The progression of corrected myopia.
This study seeks to demonstrate the existence of a feedback loop controlling myopia by comparing the prediction of a feedback model to the actual progression of corrected myopia. In addition to theoretical results, confirming clinical data are presented. The refraction of 13 continuously corrected myopic eyes was collected over a period of time ranging from 4 to 9 years from the time of their first correction. Refractive data was collected in an optometry office from myopic young subjects from the general population in Boston. Subjects were myopes, ages 2 to 22 at the time of first correction selected randomly from a larger population. All individuals were fully corrected with lenses; new lenses were prescribed every time that their myopia increased by 0.25 diopters or more. Subjects wore their spectacle lenses during the followed period. Subjects exhibit a linear time course of myopia progression when corrected with lenses. The observed rate of myopia increase is 0.2 to 1.0 diopters/year, with a mean correlation coefficient r = -0.971, p < 0.005. This report establishes that feedback control theory applies to the clinical phenomenon of progressive myopia. Continuous correction of myopia results in a linear progression that increases myopia. The Laplace transformation of temporal refractive data to the s-domain simplifies the study of myopia and emmetropia. The feedback transfer function predicts that continuous correction of myopia results in a linear progression because continuous correction opens the feedback loop. This prediction is confirmed with all subjects.