Presbyopic Contact Lens Fitting & Aftercare Flashcards
What ocular changes occurs in eyelids
- Reduced elasticity
- Atrophy of orbital fat
- Change in position of eyelids e.g. ectropion, entropion, ptosis
- Lower eyelid come away from contact of cornea
How does ocular changes to eyelids effect contact lenses
Changes dynamics of fitting of lenses and movement of lens
What ocular changes occurs to anterior eye
- Decreased corneal sensitivity
- Age related corneal degenerations
- E.G. Guttata
- Pupil size changes – pupil size decreases as older
- Lens changes
How can decreased corneal sensitivity effect contact lenses:
May not be reporting discomfort to lens where lens may be rubbing on eye
Example of age related corneal degenerations:
Guttata….
- Metal appearance on endothelium causing loss of functionality such as endothelial pump – less o2 entering eye
How does age related corneal degenerations such as guttata effect contact lenses:
- Not prevent fitting lenses but eye more prone to oxidative metabolic stress
- Less o2 entering eye
Which lenses is pupil size important in:
Multifocal lenses
What happens to pupil size as older:
Decreases
How can lens changes as older effect contact lenses:
May cause disruption to light scatter – effect quality of vision
What ocular changes occurs in the tear film
- Decrease in tear production
- Decrease in tear stability
- Decrease in goblet cell density
- Change in meibomian gland secretions
- Lid changes
- Changes to lacrimal ducts
- Change in tear osmolarity
How does a decrease in tear stability as you get older effect contact lenses:
Tears more prone to drying out
How does change in meibomian gland secretions as you get older effect contact lenses:
Effects stability
How does lid changes as you get older effect contact lenses:
Affect tear film e.g. blinking – complete blinking – drying out of eye
How does changes to lacrimal ducts as you get older effect contact lenses:
- Blockages of lacrimal ducts
- So more prone to more fluid being in eye
- This causes disruptions to tear surface – not good vision
What ocular changes to the conjunctiva can occur as get older
- Pterygium
- Pinguecula
What is a pterygium and how can it effect contact lens wear
- Vascularised growth from conjunctiva over cornea onto eye
- Contraindication for lens wear – not comfortable – abnormal
What is a pinguecula
- Small raised area on nasal or temporal conjunctival sclera area
- It has yellowish lipid deposits in it
How can pinguecula can it effect contact lens wear
How can pinguecula effect contact lens wear
- Impacts soft lens wear in terms of the edges of the lens
- Because a soft lens sits a few mm over the limbus so it could be touching on top of the pinguecula
- This might cause some friction and make the area become redder
- Impacts comfort of lens and dynamic fit of lens
- Wont effect RGP lens cause they are small so wont reach the pinguecula
What are two methods of dominance:
- Sighting test - motor
- Defocussing lens - sensory
What is identifying dominance:
Which eye do people see better in distance etc
Sighting test - motor - method of testing dominance:
- Can use a hole in piece of card or ask px to make a triangle at arms length.
- With both eyes open px fixates on a distant target
- And gradually brings triangle closer to their eyes, maintaining the target in the centre of the triangle.
- Practitioner watches which eye the triangle is moved towards, px will tend to keep dominant eye central in distance
- SO THE EYE THAT PX MOVES TRIANGLE TOWARDS AND IS IN CENTRE OF TRIANGLE = DOMINANT EYE
Defocussing lens - sensory- method of testing dominance:
- With full distance correction in trial frame ask your px to view the chart in distance
- Present a plus powered lens in front of each eye in turn
- Follow the fitting guide of lens (+1.00 to +2.00) – depends on lens option youre fitting, there will be difference in choice of plus lens
- Ask the patient when the letters on the distance chart appear worse after putting lens in front
- It will blur vision a bit
- Do the same again for the other eye and see which is the worst
- The letters will appear most blurred when the lens is in front of the dominant eye
- So the eye which the vision is blurred the most is in front of the dominant eye
What are the three presbyopia contact lens options:
- Over spectacles
- Multifocal cl’s
- Monovision
What is over spectacles lenses for presbyopes:
- Full distance correction contact lenses i.e corrected distance rx using contact lenses
- Reading less clear when wearing distance corrected contact lenses
- Need to wear px’s near ADD specs on top for their reading correction
Advantages of over spectacles
- No difference to cost, px may continue to use existing brand of CLs (if fit etc is adequate)
- Allows stable distance vision
- Clear near vision from reading glasses
- Simple and easy to use
- Inexpensive
Disadvantages of over spectacles
- Still need specs to see, therefore might be inconvenient of putting on and taking off reading glasses
- Use of specs negates some of the cosmetic benefits provided by CL wear – reason px goes for cls is to not wear glasses so this doesn’t help with that – px’s may stop cls completely if thats the case
Which sort of px’s is over spectacles lenses good for:
- An ocassional wear early presbyope
- E.g if they have an hobby that requires close detail and theyre not doing it often – quick and convenient
What is monovision lenses for presbyopes:
- Patient wear single vision contact lenses
- One eye (the dominant eye) is fully corrected for the distance
- Other (non-dominant) eye has reading prescription added to distance rx.
Which px’s will monovision lenses work for:
- For low adds
- Early presbyopes
Which px’s will monovision lenses NOT work for:
- Greater than +1.00 add = wont tolerate it cause need reading rx
- So high adds wont tolerate it
- +2.50D is the limit to the amount of difference between the two eyes that can be tolerated
Why is monovision lenses not good for those with high adds:
- Cause as the add goes up theres a greater difference between the eyes in terms of the rx
- As the difference in rx increases, the blur effect becomes more noticeable
- So it depends on their dominance, how easy it is for that px to ignore it
Why is it better to start multifocals at lower age:
When px starts multifocals later on in life i.e when they have a higher add compared to lower age and having lower add, the success rate is lower due to higher add making it harder
Advantages of monovision lenses:
- No increase in cost
- No change in lens type, only lens power
- Wider range of lens material options as using single vision lenses
- Useful for existing wearers
- Easy for practitioner to fit
- Only have to consider one eye one option
Disadvantages of monovision lenses:
- Loss of stereopsis and contrast – cause one eye is blurred more than other – not good depth perception - – not good for task that requires stereopsis
- Adaptation required
- Cannot be used with px who are monocular i.e cant use on px’s who have functional vision in one eye only
- Px must have strong ocular dominance for monovision to work - in normal binocular situation
- Not suitable for a patient with strong near visual task demands
Recent lens advances have meant this option is unlikely to be first choice
Why is multifocal lenses not good in ambylopes:
- Amblyopia involves suppression i.e one eye is stronger
- If you have suppression, you are relying on one eye so wont get good enough mesh of image quality to get better vision
- For multiofcal lenses you need both eyes to work together and have equal contribution to vision
- So multifocal lenses not suitable for amblyopes
Alternating multifocal lens design:
- Patient looks out of the distance portion = located at the top of the lens = when looking straight ahead – distance correction
- Patient looks out of near/ reading lower portion = located at the bottom of the lens = when looking down – near correction i.e on down gaze, the upper eyelid holds the lens in place so the lens stays in roughly same place as the eye translates across lens and patient looks out of lower portion
- Some texts state that the lens must move up on downward gaze to bring near portion of lens into pupil area
Disadvantage of alternating multifocal lens design:
- Not preferred option
- Cause as look down for lower reading portion, lens moves with you
- So need the eyelid to provide some resistance to keep lens in place
- If lens moves a lot during blinking, the incorrect portion of lens may be moved into the pupil region, this would cause blur - disrupt vision
- Lens stability is important and relies on lens-eyelid interaction. If don’t get lens stability vision not good
- Adaptation required
Px who read at eye level or higher.
What is important in alternating multifocal lens design:
- Lower eye lid should be no lower than the inferior limbus- this helps support lens – cause otherwise wont get lens in correct position
- Rule of thumb: approx ¾ of pupil region must be covered by the correct section of lens for successful wear for px to ignore the line
- On downward gaze, lens should be lifted by at least 2mm
- In normal lighting, the top of the segment should be level with or slightly below the inferior pupil margin i.e segment to be at lower pupil
- Lens needs to be stabilised e.g. using prism, or truncation
Advantages of alternating multifocal lens design:
- Binocularity – both eyes seeing both things
- Good visual quality
- RGP lenses – so good vision
- Stereopsis should be unaffected
Which profession is alternating multifocal lens design not good for:
Where for near they are looking straight ahead e.g plumber
Examples of alternating multifocal lens design for RGPs:
- Fused segmented bifocal
- Solid segmented bifocal
Simultaneous multifocal lens design:
- Two images placed simultaneously on the retina i.e both distance and near correction placed simultaneously on the retina = brain ignores image it doenst need
- Having both images on retina in both eyes allows clear vision i.e when looking in distance, youre looking past blurry image of near but when looking into near, you focus on that image
- Does not rely on lens movement
- Most common
Soft lens subcategories for simultaneous multifocal design:
- Aspheric design
- Multizone
- Zonal aspheric
Aspheric simultaneous multifocal design:
Centre distance:
- Central part used for distance
- Near powered surround
Centre near:
- Central part used for near
- Distance powered surround
Why is pupil size important in simultaneous design aspheric:
- Low illumination = larger pupil = distance VA favoured
- High illumination = smaller pupil = near VA favoured
Which px’s is simultaneous design aspheric not good for:
Small pupils
Advantages of aspheric simultaneous multifocal design:
- Does not rely on lens movement
- Stereo acuity cause both eyes working together = more natural
Disadvantages of aspheric simultaneous multifocal design:
- Dependence on pupil size
- Adaptation required – new type of lens – when first put them in not give best vision, takes time to get used to, brain needs to get used to px focussing on different distances
- Lens centration critical otherwise effects such as ghosting can occur – not give good vision
- Loss of contrast sensitivity
Multi zone simultaneous multifocal design:
- Reduced reliance on pupil size
- To enable good visual function in different lighting conditions
- Increase the number of concentric zones powered for D and N alternately = they alternate the concentric zones from distance and near
- Centre-distance multizone design
- Different rings of correction
Why is pupil size not that important in multi zone simultaneous multifocal design:
- Cause even if pupil smaller or bigger
- There will still be some rings of correction that px can look through to give them better vision rather than having to rely on one zone in aspherics
- As it has different rings of correction alternating
Zonal aspheric simultaneous multifocal design:
- Uses principles of aspheric and multi zone lenses
- Zone distribution for each add power (high, med, low) is optimised across the lens for the normal physiological change in pupil size that occurs with age – best vision possible
- Changes distribution of add across the lens
Variation of monovision lenses:
- Enhanced monovision
- Partial monovision
- Modified monovision
What is enhanced monovision:
Monovision with DV corrected in dominant eye with SV lens and a bifocal or multifocal lens in the non-dominant eye so doing monovision but using a multifocal to maintain some binocularity
What is partial monovision:
- When full near correction isn’t incorporated into the non-dominant eye, only a partial correction used
- E.G. if have +1.50 add then just give a +1.00 add to make it more tolerable
What is modified monovision (used by various manufacturers e.g coopervision)
- Dominant eye = C-D design
- Non-dominant eye = C-N design
- Multifocals have the centre near or centre distance design
- Both multifocals so getting advantage of stereopsis
When would you use partial monovision:
When monovision lenses correcting one eye for distance and one eye for near is not tolerable by px’s
Fitting considerations in presbyopes:
- History and symptoms, particular attention to occupation and hobbies
- How is the patient going to use the lenses?
- Consider the patient’s expectations – good distance and near vision ( N8 ) ( 6/6 – 6/9 )
- Refractive error – distance and near – how much difference between them
- Check sight test records for presence of other ocular conditions e.g. cataracts
- Pupil size -think about lighting and how that might affect pupil size
What lenses to avoid if px needs stereopsis:
- Monovision lenses
- E.G. golf
What lenses to suggest for office worker:
- Centre near design multifocal aspheric
- Cause majority of work done at near and
- Cause in office – brighter light conditions so near design will enhance vision in those instances
What lenses to avoid if px has suppression or big difference in refractive error between eyes:
Monovision lenses
What lenses to avoid if px has cataract:
- Multizone option
- Cause problems in lower light levels
What to explain to px for multifocal lenses:
- Explain that adaptation is part of the process – wearing lenses over week/two weeks brain gets used to the way the vision correction is working on the simultaneous design
- Vision may not be quite as good as spectacles – fine detail might not see but general good view like phone and walking around
Key points to successful multifocal fitting:
- Always follow the fitting guide for the manufacturers!!
- Identify visual needs i.e. more distance tasks/near, lighting level, level of detail they want to see
- Set patient expectations about adaptation – try it for a week, brain gets used to it and after that can see more comfortably and vision improve
- Avoid fitting to highly critical vision situations such as architects – unlikely to see fine detail – might need overspecs
- Have good centration without excessive movement
Differences in presbyopic aftercares:
- Vision Assessment
- Binocular, not monocular – cause relies on both eyes looking in distance at same time and brain ignoring bits it doesn’t need
- Real world tasks – consider the size of print
- Over Refraction
- Follow the fitting guide first
- When changing prescription for distance consider the impact on near and vice versa
- No +1.00 blur, duochrome limited, no PH
