Ocular Motility: Lecture 4: Presbyopia Flashcards
1
Q
Amplitude of Accommodation
- What does it represent?
- Should be measured from what point to what point?
a. Incorporating appropriate Compensation for what?
b. What will this effectively reduce?
A
- Max Accommodative level, or closest near focusing response, that can be produced w/maximal voluntary effort in the fully corrected eye.
- from Far point to the Near Point
a. for the Depth of Focus at Both Focal Extremities.
b. its inflated clinical estimate by about 0.5D to 1.00 D in patients w/normal Vision
2
Q
- From age 5 to about 52 yrs, what happens to accommodative amplitude?
- At 52 yrs, it effectively becomes what?
a. The Apparent residual of what really reflects what?
A
- Decreases at a rate of about 0.3 D/year
- 0
a. is about 1.00 D; which really reflects the Eye’s Depth of Focus
3
Q
- AA should be measured how?
2. Does letter size affect the measured response?
A
- Should be measured both monocularly and binocularly while the patient is viewing Near threshold-sized, HIGH Contrast Test letters
- No. not in the perceptive adult.
4
Q
- What should target Velocity be?
a. Why? - AA varies with what?
a. Greatest at what?
b. LOWEST at what?
c. Difference b/w the 2 has been reported to be as large as what?
A
- relatively slow (about 0.50 D/sec)
a. to get a Smooth and Continuous change in the Accommodative response - with the Gaze Angle of the eye.
a. w/the eye positioned down and in
b. eyes positioned in an upward gaze
c. as 3.5 D
5
Q
Minus-Lens AoA
- Push-up
a. Retinal-image size does what?
b. Retinal-image size increases up to what %? Due to what?
c. Proximal Stimulation to accommodation does what?
d. Target change is more what?
e. What happens to pupil size?
f. Stimulus change is what?
A
- a. Increases Greatly (up to 400%)
b. 3% due to the optics of accommodation
c. Increases
d. is more natural
e. It Decreases
f. Is Continuous
6
Q
Minus-Lens AoA
- Minus Lens
a. Retinal-Image Size does what?
b. Retinal-Image size Increases up to what %? due to what?
c. Proximal Stimulation to Accommodation does what?
d. Target change is what?
e. What happens to pupil size?
f. Stimulus change is what?
A
- a. Decreases slightly (up to 10%)
b. Increases up to 3% due to the optics of accommodation
c. remains constant
d. is Less natural
e. it decreases
f. it’s DISCRETE
7
Q
Overview of Presbyopia
- What does it refer to?
a. It’s sufficient to cause symptoms of what? - Refractive error: What is it?
- Ambient Temperature: What is it?
A
- Slow, normal, naturally occurring, age-related, IRREVERSIBLE Reduction in MAXIMAL AA (Recession of the near point)
a. of Blur and Ocular Discomfort or Asthenopia at the customary near working distance - Accommodative demand at the corneal plane in spectacle-corrected Hyperopes is greater than that in myopes for the same Accommodative stimulus and degree of Ametropia at the spectacle plane.
- w/the eyeball being peripheral to the body core, it may exhibit considerable surface temperature variations because of the influence of AMBIENT TEMPERATURE!
8
Q
3 Factors Considered the Primary Factors Contributing to the Age-Related Loss of Accommodation
- Modulus of ELASTICITY of the LENS CAPSULE does what?
- The Modulus of Elasticity of the LENS SUBSTANCE does what?
- The Lens size/volume does what?
a. What does this do to the Lens Capsule?
A
- DECREASES from youth to old age (elasticity = springiness)
- INCREASES SLIGHTLY from youth to about 40 yrs, and more precipitously thereafter
- INCREASES Progressively w/age
a. Makes it function less effectively. (more difficult to deform a larger body than to deform a smaller body)
9
Q
Other Factors that Contribute to Age-Related Loss of Accommodation
- An Anterior shift of Equatorial Fibers occurs because…?
a. As Lens increases in Size and Volume, what do the zonules do?
b. Overall, this does what? - What happens to the Equatorial Zonular Fibers?
A
- of the Passive movement of the Lens capsule w/Increased Lens Growth.
a. they place force on the lens capsule that passively pulls the zonules forward.
b. REDUCES the Mechanical Advantage of the Zonular Suspensory System
2. They Decrease in number, become less dense, and appear to be more fragmented, which reduces their biomechanical advantage.
10
Q
- What may contribute to as much as 20% to 33% of Accommodative Loss from Age 30 to 50 yrs?
- What happens to CHOROIDAL ELASTICITY?
a. The ciliary muscle needs to exert what?
A
- Some changes in specific aspects of the Ciliary muscle anatomy, INCLUDING overall DECREASED LENGTH of the CILIARY MUSCLE
- It progressively Stiffens up to age 35 years, with a Slower rate of increase in its modulus of elasticity thereafter.
a. a Slightly greater force with age to produce the same resultant dioptric change
11
Q
Model Components of Presbyopia
- Tonic Accommodation: Decreases about how much each year?
a. How much is there at 20 yrs?
b. at 50 yrs?
A
- About 0.04 D/Year
a. 1.80 D
b. 0.90 D (so about a 50% decrease!)
12
Q
Model Components of Presbyopia
- The stimulus AC/A ratio either remains Relatively what?
- The stimulus CA/C Ratio Does what with age?
a. At Age 20?
b. Age 55?
c. Cause?
A
- CONSTANT or DECREASES SLIGHTLY WITH AGE!
- DECREASES PROGRESSIVELY with Age
a. 090 D/MA
b. 0
c. Due to Lens saturation
13
Q
Model Components of Presbyopia
- Latency: What is it?
a. What happens to it for increasing and decreasing accommodation?
A
- Reaction times.
a. INCREASE SLIGHTLY (about 2.5 msec/year) from 20-50 yrs of age, consistent w/other age-related reaction time measures
14
Q
Model Components of Presbyopia
- TIME CONSTANT: What is it?
a. What happens to it for Increasing and Decreasing Accommodation in the Linear response region over this same period?
A
- Time to reach 63% of the Final Exponential-like response Amplitude
a. REMAINS UNCHANGED
15
Q
Model Components of Presbyopia
- the PEAK VELOCITY/AMPLITUDE RELATIONSHIP: What happens to it w/Age over the Linear Response Region?
A
- It REMAINS CONSTANT!
