The effect of proximity on open-loop accommodation responses measured with pinholes

Open‐loop accommodation levels were measured in 41 healthy, young subjects using a Shin‐Nippon SRW‐5000 autorefractor in the three viewing conditions: a small physical pinhole pupil (SP), an optically projected pinhole in Maxwellian view (MV) and in the dark (DF). The target viewed through the pinholes was a high‐contrast letter presented at 0 D vergence in a +5 D Badal lens system. Overall, results showed that SP open‐loop accommodation levels were significantly higher than MV and DF levels. Subjects could be divided into two distinct subgroups according to their response behaviour: responders to the proximal effect of the small physical pinhole (SP accommodation > MV accommodation) and non‐responders to the proximal effect of the small physical pinhole (SP accommodation ≈ MV accommodation). Correlation analysis demonstrated that open‐loop accommodation for both pinhole conditions was correlated with DF for the responders, while for the non‐responders SP and MV accommodation were correlated, but were not related to DF accommodation. This suggests that under open‐loop conditions some individuals’ accommodation levels are mainly affected by proximal and cognitive factors (responders) while others are guided primarily by the presence of the more distal target (non‐responders). In conclusion, MV reduces the proximal effect of the physical pinhole and produces open‐loop accommodation responses which are more consistent than SP and DF responses.