Ocular Motility: Lecture 2: Ocular Accommodation

Question 1

1. Accommodation: Process there changes in DIOPTRIC POWER of Crystalline Lens occur, so an in-focus retinal image of an object is OBTAINED and MAINTAINED at what?

Answer 1

1. At the HIGH-RESOLUTION FOVEA

Question 2

1. A Step input INCREASE occurs in firing frequency of NEURAL innervation to what?
2. The Contraction force of the Ciliary Muscle does what?
3. Ciliary Muscle moves what 2 ways?
4. The CILIARY RING advances about how far along w/the ciliary muscle?
5. The Choroid and Posterior Zonules stretch about how much?
6. Anterior Zonular Tension does what? What does this do to the Zonules?

Answer 2

1. the Ciliary Muscle
2. INCREASES
3. INWARD and ANTERIORLY
4. 0.5 mm along w/the Ciliary Muscle
5. about 0.5 mm
6. Decreases; Zonules Relax

Question 3

7. The Elastic Forces of the Lens capsule and the Viscoelastic Properties of the Lens cause the Lens to BECOME MORE what?
   a. Thus, the Overall Power of the Lens does what?
   b. Equatorial Diameter?
   c. Anterior Lens Poles moves ?
   d. Central Anterior ROC changes form what to what?
   e. Posterior Lens Pole may move back how much?
   f. The Central Posterior ROC decreases from what to what?
   g. The Central Thickness INCREASES by what?
   h. The Lens sinks how much as a result of what?

Answer 3

1. More Spherical
   a. INCREASES
   b. Decreases by 0.4mm (from 10 to 9.6mm)
   c. Moves BACK 0.3 mm
   d. From 11 to 5.5 mm
   e. Back 0.15 mm
   f. DECREASES from 5.18 to 5.05 mm
   g. Increases by 0.36 to 0.58 mm
   h. Lens sinks 0.3 mm as a result of gravity

Question 4

1. Retinal Cones are stimulated by what?
2. This leads to a SUMMATED BLUR SIGNAL transmitted thru what?
3. Summated Cortical Cell Responses Formulate what signals?
4. Signal Also transmitted to what 2 places for what?
5. Supranuclear Signal goes on to what areas (nuclei) where MOTOR COMMAND is FORMULATED?
6. Motor Command transmitted to Ciliary Muscle via what 3 nerves?
7. Change in state of what?
8. Crystalline Lens DEFORMS to attain In-Focus what?

Answer 4

1. DEFOCUS
2. thru the MAGNOCELLULAR Layer of LGN to Visual Cortex
3. Sensory Blur Signals
4. To Parieto-Temporal Areas and Cerebellum, for Processing/Dissemination
5. To Midbrain/Oculomotor Nucleus/Edinger-Westphal Nucleus where Motor Command is Formulated
6. CN3, Ciliary Ganglion, and Short Ciliary Nerve
7. of Contraction of the Ciliary Muscle
8. In-focus Retinal Image and Clarity of Vision

Question 5

Time Constant and Latency Values

1. Disparity Vergence will typically PRECEDE any ACCOMMODATIVE VERGENCE CONTRIBUTION by about how much time?
   a. Why might this be Functionally Beneficial?

Answer 5

1. about 100 msec

a. Because it allows the Retinal Image to Approach the Fovea, where ACCOMMODATIVE GAIN is HIGHEST!!!

Question 6

Components of Accommodation

4 of them. What are they?

Answer 6

1. Reflex
2. Proximal
3. Tonic
4. Vergence Accommodations

Question 7

Reflex Accommodation

1. Define?
   a. Blur Input is a reduction in what 2 things?
   b. This occurs for what amts of Blur?
   c. How important is this component?

Answer 7

1. Automatic Adjustment of Refractive State to OBTAIN AND MAINTAIN a Sharply Defined and Focused Retinal Image in Response to a BLUR INPUT
   a. in OVERALL CONTRAST and CONTRAST GRADIENT of the RETINAL IMAGE
   b. for RELATIVELY SMALL AMTS of BLUR, up to 2.00 D
   c. LARGEST and MOST IMPORTANT COMPONENT

Question 8

Vergence Accommodation

1. It’s the Accommodation Induced by what 2 things?
   a. Gives rise to what RATIO? What is this Ratio in YOUNG ADULTS?
   b. How is it Measured?
   c. How important is this component?

Answer 8

1. INNATE NEUROLOGICAL LINKING and ACTION of DISPARITY (Fusional) VERGENCE
   a. to the Convergence Accommodation/Convergence (CA/C) Ratio; It’s about 0.40 D per Meter Angle (MA) in young adults
   b. Under Open-Loop Viewing Conditions (Binocular Pinhole)
   c. SECOND MAJOR COMPONENT

Question 9

Proximal Accommodation

1. Accommodation due to what?
   a. Under Open-Loop Viewing Conditions, its Contribution could become what %?

Answer 9

1. due to the influence or knowledge of apparent (or perceived) nearness of an object
   a. 80%

Question 10

Tonic Accommodation

1. It’s revealed in the ABSENCE of what things?
   a. This means that Tonic Accommodative Level in young adults is about what?
   i. What is the range though?

Answer 10

1. Blur, Disparity, and Proximal Inputs as well as any Voluntary or Unusual Learned Aspects
   a. About 1.00 D
   i. Nearly 0 to 2.00 D

Question 11

Development of Accommodation

1. During the first month of life, it appeared to relatively fixed at about what?
   a. In subsequent 3 months, it progressively became more like what?
   b. Accommodative Dynamics in response to Steps of Blur Input appear to have Adult-like Velocities by what age?

Answer 11

1. 5.00 D
   a. More Accurate and Approached Adult-like Behavior
   b. By the Age of 3 Months

Question 12

1. The Slope of Accommodative Stimulus/Response Function Remained how with Age in Young Emmetropic Children (3-14 yrs old) using what methods?
   a. What does this tell us about young children?

Answer 12

1. Relatively Constant (0.92); using Objective Methods

a. Tells us that young children have appropriate levels of Accommodation to Targets in Free Space

Question 13

Stimulus Response Curve (Slide 14/25…Listen to Lecture here)

1. What does it provide?

Answer 13

1. An Accurate, Quantitative Description of the Accommodative Response over a Full Range of Accommodative Stimuli.

Question 14

Stimulus Response Curve

1. The Initial Nonlinear Region extends from what stimulus range?
   a. This response is Primarily Influenced by what 2 things?

b. The Accommodative Response to Infinity (or 0 diopter accommodative Stimulus) is NOT ZERO. What is it? What does this tell us?

Answer 14

1. Of 0 to 1.50 D
   a. by Depth-of-Focus and Tonic Accommodation

b. It’s more like 0.25 to 0.33 D; Means that there is a “Lead of Accommodation” when viewing at Distance

Question 15

Stimulus Response Curve

1. The LINEAR MANIFEST ZONE is the Response Midregion over which a change in the Accommodative Stimulus produces what 2 things?
   a. The Slope of the Linear Response Ranges from what?
   b. Conceptually, the Accommodative System changes focus by what?

Answer 15

1. a RELATIVELY LARGE and PROPORTIONAL Change in the Accommodative Response
   a. From 0.7 to about 1.0
   b. by the MINIMUM AMT to place the Object just w/in the Eye’s Depth of Field/Focus and thus obtains a SUBJECTIVELY CLEAR and HIGH-CONTRAST RETINAL IMAGE

Question 16

Stimulus Response Curve

1. Nonlinear Transitional Zone: what is it?
   a. In this zone, progressively greater increases in what are Evident?

Answer 16

1. Region where further increases in Accommodative Stimulus Level (just beyond the upper linear manifest zone) produce progressively smaller changes in Accommodative Response (“SOFT SATURATION”)
   a. In Accommodative Error are Evident

Question 17

Stimulus Response Curve

1. What is the NONLINEAR LATENT ZONE?
   a. This region extends about how far beyond what Zone?
   b. Its initial portion defines what?

Answer 17

1. Region where further increases in the accommodative stimulus level fail to produce any additional change in accommodative response (“HARD SATURATION)
   a. Extends about 2.00D beyond the Nonlinear Transitional Zone
   b. the Amplitude of Accommodation

Question 18

Hyperfocal Refraction

1. Toward the end of refractive testing, PLUS LENSES are added then gradually reduced until no further increase in what is obtained?
2. So the Refractive End Point or Criterion is About one of “Maximum Plus for Maximum Visual Acuity” intended Mainly to ensure that there is no what present?

Answer 18

1. No further Increase in Distance VA is obtained.

2. That there’s no Latent Hyperopia Present

Question 19

Hyperfocal Refraction

1. The Retina is Optically Conjugate to a Point that’s about how far away from the individual?
   a. So, as the additional Plus lenses are reduced, what happens to the Far point?
   b. From this, They Hyperfocal Distance can be defined as what?

Answer 19

1. about 4mm away.
   a. it and its surrounding depth of field are OPTICALLY SHIFTED FARTHER AWAY IN SPACE, until the distal edge of the depth of field is Conjugate either to OPTICAL INFINITY or to a DISTANT TARGET.
   b. As the CLOSEST DISTANCE for which the eye may be Conjugate and still have a satisfactory and clear retinal image of an object at infinity

Question 20

Factors that Affect Accommodation

1. Cues for accommodation provide the requisite directional information regarding the what?
2. If all such directional info is removed, leaving only a change in BLUR PATTERN, the Accommodative system responds how?
3. On 50% of trials, the Initial Direction of the Accommodative response will be what?
   a. This requires a Second response that’s now in what?

Answer 20

1. the Blur Pattern
2. Directionally in a Chance Manner
3. will be incorrect.
   a. in the Appropriate Direction to Obtain Clear Vision

Question 21

Cues to and Influences on Accommodation

1. Optical Cues
   a. CA
   b. Spherical Aberration
   c. Astigmatism
   d. Microfluctuations
   e. Blur Asymmetry due to fixational Eye movements

Answer 21

1. Influences: Nonretinal Image
   a. Vestibular Stimulation
   b. Training/Therapy
   c. Mood
   d. Prediction
   e. Voluntary effort; Cognitive demand; Visual Imagery; Instruction Set

Question 22

Cues to and Influences on Accommodation

1. Nonoptical
   a. Size

b. Proximity
c. Apparent Distance
d. Disparate Retinal Images
e. Monocular Depth Cues

Answer 22

1. Retinal Image
   a. Spatial Frequency
   b. Contrast
   c. Retinal Eccentricity
   d. Retinal-Image Motion
   e. Luminance; Size; Depth of Focus; Disparity-driven Vergence Accommodation

Question 23

Graphs/Trends

1. High Contrast = ?
2. Low Contrast = ?
3. High Spatial Frequency (c/Deg)
4. Low Spatial Frequency?
5. Mid Range Spatial Frequency?

Answer 23

1. High Accommodative Response
2. Low Accommodative Response
3. Low Accommodative Response
4. Same as 3.
5. High Accommodative Response

Question 24

Graphs/Treands

1. Central Retinal Eccentricity to Peripheral Retinal Eccentricity?
2. Low Luminance to High Luminance?

Answer 24

1. High Accommodative Response to Low Accommodative Response (linear decrease)
2. Low Accommodative Response to High Accommodative Response (Linear Increase)

Question 25

Graphs/Trends

1. Low to High Retinal-Image Velocity (deg/sec)?
2. Retinal Eccentricity: Central to Peripheral (in regards to Depth of Focus)

Answer 25

1. High Accommodative response to Low. (Linear Decrease)

2. Low Depth of Focus to High Depth of Focus (Parabolic Increase)