The lens and vitreous Flashcards
Which one of these ocular structures has the highest refractive index?
a. Air-cornea interface
b. Vitreous humour
c. Lens
d. Aqueous humour
a. Air-cornea interface
The supply of nutrients and oxygen to and waste removal from the adult lens is performed by:
a. The lens capsule
b. Aqueous and vitreous humour
c. The pupillary membrane
d. The posterior hyaloid artery
b. Aqueous and vitreous humour
A lack of menace response may indicate a lesion:
a. Involving the facial nucleus or facial nerve
b. Along the optic nerve or in the visual cotex
c. Within the eye, optic nerve or visual cortex
d. Within the eye, optic nerve, visual cortex, facial nucleus or facial nerve
d. Within the eye, optic nerve, visual cortex, facial nucleus or facial nerve
Which one of the following techniques will allow you to localise a lesion within the lens most accurately?
a. Distant direct ophthalmoscopy
b. Direct ophthalmoscopy
c. Ultrasound
d. Slit lamp biomicroscopy
d. Slit lamp biomicroscopy
Which one of the following statements about congenital cataract is most accurate?
a. Congenital cataracts are inherited
b. Congenital cataract associated with PPM (persistent pupillary membrane) primarily involves the lens nucleus
c. Congenital cataracts in the Miniature Schnauzer are usually symmetrical and primarily involve the lens cortex
d. Congenital cataracts may occur as part of the suspected hereditary MOD (multiple ocular defects) complex
d. Congenital cataracts may occur as part of the suspected hereditary MOD (multiple ocular defects) complex
Most metabolic cataracts in dogs are associated with diabetes mellitus. Which one of the following statements is most accurate?
a. Glucose metabolism in the lens of the diabetic dog produces sorbitol, which attracts water into the lens by osmosis
b. Clefts within the lens tend to occur along the suture lines as these are the strongest part of the lens structure
c. The main pathway for glucose metabolism in the lens of the normal dog is catalysed by aldose reductase
d. Lens volume decreases as water is attracted into the aqueous humour by osmosis
a. Glucose metabolism in the lens of the diabetic dog produces sorbitol, which attracts water into the lens by osmosis
Cataract progression and resorption may stimulate uveitis. This is attributable to
a. Changes in glucose levels within the aqueous humour
b. Leakage of lens protein
c. Reduced intraocular pressure
d. Increased tension on the zonules, which originate from the ciliary body and support the lens
b. Leakage of lens protein
Which one of the following statements regarding lens instability is most accurate?
a. Primary glaucoma with secondary lens luxation, and primary lens luxation with secondary glaucoma are managed in the same way
b. Medical management of posterior lens luxation is usually effective and carries minimal risk
c. Anterior lens luxation can be difficult to identify with the naked eye unless secondary signs are present or the lens is cataractous
d. The preferred surgical treatment for anterior lens luxation is phacoemulsification
c. Anterior lens luxation can be difficult to identify with the naked eye unless secondary signs are present or the lens is cataractous
After surgical lens removal, which one of the following complications may be encountered in the immediate post-operative period?
a. Posterior synechiae between the iris and lens capsule
b. Uveitis
c. Transient drop in intraocular pressure
d. Glaucoma
b. Uveitis
Focal deposits of lipid may be seen as particles scattered through the vitreous. These particles move with the vitreous but return to a normal position once the globe is still. This is termed
a. Ciliary body cysts
b. Synchisis scintillans
c. Asteroid hyalosis
d. Vitreal membranes
c. Asteroid hyalosis
describe the blood supply of the developing lens
The developing lens is supplied by the tunica vasculosa lentis, from the hyaloid
artery posteriorly and from the pupillary membrane anteriorly
what breed has inherited congenital cataracts?
miniature schnauzer
what proportion of the lens does an incipient cataract take up?
15%
why aren’t diabetic cataracts common in cats?
they lack aldose reductase in the lens after 4 years of age
