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Related Experiment Video

Updated: Jun 21, 2026

Comparison of Agreement and Accuracy using Binocular Wavefront Optometer with Autorefractor and Phoropter
05:14

Comparison of Agreement and Accuracy using Binocular Wavefront Optometer with Autorefractor and Phoropter

Published on: September 16, 2025

Blur limits for defocus, astigmatism and trefoil.

David A Atchison1, Huanqing Guo, W N Charman

  • 1School of Optometry and Institute of Health and Biomedical Innovation, Queensland University of Technology, 60 Musk Avenue, Kelvin Grove, Qld 4059, Australia. d.atchison@qut.edu.au

Vision Research
|July 28, 2009
PubMed
Summary

This study determined how much blur from defocus, astigmatism, and trefoil people can tolerate. Ocular aberrations influenced blur perception, with trefoil being less tolerable than defocus or astigmatism.

Related Experiment Videos

Last Updated: Jun 21, 2026

Comparison of Agreement and Accuracy using Binocular Wavefront Optometer with Autorefractor and Phoropter
05:14

Comparison of Agreement and Accuracy using Binocular Wavefront Optometer with Autorefractor and Phoropter

Published on: September 16, 2025

Area of Science:

  • Optometry and Vision Science
  • Ophthalmology
  • Optical Engineering

Background:

  • Visual blur affects image quality and patient satisfaction.
  • Understanding tolerance limits for different blur types is crucial for vision correction.
  • Ocular aberrations can influence the perception of induced blur.

Purpose of the Study:

  • To quantify the noticeable, troublesome, and objectionable blur limits for defocus, astigmatism, and trefoil.
  • To investigate the role of intrinsic ocular aberrations on blur tolerance.
  • To compare tolerance limits across different types of optical aberrations.

Main Methods:

  • Subjects viewed black letter targets of varying acuity (0.1-0.6 logMAR) under cycloplegia with 5mm pupils.
  • Blur was induced using a deformable, adaptive-optics mirror in open-loop conditions.
  • Tolerance limits were assessed for defocus, crossed-cylinder astigmatism, and trefoil, with and without correction of intrinsic ocular aberrations.

Main Results:

  • Mean defocus blur limits ranged from 0.18 D (noticeable) to 1.01 D (objectionable).
  • Astigmatic blur tolerance was approximately 90% of defocus tolerance, with significant meridional effects.
  • Correcting intrinsic aberrations had minor effects, but trefoil blur showed a higher objectionable-to-noticeable ratio (3.5) compared to defocus (2.5) and astigmatism (2.2).

Conclusions:

  • Perception of blur is influenced by its type and the eye's intrinsic aberrations.
  • Trefoil aberration is perceived as more objectionable relative to its noticeable threshold than defocus or astigmatism.
  • These findings have implications for visual performance standards and the design of ophthalmic optics.