K.L. always knew he might be completely blind before reaching adulthood.

Even as a child he realized something was wrong with his eyes. Although he could see enough to navigate the world in daytime, as soon as the sun set so did his eyesight. Going out with friends was impossible at night. Eventually the world looked as if he was seeing through a large tunnel, focusing on only a tiny fraction at a time. Read more about Gene Therapy Is Successfully Treating a Common Form of Inherited Blindness