To Correct or Not Correct? Actual Evidence, Controversy and the Questions That Remain Open

The equations of ametropia: Predicting myopia

Why myopia develops, why it is reaching epidemic proportions and what is its cause are questions that puzzle many people. There is an answer to these questions and it is a simple one. This paper makes the connection between ametropic and in particular myopic development and theory to come with a summary of what we know about myopia and its governing equation. Key experiments, involving myopia and the effect of lenses in humans and animals have been done with unmistakable results. The observed effect of lenses implies a feedback mechanism. Feedback theory explains those results with mathematical precision. Disruption of emmetropization, is the mechanism behind ametropia and particularly myopia. Feedback theory for emmetropization was derived by observation of the input and output of the emmetropization feedback system in many patients. We show that it has the same equation as it is derived here independently from simple homeostasis principles. Classical observations and recent clinical studies have shown the association of many variables with myopia. They include near work, atropine, lenses, blur and outdoors versus indoors activities. We propose that human refractive development is controlled by homeostasis and based on that alone we derive the equation for the calculation of refraction for any patient and the effect of lenses. We provide software to calculate the refraction of any individual at any time. The editor of this journal makes the following statement: "This manuscript is intended for scientific discussion rather than clinical application. The present work does not intend to promote clinical under correction or no correction of myopia. Instead, clinicians should follow current clinical myopia management guidelines."

Single-vision spectacle use and myopia progression in children with low myopia, a propensity score matching study

Purpose

To investigate the impact of single-vision spectacle use on myopia progression in children with low myopia.

Methods

MYOSOTIS is a prospective myopia screening survey including all 46 primary and junior high schools in two districts of Hangzhou, China. After 1-to-1 propensity score matching (PSM), 1,685 pairs of students with low myopia were included. Group 1 was composed of 1,685 non-spectacle users at baseline, and group 2 consisted of 1,685 spectacle wearers at both survey rounds. Refraction was examined by noncycloplegic autorefraction and mean spherical equivalent refraction (SER) of both eyes was analyzed. Myopia progression was measured by average rate of change in SER (r∆SER) between two survey rounds and compared between the two groups.

Results

After PSM, no significant difference in age, sex ratio, SER, and uncorrected visual acuity (VA) between the two groups was found at baseline. For myopic progression, r∆SER showed no significant difference between the two groups (− 0.67 ± 0.97 versus − 0.69 ± 0.81 diopter/year, P = 0.448). After adjusting for age, sex, SER, and VA, the difference in r∆SER between the two groups was not significant (− 0.031, 95% CI − 0.089 ~ 0.028 diopter/year, P = 0.302). In the subgroup analyses stratified by age and SER, and in the sensitivity analyses by eye side, there was still no significant difference in myopia progression between the two groups.

Conclusions

Our study indicates that single-vision spectacle use has no impact on myopia progression in children with low myopia. Spectacles are recommended in children with low myopia if their visual acuity has interfered with the daily life.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00417-021-05423-6.

The cause of myopia development and progression: Theory, evidence, and treatment

I review the key findings and our current knowledge of the cause of myopia, making the connections among the reliable observations on myopia development and theory to arrive at a summary of what we know about myopia, the proposed prevailing theory, and applicable action. Myopia is reaching epidemic proportions. It is estimated that half of the world's population will be myopic by 2050 unless new strategies to fight myopia are developed. Our high-level mathematical description of myopia is translated into clinical applications involving effective treatment and prevention. A regulating mechanism controlling the refraction of the eye is intimately related to myopia. The approach at hand is to review our knowledge about emmetropization, connecting myopia and emmetropization feedback theory to unveil the cause of myopia. Many observations discussed here test the validity of feedback theory positively. The cause of human myopia fits perfectly with the idea that emmetropization, in particular its feedback theory implementation, is the controlling mechanism behind myopia. They include near work, atropine, lenses, defocus, and outdoor versus indoor activities. The key findings in myopia research point the same way: myopia is the result of corrective lenses interfering with emmetropization. We have enough knowledge to answer the question of whether myopia can be reversed or prevented. There is no need to have mathematical skills to apply theory to real cases. It is enough to know the predictions of the feedback theory of emmetropization.