I’ve dealt with this problem all my life – i have high powered glasses (-6 and – 8, with some cylindrical /spherical tweaks). My glasses work great. But i wore them while swimming in the crystal blue Mediterranean, and when I’m diving in, i realized the glasses aren’t effective. I understand the wavy reflective patterns interrupting, but why cant I focus on anything easily?
In: Physics
To do their thing your glasses have to (de)focus light in a specific way to correct for your eyes. The change in direction happens when light changes the material in travels in: normally from air to glass/plastic, then back to air, and into your eyeball.
But the change is stronger the more different the materials are*. Air is quite different from the glasses, so it changes significantly. But if there is only water, no air, then the change is much less. So the light is changed only a bit and the glasses cannot properly do their job anymore.
It also doesn’t help that the change from air to eyeball (mostly water) is now essentially gone, too.
*: more precisely it depends by what factor the speed of light changes, denser stuff typically having slower speeds.
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