Noticeable, troublesome and objectionable limits of blur

AbstractWe investigated limits at which induced blur becomes noticeable, troublesome and objectionable. We used 15 cyclopleged subjects, a Badal optometer with lines of three high contrast letters as targets, 3–6mm artificial pupils, and 0.0–0.7logMAR letter sizes. For 0.0logMAR size, mean “noticeable” blur limits were ±0.33D, ±0.30D and ±0.28D at 3mm, 4mm and 6mm, respectively, but increased by about 70% for 0.7logMAR letters. All limits reduced by about 17% as pupil size increased from 3mm to 6mm. Letter size had a significant influence on all blur limits (1.6–2.1 times), but blur direction had no significant effect. Magnitudes of “troublesome” and ‘objectionable” limits were 1.6–1.8 times and 2.1–2.5 times relative to “noticeable” limits, respectively. Our results suggest criteria for troublesome and objectionable blur are relatively unaffected by letter size