Ralph and Piggy are the first two boys to appear on the island after a plane conveying them to safety has been attacked. Piggy reveals to Ralph in this first encounter that he has been wearing spectacles since he was three. In many respects Piggy is both physically and health-wise a weak boy. He has asthma so he has been warned by his guardian not to run; and he wears spectacles because he has sight challenges.
Piggy's glasses are one of the symbols in the novel which are significant to the meaning of the novel. Apart from the conch, the glasses appear to be the next most significant symbol which bear directly on the survival strategies of the boys. After the boys have settled on the issue of the need to have a Chief and the use of the conch as a symbol of authority, the next challenge confronting them is the issue of rescue. This challenge is projected to be addressed by setting up a fire on top of the mountain. Piggy's glasses becomes the useful tool to light the pile of wood for this purpose. Jack instantly points to the glasses and there is a general agreement by the boys. Both Jac and Ralph jointly use the glasses to light the fire.
The general enthusiasm which greets the setting up of the fire is shortlived as Jack and his group fail to watch over it. He leads his hunters on hunting adventures and the fire dies down, which makes the dream of rescue to fail when a ship passes by on the sea. However, Ralph leads Piggy and Samneric to re-light the fire. Again Piggy's glasses are used to reenliven the boys' rescue attempts. Even though Jack is not so much concerned about the fire at this point, the significance of the fire is underscored by the equally important glasses.
Unfortunately, the glasses are stolen by Jack's group in a raid they carry out on the shelter where Ralph, Piggy and Samneric are now camping. Here the glasses are significant in two respects. First is their importance to the tribe. The hunters realize once again that much of their survival depends on having a fire with which they can roast meat and light their part of the island. Second is its significance to the plot. The event of stealing the glasses signifies the beginning of the events that culminate in the final peace and order on the island. Piggy's glasses are partially broken at this point. The attempt to recover the glasses leads to the climax of the story. Jack captures Samneric and engages Ralph in a physical fight. Finally a rock falls and kills Piggy, destroying the conch and breaking the glasses.
Thus, the glasses are not only a symbol of Piggy's weakness as a character but also significant to the development of the plot of the novel.