIU

Answer 18

• inflammation or uveitis
  
  • due to reaction to lens antigens in aqueous humor
• CS
  
  • flare
    
    • inc protein
  • miosis
  • hypotony
  • dark ‘muddy’ iris
  • hyperemic episcleral blood vessels
• LIU must be treated before cataract removal

Question 19

Etiology cataracts in dogs

Answer 19

• inheritance
• congenital
• diabetic
  
  • hexokinase saturated by glucose
  • glucose enters sorbitol pathway
  • converted to sorbitol by aldose reductase

Question 20

Diabetic cataracts

dogs

Answer 20

• form with new lens fibers at equator
  
  • equatorial vacuoles
  • water clefting (sutures separate)

Question 21

Diabetic cataracts in cats

Answer 21

• not as frequent in cats
  
  • lower aldose reductase activity than dogs
• progress more slowly

Question 22

Cataracts in cats

test question

Answer 22

• most common cause
  
  • secondary to uveitis
• Other causes
  
  • trauma
  • gluacoma
  • lens lux

Question 23

Cataracts in horses

test question

Answer 23

• most common cause
  
  • Equine Recurrent Uveitis (ERU)
  • 41% ERU cases develop cataracts

Question 24

Cataract TX

Medical

Answer 24

• No effective medical therapy yet
  
  • Kinostat
    
    • on market Sept 2016 or Dec
    • inhibits aldose reductase in lens
    • TID
    • great for small equatorial cataracts

Question 25

Cataract SX

Answer 25

* phacoemulsification and IOL placement * surgical case selection 1. cataracts with visual impairment 2. retina must be functional * R/O retinal detachment 3. LIU controlled by corticosteroids and/or NSAIDS 4. KCS, keratitis, glaucoma must be controlled 5. patient in general good health, amenable to intensive handling 6. Owner compliant and can afford tx 7. Counsel owners about older dogs with * cognitive dysfunction * senility * motor deficits * behavior issues

Question 26

Cataract removal procedure phaco

Answer 26

* phacoemulsification and aspiration 1. A small corneal incision is made 2. Circular portion of anterior lens capsule removed 3. High frequency ultrasonic tip * breaks up * aspirates cataract * infuses fluid to maintain formed eye

Question 27

Post op cataract surgery IOLs

Answer 27

* hyperoptic post op (Farsighted) * artificial lens implant can improve vision * 41D (IOL) * Pseudophakic * animal with an IOL implant * Aphakic * animal with no lens * still visual * IOLs available for cats and horses * Not routinely used

Question 28

Postop complications of phace and IOLs

Answer 28

* Corneal ulceration * anterior uveitis * corneal edema * suture line dehiscence * endothelial decompensation * ocular hypertension * intraocular fibrin formation * acute endophthalmitis * hypopyon * hyphema * IOL lux \*success is about 90-95%

Question 29

Displaced lenses

Answer 29

* lens lux: all zonules torn * anterior lux * posterior lux * Subluxation: some zonules torn * partial displacement

Question 30

Etiology of lens luxations

Answer 30

* Primary * zonular defects * common in terriers * autosomal recessive trait * commercial testing available * Occurs between 2 and 6 years of age * Secondary * glaucoma * anterior uveitis * intumescent cataract * intraocular tumors

Question 31

Lens lux CS

Answer 31

* **Aphakic crescent** * **​**pathopneumonic * Iridodonesis * Movement/shaking of iris * Vitreous fibrils floating through pupil into anterior chamber * Posterior lux * Deep anterior chamber and flat iris * Anterior lens lux * shallow anterior chamber * corneal edema * Glaucoma * chicken or the egg....

Question 32

Management of lens lux

Answer 32

* Lens sublux * monitor and midical tx * aggressive tx contraindicated * Control secondary issue * miotics * IOP control * Posterior lens lux * medical therapy * aggressive tx contraindicated * causes less damage than anterior lux * Anterior lens lux * medical therapy and monitoring * Intracapsular lens extraction (ICLE) * Phacoemulsification w/ capsular tension rings

Question 33

Sulcus Intraocular lens fixation for anterior lens luxation

Answer 33

* Sulcus IOL after anterior lens lux removal * Lens sutured in place

Question 34

Multiple punctate pigment foci

Answer 34

* AKA * pigment nest * located on central anterior lens capsule * remnant of pupillary membrane * common incidental finding * doesn't usually impair vision * No correction