Purchase this article with an account.
L. Thondikulam Easwaran, W.R. Bobier; Dynamic Measures of Accommodation Through Plus Lens Addition . Invest. Ophthalmol. Vis. Sci. 2005;46(13):5593.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: When plus lens additions are worn in, pre–presbyopic subjects show over–focusing during closed loop viewing of a near target. This finding is sustained when reading is prolonged up to 30 min. This investigation looks at both open and closed loop accommodative responses during prolonged reading through near addition lenses. Methods: Sixteen adults (Mean age = 22.75 ± 1.94 yrs) participated in the study. Their mean refractive error was –0.95 ± 1.1 D (Range = 0 to –3D). During the study, each subject read a text material positioned at 33cm over a 30–minute time period in 3 different trials (habitual correction, 1D and 2D adds). Dynamic measures of accommodation (PowerRefractor, Multichannel Co) were taken for 60–second intervals at reading onset and then at 10, 20 and 30 minutes. Tonic accommodation was measured at the beginning and end of each 30 minute reading trial using a 0.2 cpd Difference of Gaussian target set at 3m. For each subject and for each trial, the accommodative responses were averaged over the 60–second period across the 4 time intervals. Results: Data from 6 subjects could not be used due to their pupils constricting below tolerance levels of the PowerRefractor. Only measures having pupil sizes of 4mm and above were used. Reflex accommodation reduced proportionately with lens addition. However, there was a statistically significant (p <0.05) incremental over–focussing of 0.07 ± 0.08 and 0.61 ± 0.06 with the +1 and +2D lens additions. Accommodation increased slightly over time. Slopes of the functions plotting this increase over time for the 3 trials (no lens, +1D, +2D) declined as the add power increased (y = –0.01x –2.49, R2 = 0.92, p = 0.04; y = –0.01x –2.98, R2 = 0.91, p = 0.05; y = –0.002x –3.58, R2 = 0.23, p = 0.51). No significant change over time was found with 2D add. Tonic accommodation significantly increased (0.83D) following prolonged reading without near adds. This was attenuated (0.09D for +1D and 0.07D for +2D) when reading adds were used. Conclusions: Near adds reduce accommodative lag but lead to over focussing. Changes in tonic accommodation reduce the accommodative lag when reading is prolonged but tonic changes appear to increase over focusing when viewing through 1D adds. The degree of tonic accommodative change appears dependent upon the magnitude of the output of reflex accommodation.
This PDF is available to Subscribers Only