Ocular Motility: Lecture 3: Accommodation and Pupil

Question 1

1. Do very small changes in ocular focus have any effect on retinal image?
   a. What about image Quality?
   b. Why is this important?

Answer 1

1. No. Very little effect.
   a. Image quality will deteriorate progressively as the ERROR OF FOCUS INCREASES

b. Because if there wasn’t any tolerance for Accommodative Error, and precise conjugacy of focus were lacking, a Blurred Perception would result.

Question 2

1. Depth of Focus INVERSELY PROPORTIONAL to what 2 things?
   a. It’s DIRECTLY PROPORTIONAL to what?

b. Depth of Focus is relatively what? (small or large) in a 1 month-old Infant?
c. . What happens over the Next 2 Months?

Answer 2

1. to Ocular Focal Length and Pupil Size
   a. to the Just Detectable Retinal Blur Circle

b. Large (at least +/- 1.00 D)
c. It reduces Rapidly over the next 2 months

Question 3

What happens to the Total Depth of Focus as Pupil Diameter increases (mm)?

Answer 3

It decreases quite a bit!

Question 4

1. What is the Input or stimulus change for accommodation?
2. What is it for Disparity Vergence?
3. What do these 2 things sum with?
4. The difference represents what?

Answer 4

1. Target Distance in Diopters later converted to Retinal Defocus/Blur
2. Target Distance in Meter Angles Later Converted to Retinal Disparity
3. They sum with the Negative Feedback Response of the Respective System at that moment
4. the INITIAL SYSTEM ERROR

Question 5

1. DEAD SPACE OPERATOR: This represents what 2 things?

a. This component allows some what?

Answer 5

1. the Depth of Focus for Accommodation and Panum’s Fusional Areas for DISPARITY VERGENCE.
   a. some Small Neurosensory-Based System Error to be tolerated w/o ADVERSE Perceptual Consequences (like Blur and Diplopia Respectively)

Question 6

1. What does THE GAIN represent?
   a. What does it do with the INPUT SIGNAL ERROR?

b. The Gain Term and All the Elements in its direct Forward Pathway Dynamically Represent what?

Answer 6

1. the Experimentally Derived Open Loop Gain of the System
   a. MULTIPLIES the INPUT ERROR SIGNAL
   b. the FAST SUBSYSTEM

Question 7

1. Once the FAST SYSTEM RESPONSE is COMPLETED and only a small steady-state Error exists, what Is ACTIVATED?
   a. What is its Input?
   b. What does its Output go to?
   c. Adaptive, or Slow Subsystem Acts to Sustain what?
   i. What does this presumably prevent?

Answer 7

1. the Adaptive Loop is then Activated
   a. It’s the OUTPUT of the GAIN ELEMENT
   b. Goes back into the SAME GAIN ELEMENT
   c. to Sustain the MOTOR RESPONSE for a PROLONGED PERIOD
   i. This presumably Prevents or Minimizes System Fatigue and Correlated Near-work Symptoms

Question 8

1. This CROSSLINK GAIN TERM multiplies what?
2. For Accommodation, this new value represents what?
   a. Whereas, for convergence, it represents what?

Answer 8

1. Multiplies the OUTPUT of the DIRECT PATHWAY GAIN TERM
2. the Effective AC/A Ratio
   a. it represents the Effective CA/C Ratio (or CAIC ratio…)

Question 9

1. What does TONIC INPUT Presumably reflect?
   a. These tonic terms have NEGLIGIBLE INFLUENCE on what?
   i. And only Modest influence on what?

Answer 9

1. the Midbrain Baseline Neural Innervation
   a. on the Overall Closed-loop Near Response
   i. and only modest influence on the FAR RESPONSE

Question 10

1. GAIN OUTPUT is directed to what?
   a. What does this do?
   b. To form what?

Answer 10

1. to the Summing Junction
   a. It SUMS w/the CROSSLINK OUTPUT, the PROXIMAL OUTPUT, and the TONIC OUTPUT

b. to form the FINAL COMBINED SIGNAL to drive the RESPECTIVE SYSTEM

Question 11

1. The Output of the Summing Junction proceeds to what 2 Centers?
   a. To formulate Formulate what?
   b. It then Advances to INNERVATE the Appropriate peripheral apparatus: which is what?

Answer 11

1. to Cortical and Subcortical Centers related to Accommodation.
   a. the BASIC NEURAL SIGNAL
   b. it’s the CILIARY MUSCLE and LENS COMPLEX for ACCOMMODATION and the Extraocular Muscles for VERGENCE

Question 12

1. Minus Lenses Increase the Demand for what? This is accompanied by an INCREASE in what?
2. Increased Vergence Response will place images on what?
   a. What does this result in unless it’s compensated by a reduction in what?
3. Divergence Response will lead to a DECREASED what?
   a. Due to what?
4. Reduction in CA must be compensated for to prevent what?
   a. This occurs via what?

Answer 12

1. for Blur-Driven Accommodation; in Accommodative Convergence
2. on Non-Corresponding Retinal Points.
   a. Causes Diplopia unless compensated by a Reduction in the Output of Disparity Vergence
3. to a Decreased Convergent Accommodation (CA)
   a. Due to the Convergent Accommodation to Convergence, or the CA/C Ratio
4. the Target from becoming Blurred
   a. Via an INCREASE in Blur-driven Accommodation

Question 13

Positive Relative Accommodation (PRA)

1. Increased Blur-Driven Accommodation Leads to what?
2. Which leads to?
3. Which leads to what?
4. Which sends feedback to what?

Answer 13

1. Increased Accommodative Convergence
2. Decreased Disparity Vergence (Ie. Disparity Divergence)
3. Decreased Convergent Accommodation
4. Feedback to the Increased Blur-driven Accommodation (Causes Increase in Blur-driven Accommodation)

Question 14

Negative-Relative Accommodation (NRA)

1. Decreased- Blur-driven Accommodation leads to what?
2. Which leads to what?
3. Which leads to what?
4. Which causes what?

Answer 14

1. Decreased Accommodative Convergence (Ie…Accommodative Divergence)
2. Increased Disparity Vergence (i.e. Disparity Divergence)
3. Increased Convergent Accommodation
4. Feedback to cause more Decreased Blur-Driven Accommodation

Question 15

Training of Accommodation

1. 1 study: 3 Optometry students w/symptoms to focusing difficulties at near were treated using standard vision training procedures.
   a. They trained themselves at home for 20 minutes each day for 4.5 to 7 WEEKS, and objective measurements of dynamic accommodation were made each week.
   b. During treatment, what did they Exhibit?
   c. What increased?
   d. What do these results prove?

Answer 15

1. b. SIGNIFICANT Reductions in time constant and latency of Accommodation that correlated well w/reduction of symptoms
   c. Flipper rates increased and symptoms were either markedly diminished or no longer present at the termination of therapy!!!
   d. That vision training resulted in Objective improvement of Accommodative Function

Question 16

Duane’s Classification of Accommodation Anomalies

1. Accommodative Insufficiency: Accommodation is Persistently lower than expected for what?
   a. What is the Hallmark of Accommodative insufficiency?
   b. What is its MAIN SYMPTOM?
   c. Ill-sustained Accommodation –> ? –> ?

Answer 16

1. for the patient’s age.
   a. Reduction of Accommodative Amplitude by 2.00 D or more.
   b. General Asthenopia Related to Near Work
   c. –> Paralysis (or Paresis) of Accommodation –> Unequal Accommodation

Question 17

1. Accommodative Excess: What is it?
2. Accommodative Infacility:
   a. What are the Accommodative Dynamics?
   b. What happens to them in Accommodative Infacility?
   c. Change in Accommodation only occurs with what?

Answer 17

1. Accommodation that’s Persistently Higher than Expected for the Patient’s Age
2. a. Latency, Time Constant, and Peak Velocity
   b. They’re Slowed
   c. with Effort and Difficulty, in the presence of Normal Response Magnitude.

Question 18

Effects of Drugs on Accommodation

1. The Parasympathetic Branch provides what?
   a. It has what kind of Effect?
   b. This results in an INCREASE in what?
   c. And a DECREASE in what?
2. It’s a rapidly acting system. It participates in ALL GeNERAL Dynamic Changes in Accommodation that typically have a TOTAL RESPONSE time of what?
   a. Stimulation of this system also affects what?
3. There’s an INVERSE Relation b/w what 2 things?
   a. This produces what?
   b. Parasympathetic Branch releases what at the Receptor site?

Answer 18

1. the PRIMARY NEURAL CONTROL over the entire range of Accommodation
   a. an EXCITATORY EFFECT (an INCREASE in its ACTIVATION LEVEL)
   b. in ACCOMMODATION
   c. in its activation results in a decrease in Accommodation
2. of 1 SECOND or SO.
   a. Affects Pupil Diameter
3. LEVEL of Excitation and Pupil size
   a. Pupillary Miosis w/HIGH Amts of Accommodation
   b. ACH at the Ciliary Muscle Receptor Site

Question 19

Sympathetic Branch

1. What does it play in control of Accommodation?
2. It has what kind of effect?
   a. AN INCREASE in its ACTIVATION LEVEL RESULTS in what?
3. Initiation of the Sympathetic Activation takes about how long?
4. Max Stimulation requires how much time?
5. The Sympathetic Level of Activity and its effect on Refractive State are DIRECTLY RELATED to what?
6. Sympathetic Branch Releases what?
   a. It is believed to be too what?

Answer 19

1. a Secondary role in the control of accommodation.
2. An INHIBITORY EFFECT
   a. in a REDUCTION in ACCOMMODATION
3. Takes about 5-10 seconds
4. 10-40 Seconds
5. to Parasympathetic Level of Activity
6. Noradrenaline at the CILIARY MUSCLE RECEPTOR SITE
   a. to be too slow-acting to affect Accommodative Dynamics

Question 20

Sympathetic Receptors in the Ciliary Muscle

1. ALPHA RECEPTORS: Activation produces:
   a. What in regards to Amplitude of Accommodation?
   b. Accommodative Stimulus-Response Function?
   c. Tonic Accommodation?
2. how are these explained?

Answer 20

1. a. REDUCTION
   b. Midrange Slope of the Accommodative Stimulus-Response Function
   c. No EFFECT on Tonic Accommodation
2. By the fact that the Sympathetic effect is MAXIMAL where the Parasympathetic stimulation is GREATEST (at the NEAR-POINT of ACCOMMODATION), and thus is Minimal at the FAR-Point and Nearby Tonic Level.

Question 21

Sympathetic Receptors in the Ciliary Muscle

1. Beta-1 Receptors: Comprise what % of the TOTAL Beta receptor population in the Iris/Ciliary Body Complex?
2. Beta-2 Receptors: What do they provide to the Ciliary Muscle?
   a. % that are Beta 2 receptors?
   b. These can have an INFLUENCE on what?

Answer 21

1. 10%
2. the Primary Sympathetic Stimulation to the Ciliary Muscle
   a. about 90%
   b. on Tonic Accommodation

Question 22

Parasympathetic Receptors in the Ciliary Muscle

1. What are the main ones Primarily involved in Basic Ciliary Muscle Contraction?

Answer 22

1. M3 Receptors

Question 23

1. Parasympathomimetics: What do they mimic?
   a. What have they been used in the treatment of?

b. How can they work?

c. What do Indirect-Acting ACHE Inhibitors do?
i. What does this result in?
ii. They also produce what?
iii. Examples?

Answer 23

1. Parasympathetic System
   a. Accommodative Esotropia

b. Indirect or Direct Acting
c. Prevent breakdown of ACH by binding the enzyme.
i. INCREASED AMT of ACH at the NERVE TERMINALS and thus GREATER ACTIVITY!
ii. Pupillary Miosis
iii. PILOCARPINE, carbachol, and methacholine

Question 24

1. Parasympatholytics: What are they?
   a. What do they prevent?
   b. What do they produce?
   c. Include what 4 drugs?

Answer 24

1. Antimuscarinic Drugs: Inhibit Parasympathetic System by binding to the Muscarinic ACH receptors
   a. Prevent ACH from acting
   b. Mydriasis and Loss of Accommodation
   c. ATROPINE, CYCLOPENTOLATE, HOMATROPINE, and TROPICAMIDE (STop ACH)

Question 25

1. Sympathomimetics: What kind of drug are they?
   a. How do they work?
   b. What do they produce?
   c. Drugs: Include what 3?

Answer 25

1. Alpha-Receptor Agonist Drugs
   a. Mimic Action of Sympathetic System by Imitating (direct acting) or Potentiating (Indirect Acting) the Action of Noradrenaline (PRIMARILY on the DILATOR MUSCLE of the IRIS)
   b. Pupillary Mydriasis
   c. Phynylephrine (NEo-Synephrine), Hydroxyamphetamine (Paredrine), and COCAINE

Question 26

Sympatholytics

1. What do they act on?
2. Primary drug in this category?
   a. What does it bind to?
3. What other drug is there?
   a. What does it do?

Answer 26

1. Beta-receptor ANTAGONIST. Blocks the Action of the Sympathetic System
2. TIMOLOL (nonspecific Beta Blocker)
   a. Binds to the receptors in general and Prevents their stimulation
3. BETAXOLOL: Specific Beta-1 Blocker
   a. INCREASES ACCOMMODATIVE RESPONSE

Question 27

1. Pupillary Latency Ranges from what times?
   a. Increases as what Decreases?
   b. It’s also found to exhibit a statistically significant but Normal age-related increase of about how much?

c. Latency of how much at 20 years to how much at 70 yrs of age?
2. Mean Pupillary Diameter was shown to decrease Approximately how much?

Answer 27

1. 180 to 500 msec.
   a. Increasing as LIGHT INTENSITY was decreased.
   b. of about 1 msec/year
   c. 235 msec at 20 yrs to 280 at 70 yrs
2. by about 0.3 mm/decade