Why do anime/manga characters have big eyes? Going as far back as Astroboy, anime and manga characters have had big eyes.

What is basis of this trend? How and where did this originate?
Anime characters having large eyes is generally attributed to Osamu Tezuka{1}, an artist prolific enough to be called the "father of manga", and the creator of Astro Boy, the source of the image you shared in your question (among other manga).

At the time of Astro Boy (1952), Tezuka was inspired by precursors in animation, largely those of Walt Disney, but including others as well, before adapting them to a more Japanese stylization. Two such characters who served as inspiration were Mickey Mouse and Betty Boop:

 

It is from Astro Boy and Tezuka's other works that a lot of modern manga and anime style evolved, and the big eyes are one of the things that stuck around. Fred Ladd, the man responsible for bringing Astro Boy to the United States, corroborates this, saying that Betty Boop was indeed one of Tezuka's favorite characters. The "runaway" success of Astro Boy was what led other studios to imitate Tezuka's style.{2}

It is also the case that the large eyes tend to look "cuter", much like they were intended to on characters like Mickey Mouse and Bambi. This continues in anime and manga; younger characters tend to have the largest, "cutest" eyes, while older characters generally have smaller (and often sharper) eyes, which can be seen in this image containing Hunter x Hunter characters:



So, while the style Tezuka used&mdash;which has carried on in new anime and manga media ever since&mdash;was largely based on Western animation style, the eyes can still serve as a good way to indicate personality or the feel of the character that the viewer is supposed to have.

Sources and other Links


Wikipedia sources this to "Watching Anime, Reading Manga: 25 Years of Essays and Reviews".
MIT Anime Resources: Big Eyes (2008-07-23)
TVTropes on Anime (a very brief mention)
Wikipedia on anime eye styles