[Near triad meter--dynamic measurement of pupillometry with horizontal eye tracker by accommodative stimulation]

A newly developed "Near Triad Meter" is a useful tool to record the dynamics of pupils and horizontal eye movements in both eyes simultaneously with the accommodative stimuli. The responses show insufficiency or strain for accommodation. In this study the objective accommodative power (in diopters, D) is calculated by the measurement of pupillary constriction-ratio(CR) and compared in 4 age groups to find the age-related decrement of diopter values.

A clearly visible accommodative target was moved back-and-forth from 50 cm to [near point + 1 D] (maximum accommodative stimulus; MAS). The speed was regulated constant for diopter movement. Pupillometry and eye tracker were recorded simultaneously with MAS in both eyes together. Three trials were done on 42 volunteers in each age group from 20-year-olds to 50-year-olds and the most reliable recording was used to measure the CR. Eighteen well-responding volunteers were selected to make the standard curves of CR by step-by-step accommodative stimuli. The mean CRs of initial tests with MAS were applied to the age-matched standard curves to calculate the maximum accommodative diopter value.

The mean CRs versus MAS in each age group were 48%/7.2 D in the 20-year group, 46%/6.9 D in the 30-year group, 35%/3.6 D in the 40-year group, and 33%/3.1 D in the 50-year group. The mean values of CR were applied to age-matched standard curves to obtain the maximum accommodative power, which was 8.0 D in the 20-year group, 9.1 D in the 30-year group, 3.4 D in the 40-year group, and 4.1 D in the 50-year group. The 20- and 30-year olds showed equal power statistically, The remarkable age-dependent difference was calculated quantitatively.

The dynamics of near response revealed the individual summation of accommodative power including depth of focus, and accommodative vergence objectively and quantitatively. This method is useful for understanding the quality of accommodative insufficiency and also the quantity of accommodative width, including presbyopia.