I’ve just listened to an online lecture on myopia management and now I’m confused. The speaker mentioned that hyperopic defocus in the retinal periphery caused axial elongation and therefore an increase in myopia and then he said that under correcting people with myopia also caused axial elongation and an increase in myopia. How is this possible?
Myopic progression is a complex area of eye care. There are lots of questions and fewer questions.
What has recently been discovered is that amacrine cells in the retina form part of the eye growth system. You might remember hearing about amacrine cells in your anatomy classes at optometry school and you probably haven’t thought of them since passing the anatomy exam. I think we will be hearing a lot more about them in the coming years.
Amacrine cells are now thought to detect the quality of focus of light on the retina. Information on focus quality is then sent to those parts of the eye which control eye growth. Amacrine cells are able to distinguish between sharp and no-sharp focus and even between myopic defocus from hyperopic defocus. It’s not clear to me how they can do that but there is good evidence to show that they can.
There are also several genes that operate in the eye growth system. Having one or more of these ‘myopia genes’ accentuates the risk for myopia in situations of poor retinal focus.
Why is myopia decreased with peripheral myopic defocus but increased with foveal myopic defocus
Undercorrecting myopes doesn’t work.
Hyperopia at fovea is a buffer for myopia
Premyopia < +0.75 to -0.50
In an emmetropic range at an age they shouldn’t be.