Test 117  (ocular miscellaneous)

1. Oxidative damage to the lens from free radicals are prevented by: 

a. vitamin E

b. vitamin C

c. vitamin A

d. catalase

e. crystallins

Answera.T  b.T  c.F  d.T  e.F
In addition to vitamin C and E, catalase, superoxide dismutase and glutathione are protective against oxidative damage to the lens from free radicals.
 

2. The concentration of vitreous hyaluronate is decreased in the
     following conditions:

a. myopia

b. vitreous haemorrhage

c. diabetes mellitus

d. aphakia

e. inflammation

Answera.T   b.T   c.T  d.T  e.T

 
3. The following are true about photoreceptors:

a. they are no rods in the fovea

b. there are 2 rods for every cone in the human eye

c. the highest density of rod is found outside the macula

d. the cones are 100 to 1000 times more sensitive to light 
    than rods

e. a typical photoreceptor takes 24 hours to renew its 
    outer segments

Answera.T   b.F  c.F  d.F  e.FThe ratio of rods to cones is 20:1. The highest density of rod is found 1.2 to 1.7 mm from the fovea. The rods are 100 to 1000 times more sensitive to light than rods. A typical photoreceptor takes 10 days to renew its outer segments. 
.

4. True statements about the cornea include:

a. Bowman's membrane is secreted by the epithelium

b. Both epithelium and endothelium are nourished by 
    the aqueous

c. the thickness of Descemet's membrane remains 
    constant throughout life

d. the stroma is made up mainly of type III collagen

e. the Descemet's membrane is made up mainly of type
    IV collagen

Answera.F  b.F  c.F  d.F  e.T
The Bowman's membrane is the anterior condensation of the anterior stroma. The epithelium is nourished by the tear film whereas the endothelium by the aqueous. The Descemet's membrane is being laid down throughout life by the endothelium. The stroma is made up of type II collagen.

5. True statements about the cornea include:

a. the cornea sensation is supplied by the anterior ciliary 
    nerve

b. the corneal nerves loss their myelins immediately after 
    they enter the cornea

c. the cornea is more sensitive at the apex then at the 
    periphery 

d. the corneal sensation is impaired by topical b blocker

e. the corneal diameter is increased in keratoconus

Answera.F   b.F  c.T  d.T  e.T
The corneal sensation is supplied by branches of the long posterior ciliary nerve. The corneal nerves loss their myelins before they enter the cornea.

 
 

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