Dynamic accommodation responses following adaptation to defocus.

Area of Science:

• Ophthalmology
• Vision Science
• Physiological Optics

Background:

• Adaptation to blur influences subjective blur sensitivity in emmetropes and myopes.
• Blur is a key factor in dynamic accommodation responses.
• Previous studies focused on the magnitude of accommodation response after blur adaptation.

Purpose of the Study:

• To investigate the effect of blur adaptation on dynamic accommodation responses to target vergence changes.
• To assess changes in accommodation response to step and sinusoidal vergence changes after myopic defocus adaptation.

Main Methods:

• Eighteen subjects (emmetropes, early-onset myopes, late-onset myopes) adapted to 0.00 D, +1.00 D, or +3.00 D myopic defocus for 30 minutes.
• Accommodation responses were recorded using an autorefractor during 2.00 D step and sinusoidal (0.2 Hz) vergence changes.
• Data analyzed for accommodation latency, response times, magnitude, gain, and phase lag.

Main Results:

• Blur adaptation did not affect accommodation latency but increased response times to step vergence changes.
• Adaptation to +1.00 D and +3.00 D myopic defocus significantly increased response times.
• Adaptation to +3.00 D increased accommodation response magnitude for step changes and increased phase lag for sinusoidal changes, with no effect on gain. These effects were consistent across refractive groups.

Conclusions:

• Adaptation to degraded visual stimuli leads to increased accommodation for approaching targets.
• Increased response times and phase lags in dynamic accommodation were observed after blur adaptation.
• The contrast constancy theory may explain these observed changes in dynamic accommodative behavior.