Abstract
Purpose: :
Our previous retrospective study (Bullimore et al. IOVS 2002;43:2110-2113) reported a five-year rate of myopia progression (at least -0.75 D) of 35.7% in 291 adults aged 20-40 years. 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 five-year progression data.
Methods: :
Subjects between 25 and 35 years of age, with at least -0.50 D spherical equivalent of myopia (cycloplegic auto-refraction), were recruited from the faculty and staff of The Ohio State University. Progression was defined as an increase in myopia of at least -0.75 D spherical equivalent as determined by cycloplegic auto-refraction. Annual testing included visual acuity, non-cycloplegic auto-refraction and auto-keratometry, phoria, accommodative lag, response AC/A ratio, cycloplegic auto-refraction, videophakometry, ultrasound, and partial coherence interferometry (IOLMaster).
Results: :
Three-hundred ninety-six subjects were enrolled in SPAN. The mean (± SD) age at baseline was 30.7 ± 3.5 years, 66% were female, 80% were Caucasian, 11% were African-American, and 8% were Asian/Pacific Islander. The mean level of myopia (spherical equivalent) was -3.54 ± 1.77 D. At the time of submission, 219 subjects had completed their five-year follow up visit. Of these, 10 (4.6%) had confirmed progression of -0.75 D with a mean increase of -1.05 ± 0.25 D and a mean increase in axial length of 0.39 ± 0.24 mm. Using the less conservative criteria of -0.50 D gave a progression rate of 15.5%, a mean progression of -0.76 ± 0.24 D and a mean increase in axial length of 0.27 ± 0.19 mm.
Conclusions: :
The progression of myopia in adults is less common than previously reported. Assuming that a 0.1 mm increase in axial length is associated with 0.25 D of myopia progression, the majority of the myopia progression in this cohort is due to axial length elongation.
Keywords: myopia • clinical (human) or epidemiologic studies: risk factor assessment • refractive error development