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Praveen Kumar Bandela, Shrikant R Bharadwaj, Arthur Ho, Eric B Papas; Real-time manipulation of blur-driven accommodation using an electrically-tunable lens: a feasibility study. Invest. Ophthalmol. Vis. Sci. 2021;62(8):2060.
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The ability to manipulate accommodative response real-time during an experiment will be useful to study the properties of feedback-driven accommodation and its interaction with vergence and pupils. Usage of pinholes or low spatial frequency targets may render the blur-feedback open-loop, but they do not allow real-time manipulation of blur input. This feasibility study describes a technique for real-time manipulation of blur-driven accommodation using an electrically- tunable lens coupled with a dynamic, infrared (IR) photorefractor.
Real-time manipulation of an accommodative response was achieved by measuring the response of one eye dynamically at 50 fps using the Plusoptix PowerRef 3 photorefractor (PR) and synchronously feeding a low-pass filtered version of its output to a calibrated electrically-tunable lens (ETL, Optotune, EL-16-40-TC-VIS) placed along the visual axis of the participant. In Experiment 1, the PR output of the target fixing eye was added to the ETL placed in front of the fellow eye occluded using an IR filter. In Experiment 2, the ETL dynamically subtracted the PR output of the consensual accommodative response from the IR filter occluded eye from the direct response of the eye viewing an accommodative target. These experiments were performed on two young adults (26 and 34 yrs) viewing a broadband spatial frequency target located at 100 and 40 cm from the fixating eye.
Low-pass filtering of the PR output by 50Hz resulted in the ETL smoothly altering its dynamic power, with a fixed delay of only 20 ms. In Experiment 1, the mean refraction of target fixing and the fellow eye was -0.69 ± 0.04 D and 1.00 ± 0.10 D in both subjects before initiation of manipulation. The fellow eye PR output decreased to 0.36 ± 0.19 D after initiation of manipulation, as predicted from the addition of optical power by the ETL. In Experiment 2, the mean consensual accommodative response was 1.03 ± 0.14 D before initiation of manipulation. The direct PR output decreased to 0.41 ± 0.06 D after manipulation, as may be predicted from the subtraction of optical power by the ETL.
These results indicate that the dynamic coupling between the PR and ETL allows real-time manipulation of blur-driven accommodation with negligible temporal delays. This set-up has the potential to be used in studies of the near-triad seeking dynamic manipulation of blur input.
This is a 2021 ARVO Annual Meeting abstract.
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