Prebyopia 1/2 - Week 5

Question 1

What are 3 possible causes of Presbyopia?

Answer 1

• loss of lens elasticity
• changes in lens curvature
• loss of power of the ciliary muscles

Question 2

What diopter of accommodation corresponds to the moment when the ability of the eye first becomes insufficient for satisfactory near vision without corrective plus glasses?

Answer 2

4 diopters of accommodation

Question 3

At what age does presbyopia (the symptoms) usually start? Does this vary based on region?

Answer 3

In Europe, North America, Aust: Around 42-48yrs old

For people living closer to equator: 30s to early 40s yr olds

Question 4

Describe the Lenticular and Extralenticular theories of Presbyopia

Answer 4

Lenticular - changes to the lens and capsule

Extralenticular - changes to ciliary muscle. And changes to elastic components of zonule/ciliary body

Question 5

Where is the lens capsule thickest?

Answer 5

At the equator

Question 6

How does the lens capsule thickness change as you age?

Answer 6

Goes from being the thickest at the equator and gradually shifts to the anterior pole, such that it is then thicker at the anterior pole

Question 7

What is the typical near-point for people of the following ages:

• 20
• 50
• 70

Answer 7

20: Near point at 10cm
50: Near point at reading distance
70: Near point at 4 metres

Question 8

What near requirements of the patient should you take into consideration when correcting near vision?

Answer 8

• Near tasks undertaken
• Range of working distances needed
• Environment in which near tasks undertaken (e.g. looking down, looking up, etc for near)
• Duration of near tasks

*NERD - Near, Environment, Range, Duration

Question 9

Describe the procedure for determining near addition

Answer 9

Place distance correction in trial frame
Adjust trial frame to patient’s near PD
Use initial add formula to estimate and insert a ‘near add’
Use a habitually illuminated near reading chart and check for N5 at habitual
Move reading chart closer until first sustained blur, then move it away until N5 can no longer beread
If range too far away, add +0.25DS. If range to close, add -0.25DS.

Question 10

Why do you typically NOT use a phoropter for the near addition procedure?

Answer 10

Because the phoropter is much more intrusive and the eyes won’t be in a natural position for reading. Doesn’t properly simulate a real environment

Question 11

Why do you want a good illumination reading chart for near addition?

Answer 11

Because we don’t want to cause glare or have too bright as this will reduce pupil size and increase depth of focus, which is likely to differ from habitual environment

Question 12

What is the lowest diopter of near addition that we generally prescribe?

Answer 12

+0.75DS

Question 13

What is the range of near addition prescriptions that we typically prescribe?

Answer 13

+0.75DS - +2.50DS

Question 14

Name 2 scenarios where we would prescribe a near addition of more than +2.50DS

Answer 14

• if patient has a very close working distance

- if patient has poorer V.A (basically if 6/9.5 or worse)

Question 15

What are the recommended near additions for the following ages:

• 45
• 50
• 55
• 60

Answer 15

45: 0-+1.00DS
50: +1.00-+1.75DS
55: +1.50-+2.25DS
60: +1.75-+2.50DS

Question 16

Which of the following patients is likely to experience the effects of presbyopia first? Myopes or Hyperopes?

Answer 16

Hyperopes

Question 17

What is the general guide for estimating near add with respect to age?

Answer 17

50 years old = +1.00DS +/- 0.25 for +/- every 2 years

Question 18

What are the formulas we use for determining near addition based on working distance and amplitude? Do we use these formulas for prescription?

Answer 18

Initial add = 1/working distance -1/2NPA
Initial add = 1/working distance - 2/3NPA

• using binocular NPA. WD is in metres.

We only use these formulas to get an INITIAL ESTIMATE

Question 19

What happens with a higher near addition?

Answer 19

The higher the near addition, the smaller the working range of clear vision

Therefore we should NOT overplus the patient’s near addition

Question 20

When deciding between 2 near additions, which one should we prefer?

Answer 20

The one with the least +ve.

Question 21

Where would the ideal best near addition place the near working distance of the patient?

Answer 21

Slightly closer than the middle of range of clear normal vision

Question 22

How should you record the final near add?

Answer 22

Write the value of the near add, the level of near vision it provides (e.g. N5), the habitual working distance and range of clear near vision provided

Question 23

What are some other techniques to determine near addition? (3)

Answer 23

• Binocular Cross Cyl
• Duochrome
• Polarized techniques (rarely used)

Question 24

How does Binocular Cross Cylinder work?

Answer 24

Patient observes horizontal and vertical lines at near with a 0.50D cross cyl added in both eyes [minus axis vertical]
Patient asked which set of lines are blacker and clearer:
- if under-plused: horizontal lines clearer
- if over-plused: vertical lines clearer

Question 25

What technique do we often use to determine near addition for a first time presbyopic patient?

Answer 25

Binocular Cross-Cyl. Usually, we don’t need many diopters of near add so it’s just faster

Question 26

What are the disadvantages of the Binocular Cross Cyl?

Answer 26

• It is behind a phoropter

- more complex technique and less natural viewing target

Question 27

Describe the duochrome test at near

Answer 27

Red focuses behind green wavelengths. Aim is to centre them onto the retina. If undercorrected at near, green is clearer. If overcorrected, red is clearer

Question 28

If a patient reports green is clearer for duochrome at near, what would you do?

Answer 28

Just leave on green as eye naturally has lag of accommodation

Question 29

Name 4 presbyopia correction apparatuses

Answer 29

• Readers
• Multifocals
• Bifocals
• Extended focus lenses: near-intermediate

Question 30

What are the disadvantages of duochrome/bichromatic tests for near addition?

Answer 30

• chromatic aberration of eye at near is different to distance
• in elderly patients, the yellowing of the lens affects results, causing a bias for red

Question 31

What type of contact lens options are there for correcting presbyopes? (other than simple near add)

Answer 31

Bifocals

Monovision CLs

Question 32

What are alternating vision bifocal contact lenses?

Answer 32

are so named because your pupil alternates between the 2 powers, as your gaze shifts upwards or downwards

Question 33

Describe simultaneous vision bifocal contact lenses

Answer 33

require your eye to be looking through both distance and near powers at the same time. Your visual system learns to select the correct power choice depending on how close or far you’re trying to see

Question 34

Name the 2 types of simultaneous vision bifocal contact lenses

Answer 34

1. Concentric ring designs

2. Aspheric designs

Question 35

What are Monovision contact lenses?

Answer 35

You wear a contact lens on one eye to correct distance (typically dominant eye), and other eye to correct near.

Typically results in clear vision with both eyes open for all distances

Question 36

What combination of colours would theoretically be better for ducochrome at near? But why doesn’t this work in practice?

Answer 36

Blue and Yellow. Doesn’t work in practice due to the low energy of blue

“sounds good, doesn’t work”

Question 37

Name and describe 4 surgical options for presbyopia

Answer 37

• Monovision Lasik: to correct one eye for distance and one for near
• Monovision and Conductive Keratoplasty: using controlled radio-frequency energy to shrink collegen fibres in periphery to steepen cornea of one eye to view near objects
• Refractive lens exchange - replace lens with an accommodating IOL
• Corneal Inlays - small disc inserted in corneal flap to either change corneal power or reduce aperture to increase depth of focus