Most of the major news sources are reporting that today April 24 is the 25th anniversary of the launch of the Hubble Space Telescope. Those stories are plentiful and easy to find. Many of the stories emphasize the amazing images and greater understanding that has come from Hubble.
Some of the stories also describe the tremendous disappointment of scientists when the first images were released. They were out of focus and could not be adjusted without a repair mission. The mirror was made with a slightly wrong curvature. Something called spherical aberration.
NASA Jet Propulsion Laboratory released this video about the repairs that had to be made in order for Hubble to perform at its best. In principle, the astronauts on a Shuttle mission installed a new camera instrument that added corrective glasses to the light path. It is a common fix for our own vision. It fixed Hubble, too.