Neuroscience and Neurology

Why does the eye develop myopia?

Dr. Barbara Swiatczak

Institute of Molecular and Clinical Ophthalmology Basel (IOB) 

Myopia (near-sightedness) is the most common eye disorder in young people worldwide. The disease is characterized by eyeballs too long for their optical power which causes distant objects to be seen blurred or out of focus. Although myopia can be corrected by spectacles, contact lenses, or laser surgery, none of these interventions can stop further eyeball elongation leading to the development of high myopia which increases the risk of retinal complications.

In the process of eye growth and development children's eyes undergo adjustments to achieve the best possible image quality and sharp vision by matching eye length to its optical power (perfectly seeing eyes are called “emmetropic“). For Barbara Swiatczak and her colleague, one crucial question remained unanswered: Despite this tightly controlled mechanism of eye growth, why do some children develop myopia while others remain emmetropic? Why does the retina seem „to give up“ during myopia development? 

They knew that the visible light contains blue, green and red light with different wavelengths. Green light focuses on the retina creating a sharp image while blue light is focused in front of the retina, and red light behind the retina, imposing blur. Since the myopic eye is too long, red light is in better focus than green light. On the other hand, the hyperopic eye (far-sightedness) which is too short sees blue light in better focus. The innovative approach of the scientists was to trick the retina by digital filtering of the separate colour channels in order to trigger changes in the eye length. They developed two digital filters: the “red in focus” filter which imitates the myopic eye, and the “blue in focus” filter which mimics a hyperopic eye. When young adults watched a movie with the “red in focus” filter, their retina triggered eye shortening. Conversely, the “blue in focus” filter induced eye elongation. Surprisingly, these changes were only observed in emmetropic but not myopic eyes. 

The findings of this study resolve a long-standing ophthalmologic question. Apparently, the myopic retina no longer detects chromatic defocus and therefore can no longer generate growth-inhibiting signals, but instead triggers more eye elongation and myopia progression. The results also suggest a new non-invasive strategy to inhibit early myopia development: keeping the red image plane on a computer screen sharp but low pass filtering the blue.

Myopia: why the retina stops inhibiting eye growth. Barbara Swiatczak*, Frank Schaeffel*. Sci Rep. 2022 Dec 15;12(1):21704)
* contributed equally