Test 29
1. A lens has the following power +4.00/+2.00 X 90:
a. the spherical equivalent is +5.00D

b. the horizontal focal length is 25cm 

c. the vertical focal length is 50cm

d. the circle of least confusion is midway between
    the two focal lengths

e. is similar to one with the power +6.00/-2.00 X180

2. A 15 year old boy was given glasses for the time with the following 
    OD: -0.50  / +1.75 X  150 
    OS: -0.50 / +1.50  X  22 
    He returns few days later says he cannot wear them due to ocular 
    discomfort. The power and the interpupillary distance are checked 
    and found to be accurate:
a. the problem is likely to be distortion due to meridional 

b. the discomfort can be reduced by reducing the 
    cylindrical power while maintaining the spherical 

c. the discomfort can be reduced by rotating the cylinder 
    towards 1800

d. the discomfort can be reduced by increasing the vertex

e. the discomfort can be reduced by changing the 
    cylindrical lens to minus power


3. The following are true about light:

a. the range of visible wavelength is from 100 to 700nm 

b. light with a wavelength of more than 700nm is 
    in the ultraviolet spectrum

c. infrared is not visible to the eye

d. shorter wavelength is bent more than longer wavelength
    when passes through a plus lens

e. green light is bent more than red light when passing
    through a prism

4. Wavefront analysis: 
a. measures higher order optical aberration

b. measures chromatic aberration 

c. measures monochromatic aberration

d.  is affected by the pupil size

e. can be measured with Tscherning aberrometry

5. The following are true about the Stiles-Crawford effect :

a. the central retinal cones are maximally stimulated by 
    light entering the eye through the pupil parallel to the 
    visual axis

b. light entering the pupil obliquely has a significant effect
    on scotopic stimulus

c. light entering the pupil 3 mm from the physiologic 
    centre of the eye significantly affect the photopic 

d. it reduces the effect of spherical aberration of the
    lens on the fovea

e. it can be used to evaluate photoreceptor misalignment
    in retinal disease

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