The Effect of Dioptric Blur on Sight-Reading Music

Previous studies showed that dioptric blur degrades visual acuity and the critical print size for text reading. This study investigated whether dioptric blur affects sight-reading music, hypothesising that its effect on pitch and rhythm accuracy might differ.

Eighteen young piano-players with normal vision played a Yamaha keyboard using the right hand while sight-reading short music pieces. Testing was conducted monocularly with dioptric blur (no lens, +1.00D, +2.00D, +3.00D and +4.00D) using convex trial lenses placed on the dilated right eye and with a 3 mm artificial pupil. Stimuli were 12-measure pieces (4 measures per line) with similar spatial complexity, printed in 11 note sizes ranging from -0.40 to 0.80 logMAR (defined as notehead height). A function of accuracy versus note size was obtained at each blur level. The threshold note size (TNS), defined as the note size corresponding to 80% maximum accuracy, was derived for each blur level for pitch and rhythm.

Visual acuity, pitch perception and rhythm perception were all susceptible to dioptric blur; however, this degrading effect can be compensated for by magnification. TNS was higher for pitch than rhythm across blur levels and remained unaffected until surpassing the critical blur level (CBL). Beyond the CBL (+1.49 D for pitch and +1.00 D for rhythm), TNS increased with blur, rising faster for pitch (0.19 logMAR per blur level) than rhythm (0.14 logMAR per blur level). The variation of TNS can be predicted partially by the change of visual acuity with increasing dioptric blur (r = 0.68 for pitch, 0.60 for rhythm).

These findings highlight the importance of visual perception in music reading, with implications for music education and performance, particularly for individuals with visual impairments or in situations where visual clarity is compromised.