Chapter 5 of Silas Marner is significant because of its climactic content. It is here where we find Silas at his most content. He is content about his hidden gold, and he is superbly happy about the piece of pork that he is about to feast on. Elliot's description of Silas's joy instills in the reader a sense of comfort and security that is wildly thrown away seconds later, when Silas realizes that his gold is gone.
As readers, we award meaning to specific details of a story. Although the short-sightedness of Silas is only mentioned once in the chapter, it can serve as foreshadowing of what is to come.
He reached his door in much satisfaction that his errand was done; he opened it, and to his short-sighted eyes everything remained as he had left it... He trod about the floor while putting by his lantern and throwing aside his hat and sack, so as to merge the marks of Dunstan's feet on the sand in the marks of his own nailed boots.
It is his short-sightedness that prevents Silas to see that there are marks of his floor. His eyesight, which donned on him the huge eyes that makes Silas;s appearance so odd and unique, has officially failed him when he needed it the most.
However, we can also see his shortsightedness metaphorically, because the two times that Silas has been involved with a robbery he could have "seen it coming", no pun intended. If Silas were not so easy to fall into monotone routines, and if he took it upon himself to look more closely at things, he would have known that the people of Lantern Yard were not true friends. Similarly, had he had a sharper eye to notice human behaviors, and detect patterns in his own life, he could have been more careful about the way that he kept his gold.
The main flaw of Silas's character, then, is precisely his limited range of human connections. Even in Lantern Yard, Silas kept himself surrounded by a small group of people. In Raveloe, he refuses to open up and be a normal part of the community. It is until he suffers a second major blow that he finally (and literally) opens his eyes to reality and understands the importance of living in community.