What does Phillip mean when he says of Timothy, "His eyes were becoming mine," in Theodore Taylor's The Cay?

By the end of the fourth chapter in Theodore Taylor's The Cay, Phillip awakens with his head no longer hurting but his vision growing hazy. He awakens another time to find he has gone completely blind. After a moment of hysteria, he falls asleep again and awakens in the fifth chapter calmer and aware that he must now rely on his sense of sound and Timothy's own eyes to know what's going on around him. Towards the middle of the chapter, when Phillip comments that Timothy's "eyes were becoming mine," he means that he is opening up to Timothy enough that he can ask Timothy what he sees and rely on Timothy's vision as his own.Phillip must first begin relying on Timothy's eyes to spot any planes or ships in the region. At the start of Chapter 5, they both hear a motor, and Timothy is the one who is able to see it is a plane and where it is located. But, soon enough, Timothy sees the plane fly off, and Phillip hears the sizzling sound as Timothy uses the ocean water to douse the torch he had lit to attract the plane's attention. Next, Timothy must be Phillip's eyes to warn him of the dangers of sharks as Phillip crawls too close to the edge of the raft. By the middle of the chapter, Phillip asks Timothy, "Tell me what's out there, Timothy." Timothy reports seeing "miles o' blue wattah," a fish jump out of the water, a turtle that had passed by them a while ago, a clear blue sky, and a bird called a booby feeding on the flying fish; the booby Timothy saw was of a variety of boobies that have blue faces and blue feet, called blue-faced boobies. Though Phillip laughs at the name of the bird, Timothy remains serious and explains that the sight of the bird is a good sign because the birds nest on the shore; therefore, seeing a blue-faced booby means that their raft is close to shore.