Question

What was the process by which the first living organisms discovered light and developed light-sensitive organs, such as eyes?

Answer 1

No life form "knew" that there was any need to develop eyes. At some point after life first appeared on Earth, an accidental mutation in some organism caused certain nerve endings to become light sensitive. This new trait increased the survival probability for this species which means it produced more copies of itself than other species without the mutation. Over a very long period of time, this first primitive "eye" mutated even more, gradually evolving into the modern eye.

Answer 2

The first life forms were plants which need light to survive

Answer 3

On top of the other answers, it's no coincidence that our eyes are most efficient at picking out optical wavelengths, particularly green (530 nanometer wavelength). This is the wavelength that the sun's radiation peaks at. Hence, if we ever come across any aliens from a different solar system and the star at the center peaks in a different band, they will have different sized eyes (which will most likely still be spherical in shape, like ours). If they were near a star with long wavelengths (like infrared or radio even), they will have HUGE eyes, as will many animals on said planet. If the star they are near peaks in the shorter wavelengths (and they can survive the higher intensity radiation) such as ultraviolet or xray, then they will have much smaller eyes. . . Ok, enough.....