Minimum amount of astigmatism that should be corrected

Area of Science:

• Ophthalmology
• Optometry
• Visual Science

Background:

• Astigmatism is a common refractive error affecting visual clarity.
• Understanding the impact of low astigmatism on visual performance is crucial for clinical practice.

Purpose of the Study:

• To assess the effect of small astigmatism amounts on visual acuity.
• To determine the minimum astigmatism correction needed for optimal visual performance.

Main Methods:

• Wavefront sensing measured astigmatism and higher-order aberrations (HOAs) in 54 young eyes (0.0-0.5 D).
• Astigmatism was corrected using a cross-cylinder device; visual acuity (high/low contrast) and image quality were measured.
• Image quality metrics were calculated for natural astigmatism, corrected astigmatism, and astigmatism alone (HOAs removed).

Main Results:

• No significant correlation found between astigmatism amount and visual acuity.
• High-contrast visual acuity improved from 0.3 D astigmatism, but with significant inter-subject variability.
• Low-contrast visual acuity showed random changes with astigmatism correction; image quality improved but did not correlate with visual performance.
• HOAs limited image quality deterioration from astigmatism exceeding 0.3 D.

Conclusions:

• Astigmatism below 0.5 D typically does not degrade visual acuity.
• Clinical visual benefits from precise correction of astigmatism under 0.5 D are likely limited.