Presbyopia Flashcards
What is the number one reason why people go to see their eye doctor?
Blur at near
Accommodation peaks at 8 and is on a steady decline from there, no little to no accommodation by age 50
Are conventional bifocals/ PALs always going to work for patients?
No, they require you to look through the bottom
Describe the function of a near add.
Near add reduces the accommodative stimulus, allowing presbyopic patient to view a near target
If near target is at the first focal point of the lens, then the image will lie at optical infinity and the stimulus to accommodation will be zero (no accommodation for distance)
Describe the amount of optical magnification produced by a near add.
Optical magnification is minimal
Lenses magnify allowing the observer to hold the object closer and will still be seen in focus so the image subtends a larger angle on their retina
The higher the add the closer the position of near focus (+1.00Add focuses 1m away, +4.00Add focuses 25cm away)
How does near add affect DOF?
The higher the ADD the smaller the range of clear vision and the closer they will be focused
Should we be prescribing high ADDs?
No want to prescribe the lowest add a possible to give largest range of clear vision while putting their preferred viewing distance in the middle of the range of clear vision
Where in the DOF we want the near add to fall?
In the middle
Ex: If patient wants to read at 40cm with DOF of +/-0.50D, prescribe a +2.50ADD to give clear vision from 50cm (2D) to 33cm (3D)
What amount of accommodation do we assume the patient has when prescribing an ADD?
Assume that the patient can maintain 50% of their amplitude for a sustained period of time
If patient has this residual accommodation we lower the ADD
What methods can we perform to determine the near ADD?
Dynamic cross cylinder
Plus build up
Add based on age
Proportion of amplitude
Dynamic retinoscopy
NRA/PRA balance
Near duochrome
(Reading performance must always be chanced after performing these tests)
How can Dynamic crossed cylinder (FCC) be used to determine ADD?
Expect presbyopes to have a lag of accommodation (horizontal lines are clearer)
Add plus lenses until clear
This is the tentative ADD
How can plus build up be used to determine ADD?
Adding plus lenses moves the DOF closer to the patient (and the near target)
Add plus until the patient is just able to see the near target clearly
Right (proximal) side of DOF will align with near target
ADD AN EXTRA +0.25D B/C WE WANT THE ADD IN THE CENTER OF THE DOF
What are the ADDs based on patient’s age with viewing distance of 40cm?
Age: ADD:
40. 0
45. +1
48. +1.25
50. +1.50
52. +1.75
55. +2.00
60. +2.25
65. +2.50
Varies with ethnicities
How can we use proportion of amplitude to calculate ADD?
ADD= working distance (D)- half amplitude (D)
How can we use dynamic retinoscopy to determine ADD?
Usually sheard’s retinoscopy
Used to determine accommodative response to a given stimulus
Plus lenses introduced over distance until neutral reflex
Some ODs choose to leave small lag of accommodation
Subtract distance Rx to the lenses that give a neutral reflex
How can we use NRA/PRA balance to determine ADD?
Use other technique to determine tentative add
Use this add to perform NRA/PRA testing through
Take range of clear vision (PRA NRA) and the value in the middle is the add
Determine the NRA/PRA through ADD
