presbyopic fitting and afterare Flashcards
What happens to eyelids in presbyopia px?
Reduced elasticity, due to atrophy of the orbital fat. This will change the position of the eyelids
How does the anterior eye change over time?
- reduced corneal sensitivity
- age related corneal degenerations e.g. guttata
- pupil gets smaller
- lens gets thicker and yellow
how does the tear film change over time?
- less tear production
- tear stability
- goblet cell density decreases
- change in Meibomian gland secretion
- lid changes
- epiphora due o blocked lacrimal duct
What happens to Conjunctiva with age?
pinguecula
pterygium
what is more common, pinguecula or pterygium?
pinguecula
if a px has pinguecula, what happens when they wear CLs?
can still wear them, lens edge may start rubbing against it which will make it more red and affects dynamic lens wear
what are the MOTOR method of identifying ocular dominance?
- sighting test
how do you do the sighting test?
ask px to make a triangle at arms lenght
px fixates on a distant target and bring hand closer to eye keeping the target in the centre
what is the SENSORY method of identifying dominance?
defocussing lens
how do you use the defocussing lens theory to identify ocular dominance?
use distance rx
present +ve lens (according to fitting guide) on one eye at a time
ask px when the letters are worse
most blurred eye = dominant eye
which way of identifying dominance is better?
defocussing lens
what are the 3 different presbyopic CL options?
over specs
multifocals
monovision
how do you use CL over spectacles?
CLs are dist corrected
use reading specs when reading
advantages of over specs method?
- no diff to cost (px can use existing brand of CL)
- allows stable distance vision
- simple, inexpensive, easy to use
disadvantages of over specs method?
- still need specs to see - inconvenient
- negates cosmetic benefits provided by CL wear
how does monovision work?
- dominant eye is fully corrected for the distance
- non-dominant eye is fully corrected for reading
who is monovision good for?
low adds
what is the limit to the ADD allowed for monovision?
+2.50D
advantages for monovision?
- no increase in cost
- no change in lens type
- wider range of lens material options as using single vision lenses
- useful for existing wearers
- easy for practitioners to fit
disadvantages for monovision?
- loss of stereopsis and contrast
- adaptation required (all multifocal options)
- cannot be used with px who are monocular
- px must have strong ocular dominance (cannot be amblyopic)
- not suitable for a px with strong near visual task demands
what is the alternating design ?
2 distinct sectors - basically like a bifocal
on down gaze upper eyelid holds the lens in place and px looks out of the lower portion for reading/near vision
what do you need for an alternating design?
good tension in lower eyelid
lower eyelid no lower than the inferior limbus
what is the rule of thumb for an alternating design?
approx ¾ of pupil region must be covered by the correct section of lens for successful wear – for them to be able to ignore this line
advantages of alternating designs
- binocularity
- good visual quality
- stereopsis shouldn’t be affected
disadvantages of alternating designs
- lens stability relies on lens-eyelid interaction
- px who read at eye level or higher
- adaptation required
with an alternating design, how much should the lens lift by on downward gaze?
2mm
what are some examples of different alternating designs?
- fused segmented bifocal
- solid segmented bifocal
how does a simultaneous design CL work?
2 images placed simultaneously on the retina
what are the subcategories of simultaneous design?
- aspheric
- multizone
- zonal aspheric
who cannot use a simultaneous design lens?
amblyopes - need equal contribution
how does a centre near lens work?
low illumination = larger pupil = dis VA favoured
high illumination = smaller pupil = near VA favoured
advantages of aspheric lenses?
- does not rely on lens movement
- stereoacuity
diadvantages of aspheric lenses?
- dependence on pupil size
- adaptation required
- lens centration critical otherwise px can experience ghosting
- loss of contrast sensitivity due to light scatter (exaggerated by lens)
how does the multi-zone design work??
concentric zones of distance and near power
which lens type has reduced reliance on pupil size?
multi-zone
how do zonal aspherics work?
uses principles of aspheric and multi zone lenses
zone distribution for each add power (high, med, low) is optimised for the normal physiological change in pupil size that occurs with age
what is enhanced monovision?
monovision with DV corrected in dominant eye and a bifocal lens in the non-dominant eye
what is partial monovision?
When full near correction isn’t incorporated into the non-dominant eye, only a partial correction used
what is modified monovision?
Dominant eye = C-D design
Non-dominant eye = C-N design
which part of h&s do you need to pay most attention to?
occupation and hobbies
how is the px going to use the lenses?
what are some considerations for fitting?
- px expectations
- refractive error
- ocular conditions
- pupil size
- occupation and hobbies
how do you manage expectations?
- be positive
- explain adaptation is part of the process
- concentrate on real world activities
- vision may not be as good as specs but still good
- will remove the need for specs for majority of things
key points for successful multifocal fitting
- FOLLOW THE FITTING GUIDE
- identify visual needs
- set expectations about adaptation
- avoid fitting to highly critical visual situations
- have good centration without excessive movement (0.6-0.7mm)
what is the difference for presbyopic aftercares when checking vision?
binocular
real world tasks (consider size of print N8)
what is the difference for presbyopic aftercares when over refracting?
FOLLOW FITTING GUIDE
when changing rx -consider the impact on the other D or N
no +1.00 Blur, duochrome limited, no PH
