CLM - Presbyopic CL Fitting - PAP Week 1

Question 1

List the 5 types of presbyopic corrections available with contact lenses.

Answer 1

Single-vision near spectacles worn over distance contact lenses
Bifocal soft/rigid lenses
Multifocal soft/rigid lenses
Monovision
Enhanced monovision (bi/multifocal lenses in one eye, single vision lenses in the other eye)

Question 2

What 5 drugs can reduce tear volume?

Answer 2

Ibuprofen
Oestrogen
Antihypertensives
Antidepressants
Antihistamines

Question 3

List 4 good candidates for presbyopic contact lenses.

Answer 3

Emerging presbyopes
Motivated patients
Existing contact lens wearers
Low to moderate uncorrected hyperopia

Question 4

Does astigmatism present a challenge when determining a candidate for presbyopic fitting?

Answer 4

Yes, individuals with >0.75D are more challenging candidates

Question 5

List 5 baseline data needed when doing a presbyopic fitting.

Answer 5

Ocular dominance
Pupil size bright and dim
Accuate refraction - push plus
Slit lamp examination
Corneal topography

Question 6

List two advantages of using distance contact lenses with near vision spectacles worn over.

Answer 6

Simple and least expensive option

Optimum acuity for D and N

Question 7

List three disadvantages of using distance contact lenses with near vision spectacles worn over.

Answer 7

There may be a desire to avoid glasses
Demotivating existing CL wearer
Patient needs multiple forms of correction

Question 8

What is an alternating vision design for presbyopic contact lenses? What about simultaneous vision designs?

Answer 8

Alternating - like a bifocal, but in CL form, bottom half is near Rx
Simultaneous - concentric rings of distance and near Rx

Question 9

Are alternating vision designs used in soft or rigid contact lenses?

Answer 9

RGPs

Question 10

Describe how an alternating vision design lens can provide distance and near vision.

Answer 10

It translates up and down with gaze. When looking at a distance, the distance Rx is over the pupil.
When looking down, the lens rides up on the lower lid, and the near Rx is over the pupil.

Question 11

How are alternating vision design contact lenses stabilised (2)? What is the most important factor with this and why?

Answer 11

Prism or truncation
Adequate lid tone is the most important factor
The lower lid must be firm and not below the lower limbus

Question 12

List the four lens fitting principles for alternating vision design lenses.

Answer 12

Aim for an alignment RGP fit
-centre the lens with the eye
Truncation to rest on the lower lid
Dont fit too steeply
Different designs recommend slightly different placement of the segment

Question 13

What tends to happen if alternating vision design lenses are too steep?

Answer 13

Tend to get a nasal rotation of the near segment

Question 14

In general, where should the near segment of an alternating vision design lens be placed in line with?

Answer 14

In line with the inferior pupil margin

Question 15

List four advantages of alternating vision design lenses.

Answer 15

Good distance vision
Good near vision
Good stereopsis
Similar to spectacle bifocals

Question 16

List six disadvantages of alternating vision design lenses.

Answer 16

Unsuitable for patients with lower lid >1mm below the limbus or poor lid tension
Flat fitting lenses will be less comfortable
Lens rotation on down gaze can be problematic
Relative expense
Chair time
No near vision above primary gaze

Question 17

Describe the principle behind simultaneous vision design lenses.

Answer 17

Distance and near zones are both in front of the pupil
As fixation is directed to either N or D, one zone will produce a focussed image, the others will be blurry
Visual system needs to select the clearer image and ignore the blurry image

Question 18

List the three main designs for simultaenous vision design lenses and note whether they are pupil-dependent or independent.

Answer 18

Concentric/annular
Aspheric
Diffractive
All of these are pupil-dependent

Question 19

Describe how a biconcentric design works and what it looks like for a simultaneous vision lens. What does the performance of this design depend on?

Answer 19

It consists of only two regions, an inner circle and outer circumscribing ring
One of these regions is distance Rx and the other is near Rx
There is no intermediate zone
Performance is dependent on pupil size

Question 20

Consider a multi-zone concentric design for a simultaneous vision lens. What kind of vision distance does it favour and under what lighting conditions (2)?

Answer 20

Favours distance in extreme high and low lighting

Question 21

Describe aspheric designs for simultaneous vision lenses and how it differs to biconcentric designs.

Answer 21

Similar to biconcentric designs, but with a gradual power change

Question 22

Describe the two types of biconcentric and aspheric lens designs for simultaneous vision lenses.

Answer 22

Centre-distance

Centre-near

Question 23

Briefly describe the diffractive design for simultaenous vision lenses.

Answer 23

Central zone focusses distance through refraction
Diffractive zone plate on the back of the lens split light into two distinct focal points
Refraction and diffraction is used to corect near vision

Question 24

What happens to contrast acuity with diffractive design simultaneous vision lenses and why?

Answer 24

Some light is lost in the diffractive proccess, reducing low contrast acuity.

Question 25

How should BOZR, BVP, and/or near add be selected? How long should a clinician wait for the contact lens to settle once on the eye? What criteria should be used for fitting if a soft presbyopic contact lens?

Answer 25

Follow manufacturer’s instructions to select initial BOZR, BVP, and/or near add.
Allow 5+ minutes to allow lens to settle.
Use normal fitting criteria for soft lens fitting.

Question 26

Should a phoropter be used to measure visual acuity?

Answer 26

No

Question 27

Consider the aspheric design for simultaneous vision lenses. In what eye should the centre-distance and centre-near lens be placed?

Answer 27

Centre-distance (D lens) should be placed in the dominant eye
Centre-near (N lens) should be placed in the non-dominant eye

Question 28

List six advantages of simultaneous vision design lenses.

Answer 28

Reading position in useful positions other than down gaze
Ideal for soft lens materials
Available in disposable designs
SiHy materials
Some retention of binocularity
Area of current CL grown and R&D

Question 29

List three considerations for simultaneous vision design lenses.

Answer 29

Requires patient to accept a visual compromise
Lens centration is critical
Most designs are very dependent on pupil size

Question 30

Describe how monovision corrects for near vision.

Answer 30

One eye is prescribed for distance Rx, the other for near

Question 31

What is the reported success rate of monovision?

Answer 31

70-75%

Question 32

Which is more popular, multifocal CLs or monovision?

Answer 32

Multifocals

Question 33

Which eye should be given the distance Rx in monovision?

Answer 33

The dominant eye

Question 34

Once monovision is prescribed, what tests should be done?

Answer 34

BV tests to determine the effects on BV and stereopsis

Question 35

What does the success of monovision depend on?

Answer 35

The ability to suppress blur

Question 36

What increases the difficulty of success in monovision?

Answer 36

Higher near addition

Question 37

Up to what D does monovision tend to be successful?

Answer 37

Up to +1.75D

Question 38

How long can one expect full adaptation to monovision to occur?

Answer 38

2-3 weeks

Question 39

List 6 advantages of monovision.

Answer 39

Easy to fit
Alter only one lens for existing wearers
Less expensive than multifocals
Not dependent on pupil size
Correction of astigmatism easy
Complete range of lens modality/materials

Question 40

List 5 disadvantages of monovision.

Answer 40

Deliberate impairment of binocularity
Glare sensitivity, especially night driving
Some patients do not adapt
May require enhancement D/N glasses
Unsuitable for patients with asymmetric VA

Question 41

Is monovision an indication or contraindication for pilots needing near correction?

Answer 41

Contraindication

Question 42

Compare vision for distance, intermediate, and near for multifocals and monovision.

Answer 42

Monovision is better for distance and near

Intermediate is the same

Question 43

Compare stereoacuity and range of clear vision for multifocals and monovision.

Answer 43

Both are better wih multifocals

Question 44

Do patients generally prefer multifocals or monovision?

Answer 44

Multifocals (thought to be a threefold preference)

Question 45

How can monovision be combined with multifocals?

Answer 45

By putting a centre-distance lens on the dominant eye and centre-near lens on the non-dominant eye