Test 16
1. The following are true about the 3 and 9 O'clock staining 
    of the cornea:
a. they represent areas of poor wetting

b. they occur in incomplete blink response

c. occur more commonly with gas permeable contact lens 
    than soft contact lens

d. a lens with greater movement may solve the problem

e. give rise to corneal vascularization if untreated

2. The following are true:
a. the cornea has more refractive power than the lens

b. the centre of the cornea is steeper than the periphery in
    normal patient

c. radial keratotomy flattens the cornea

d. hypermetropia can be corrected by steepening the cornea

e. strabismus surgery can induce astigmatism.


3. A Galilean telescope used in low vision:
a. has a plus objective

b. contains a minus eyepiece lens.

c. the distance between the plus objective and the eyepiece is 
    equal to the sum of the focal lengths of the two lenses

d. produces a virtual image

e. required an image-inverting system.


4. The following are true about blurred image resulted from tilted retina:
a. the blurred image is the result of astigmatism.

b. it can be corrected with spectacle.

c. it can be corrected with contact lenses.

d. refractive surgery can correct the blurred vision.

e. cataract extraction with implant can sharpen the image

5. The following are true about the contact lens:
a. Dk values measured the oxygen permeability of a contact lens

b. the oxygen permeability depends on the thickness of the lens

c. rigid gas permeable lens always have a lower Dk than soft
    contact lens

d. PMMA contact lens do not allow oxygen penetration

e. the higher the water content of a soft contact lens the higher 
    the oxygen transmissibility.

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