Purchase this article with an account.
M.M. Day, D. Seidel, N.C. Strang, L.S. Gray, E.A. H. Mallen; The Influence of Target Vergence Upon the Magnitude of the Accommodative Microfluctuations in Emmetropia, Early–Onset Myopia and Late–Onset Myopia . Invest. Ophthalmol. Vis. Sci. 2005;46(13):2326.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: The size of the microfluctuations have previously been reported to increase with increased target vergence. This has been attributed to plant noise and increased mechanical strain on the crystalline lens during near viewing. Microfluctuations are also greater in conditions where blur sensitivity is reduced and the depth of focus is enlarged. Increased microfluctuations have previously been reported in LOMs, however it is uncertain whether this is related to either the larger accommodation lag and reduced blur sensitivity or plant noise. In this study we measure vergence induced changes in accommodation microfluctuations in a group of emmetropes (EMMs), early–onset myopes (EOMs) and LOMs. Methods: 12 EMMs, 12 EOMs and 12 LOMs viewed a high contrast (80%) Maltese cross target (angular subtense 15 deg) monocularly in a +5 D Badal optical system. Myopic subjects were fully corrected using daily disposable soft contact lenses. Accommodation responses were measured continuously at a sampling rate of 52 Hz using a modified open view Shin–Nippon SRW–5000 autorefractor. The target was presented randomly at vergence levels of 0, 1, 2, 3 and 4 D. Two minutes of data were recorded for each dioptric level. Results: LOMs showed significantly (p<0.05) larger microfluctuations when viewing distant and intermediate targets (0 – 3D) compared to EOMs and EMMs. The rms value of the microfluctuations systematically increased with increasing target vergence for the EMMs and EOMs. In contrast, the LOMs showed microfluctuations of constant magnitude for target vergences < 4 D. When viewing a near target at 4D the microfluctuations increased for all subjects and no significant differences in rms were found between the refractive groups. Conclusions: Systematic increases in accommodative microfluctuations with increasing target vergence were found in EMMs and EOMs but not in LOMs. This suggests that the magnitude of the fluctuations in LOMs may be determined by an enlarged depth of focus for distant and intermediate target vergences, whereas this may be overridden by increasing mechanical stress on the crystalline during close viewing.
This PDF is available to Subscribers Only