Open Loop Accommodation and Vergence

What causes accommodation to become open-loop?

Removal of blur feedback

What is tonic accommodation?

Myopic intermediate resting focus in absence of blur feedback

Typical TA value?

~1–1.7D (varies by method)

Best pupil size to ensure open-loop?

0.5mm

Does final TA depend on method?

No

Typical tonic vergence value?

0.6–0.9 MA

Is TV usually more distal or proximal than TA?

More distal

PIA slope?

~0.45 D per D

For which distances is PIA strongest?

≤3m

PIV slope?

~0.37 MA per MA

How much of vergence demand can proximal cues provide?

Up to ~70%

Does mental effort increase or decrease accommodation?

Either — depends on baseline

Why do subjective techniques give higher TA?

Active judgement stimulates accommodation

Can accommodation be voluntarily trained?

Yes

Do voluntary vergence changes act directly?

Likely indirect via AC/A

Do tonic accommodation and tonic vergence necessarily interact?

No clear consensus

When do cross-links primarily operate?

During phasic responses