DISP - Facial Measures and Frame Fitting - Week 5

Question 1

In what 5 situations is vertical centration very important?

Answer 1

Aspheric lenses
High index materials
Polycarbonate
High Rx, including astigmatism
PALs
BFs

Question 2

If the eye is not centred vertically on the optical centre of the lens, what needs to be done to the lens and why?

Answer 2

It needs to be tilted so that the optical axis of the lens passes through the centre of rotation of the eye

Question 3

Consider an eye that is above the optical centre of the lens. What should be done to the lens and why? Describe what angle is formed at the optical centre vs off the centre. Name what this process is known as.

Answer 3

It needs to be tilted. At the optical centre, the optical axis will make a 90 degree angle with the lens. If it is vertical, it will be less (if negative, more if positive).
Therefore the lens will need to be tilted such that this angle is now 90 degrees.
In this way, the optical axis will pass through the centre of rotation of the eye.
This is known as pantoscopic tilt.

Question 4

Do individuals tend to look above or below the horizontal? Describe how lenses are generally tilted and why this is the case.

Answer 4

Its easier to look below the horizontal than it is to look above. Lenses are generally tilted (the inferior coming more posteriorly) so that the zone of best viewing is biased to the inferior visual field.

Question 5

Describe in 4 steps how to ensure the correct degree of tilt.

Answer 5

Have the patient tilt their head back so the lens is 90 degrees to the floor.
Mark the pupil centre.
If the pupil is above the optical centre, more tilt is needed.
The optical centre drops 1mm for every 2 degrees of tilt.

Question 6

Describe how bifocals are fitted.

Answer 6

The edge of bifocals is placed on the lower limbus.

Question 7

Describe how progressives are fitted.

Answer 7

On the pupil

Question 8

Describe how trifocals are fitted.

Answer 8

At the lower pupil margin, minus 1mm

Question 9

When fitting a frame, what three things must be done first?

Answer 9

Be eye level with the patient
Be directly in front of them
Have them in a habitual posture

Question 10

How should a bifocal be fitted if a patient is already a previous wearer and happy with their segment height?

Answer 10

Position the segment in the same relative position

Question 11

In what case are the specifications for a bifocal segment the same?

Answer 11

Only if the frame is the exact same and the patient is happy with the location of the segment

Question 12

How should bifocals be fitted for children?

Answer 12

They should bisect the pupil

Question 13

If a bifocal is being used for general purposes, mainly near vision, or occasional near vision use, how does this affect the near segment height?

Answer 13

General purpose is placed at the limbus.

Occasional use is placed lower, while more in near vision use, it is placed higher, depending on the patient’s needs.

Question 14

What three considerations must be given to frame selection?

Answer 14

Shape and size must be adequate
Patient’s preference
Cosmetic appearance

Question 15

Are frames adjusted before or after being measured/fitted?

Answer 15

Adjusted beforehand

Question 16

Define back vertex distance.

Answer 16

The distance from the front of the cornea to the back vertex of the lens

Question 17

What is a distometer? Describe briefly how it works.

Answer 17

It measures the back vertex distance.
The distometer is positioned against a closed eyelid. A probe is extended from its tip to the back surface of the spectacle lens and the vertex distance read from the scale.

Question 18

What four considerations should be given if a patient suggests re-using a frame?

Answer 18

If it can withstand re-glazing
If it has been repaired previously
If the frame is old, it may be difficult to get spare parts for repair
If the style of the frame is out of fashion or on track to

Question 19

What occurs when a patient selects a frame that doesnt fit well?

Answer 19

More work in adjusting the frame to get alignment correct

Question 20

What two features of a patient influence what frames are suitable for them?

Answer 20

Face shape and hairstyle

Question 21

How can temple length affect the emphasis the spectacles have on their face shape? What face shape type does this generally apply to?

Answer 21

In patients with long face types, it can be de-emphasised by selecting a temple location in the middle of the frame rather than the top.

Question 22

List three temple arm styles and what lifestyle necessitates their use.

Answer 22

Comfort cable/riding bow - active people, unusual head position (occupational), children, heavy frames/lenses
Straight back - off and on wear
Skull - normal, everyday wear

Question 23

How can bridge design influence the appearance of nose length?

Answer 23

Particular styles can make the nose appear longer or shorter.
Frames exposing as much of the nose as possible will make it look longer, vice versa will make it appear shorter.

Question 24

Define crest and frontal angle for the nose.

Answer 24

Crest - angle of the nose from the base to the top compared to a vertical plane parallel to the brow/cheeks
Frontal - angle with which each side of the nose deviates from the vertical (medial line)

Question 25

What happens when the bridge is too flared not flared enough?

Answer 25

Too flared - only the top of the bridge crest will touch the nose and support the weight of the glasses
Not flared enough - the back of the bridge area will cut into the side of the nose, and the top of the bridge will not touch the nose, and therefore not support the weight

Question 26

Where should the upper and lower rims ideally align with on the patient’s face?

Answer 26

Upper rim - follow their eyebrow

Lower frame - follow the lines of their cheek and jaw

Question 27

What should the lower rim near the nose follow?

Answer 27

The nose contour

Question 28

How can eyebags be hidden by frames?

Answer 28

Positioning the frame wim on the lower edge of the bags

Question 29

Briefly describe guidelines for frame colour based on:
Hair colour
Hair thickness
Clothing colour preference

Answer 29

Hair colour - match light hair with light frames, dark hair can wear most frames
Hair thickness - patients with thicker, darker hair can wear heavier, darker frames
Clothing - patients with darker clothes can wear darker frames
Also good to break these rules for contrast

Question 30

What colour frames benefit’s grey hair (3)?

Answer 30

Blue/rose/silver

Question 31

What features are the following frame weights indicated for:
Heavy (1)
Medium (3)
Light (3)

Answer 31

Heavy - large rounded features
Medium - normal features, large features, small stature
Light - small, delicate features, women with childlike features, children

Question 32

What can be done to avoid prominent minification/magnification of eyes with high powered lenses?

Answer 32

Not selecting frames that are wider than the face in the temple area

Question 33

Should large vertex distances be used or avoided for high Rx hyperopes? Explain why.

Answer 33

Avoided, as this mitigates magnification of the eye