Accommodation Responds to Optical Vergence and Not Defocus Blur Alone.
To determine whether changes in wavefront spherical curvature (optical vergence) are a directional cue for accommodation.



Nine subjects participated in this experiment. The accommodation response to a monochromatic target was measured continuously with a custom-made adaptive optics system while astigmatism and higher-order aberrations were corrected in real time. There were two experimental open-loop conditions: vergence-driven condition, where the deformable mirror provided sinusoidal changes in defocus at the retina between -1 and +1 diopters (D) at 0.2 Hz; and blur-driven condition, in which the level of defocus at the retina was always 0 D, but a sinusoidal defocus blur between -1 and +1 D at 0.2 Hz was simulated in the target. Right before the beginning of each trial, the target was moved to an accommodative demand of 2 D.



Eight out of nine subjects showed sinusoidal responses for the vergence-driven condition but not for the blur-driven condition. Their average (±SD) gain for the vergence-driven condition was 0.50 (±0.28). For the blur-driven condition, average gain was much smaller at 0.07 (±0.03). The ninth subject showed little to no response for both conditions, with average gain <0.08. Vergence-driven condition gain was significantly different from blur-driven condition gain (P = 0.004).



Accommodation responds to optical vergence, even without feedback, and not to changes in defocus blur alone. These results suggest the presence of a retinal mechanism that provides a directional cue for accommodation from optical vergence.
Department of Optics and Optometry and Vision Sciences, University of Valencia, Burjassot, Valencia, Spain 2Interuniversity Laboratory for Research in Vision and Optometry, Mixed group UVEG-UMU, Valencia-Murcia, Spain.
Antonio J
AJ
Del Águila-Carrasco
Department of Optics and Optometry and Vision Sciences, University of Valencia, Burjassot, Valencia, Spain 2Interuniversity Laboratory for Research in Vision and Optometry, Mixed group UVEG-UMU, Valencia-Murcia, Spain.
Iván
I
Marín-Franch
Department of Optics and Optometry and Vision Sciences, University of Valencia, Burjassot, Valencia, Spain 2Interuniversity Laboratory for Research in Vision and Optometry, Mixed group UVEG-UMU, Valencia-Murcia, Spain.
Paula
P
Bernal-Molina
Department of Optics and Optometry and Vision Sciences, University of Valencia, Burjassot, Valencia, Spain 2Interuniversity Laboratory for Research in Vision and Optometry, Mixed group UVEG-UMU, Valencia-Murcia, Spain.
José J
JJ
Esteve-Taboada
State College of Optometry, State University of New York, New York, United States.
Philip B
PB
Kruger
Department of Optics and Optometry and Vision Sciences, University of Valencia, Burjassot, Valencia, Spain 2Interuniversity Laboratory for Research in Vision and Optometry, Mixed group UVEG-UMU, Valencia-Murcia, Spain.
Robert
R
Montés-Micó
Interuniversity Laboratory for Research in Vision and Optometry, Mixed group UVEG-UMU, Valencia-Murcia, Spain 4Instituto Universitario de Investigación en Envejecimiento (IUIE), University of Murcia, Murcia, Spain.
Norberto
N
López-Gil
D000065:Accommodation, Ocular / Q000502:physiology*; D000328:Adult; D001251:Astigmatism / Q000175:diagnosis / Q000503:physiopathology*; D003290:Convergence, Ocular / Q000502:physiology*; D003463:Cues; D005260:Female; D006801:Humans; D008297:Male; D010775:Photic Stimulation / Q000379:methods; D012029:Refraction, Ocular; D014792:Visual Acuity