I know myopia is caused by elongation of the eyeball. When the eye is too long, light entering the eye balls falls in front of the retina instead of on it.
However I do not quite understand how this leads to the "blur" we observe. If part of the light entering the eyeball "misses" the retina shouldn't the observed effects simply be a reduction in the brightness of the object - as if I were standing in a less illuminated place? For example, if I take off my glasses in broad daylight my retina is getting a far greater dose of light than when I'm indoors (wearing my glasses) under artificial lighting. Yet the world still looks blurry outside (without glasses) and clear indoors (with glasses).
What causes the blur effect? If less light is hitting the retina it should simply look less illuminated, not blurry.