Disorders of the Lens

Question 1

Nuclear sclerosis (4)

Answer 1

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

Question 2

Lens function in light refraction (1)

Answer 2

1) component of eye’s focusing apparats

Question 3

Lens function in accommodation (2)

Answer 3

1) active process of focusing on near objects
2) poorly developed in domestic species

Question 4

Congenital Lens Disorders (6)

Answer 4

1) Aphakia (rare)
2) Microphakia (rare)
3) Spherophakia
4) Coloboma
5) Lenticonus
6) Vascular anomalies (most common)

Question 5

Embryonic Vascular Anomalies of Lens (3)

Answer 5

1) Persistent pupillary membrane
2) persistent hyaloid artery
3) PHP/PHTVL

Question 6

Cataracts (4)

Answer 6

1) light obstructing opacity of lens
2) very common lens disease
3) may result in significant vision deficit
4) many causes

Question 7

Causes of cataracts in DOGS (3)

Answer 7

1) Heredity
2) old age
3) Metabolic

Question 8

Cause of Cataracts in CATS & HORSES (1)

Answer 8

1) Uveitis

Question 9

Cataract Classification

Answer 9

1) Etiology
2) age of onset
3) stage of progression
4) location

Question 10

Cataract progression (1)

Answer 10

1) Predictability depends on etiology and age

Question 11

Clinical stages of Cataracts (4)

Answer 11

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

Question 12

Consequences of Cataract (4)

Answer 12

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

Question 13

Lens induced uveitis (4)

Answer 13

1) immune reaction to lens proteins
2) causes: cataract & lens rupture
3) topical corticosteroids
4) lens removal if lens is ruptured

Question 14

Lens luxation (3)

Answer 14

1) dislocation of the lens
2) anterior or posterior
3) anterior most problematic

Question 15

Clinical signs of lens luxation (4

Answer 15

1) blepharospasm/epiphora
2) red eye
3) cloudy eye
4) diminished vision

Question 16

Primary lens luxation etiology (3)

Answer 16

1) hereditary zonule defect (potential to be bilateral
2) most commonly seen in dogs (terriers)
3) 3-7 years

Question 17

Secondary lens luxation etiology (4)

Answer 17

1) uveitis
2) hypermature cataract
3) senescence
4) trauma

Question 18

Lens luxation complication (4)

Answer 18

1) corneal edema
2) retinal detachment
3) Uveitis
4) corneal edema

Question 19

Management of anterior luxation (2)

Answer 19

1) may cause acute severe glaucoma EMERGENCY
2) surgical lens extraction or physical displacement of lens into back of eye

Question 20

Management of posterior luxation/subluxation (2)

Answer 20

1) trap lens in posterior segment
2) surgical removal

Question 21

Asteroid Hyalosis (4)

Answer 21

1) small white spherical bodies within vitreous
2) calcium-lipid composition
3) degenerative disorders
4) older dogs

Question 22

Syneresis (4)

Answer 22

1) Vitreous liquefacation
2) age related degenerative change or secondary to posterior segment inflammation
3) uncommon primary disorder
4) may predispose to retinal detachment