Test 34

1. Regarding tilting of the intraocular lens:

a. it occurs more commonly in capsulotomy than 
    capsulorrhexis

b. with-the-rule astigmatism occurs when the lens rotates 
    around its vertical axis.

c. biconvex lens design is least affected by lens tilt

d. meniscus lens design is most affected by lens tilt

e. it can be detected by comparing the corneal 
    astigmatism with the refractive astigmatism

Answera.T   b.F   c.T   d.T   e.T
Capsulorrhexis ensures in the bag implantation. 
With-the-rule astigmatism occurs when the lens rotates around its horizontal axis. 

2. The following are features of congenital ptosis due to dystrophic 
    levator muscle:

a. movement of the lid with jaw movement

b. failure of the involved eye to elevate

c. a high skin crease

d. failure of the lid to lower with downgaze

e. lagging of the eyelid during downgaze

Answera.F   b.F   c.F   d.T   e.T
A dystrophic muscle is associated with poor
skin crease and failure of the eye to descend on downgaze.

3. The following lasers work by disrupting the molecular bondings:

a. YAG laser
b. argon laser
c. diode laser
d. excimer laser
e. carbon dioxide laser

Answera.T    b.F   c.F   d.T   e.F
Argon, diode and carbon dioxide lasers work through thermal effects.

4. With regard to A-scan ultrasound:

a. it has a frequency above 2 kilohertz.

b. in a phakic eye, a good A-scan will give three tall 
    spikes

c. ultrasound travels faster through a cataractous eye than 
    an aphakic eye

d. the true optical axial length is greater than the distance 
    to the ultrasound spike measured from the retinal 
    surface

e. ultrasound travels slower in the silicone oil than in 
    vitreous.

Answera.F   b.F  c.T   d.T   e.T
Ultrasound has a frequency of more than 20 KHz.
In a phakic eye, four tall sharp spikes are obtained. The first one from the cornea, second one from the anterior surface of the lens, the third one from the 
posterior surface of the lens and the final one from 
the retina. The true optical axial length is from the anterior cornea to the photoreceptors but the retina 
spike is produced by the sound hitting the inner layer of the retina.

5.  The following are true about atropine:

a. it is a muscarinic cholinergic antagonist.

b. the onset of cycloplegia usually precedes that of
    mydriasis.

c. its mydriatic effect usually lasts longer than its
    cycloplegic effect.

d. its mydriatic effect can be readily reversed with topical
    pilocarpine.

e. in a hypermetropic patient, topical atropine will give a 
    final refraction which is more plus than one without
    topical atropine.

Answera.T   b.F   c.T   d.F   e.T
Atropine is a muscarinic cholinergic antagonist. 
The onset of mydriasis precedes that of cycloplegia and tends to last longer. Topical pilocarpine only 
partially reverses the effect of mydriasis caused by 
topical atropine. Cycloplegia increases hypermetropia and thus more plus during refraction.

 

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