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Astigmatism impact on visual performance: meridional and adaptational effects
Maria Vinas1, Pablo de Gracia, Carlos Dorronsoro
1*BOptom, MSc †BOptom, MSc, FAAO ‡PhD Instituto de Óptica, Consejo Superior de Investigaciones Científicas, Madrid, Spain (MV, PdG, CD, LS, SM); and Essilor International, Research and Development, Vision Science Department, Saint-Maur, France (GM, MH).
Summary
Visual performance is axis-dependent for astigmatism, with natural astigmatism orientation showing reduced visual acuity (VA) impact. Astigmatism correction does not alter this bias, even with added coma.
Area of Science:
- Ophthalmology
- Visual Science
- Optometry
Background:
- Subjects adapt to astigmatism, recalibrating perceptually upon correction.
- The impact of prior astigmatism adaptation on visual performance and axis dependency is not fully understood.
- Potential changes in visual performance after astigmatism correction and interactions with other aberrations require investigation.
Purpose of the Study:
- To investigate the axis-dependency of astigmatism's effect on visual acuity (VA).
- To determine if prior adaptation to astigmatism influences VA and its recalibration after correction.
- To explore the combined effects of astigmatism and coma on VA.
Main Methods:
- Visual acuity was measured in astigmats and non-astigmats under induced astigmatism and coma.
- Astigmatism (1.00 D) was induced at various orientations (natural axis, perpendicular, 45 degrees).
- Longitudinal measurements up to 6 months were conducted, with astigmats receiving correction.
Main Results:
- Astigmatism induction at 90 degrees caused less VA reduction in non-astigmats compared to 0 or 45 degrees.
- Astigmats showed the least VA decrease when astigmatism was induced along their natural axis.
- Six months of correction did not eliminate the bias towards the natural axis; interactions with coma also varied by orientation.
Conclusions:
- Visual acuity is significantly influenced by the orientation of astigmatism, even in individuals without prior astigmatism.
- Previous exposure to astigmatism creates a bias towards the natural axis, affecting visual performance.
- Astigmatism correction does not override this natural axis bias, despite perceptual recalibration.
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