Lec 10 Presbyopic CL

Question 1

Current methods to correct presbyopia with CL

Answer 1

CLs for single vision + SVN

Mono vision CL

Multifocal/bifocals

Modified mono vision

Question 2

How to test which eye should get the distance correction with mono vision (lens method not triangle)

Answer 2

Plus tolerance test
- px full distance correction and looks at VA chart at distance

• BE open, put +0.5D or +1 over RE and then LE
• the more comfortable eye is near eye so non dominant

Question 3

Advantage of mono vision

Answer 3

Cheap

Easy way to provide distance and near

Uses standard technique for lens selection and fitting

Question 4

Effect of mono vision on vision performance

Answer 4

VA loss of 1/2 a line

Stereo loss of 40sec arc

Contrast sensitivity loss 7%

Px may need hear turn

No peripheral loss

Question 5

Types of multifocal and bifocal lenses

Answer 5

Translating/alternating (ONLY RGP version works)

Simultaneous

• concentric optics
• aspheric optics
• diffractive optics

Question 6

How does a rigid translating bifocal work

Answer 6

Near seg is on lower part of lens so relies on lens moving up on downgaze

This translating movement can be achieved by a prism ballast or truncation

Question 7

How to fit a rigid translating bifocal

Answer 7

Use bifocal trial lens

Get good NaFl pattern and centration

Find where near seg is relative to lower pupil margin in primary gaze and in downgaze

Question 8

Advantage of RGP bifocals

Answer 8

Good distance and near VA

no contrast loss

No BV loss

Not really affected by pupil size

Question 9

Disadvantage if translating RGP bifocals

Answer 9

Hard to get adequate translation

Discomfort from prism or truncation

Less o2 from prism

Need trial set

Question 10

What’s simultaneous vision

Answer 10

When more than 1 power is presented at the same time so 2 images projected on retina with one in focus and other blurred

Uses higher cortical suppression of non focused image

Question 11

What are concentric bifocals

Answer 11

Have 2 or more optic zones covering the pupil with a centre D and N surround

OR

centre N and D surround

Question 12

What are aspheric designs for simultaneous vision

Answer 12

There’s a blend of powers allowing less spherical aberration(?)

Question 13

In a concentric design what happens as you increase the add power

And clinical pearl

Answer 13

The distance zone decreases
So to fit more add pose there can be more Crowding/aberrations into the distance zone

Don’t underplus the distance Rx or else need higher add

Question 14

How are aspheric RGPs for presbyopia designed

(Back surface aspheric)

• note front surface aspheric just gives higher add on front

Answer 14

Back surface aspheric
- higher asphericity to cause increase in add

• central pooling steep which can cause corneal moulding
• limit +1.5 add
• requires some translation to see full add power

Question 15

Compare between aspheric RGP and translating RGPS

Answer 15

Aspheric easy fit and often fit steeper than K VS translating harder and fit flatter

Aspheric may have visual compromise but translating doesn’t if positioned well

Aspheric good intermediate vision but translating NONE

aspheric possible fit empirically but translating = diagnostic fit

Question 16

Advantage of simultaneous vision

Answer 16

Easy to fit and refit lens wears

Diagnostic lenses allow trial wear which is important for checking adaptation

Question 17

Disadvantage of simultaneous designs

Answer 17

Change in pupil affects ratio of distance and near

Glare increases with dim light

Loss of VA/Contrast

Decentration causes aberrations like coma

Question 18

What’s a modified mono vision

Answer 18

Using multifocal CL unconventionally

Good for astig in one eye, px needing high add,

Question 19

Example of modified mono vision for astig

Answer 19

SV toric + multifocal intermediate and near

• need this as not much multi focal that gives both add and corrects for astig

Question 20

Example of modified mono vision for high add that does lots of near work

Answer 20

SV near + multifocal with low add (distance and intermediate)

high add in absolute presbyopes means distance area is crowded so by giving SV near u done need high add anymore

Question 21

Example of modified mono vision for px with high Add and wants good range

Answer 21

Multifocal distance + multifocal near

High add in near eye gives good near but also gives range while low add in distance also gives good range and distance

Question 22

Example of modified mono vision for high add px and works mainly at distance

Answer 22

SV distance + multifocal with high add

SV distance good for distance and then the high add gives some range and good near