Lens

Question 1

Pathology of the lens is mostly limited to what

Answer 1

transparency or stability

Question 2

The most common lens changes seen in domestic animals

Answer 2

nuclear sclerosis and cataracts.

Question 3

Nuclear (lenticular) sclerosis

Answer 3

normal aging process;Nuclear sclerosis is a loss of transparency due to compression and dehydration of the nucleus (center) and it appears as cloudy, hazy, blue or grey.

Question 4

what can the patient see with nuclear (lenticular) sclerosis

Answer 4

The patient can see through it but more light is required to stimulate the rods and cones for vision. Advanced nuclear sclerosis may become dense enough to become a cataract (opaque and cannot see through it).

Question 5

Normal time of onset of nuclear sclerosis

Answer 5

Dogs- over 6 years
Cats – over 9 years
Horses – over 15 years

Question 6

Cataract

Answer 6

Any opacity in the lens.

Cataracts can be categorized by: age of onset, location, degree of maturity and cause.

Question 7

degrees of maturity

Answer 7

incipient
immature
mature
hypermature

Question 8

incipent

Answer 8

Very small opacity, not likely noticed by owner (<15%)

Question 9

Immature

Answer 9

Easily visible, but not completely formed, fundus reflex present: includes all stages between incipient and mature cataract.

Question 10

Mature –

Answer 10

Fully formed cataract – no fundus reflex can be seen through it

Question 11

Hypermature

Answer 11

Cataract starts to contract, liquefy; lens capsule wrinkling; causes LIU

Question 12

primary causes of cataracts

Answer 12

Hereditary in many dog breeds; rare in cats and uncommon in horses

Question 13

Secondary causes of cataracts

Answer 13

Cataract develops secondary to another disorder
Aldose reductase
Trauma
Uveitis
Glaucoma
Intraocular neoplasia
Retinal degeneration

Question 14

Metabolic causes of cataracts

Answer 14

DM (diabetes mellitus) – In dogs, elevated serum glucose causes increase in aqueous glucose levels which enters the lens, overwhelms the normal metabolic pathway and is shunted via aldose reductasesorbitol. This molecule is too large to leave lens through the capsule and creates an osmotic gradient drawing water into the lens, causing lens fiber swelling and cataract formation. This can occur quite rapidly and sometimes causes the lens capsule to rupture.

Question 15

sequalae to cataracts

Answer 15

Lens Induced Uveitis (LIU)

Question 16

sequalae to lens perforation or surgery.

Answer 16

Lens induced (post traumatic) sarcoma

Question 17

Lens Luxation / Subluxation breeds associated

Answer 17

breed associated (Jack Russell Terrier, most terrier breeds, Heelers)

Question 18

Gene that predisposes animals to lens luxation/subluxation

Answer 18

The gene has been identified in several breeds that affects the protein integrity of the lens zonules causing luxation.

Question 19

Secondary luxation subluxation

Answer 19

glaucoma, chronic uveitis

Question 20

what kind of luxation/subluxation is considered an emergency?

Answer 20

Anterior lens luxation is an emergency! It is usually very painful, and may cause irreversible damage to the corneal endothelium, and/or secondary glaucoma.

Question 21

what type of luxation/suluxation is NOT an emergency?

Answer 21

A posterior lens luxation may cause pain and inflammation, but is not a surgical emergency.