PURPOSE: The Study of Progression of Adult Nearsightedness (SPAN) is a five-year observational study to determine the risk factors associated with adult myopia progression. Here we report the relation between accommodative lag and AC/A ratio at baseline and five-year progression of myopia.
METHODS: Subjects 25 to 35 years of age, with at least-0.50 D spherical equivalent of myopia, were recruited from the faculty and staff at the Ohio State University. Annual testing included visual acuity, auto-keratometry, phoria, cycloplegic auto-refraction, videophakometry, ultrasound, and partial coherence interferometry (IOLMaster). Accommodative lag and response AC/A ratio were measured using a modification of the Canon R-1 auto-refractor. Accommodative response (5 readings) to Badal-system-stimuli of 0, 2, and 4 D was measured using the auto-refractor while subjects wore their habitual correction. The left eye was occluded with an infrared filter, convergence monitored by video capture of Purkinje images I and IV, and eye position data later extracted using Image Analyst.
RESULTS: Three-hundred ninety-six subjects were enrolled in SPAN. The mean (± SD) age at baseline was 30.7 ± 3.5 years and the mean level of myopia (spherical equivalent) was-3.54 ± 1.77 D. To date, 260 subjects have completed their five-year follow up visit. Of these, 43 (16.5%) had a five-year progression of-0.50 D or more. Progressors were more myopic at baseline than non-progressors (–4.68±1.60 D vs.-3.33±1.71 D; t = 4.79, p < 0.001), but did not differ in terms of age (t = 1.27, p = 0.21). Baseline response AC/A did not differ between the two groups (t = 0.12, p = 0.91), but baseline accommodative lag for a 4-D target was significantly lower in progressors than in non progressors (0.34±0.45 D vs. 0.54±0.42 D; t = 2.80, p = 0.006).
CONCLUSIONS: Contrary to one of the study’s hypotheses, accommodative lag was significantly lower in adults whose myopia progressed than in those who were relatively stable.
ADDITIONAL COMMENTS: Support: NIH Grants R01-EY012952 and R24-EY014792