Accommodation And Presbyopia II Flashcards Preview

Optics Block 7 > Accommodation And Presbyopia II > Flashcards

Flashcards in Accommodation And Presbyopia II Deck (59)
Loading flashcards...
1

A -2.00D myope is overminued. She wears a -4.00D spec correction. If she has an 8D Amp of accommodation, what is the location of her near point when wearing her glasses?

16cm in front of her eyes


She is a +2.00D with her glasses. Take that away from the 6D amp of accommodation and you get 6. Inverse that and you get 16cm in front of her eyes

2

You measure the Rx. Of a 5 year old in an autorefractor. Your ret showed +1.ooD. The autorefractor show -3.00D. Which form of accommodation might account for the different results

Proximal accommodation

3

Your 45 year old patient says he has no problems with either reading or distance. You measure the spec Rx as:
OD: -1.00 -0.25 +180. +1.00
OS: +0.25 -0.50x170. +1.00

Objective presbyopia

4

Which is the most correct theory of the method for accommodation

Ciliary muscle contraction cause relaxation of the lens zonules

5

What does accommodation do

Causes zonules to relax. The lens balls up, increases space between ciliary body and lens

6

Lens capsule with age

Becomes less pliant

7

What does the lens capsule becoming less compliant have to do with accommodation

Causes progressive decrease in accommodative capacity

8

What could defeat efforts to produce an accommodative IOL placed inside the lens capsule

The lens capsule becoming more pliant with age

9

Shrinkage. Fibrotic tissue condenses and shrinks together and forms small hole

Phimosis

10

Primary factors leading to presbyopia

1. The modulus of the elasticity of th elens capsule decreases with age
2. The modulus of the elasticity of the lens substance increases slightly
3. The lens size/volume increases progressively with age

11

Why does the modulus od the elasticity of the lens capsule decrease with age

It becomes progressively less stiff and mroe compliant

12

Why does the modulus of the elasticity of the lens substance increase slightly with age

-the lens substance becomes stiffer, more plastic, and more sclerotic-like with age
-thus the energy required to deform the lens substance itself increases with age, with this energy being proportional to the modulus of elasticity

13

What factor contributes to 44% of the loss of accommodation

The modulus of the elasticity of the lens substance increases slightly

14

The lens size/volume increases progressively with age and presbyopia

-this makes the lens capsule function less effectively
-it is more difficult to deform a larger body than to deform a smaller body, especially with a concomitant change in shape

15

What factor contributes to 55% of the loss of accommodation

The lens size/volume increases progressively with age

16

What are the two main factors that cause presbyopia

The size increases and becomes stiffer (lens)

17

What is presbyopia not caused by

Zonular elasticity
Ciliary muscle power
Control pathways and structures

18

Zonular elasticity and age

Remains constant

19

Ciliary muscle power and age

Increases from youth to 45

20

Control pathways and structures of the eye throughout presbyopia

Remain constant

21

What two structures change and cause presbyopia

Lens and lens capsule

22

When does amp of accommodation start dropping

About 50

23

When is amp amp accommodation about 0

75

24

Mean amp of accommodation

18.5-(0.30*age)

25

Minimum amp of accommodation

15-(0.25*age)

26

Max amp of accommodation

25-(0.40*age)

27

What might be a common add given to a 50 year old patient

+1.50D

28

Minimum expected amp for 40-44 years

5.00 to 4.00

29

Range of near adds for 40-44

+0.75 to +1.00

30

Minimum expected amp for 45-49

3.75 to 2.75