Amplitude of Accommodation in Schoolchildren.
Hofstetter's equations are based on studies of Amplitude of Accommodation (AA) with methodological limitations, particularly in the case of children younger than 10 years of age. The aim of this study is to evaluate AA by age, gender, economic status, and time of day as well as accommodative insufficiency prevalence. A cross-sectional study was conducted with 867 schoolchildren aged 6-16 years attending two public schools in the urban area of the South Brazilian city of Pelotas. Subjective refraction was performed using a monocular fogging method to standard end point of maximum plus for best visual acuity (20/25). AA was assessed using the push-up method. The median AA value was 14.3D (P25 13.3-P75 16.7) among children aged 6-16 years, being 15.5D (P25 14.3D-P75 16.7) among children aged 6-10 years, 14.2D (P25 12.5D-P75 15.4) among 11-13-year-olds, 13.3D (P25 12.5D-P75 15.4) among children aged 14-15 and 12.9D (P25 11.1D-P75 14.3) among those aged 16. AA variability was 2.4D in those aged 6-8, 3.4D in children aged 9-12, and 2.9D in those aged 13-16. There was no significant difference in median AA according to gender, time of examination, or economic status; 2.8% of children showed AA of less than 2D lower than Hofstetter's minimum reference value. This study reports AA in a large sample of children and therefore may contribute to current knowledge on AA norms. In order to avoid the impact of outliers, it proposes the use of the median and percentiles to define AA standards by specific age. A set of studies using precise AA measurement and large sample size are needed to determine clinical standards for AA.