Abstract
Purpose :
While theoretical models envision the possibility that accommodative microfluctuations aid in deciphering the sign of defocus, empirical evidence for the same remains ambiguous. This study investigated this issue by determining the initial direction and dynamics of blur-driven accommodation through real-time manipulation of these microfluctuations.
Methods :
A PlusOptix PowerRef3™ photorefractor recorded the ocular refraction of 10 young adults (23.8±3.8yrs) at 50Hz while they fixated on a Maltese cross stimulus that stepped between 1D and 3D demands with randomized onset time. The difference between two consecutive refraction data points was considered as an accommodative microfluctuation and its sign-reversed values were synchronously fed into an Optotune™ electrically tunable lens (ETL) to neutralise the microfluctuations in real-time. The initial direction, magnitude, latency and peak velocity of the step response was determined while manipulating the ETL accommodative microfluctuation feedback relative to baseline viewing.
Results :
ETL manipulation of accommodative microfluctuations did not alter the proportion of step responses with correct initial direction (median(IQR) accommodation: 73.2 (56.1 – 81.8) %; disaccommodation: 75.0 (47.8 – 80.0)% or their response magnitudes (accommodation: 1.97±0.40D; disaccommodation: 1.95±0.40D), relative to baseline (correct response proportion 83.3 (73.0 – 92.3) %; response magnitude: 1.83±0.37D) (p≥0.09, for all). Response latency increased (accommodation: 275.8±38.1ms; disaccommodation: 322.3±82.6ms) and peak velocity decreased (accommodation: 5.37±1.6D/s; disaccommodation: 5.94±1.9D/s) with ETL manipulation, relative to baseline (latency: 276.8±59ms; peak velocity: 6.96±2.0D/s), but none were statistically significant (p≥0.05, for all).
Conclusions :
The accommodative system responds in the desired direction despite neutralization of accommodative microfluctuations. While the response dynamics may have slowed-down in the absence of these microfluctuations, reflecting a conservative strategy, the change appears marginal and inconsequential for accommodation control. Overall, the results do not support the idea that accommodative microfluctuations aid in deciphering the direction of accommodation. Their role may be limited to maintaining the steady-state response.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.