Functional changes in the myopic retina compromise emmetropization

Abstract

During emmetropization, the retina analyses the focus of the image and generates appropriate biochemical signals to control choroidal thickness and scleral growth. Using commercially available optical low coherence interferometry (the Lenstar LS 900), changes in eye length in the micrometre range can be picked up already after 30 min when young human subjects watch movies that were digitally filtered. We found that the emmetropic retina can distinguish real optical positive defocus from simulated/calculated defocus. It triggered choroidal thickening in the first case, and thinning in the second. Strikingly, the myopic retina was not responsive, and the choroid became thinner in both cases. Longitudinal chromatic aberration (LCA) would be a perfect signal to tell the retina where the focal plane is. We simulated chromatic defocus in our movies. Either the red or the blue plane of the RGB format was spatially filtered to simulate chromatic defocus. When blue was ‘in focus’, eyes became longer, but when red was ‘in focus’ eyes became shorter. Again, myopic eyes did not respond, suggesting that the myopic retina no longer responded to LCA. Taken together, we found that the myopic retina had undergone functional changes such that no growth‐inhibiting signal was generated. As a consequence, eye growth would become open loop, explaining why myopia does not inhibit itself.