Predicting future myopia from changes in choroidal thickness.

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In 1995, Josh Wallman and colleagues have stated, based on experiments in young chickens, that choroidal thickness changes behind the retina can be considered “a third mechanism of focusing the eye” since the choroid becomes thicker when the focal plane is front of the retina, and thinner when it is behind. Obviously, in both cases, the retina is moved closer to the focal plane. The changes occur before eye growth has changed and their predictive power has major implications. Thanks to recent advances in optical coherence tomography (OCT), an increase in choroidal thickness can now be measured non-invasively and with high resolution (<10 µm) also in humans. Such changes can be used to predict future myopia, both in animal models and children. However, there are cases where axial eye growth increased even though the choroid became thicker. We propose experiments to find out under which conditions this may happen, using the animal model of the chicken. In a special “chicken arena”, artificial visual stimuli will be applied. Furthermore, since it is still not known how choroidal thickness changes translate into scleral growth changes, we will study the time courses of the signalling cascades from retina to choroid and sclera, by quantifying known biomarkers over time. We will also study the potential role of melanopsin on choroidal thickness. While these experiments will be done in chickens, they have fundamental implications when it comes to predicting future myopia also in children from choroidal thickness changes, and studying inhibition of myopia by novel artificial visual stimulation paradigms.