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Clara Benedi-Garcia, Miriam Velasco-Ocana, Carlos Dorronsoro, Martha Hernandez, Gildas Marin, Susana Marcos; Perceived best focus and visual performance upon induction of astigmatism in presbyopes. Invest. Ophthalmol. Vis. Sci. 2019;60(9):3726. doi: https://doi.org/.
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Earlier work showed shifts in Best Focus (BF) when astigmatism is induced on young emmetropes. Here we studied BF and Visual Acuity (VA) upon astigmatism induction in presbyopes
BF and VA were measured in 28 subjects (under cycloplegia with tropicamide 1%) 3 groups: G1 young emmetropic group (n=10; 29.3±6.5yrs; -0.5±0.5D; C (Cyl ≤0.25D). G2 emmetropic presbyopic group, (n=8; 62.6±6.3yrs; -0.5±1.5D; C ≤0.25D; Add 2.4±0.35D). G3 myopic astigmatic presbyopic (n=10; 56±4yrs; -0.8±1.84D; C -1.52±0.4D; Add 2.28±0.28D). A custom Adaptive Optics system was used, with a Hartmann-Shack wavefront sensor (32x32 microlenses; HASO, ImagineEyes), a Superluminescent Diode (l=827mm), an electromagnetic deformable mirror (52 actuators; MIRAO), a motorized Badal system and a psychophysical channel (CRT monitor). The system allows correction of high order aberrations (AO) and astigmatism induction (0.5, 1, 1.5 & 2D; axis 180, 45 & 22.5deg). Subjective BF was searched with a staircase method and a Badal system. VA was measured with a tumbling E letter (8 orientations) and QUEST. Differences with induced astigmatism of BF and VA, between groups was evaluated with One-way ANOVA
BF shift with induced astigmatism differed significantly across groups, in general correlated with the amount of astigmatism induced. In particular, BF shifted significantly towards negative values in G1 (NoAO, shifts of -0.24/-0.59D; p<0.05) and toward more positive values in G3 (AO, shifts of +0.24/+0.41D; p<0.05). We did not find that the orientation of the induced astigmatism resulted in statistically significant differences in BF shift, although BF shift G3 was statistically different from G1 for induction @180(p=0.0012) & 45deg (p=0.013). All groups experienced a larger decrease in VA (AO) when astigmatism was induced @45deg (0.65/0.8 on average) and it was significantly less degraded in G3 than G1(p=0.00045) and G2(p=0.046)
Current work expands on prior work in young subjects that found that best focus with induced astigmatism is largely influenced by native astigmatism and VA is less degraded by astigmatism induction in astigmats. Similar effects are largely found in presbyopic astigmats, suggesting that long-term adaptation to oriented blur is likely the origin. The moderate effect found in non-astigmatic presbyopes suggests that presbyopic-correction progressive lenses could trigger this adaptation
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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