Test 10
1. The following are true about aphakia:
a. the refractive power of the eye is reduced
b. the anterior focal length is increased
c. an anterior chamber lens implant minimize the image size
d. a posterior chamber lens implant does not alter the image size
e. image magnification does not occur with contact lens correction of aphakia 

2. The following are true about biometry in a general population in the UK:
a. 96% of axial lengths fall within the range 21.0 to 25.5mm 
b. 98% of K readings fall within the range 40 to 48D
c. the difference in the axial lengths between the two eyes of an individual is usually 
    less than 1 mm
d. SRK/T formula is more accurate than SRK/II in the calculation of intraocular lens
e. SRK/T formula is more accurate than the Holladay formula in intraocular lens 


3. In the calculation of the intraocular lens, the following will give an axial length which is shorter than expected:
a. pseudophakia 
b. silicone oil 
c. corneal decompensation
d. aphakia
e. choroidal effusion


4. With regard to the back vertex distance (BVD):
a. it is directly related to the back vertex power
b. a hypermetrope can increase the effective lens power by slipping the glasses down 
    the nose
c. it is increased in a patient with thyroid eye disease
d. a +4D hypermetrope needs a stronger prescription if contact lenses were used
e. the effective lens power of a concave lens is increased by moving the lens towards 
    the cornea

5. The following features of the eye reduce optical aberrations:
a.  presence of pigment on the iris
b. a flatter peripheral cornea
c. relative insensitivity of the cones to oblique light
d. presence of xanthophyll
e. absorption of long wavelength by the crystalline lens

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