Test 21
1. A 50 year-old man has refractive errors of 
Right eye -3.00DS   Add +2.00
Left  eye -3.50 DS   Add +2.00
    He likes to wear contact lenses so that one eye is used for distance 
    and the other for reading ie. monovision correction. The following 
    are true:
a. the dominant eye is usually selected for near vision

b. if the right eye is chosen for reading, the contact lens 
   power should be around +1.00Ds

c. if the left is chosen for reading, the contact lens power 
   should be around -1.50 DS

d. his stereopsis will be reduced

e. his contrast sensitivity will be reduced

2. The following are true about contact lenses:

a. both regular and irregular astigmatism can be corrected 
    by rigid gas permeable contact lens

b. contact lens correction of hypermetropia increases the 
    size of the retinal image

c. symptoms of presbyopia are increased in contact lens 
    correction of high myopia

d. aniseikonia is reduced if unilateral refractive ametropia 
    is corrected with contact lens

e. aniseikonia is reduced if unilateral axial ametropia is 
    corrected with contact lens

3. The following are true about tilting of the intraocular lens:

a. it is the major cause of post-operative astigmatism

b. it causes an increase in the spherical power

c. a tilt of the lens around its vertical axis causes 
    against-the-rule astigmatism

d. a 20 degrees tilt of the lens induces 4D of astigmatism

e. it is commoner with anterior than posterior chamber 
    lens implant

4. Foldable intraocular lenses can be made from:

a. acrylic 

b. silicone


d. hydrogel

e. poly-HEMA


5. Regarding spherical aberration:
a. spherical aberration of a spherical lens occurs due to 
    stronger refraction of paraaxial rays than peripheral rays

b. aspherical lens reduces spherical aberration

c. planoconvex lens reduces spherical aberration

d. bull's eye retinoscopic reflex in children is the result 
    of spherical aberration

e. dilatation of pupil increases spherical aberration


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