title: Visual acuity and the accuracy of the accommodative response.
abstract: Previous investigators have observed that some subjects show large amounts of accommodative lag. We hypothesized that less accurate accommodation might be associated with poorer visual acuity and/or smaller pupil sizes. Sixty subjects (30 emmetropes and 30 myopes) aged 20-30 years, participated. All had best-corrected visual acuity of 6/6 or better [mean = -0.10 +/- 0.07 logarithm of the minimum angle of resolution (logMAR)]. Subjects monocularly viewed reduced Bailey-Lovie charts through a +6.50 D Badal lens on a Canon R1 auto-refractor. Visual acuity, accommodative response and pupil diameter were measured for 0, 2 and 4 D accommodative stimuli. For accommodation measurements (N= 10) subjects were instructed to fixate the smallest letters that they could read. The mean accommodative response was +0.22 +/- 0.28, +1.83 +/- 0.23 and +3.71 +/- 0.27 D for the 0, 2 and 4 D stimuli, respectively. The mean visual acuity was -0.06 +/- 0.10, -0.11 +/- 0.07 and -0.11 +/- 0.07 logMAR for the 0, 2 and 4 D stimuli, respectively. Visual acuity for the 0 D stimulus was significantly poorer than for other conditions (p < 0.001) and associated with increased accommodative lead (p < 0.01). There was also an association between visual acuity and accommodative response (or lag) for the 4 D stimulus (p=0.002). The emmetropes showed significantly better visual acuity than the myopes (p= 0.004). No significant difference was observed in the accommodative response between emmetropes and myopes. Pupil diameter was not associated with the accuracy of the accommodative response (p > 0.17). Increased accommodative lead (0 D stimulus) and accommodative lag (4 D stimulus) are associated with decreased visual acuity. Smaller pupil diameters are not associated with increased accommodative lag.
authors.affiliation: College of Optometry, The Ohio State University, Columbus 43210, USA. subbaram.1@osu.edu
authors.forename: Manoj V
authors.initials: MV
authors.lastname: Subbaram
authors.forename: Mark A
authors.initials: MA
authors.lastname: Bullimore
mesh_terms: D000065:Accommodation, Ocular; D000328:Adult; D006801:Humans; D009216:Myopia / Q000473:pathology / Q000503:physiopathology; D011680:Pupil; D012030:Refractive Errors / Q000473:pathology / Q000503:physiopathology*; D014787:Vision Tests; D014792:Visual Acuity