Disorders of the Lens Flashcards
Nuclear sclerosis (4)
1) compaction of fibers in lens center
2) detectable by 6-7 yrs in dogs & cats; 8-10 in horses
3) does not obstruct light/affect vision
4) looks like a lens within a lens
Lens function in light refraction (1)
1) component of eye’s focusing apparats
Lens function in accommodation (2)
1) active process of focusing on near objects
2) poorly developed in domestic species
Congenital Lens Disorders (6)
1) Aphakia (rare)
2) Microphakia (rare)
3) Spherophakia
4) Coloboma
5) Lenticonus
6) Vascular anomalies (most common)
Embryonic Vascular Anomalies of Lens (3)
1) Persistent pupillary membrane
2) persistent hyaloid artery
3) PHP/PHTVL
Cataracts (4)
1) light obstructing opacity of lens
2) very common lens disease
3) may result in significant vision deficit
4) many causes
Causes of cataracts in DOGS (3)
1) Heredity
2) old age
3) Metabolic
Cause of Cataracts in CATS & HORSES (1)
1) Uveitis
Cataract Classification
1) Etiology
2) age of onset
3) stage of progression
4) location
Cataract progression (1)
1) Predictability depends on etiology and age
Clinical stages of Cataracts (4)
1) Incipient: <15% of lens affected
2) immature: >15% of lens affected can still see tapetum reflection
3) mature: no tapetum reflection
4) hypermature: resorption of lens fibers, lens looks wrinkly
Consequences of Cataract (4)
1) vision loss
2) no effect on PLR or dazzle reflex
3) lens induced uveitis (hypermature)
4) may lead to secondary glaucoma or retinal detachment
Lens induced uveitis (4)
1) immune reaction to lens proteins
2) causes: cataract & lens rupture
3) topical corticosteroids
4) lens removal if lens is ruptured
Lens luxation (3)
1) dislocation of the lens
2) anterior or posterior
3) anterior most problematic
Clinical signs of lens luxation (4
1) blepharospasm/epiphora
2) red eye
3) cloudy eye
4) diminished vision
Primary lens luxation etiology (3)
1) hereditary zonule defect (potential to be bilateral
2) most commonly seen in dogs (terriers)
3) 3-7 years
Secondary lens luxation etiology (4)
1) uveitis
2) hypermature cataract
3) senescence
4) trauma
Lens luxation complication (4)
1) corneal edema
2) retinal detachment
3) Uveitis
4) corneal edema
Management of anterior luxation (2)
1) may cause acute severe glaucoma EMERGENCY
2) surgical lens extraction or physical displacement of lens into back of eye
Management of posterior luxation/subluxation (2)
1) trap lens in posterior segment
2) surgical removal
Asteroid Hyalosis (4)
1) small white spherical bodies within vitreous
2) calcium-lipid composition
3) degenerative disorders
4) older dogs
Syneresis (4)
1) Vitreous liquefacation
2) age related degenerative change or secondary to posterior segment inflammation
3) uncommon primary disorder
4) may predispose to retinal detachment
