LENSOMETRY Flashcards

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created 4 months ago by OpticalNcle
The most important instrument used in the optical dispensary.
updated 4 months ago by OpticalNcle
Subjects:
optical, optician, abo, lensometry
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1

LOCKING LEVER

Used to raise or lower the position of the lensometer for user's height or posture.

2

ADJUSTABLE EYEPIECE

To view readings and callibrate lensometer as needed.

Must be callibrated before each user begins.

3

EYEPIECE RUBBER EYE CUP

Prevents light from coming in, allows for for more clear readings, protects the lens, and protects users eyewear.

4

CHROME KNURLED SLEEVE

Rotatates the recticle to move the prisim base into focus.

5

RETICLE

A series of numbered circles the user sees to measure the amount of prism as well as the direction of the base.

6

PRISIM COMPENSATING DEVICE

Used whenever a prism is of more than 5D is present.

7

LENS TABLE

Where the glasses and lens sit to ensure they are level and on axis.

8

LENS TABLE LEVER

To raise of lower the glasses or lens for OC heights or sitting positions.

9

LENS STOP

Where the back of the lens rests.

10

LENS HOLDER

Holds the lens in place again the lens stop. It is a spring loaded arm with a non-scratch piece called the GIMBAL, which rests and holds the lens in place.

11

LENS MARKER

Or SPOTTING DEVICE. Three spring loaded pins that horizontally mark the lenses to idenifiy OC and outer reference points.

12

POWER DRUM

Hand wheel with numbered scale from +20.00D to -20.00D used to detirmine the sphere and cylinder power of a lens, usually in .12 diopter steps. A spherical RX has one reading, a toric RX has two readings.

- Plus values turn wheel up or away from user

- Minus values turn wheel down or towards user

13

AXIS WHEEL

To measure the axis of the lens.

14

A LENSOMETER MEASURES

  • Sphere power
  • Cylinder power
  • Clyinder axis
  • Posistion of optical center
  • Amount of prisim
  • Direction of prisim base

15

BACK VERTEX POWER (BVP)

The reading when the glasses are positioned on the lensometer facing towards the user. The exception is when getting the lined bifocal or trifocal RX reading, the glasses are posistioned away from user.

16

STEPS TO CALIBRATE LENSOMETER FOR EACH USER

  1. Cover light source with piece of paper over lens stop where you would mount the lens.
  2. Look through the eyecup and turn the eyepiece until the reticle is in focus.
  3. Set the power wheel to a high minus power.
  4. Remove the paper and turn the power drum toward 0.00 until the light is focused.
  5. Verify that is the light is focused at 0.00. If not, repeat steps.

17

VERIFYING A LENS FROM A KNOWN RX

  1. Set lensometer to user.
  2. Ensure reticle is centered in prisim target.
  3. Verify higher power first to allow for better accuracy. You can read a false prism going from lower RX to higher RX.
  4. Set power drum to SP power on RX
  5. If CYL, position the axis wheel.
  6. If no CYL, all lines on the target should be in focus. If not rotate power drum until it becomes into focus and notate power.
  7. Observe SPH lines, they should be straight and unbroken. If not, rotate axis wheel until straight and unbroken and notate new axis.
  8. Rotate the power drum until the lines indicating the CYL power comes into focus and notate the reading on the power drum.
  9. The difference between the two powers you just notated are equal to the power of the CYL.

18

NEUTRALIZING A LENS FROM AN UNKNOW RX

  1. Set lensometer to user.
  2. Rotate power drum until the target come into sharp focus. If all the lines come into focus at same time the lens only contains a SP RX.
  3. Rotate the axis wheel and power drum simultaneously until the spherical lines come into focus and are straight and unbroken. Note the markings on the axis wheel and power drum.
  4. Rotate the power drum until lines indicating the CLY power come into focus and notate.
  5. The difference between those two powers are your CYL power.

19

PRACTICE - What is the RX?

1ST READING: +3.00

2ND READING: +2.00

AXIS: 70

+3.00 -1.00 x 70

20

PRACTICE - What is the RX?

1ST READING: -1.50

2ND READING: -2.25

AXIS: 0

-1.50 -0.75 Xx180

21

PRACTICE - What is the RX?

1ST READING: +.075

2ND READING: -1.00

AXIS: 121

+.75 -1.75 x121

22

READING A RETICLE WHICH IS DIVIDED INTO 4 QUADRANTS

RIGHT EYE

Q1= Nasal - Base Up/In

Q2=Temporal - Base Up/Out

Q3=Temporal - Base Down/Out

Q4= Nasal - Base Down/In

23

READING A RETICLE WHICH IS DIVIDED INTO 4 QUADRANTS

LEFT EYE

Q1= Temporal - Base Up/Out

Q2=Nasal - Base Up/In

Q3= Nasal - Base Down/In

Q4= Temporal - Base Down/Out

24

VERIFY A PROGRESSIVE RX ON A LENSOMETER

  1. Set lensometer to user.
  2. Set the distance power on power drum and clamp the lens to OC. Use the NL centration chard to ID the FH in relation to the FRP. The distance reference zone is indicated above that fitting cross.
  3. Calculate the near power of the lens by adding the ADD power and set the power drum and clamp the lens to the near power of the lens using the NL chart.
  4. Once you have verified the distance and reading powers are correct, you know the intermediate power will also be correct.

25

READING BIFOCAL LENSES IN A LENSOMETER

  1. Set lensometer to user.
  2. Follow distance power steps.
  3. Calculate he near power of the lens and set the power drum. Turn the glasses around so that now you can read the FRONT VERTEX POWER (FVP) and clamp the lens to the near power of the lens below the segment line.

If you are reading a PLUS power lens with an ADD power of +2.00 or more read the the lens using the BACK VERTEX POWER (BVP).