Optimal stimulus demands for objective measurement of monocular accommodative amplitude

Accommodative amplitude is commonly measured in the clinical setting using subjective measures that overestimate true accommodative ability. This study identifies optimal near demands for objective measurement of amplitude in children and young adults with the goal of developing ways to accurately and efficiently measure amplitude in a clinical setting.

This study aims to determine the optimal physical stimulus demands to objectively measure the accommodative ability of the eye that will elicit maximum accommodative amplitude for the majority of children and young adults.

100 participants aged 5 to 24 years underwent monocular measures of accommodation with an open-field autorefractor at 13 stimulus positions (40cm to 3.3cm = 2.5 to 30D) while viewing a 0.9mm "E." The greatest accommodative response was identified as the accommodative amplitude. Quadratic plateau models of accommodative response by demand for four age bins (5 to 9, 10 to 14, 15 to 19, and 20 to 24 years) identified demands or combinations of demands most likely to elicit maximum amplitude. Comparison of accommodative response found by different combinations of demands was made to accommodative amplitude identified by the 13 stimulus position protocol. The locations identified were then applied to two previously published cohorts (n = 143) tested with the same methodology to validate the use of fewer stimulus demands.

Stimulus positions 10.5 and 12D combined identified the highest percentage of participants within 1D of true accommodative amplitude; 80% for 5 to 9, 96% for 10 to 14, 96% for 15 to 19, and 92% for 20 to 24. The 5 to 9 year bin had the largest number of participants who were not identified (5), followed by the 20 to 24 bin (2), and the 10 to 14 and 15 to 19 bins (1 each). The average difference from true amplitude for participants not correctly identified was -1.52D (SD = 0.3), -1.24D (SD = 0.1), -1.84D, and -1.23D, respectively. Comparison with two previous cohorts showed good success in the identification of true amplitude within 1D for each age bin using the 10.5 and 12D stimulus positions: 84% for 5 to 9, 88% for 10 to 14, 86% for 15 to 20, and 84% for 21 to 24.

Utilizing accommodative response measures at 10.5 and 12D stimulus demands combined identifies true accommodative amplitude in the majority of individuals from 5 to 24 years old.