CL Fitting for Presbyopia Flashcards
1
Q
What questions do you need to ask a presbyope trying CLs for first time?
A
- All usual questions but ensure find out:
o Full time or part time? – most multi focal stake bit to adapt to so if part time go for easier to adapt to lens
o Visual priorities? distance, near or intermediate? – different lens designs have different emphasis on different distances so ask hobbies/occupation
o Dry eye? – much more prevalent in these pxs
o Hobbies & occupation?
o Would they be happy with any visual compromise? – varies specs also have visual compromise, would they be happy with a bit worse near but they can see the computer?
More limited in toric lenses
o VDU use? - Set px expectations – there can be a compromise with different options – discuss pros & cons (try to be positive or px will not be interested)
2
Q
What questions do you need to ask someone entering presbyopia who is already wearing CLs?
A
- What problems are they having? – ask each visual distance separately
- How is it affecting daily life?
- How are their lenses otherwise? Can be opportunity to solve other problems or improve health of eyes
3
Q
What is the simplest option for presbyopes who want to wear CLs?
A
- Often v successful
o Reading glasses over top of contact lenses - Especially when px doesn’t need reading correction all time or they are doing intensive tasks – may in early presbyopia
- Can be v successful in complex Rxs – e.g. particularly complex RGP
4
Q
Describe monovision in presbyopic soft CL wear?
A
- One eye corrected for distance & other for different distance i.e. one for near & one for far (could be computer too)
- Visual system can alternate central suppression when alternating between distance & near
- Hopefully no, or only a slight reduction in distance VA & no significant reduction in near VA
- All forms of soft or rigid lenses can, in theory, be used – essentially just altering the sphere in one eye
- Fitting Monovision:
o No one predictive test for success – trial & error
o Make sure cyls >0.75D are corrected – don’t want one eye to already be on a reduced VA
o Check BVA – should be similar to glasses (good indicator of success)
o Over-refraction to test add – full distance in one eye (dominant eye) & near in other eye (non-dominant eye) then check DVA & NVA binocularly
o Adjust as necessary – can tweak near add - Who Is It Not Suitable For?:
o Compromised VA – either binocularly or monocularly
o Distance VA <6/12
o Avoid pxs who need v precise vision required for distance or near - Establishing Ocular Dominance (+1.00D Sensory Test):
o Full correction in trial frame/phoropter
o Have px look at smallest line they can see – both eyes open
o Introduce +1.00D lens in front of right then LE
o Ask whether 1 (in front of RE) or 2 (in front of LE) is clearer
o If it is 1 then LE is dominant as RE being blurred hasn’t affected px as much (vice versa if px says 2)
o Dominant eye corrected for distance – px likely needs good distance VA for driving etc
o Non-dominant eye corrected for near
5
Q
What are the advantages and disadvantages of monovision in presbyopic CL wear?
A
- Advantages:
o Good for early presbyopia – problems come from about +2.00 upwards
o Easy to fit – range of lens designs, materials & modalities – these are standard lenses just changing the Rx
o Can be reduced chair time if px already wearing lenses as not worried/looking as much at the fit but may take a while to adjust to the mono vision so may not be reduced chair time
o Less costly – since just using standard lenses - Disadvantages:
o Reduced stereopsis & contrast – effectively making px monocular
o Glare when driving at night
o Adaptation period (suppression) – can take bit of getting used to – earlier in presbyopia you start it the better as add is smaller
o Intermediate vision (higher add) can reduce near add to improve intermediate & incorporate reading specs for intensive close work – if sharpen the intermediate (decrease the add) then near add will be slightly worse
o Unsuitable for monocular pxs
6
Q
Describe modified monovision in presbyopic soft CL wear?
A
Modified Monovision:
o Reducing distance power slightly in dominant eye to help with near or vice versa (reducing near in non-dominant eye to help with distance)
o Reducing add to allow most tasks to a satisfactory level & then having reading glasses for small print
o Dominant eye with single vision distance, non-dominant with a multifocal – if distance is priority
o Dominant eye with single vision near, non-dominant with distance-bias multifocal (or just distance) – if near is priority
TRIAL & ERROR – go for most straight forward one first then try other things afterwards
7
Q
Describe alternating design in presbyopic soft CL wear?
A
- Majority are RGP - so often good for complex Rxs
- Distance & near powered portions
- Similar to a conventional bifocal spec lens
- Stabilised with prism, truncation or both
- Challenges:
o Lower lid position, must be no lower than inferior limbus otherwise translation (switch from distance to near) is less effective
o Need lower lid to have enough muscle tone to nudge lens up as px looks down
E.g. older pxs with lower lid laxity may not be suitable
o Pupil size, ambient (natural lighting) pupil size >3mm may interfere with near portion when looking in distance & vice versa - Fitting:
o Aim for an alignment fit or with slight central touch, lens should sit slightly low – alignment to slightly flat
o 2mm smaller than HVID to encourage inferior centration – larger lens fit tighter so go smaller
o Generally aim for the upper line of the near segment to be in line with the lower pupil margin in ambient lighting
When px looks down, at least 75% of the pupil should be within the near segment – 100% would be ideal but 75% okay
o White light in this assessment could cause minimum pupil size so looks like pupil all within near seg but then in px’s normal light levels it may not be
Have SL illumination to a normal room level – not too high
8
Q
Describe simultaneous design in presbyopic soft CL wear?
A
- Distance & near (& intermediate) are both in front of pupil at same time – all are presented at once
- Depending on target then one zone produces a clear image & other a blurred image
- Relies on visual system being able to ignore the out of focus image
- Therefore, there can be a reduction in image quality compared to a single vision correction
o This reduction may be acceptable to some and unacceptable to others – often depends on the px expectations that were set at the start of the fit - Pupil size may mean more of one zone than other is being covered
o Biconcentric designs – not used as often anymore due to development of new designs
Centre Distance – distance vision will improve in bright light -> if need px to have really good distance vision during day when lights are bright (and pupil will be small)
Centre Near – distance vision will improve in low light (puts distance vision into the large pupil) -> if need to have good near vision during day – will concentrate the small pupil into the near area
Can do centre distance in one eye and centre near in other
o Multizone concentric designs
To minimise impact of pupil size
Should favour distance vision in extreme bright (pupil v small) & extreme low light (pupil v large) & provides a more equal distribution in ambient lighting (pupil medium size)
Theory: no matter what pupil size have you will be hitting both distance and near and visual system will have to process what looking at
Multizone Concentric Modified Monovision – added intermediate zone – can be centre distance or centre near
o Aspheric designs
Gradual change from central zone to periphery – theory is that is also covers the intermediate portion
Can choose centre near or centre distance – standard to put centre distance in dominant eye and centre near in non-dominant eye
May need to try different manufacturers as different designs can lead to different dioptric power maps (failing with one aspheric lens doesn’t mean you’ll fail with all aspheric lenses)
3 types: - Back surface
- Front surface
- Zonal
9
Q
Why is pupil size important in presbyopic soft CL wear?
A
- Smaller with age
- Some multifocal designs reflect this as higher add design tends to be focused on middle of lens
o Higher add has less impact in distance as pupil will only be small when px looking at near - Research has shown smaller pupils in hyperopes than in myopes
- Low add - much larger zone of near
o High add is concentrated much more in centre where pupil will be small
10
Q
Give examples of daily disposable multifocal soft CLs?
A
11
Q
Give examples of monthly replacement multifocal soft CLs?
A
12
Q
Give examples of monthly replacement toric multifocal soft CLs?
A
13
Q
Give examples of weekly/fortnightly replacement multifocal soft CLs?
A
14
Q
What are the specialist company options for multifocal CLs?
A
- Mark Ennovy:
o Daily, monthly & 3-monthly replacement lenses
o Extended Rx ranges (+/- 30D & up to 8D of astigmatism)
o Up to 4D add
o TD of 11.50-16mm & base curve of 6.50-9.80mm available with different lenses - David Thomas (bought over by Menicon)
o Daily, monthly & longer term replacement lenses
o RGP multifocals
Look at manufacturer’s guidelines - v important for presbyopia fitting
15
Q
Describe RGPs for presbyopic CL wear?
A
- Monovision suitable for pretty much any RGP lens
- Alternating design – most are RGPs – 2 zones often
o Technically can get a trifocal RGP (v similar to trifocals specs – 3 distinct areas) – can be tricky to adapt to and get used to
