Varifocals Measurements and Markings L3

Question 1

Features of Enhanced Readers

Answer 1

• Larger intermediate and near
• Restricted distance - good for walking around in an office but not suitable for driving
• Good for office use and as a second pair - Some get limited peripheral distortion

Question 2

What is Varifocal?

Answer 2

A progressive surface that varies in curvature to provide a gradual increase in power down along a central corridor. Cosmesis is excellent - it looks like a single vision lens

Question 3

Varifocals and distortion along the edges

Answer 3

• Known as oblique surface astigmatism
• More of a problem with an increase in add, even if distance vision doesn’t change
• More problematic with driving because px wants to glace over to the side to check mirrors
• When dispensing 1st time and at collection, good communication is key ie where to position hear etc

Question 4

Best candidates for varifocals?

Answer 4

• People with multitasking jobs who use all vision, distance, intermediate and near vision e.g. like a teacher.
• Previous progressive lens wearers
• Children with accommodative problems
• Those with Low adds
• Individuals who are highly motivated (they really want them

Question 5

Which patients require consideration (can still be fitted but you just have to consider/communicate a few things before prescribing)?

Answer 5

• Presbyopes with relatively high add >2.25 - Prev wide segment bifocal wearers (remember the width of the segment decreases)
• Individuals sensitive to vertigo or motion sickness (because of the distortion at the sides)
• Those with Anisometropia - due to weight diff and differential prism
• Individuals particularly sensitive to changes in vision
• Eye movers/ people who require wide visual areas

Question 6

Fitting Procedure for Progressive Lenses

Answer 6

• Select the frame
• Pre adjust the frame
• Measure the fitting heights
• Meaure the distance PDs (monocularly)
• Verify blank size
• Take free form measurements

Question 7

Measurements when dispensing

Answer 7

• Pupil distance (Must be done monocularly - because not everyone has a symmetrical face - and its important pupils lie in corridor otherwise they will experience distortion).
• Heights
• Panto tilt - so tilt inwards so that bottom of the lens is closest to the eye.
• Face wrap - make sure lens are following curvature of the face (this would involve lens angled in towards ears)

Question 8

Pupil distance

Answer 8

• More important to do mono PDs with varis due to surface astigmatism
• Mono PDs means setting PDs through that clear corridor

Question 9

Heights

Answer 9

• Check depth to lower rim from pupil centre to ensure lens can fit all 3 rxs
• Pxs require at least 10mm above the eye to the rim for varifocals

Question 10

Pantoscopic Tilt

Answer 10

• Gives a larger/wider reading section (larger FOV)
• A good tilt is 10-12 degrees

Question 11

Face Wrap

Answer 11

= The inclination of the temporal edge of each lens towards the face ensuring that the frame front allows the natural frontal curvature of the skull

• It brings the peripheral distance zone closer to the eye increasing the FOV
• This also moves the peripheral areas of distortion out of the wearers immediate FOV

Question 12

How can you avoid px not getting along with varis?

Answer 12

• Taking correct measurements
• Making sure px adopts a natural head position when measurements are being taken
• Educate px on what to expect
• Px has reasonable expectations

Question 13

Why do we require prism thinning in varis?

Answer 13

• To equalise the edge thickness of the finished lens because of the diff curvatures on the lens
• 2/3 of the add base DOWN is worked onto the lens surface, this reduces the thickness at the top of the lens

Question 14

Four considerations into choosing a progressive lenses

Answer 14

• size and location of the useful areas - width and length of the corridor - rate of power change in the corridor - the location, magnitude and axis of unwanted spherical and cylindrical refractive powers

Question 15

What is the adaptation period for a varifocal?

Answer 15

1 month

Question 16

Why is pupil distance (monocularly) really important?

Answer 16

It dictates which part of the lens the Px looks through.

Question 17

What do you need to ensure you always do when it comes to fitting varifocals?

Answer 17

Select Frames first then do measurements to ensure that all three segments can fit on the lens in the glasses in accordance with their measurements.

Question 18

What is the rough standard for Pantoscopic tilt?

Answer 18

10-12 degrees but manufacturers will state their own conditions sometimes.

Question 19

What is an orthoscopic angle?

Answer 19

When the glasses lie flat - there is no tilt to them.

Question 20

If a patient complains about a pair of varifocals and you see them having to turn their head to view things what has most likely been done wrong with the precribing of the varifocals?

Answer 20

The PD has been taken incorrectly thus pupils are lying in an area of distortion ( this normally happens because Binocular PD was taken rather than Monocular PD)

Question 21

What is the misconception with Prism thinning?

Answer 21

The misconception is that its about making the lens thinner when in actuality its about making the lens of even thickness.

Question 22

Why does the need for prism thinning occur?

Answer 22

As the radii of curvature is always changing throughout lens and getting steeper towards the bottom you will find the top part of the lens tends to be thicker.

Question 23

In what case does prism thinning not work well?

Answer 23

It works well in majority of classes but will not work well if px has different adds in each eye.

Question 24

How do you choose a progressive lens?

Answer 24

Find out the needed size and location of the useful areas The width of the corridor and length. Rate of power of change in the corridor.

Question 25

What are the benefits of single vision glasses?

Answer 25

Often (but not always) cheaper than more complex lenses. Px has a wide segment to view through - good for those e.g. who are prolific readers.

Question 26

What should you discuss with the px about getting varifocals?

Answer 26

Question 27

Explain why a patient who tilts their head up when marking up for varifocals may non-tol.

Answer 27

Because thats not their natural viewing position thus all your markings are off and so when px uses the glasses naturally they will be looking through a distortion area.

(Non-tool just means mess up)