Test 208 (Past MCQs)

1. The following are true about homocystinuria:

a.       it is an autosomal recessive disorder

b.       recurrent thrombosis occurs due to increased
          platelet adhesiveness.

c.       myopia is common

d.       mental retardation is common

e.       there is failure of conversion of homocystine 
          to cystine

 
Answera.T  b.T  c.F  d.T  e.F
Homocystinuria is an autosomally recessive disorder  caused by a deficiency of the enzyme cystathionine  beta-synthetase responsible for the conversion of the amino acid homocystine to cystathionine. There is an increased in platelet adhesiveness which predispose  the patient to recurrent thromboembollic attacks  especially during anaesthesia. The patient has the same habitus as Marfan's syndrome. Some form of mental  retardation is common. Lens subluxation and myopia are common ocular complications.l
l

2.  Reduced ipsilateral pain sensation typically occurs in the following 
     area following a blow-out fracture:

a. upper teeth

b. forehead

c. tip of the nose

d. upper cheek

e. angle of the jaw
 

Answera.T  b.F  c.F  d.T  e.F
A blow-up fracture can compress the infraorbital nerve leading to loss of sensation in the upper cheek and the upper teeth. 

3. Hypermetropia:

a. occurs with flattening of the cornea

b. occurs in eye with short axial length

c. develops presbyopia much earlier than myopia

d. has a high state of accommodation

e. can be corrected with a diverging lens

 
Answer
a.T   b.T  c.T  d.T  e.F
In hypermetropia, the image is focused behind the eye and this can occur in an eye with flat cornea or short axial length. To obtain clear vision, hypermetropic eye is always in a state of accommodation and this leads to an earlier development of presbyopia than emmetropia and myopia. Hypermetropia is corrected with a converging lens.

. 

4. The following are true about the fluorescein sodium: 

a. it stains collagen

b. it enters the choroidal circulation rapidly through the 
    posterior ciliary arteries

c. it is bound mainly to the red blood cells in the circulation

d. it does not leak through the normal capillaries of the 
    central nervous system

e. it is useful for studying the choriocapillaris
 

Answer
a.T  b.T  c.F  d.T  e.F
Fluorescein sodium leaks through the capillaries of most body organs except the central nervous system and the retina. It enters the choroidal circulation rapidly  through the posterior ciliary arteries. It is 80% protein bound in the circulation mainly to the albumin. Visualization of the choriocapillaris is difficult as the dye leaks through it rapidly. ICG is better for visualization of the choriocapillaris.

5. The cornea: 

a. contains three Purkinje's images

b. contains unmyelinated nerve fibres

c. increases in thickness with age

d. does not regenerate following injuries

e. is thinner centrally than peripherally

 
Answer
a.F   b.T  c.T  d.F e.T
The cornea contains two Purkinje's images: one in
the front and the other in the back surface of the 
cornea. The cornea increases with age. The epithelium layer of cornea regenerates readily following injury. The cornea is thinner centrally than peripherally.

 

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