Symbolism, Imagery, Allegory
There is definitely an association in The Giver between those who can receive memories and those who have light eyes. There isn't really any explanation for why this is, and it would pretty useless for us to sit around and speculate about why this is, logically or scientifically. It's better to think about it as an artistic device that Lowry used to help us make certain connections. For one, Jonas's role as The Receiver is in some way pre-destined. He was just born with the right attributes to be The Receiver. It fits. He's supposed to do this. Light eyes also clue us in to the fact that Jonas and The Giver share a special bond, something that others, try as they might, will never have. Likewise, eyes signal the close bond that will form between Jonas and Gabriel; we suspect something is up even before Jonas transfers memories to the little tyke
But why eyes? And why light eyes? Jonas himself says that he always thought there was something peculiar about this feature, that it somehow signified "depth." Indeed, Jonas has a way of seeing deeper than others. The way he perceives the world is different – more reflective, more contemplative, more insightful – so it makes sense that his eyes appear different than everyone else's.