Chapter 5 Lensometry

Question 1

An automated lensometer may be disadvantageous in identifying:
a) optical centers
b) add powers
c) prisms
d) warped lenses

Answer 1

D- warped lenses

Question 2

All of the following are true regarding automated lensometers except:
a) they should be set on an antistatic mat
b) they should not be placed and used in direct sunlight
c) the internal lenses and mirrors can be cleaned by removing the instrument housing
d) the computer components are sensitive to dust

Answer 2

C- the internal lenses and mirrors can be cleaned by removing the instrument housing

Question 3

The first step in reading a pair of glasses with the manual lensometer is to:
a) position the glasses in the holder with the temples away from you
b) position the glasses in the holder with the temples toward you
c) clean the lenses before reading
d) adjust the eye piece of the instrument

Answer 3

D- adjust the eye piece of the instrument

Question 4

When adjusting the lensometer eye piece:
a) you should wear your own habitual correction
b) the lensometer’s power dial should be set to your prescription
c) the lensometer’s axis indicator should be set to 180
d) the lensometer’s axis indicator should be set to match your own astigmatism

Answer 4

A- you should wear your own habitual correction

Question 5

Before adjusting the lensometer eye piece:
a) turn the eye piece to the most minus position
b) turn the eye piece to the most plus position
c) turn the eye piece to an axis of 180 d) turn the eye piece to the axis of your astigmatism

Answer 5

B- turn the eye piece to the most plus position

Question 6

A lens can be read in a lensometer in plus or minus form:
a) by changing the axis 180 degrees
b) by changing the axis 90 degrees
c) by changing the axis 360 degrees
d) by changing the axis 45 degrees

Answer 6

B- by changing the axis 90 degrees

Question 7

The proper position of glasses on the manual lensometer is:
a) bottom edge of frame against the frame stage, temples facing away
b) top edge of frame against the frame stage, temples facing away
c) bottom edge of frame against the frame stage, temples facing toward you
d) top edge of frame against the frame stage, temples facing toward you

Answer 7

A- bottom edge of frame against the gram stage, temples facing away

Question 8

When beginning to read the right lens, the first step is to:
a) try to center the target by moving the stage
b) move the stage so the target is in the uppermost part of the field
c) move the stage so the target is in the lower part of the field
d) change the eye piece again to refocus

Answer 8

A- try to center the target by moving the stage

Question 9

Which target is analyzed first?
a) the instrument makes this selection b) the circular mires
c) the wide/triple lines
d) the narrow/single lines

Answer 9

D- the narrow/single lines

Question 10

If the narrow/single line and wide/triple lines of the lensometer target do not clear at the same time, the lens is: a) bicentric
b) spherical
c) plano
d) spherocylindrical

Answer 10

D- spherocylindrical

Question 11

You are reading the right lens, and the narrow lines appear broken. This means you need to adjust the:
a) eye piece
b) lens table
c) axis wheel
d) power wheel

Answer 11

C-axis wheel

Question 12

You have taken the following lensometer reading: The narrow/single line clears at -2.00. The wide/triple lines clear at -3.00. Axis is on 083. The prescription is:
a) -2.00 - 3.00 × 083
b) -2.00 - 1.00 × 083
c) -2.00 - 1.00 × 173
d) -3.00 + 1.00 × 083

Answer 12

D) -3.00 +1.00 x 083

Question 13

You have taken the following lensometer reading: The narrow/single line clears at +2.25. The wide/triple lines clear at -0.25. The axis is on 178. The prescription is:
a) +2.25 - 0.25 × 178
b) +2.00 - 0.25 × 178
c) -0.25 + 2.50 × 088
d) +2.25 - 2.50 × 088

Answer 13

C) -0.25 + 2.50 x 088

Question 14

You have centered and read the distant portion of the right lens of a pair of bifocals. What is the next step? a) move the stage up to read the bifocal segment
b) switch to the left lens, center, and read its distant portion
c) switch to the left lens and note the position of the target
d) turn the glasses over and read the front power of the right lens

Answer 14

C- switch to the left lens and note the position of the target

Question 15

The power of a bifocal will be the difference between:
a) the axes of the distant and bifocal portions of the lens
b) the point where the wide lines clear on the distant part of the lens and where the thin lines clear on the bifocal
c) the point where the narrow/single lines clear on the distant part of the lens and where they clear on the bifocal
d) the point where the narrow/single lines clear on the distant part of the lens and where the wide lines clear on the bifocal

Answer 15

C- the point where the narrow/single lines clear on the distant part of the lens’s and where they clear on the bifocal

Question 16

The distance portion of the lens prescription is -1.25 sphere. You are now reading the bifocal add, and the lensometer dial reads +1.50. The add should be recorded as:
a) +1.50
b) +0.25
c) +0.75
d) +2.75

Answer 16

D) +2.75

Question 17

The distant portion of the lens prescription is +1.25 (narrow/single lines) - 1.25 (wide/triple lines) × 180. You are now reading the bifocal add, and the narrow lines clear at +3.00. The add should be recorded as:
a) +3.00
b) plano
c) +1.75
d) +4.25

Answer 17

C) +1.75

Question 18

To read the bifocal portion of an aphakic spectacle lens:
a) the distance and bifocal spherical power should be read with the temples toward the technician
b) the distance and bifocal spherical power should be read with the temples away from the technician
c) one need only read the distance spherical power, because all aphakic lenses have a +3.50 add
d) one must adjust the eye piece to compensate for the high amount of plus power

Answer 18

A- the distance and bifocal spherical power should be read with the temples toward the technician

Question 19

Regarding the power of the midlevel trifocal lens segment:
a) it is impossible to read the power on the lensometer
b) it is always half the power of the bifocal
c) it is always twice the power of the bifocal
d) it can be read using the lensometer

Answer 19

D- it can be read using the lensometer

Question 20

Prism direction is indicated in the lensometer by:
a) the rings in the reticle
b) the number of lines in the target
c) the position of the target
d) the position of the glasses on the stage

Answer 20

C- the position of the target

Question 21

If the target can be centered in the lensometer, how does one determine whether or not there is induced prism due to decentration?
a) by marking the centers
b) by marking the centers and measuring the distance between them c) by marking the centers and observing the glasses on the patient d) decentered lenses cannot be centered in the lensometer

Answer 21

C- by marking the centers and observing them he glasses on the patient

Question 22

The target of the right lens is displaced to the right, and the lines cross at the third ring. The prism power and direction is:
a) 3 prism diopters base-out
b) 3 prism diopters base-in
c) 1.5 prism diopters base-out
d) 1.5 prism diopters base-in

Answer 22

B- 3 prism diopters base-in

Question 23

The target of the left lens is displaced to the right, and the lines cross between the first and second rings. The prism power and direction is:
a) 1 prism diopter base-in
b) 2 prism diopters base-out
c) 1.5 prism diopters base-in
d) 1.5 prism diopters base-out

Answer 23

D- 1.5 prism diopters base-out

Question 24

Base-out prism is induced when:
a) the optical center separation is greater than the pupillary distance with minus lenses
b) the optical center separation is less than the pupillary distance with minus lenses
c) the optical center separation is less than the pupillary distance with plus lenses
d) the optical separation is offset vertically with plus or minus lenses

Answer 24

B- the optical center separation is less than the pupillary distance with minus lenses

Question 25

To check a manual lensometer for accuracy:
a) adjust the eye piece then read a trial lens
b) set the target lines for your refractive error, then see if they are clear
c) set the eye piece at zero, then read a trial lens
d) set the eye piece at zero, and see if the target lines clear at plano

Answer 25

A- adjust the eye piece then read a trial lens

Question 26

All of the following pertain to maintenance of a manual lensometer except:
a) reset the eye piece to zero after each use
b) turn off the instrument when not being used
c) cover the instrument when not in use
d) do not put too much ink on the ink pad

Answer 26

A- reset the eye piece to zero after each use