Phillip notices "that Timothy always changed the subject when (they) began to talk about (Phillip's) eyes...he would make any kind of an excuse". The reason for this is most probably because Timothy does not know what is wrong with Phillip's eyes and is powerless to remedy it. He cannot offer Phillip any solutions to alleviate his blindness, yet at the same time he does not want to cause Phillip to give up hope that he will one day see again.
In Chapter 10, Phillip asks Timothy to describe what he (Phillip) looks like after so much time on the island. Timothy says he is "veree brown an' veree lean". Phillip then asks Timothy what his eyes look like, and Timothy responds that "dey look widout cease...dey stare". Timothy then thinks about a friend in Barbados who was hit on the head and became temporarily blind; he says vaguely that his friend was blind for "many mont'", although earlier he had said it had only been for three days. When Phillip points this discrepancy out, Timothy replies, well...'twas a long time ago...but 'e got 'is sight back, to be true", and then he starts to talk about the work they need to do today. This is when Phillip realizes that whenever they talk about Phillip's eyes, Timothy changes the subject (Chapter 10).