Blindness describes the experiences of a small group of people who are among the first to go blind in a nearly sudden, universal epidemic of blindness. The primary interest in the story is its account of how human behavior would change under such circumstances. The basic premise is implausible, but could be easily forgiven if it served to illustrate some important idea. It does not. Furthermore, many of the actions of the characters are less than believable. During the epidemic, there is one woman who retains her sight. There is no explanation for the exception. Her purpose in the novel appears only to allow the other characters some greater degree of freedom to cope with their situation.
Saramago's writing occasionally hints of a broader meaning of the blindness, but he is never clear, and his hints are too infrequent and unintelligable for any text-based interpretation to emerge. If Blindness is an allegory, it is hopelessly obscure. What is left is a simple exploration of how an epidemic of blindness might lead to social chaos and psychological stress -- not a terribly surprising consequence. For a more meaningful examination of how people behave under extreme stress, one would do much better to read Elie Wiesel's account of his actual experiences during the Holocaust in Night.