Disorders Of The Lens

Question 1

Anatomic regions of the lens

Answer 1

Capsule
Cortex
Nucleus

Question 2

Lens metabolism & growth

Answer 2

Nutrition of aqueous humor, Anterior lens epi
Equatorial mitotic cell population = continuous growth

Question 3

Nuclear sclerosis

Answer 3

Compaction of fibers in lens center
Detectable in 6-7Y dogs, 8-10y horses
Does not obstruct light/affect vision
Differential - cataract

Question 4

Lens function

Answer 4

Light refraction - focusing apparatus, active process of focusing sight, poorly developed in dom species

Question 5

Congenital lens disorders

Answer 5

 Aphakia — - missing lens
Microphakia — - tiny lens
Spherophakia — - misshapen, round instead of oval
Coloboma — - lack of lens
Lenticonus — - elongation of lens capsule/vortex
Vascular anomalies - most common issue

Question 6

Embryonic vascular anomalies of lens

Answer 6

PPM - remnants of embryonic nutritional vessels
Persistent hyaline artery - ^^ similar
PHPV/PHTVL - different degrees of vessel remnants

Question 7

Cataracts

Answer 7

Light obstructing opacity of lens
Very common disease
Can cause significant vision deficit, various causes

Question 8

Causes of cataracts

Answer 8

Heredity*
Old age*
Metabolic*
PRA
Glaucoma
Lens instability
Uveitis ***
Vascular anomaly
Trauma
Nutritional
* - dogs
** - cats & horses

Question 9

cataract classification

Answer 9

Etiology
Age of onset
Stage of progression
Location in the eye

Question 10

Clinical staging of cataracts

Answer 10

Incipient - <15% of lens affected
Immature - >15% affected, tapetum is still visible
Mature - no tapetum reflects
Hyper mature - absorption of cataract material, more induce lens uveitis

Question 11

Consequences of cataracts

Answer 11

Vision loss - functional vision, no appreciable effect on PLR or dazzle
Lens induced uveitis - esp w hyper mature, can lead to secondary glaucoma or retinal detachment

Question 12

Management of cataracts

Answer 12

Medical - none or no cure XX eye drops
Surgical - lens extraction techs, artificial lens

Question 13

Lens extraction methods

Answer 13

Phacoemulsification - standard of care for removal
Intracapsular lens extraction - indicated for lens instability /luxation

Question 14

Lens induced uveitis

Answer 14

Immune reaction to Lens proteins
Causes:
Cataracts - all forms, rapid progression/chronic
Lens rupture - trauma /swollen cataract

Question 15

TX and PX for lens induced uveitis

Answer 15

Topical corticosteroids
Lens removal if ruptured
Complications & prognosis

Question 16

Lens luxation

Answer 16

Dislocation of lens - anterior* or posterior
Findings:
Blepharospasm/epiphora
Red/cloudy eye
Diminished vision

Question 17

Signs of lens instability /sublux

Answer 17

Deep/shallow anterior chamber
Iridodenesis
Phacodenesis
Vitreous in anterior chamber
Aphakic crescent

Question 18

Primary luxation

Answer 18

Hereditary zonule defect
Most common in dogs

Question 19

Secondary luxation

Answer 19

Uveitis
Hyper mature cataract
Senescence
Trauma

Question 20

Predisposed breeds for primary lens lux

Answer 20

Spontaous degeneration of zonules = luxation
Terriers***

Question 21

Managing anterior luxation

Answer 21

Cause acute severe glaucoma = emergency
Surgical lens extraction into back of eye

Question 22

Management of posterior luxation/sublux

Answer 22

Trap lens in posterior segment
Topical mitotic therapy
Surgical removal

Question 23

Disorders of vitreous

Answer 23

Vitreous hemorrhage
Hyalitis
Asteroid hyalosis
Degeneration/syneresis

Question 24

virtuous chamber anatomy

Answer 24

75% of globe
99% H2O
1% collagen and HA
Low cellularity

Question 25

Congenital disorders of VC

Answer 25

Persistent embryonic vasculature
Persistent hyaloid artery
PHPV/PHTVL

Question 26

Vitreal hemorrhage

Answer 26

Hypertension, trauma, retinal detachment, coagulopathy, neoplasia
Resolves slowly
Traction band formation - maturing hemorrhage associated fibrin may organize into bands
May cause retinal detachment

Question 27

Asteroid hyalosis

Answer 27

Small white spherical bodies within vitreous
Calcium lipid composition
Degenerative disorder - spontaneous/incidental, associated w intraocular neoplasm
Occurs in older dogs

Question 28

Syneresis

Answer 28

Virtuous liquefaction
Age related degenerative change or secondary to posterior segment inflammation
Uncommon primary disorder - Italian greyhound, whippets
Predispose to retinal detachment