Disorders Of The Lens Flashcards
Anatomic regions of the lens
Capsule
Cortex
Nucleus
Lens metabolism & growth
Nutrition of aqueous humor, Anterior lens epi
Equatorial mitotic cell population = continuous growth
Nuclear sclerosis
Compaction of fibers in lens center
Detectable in 6-7Y dogs, 8-10y horses
Does not obstruct light/affect vision
Differential - cataract
Lens function
Light refraction - focusing apparatus, active process of focusing sight, poorly developed in dom species
Congenital lens disorders
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
Embryonic vascular anomalies of lens
PPM - remnants of embryonic nutritional vessels
Persistent hyaline artery - ^^ similar
PHPV/PHTVL - different degrees of vessel remnants
Cataracts
Light obstructing opacity of lens
Very common disease
Can cause significant vision deficit, various causes
Causes of cataracts
Heredity*
Old age*
Metabolic*
PRA
Glaucoma
Lens instability
Uveitis ***
Vascular anomaly
Trauma
Nutritional
* - dogs
** - cats & horses
cataract classification
Etiology
Age of onset
Stage of progression
Location in the eye
Clinical staging of cataracts
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
Consequences of cataracts
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
Management of cataracts
Medical - none or no cure XX eye drops
Surgical - lens extraction techs, artificial lens
Lens extraction methods
Phacoemulsification - standard of care for removal
Intracapsular lens extraction - indicated for lens instability /luxation
Lens induced uveitis
Immune reaction to Lens proteins
Causes:
Cataracts - all forms, rapid progression/chronic
Lens rupture - trauma /swollen cataract
TX and PX for lens induced uveitis
Topical corticosteroids
Lens removal if ruptured
Complications & prognosis
Lens luxation
Dislocation of lens - anterior* or posterior
Findings:
Blepharospasm/epiphora
Red/cloudy eye
Diminished vision
Signs of lens instability /sublux
Deep/shallow anterior chamber
Iridodenesis
Phacodenesis
Vitreous in anterior chamber
Aphakic crescent
Primary luxation
Hereditary zonule defect
Most common in dogs
Secondary luxation
Uveitis
Hyper mature cataract
Senescence
Trauma
Predisposed breeds for primary lens lux
Spontaous degeneration of zonules = luxation
Terriers***
Managing anterior luxation
Cause acute severe glaucoma = emergency
Surgical lens extraction into back of eye
Management of posterior luxation/sublux
Trap lens in posterior segment
Topical mitotic therapy
Surgical removal
Disorders of vitreous
Vitreous hemorrhage
Hyalitis
Asteroid hyalosis
Degeneration/syneresis
virtuous chamber anatomy
75% of globe
99% H2O
1% collagen and HA
Low cellularity
Congenital disorders of VC
Persistent embryonic vasculature
Persistent hyaloid artery
PHPV/PHTVL
Vitreal hemorrhage
Hypertension, trauma, retinal detachment, coagulopathy, neoplasia
Resolves slowly
Traction band formation - maturing hemorrhage associated fibrin may organize into bands
May cause retinal detachment
Asteroid hyalosis
Small white spherical bodies within vitreous
Calcium lipid composition
Degenerative disorder - spontaneous/incidental, associated w intraocular neoplasm
Occurs in older dogs
Syneresis
Virtuous liquefaction
Age related degenerative change or secondary to posterior segment inflammation
Uncommon primary disorder - Italian greyhound, whippets
Predispose to retinal detachment
