3? Flashcards
(24 cards)
A kid gets retted at +1.00 and auto refraction gives you -2.00. What kind of accommodation is responsible?
Proximal accommodation
What is the most correct theory of accommodation?
Ciliary muscle contraction cause relaxation of the lens zonules.
NOT CHANGE IN PUPIL SIZE OR CHANGE IN LENS POSITION
Pt has no problems with reading or distance, you get a ret with an add of +1.00 and the right eye slightly myope and left eye slightly hyperope. What kind of presbyopia?
Objective presbyopia
-basically they have like monovision.
When the zonules relax, what happens to the distance between the anterior part of the lens and the posterior part?
It gets longer. The lens becomes more round
Of the lens and the capsule, which one becomes more elastic?
Capsule is more stretched, so more elastic, lens gets less elastic/more dense
What are the three things part of the primary factory leading to presbyopia?
- Lens capsule gets more stretched
- Lens becomes more stiff
- Lens size/volume increases with age
Which factor contributes to 44% of the loss of accommodation?
The lens becoming more stiff
What are the three factors that do not cause presbyopia?
- zonules elasticity (it remains constant)
- ciliary muscle power (it actually increases with age)
- control pathways and structures (remain constant)
What does the amplitude of accommodation usually start at (10 years old)?
12.5D and decreases with age
What is hofsetter’s formula?
Mean: 18.5-(0.30)(age)
Min: 15-(0.25)(age)
Max: 25-(0.40)(age)
What is the min, mean, and max for a 10 year old?
12.5,15,21D
What is the first stop for your patients for add?
0.75D
If a patient thinks they need to up their add, how much do you add?
Usually no more than 0.25 or 0.50
Add is prescribed mostly based off?
Age. Usually start 0.75 and bump it up 0.25/0.5 each time.
What is a common add given to a 50 year old patient?
+1.50D
What is lag/lead accommodation? What is it measured with?
- disparity between retinal defocus and accommodative mechanism
- measured with retinoscopy
What is accommodative spasm?
- you focus too much (lead)
- you turned yourself into a myope (accommodate for a long period of time and now you can’t relax)
- latent hyperopia
How could you get rid of accommodative spasm?
- fog them over and over again
- use cyclo to help relax ir
- sudden unfogging: +/- 2.00 trial lens to fog then rapid bring them out of it.
What is accommodative facility?
- have them look at something near (40cm) then flip between +2 and -2 and have them tell you when they get a clear image
- measure number of cycles in 60 seconds.
When measuring accommodative facility, what amount of accommodation are you switching between?
- 4D switch
- from 4.50 to 0.50
Would monocular for binocularly be a faster accommodative facility?
Monocular would be 2-3 CPM faster than binocular
How do myopes accommodate? Hyperopes?
- myopes accommodate less
- hyperopes accommodate more
What is the accommodation for an emmetrope equal to?
The stimulus to accommodate.
-depth of field may reduce stimulus
Someone with contact lenses has what kind of accommocateion? Glasses?
CL-same as emmetrope
Glasses-use vertex distance of glasses to calculate accommodative demand at cornea.
