In act 2 of Waiting for Godot, Pozzo seemingly goes blind overnight. He yells for help and tries to get away. Vladimir calls after him, assuring Pozzo that no one will hurt him.
Meanwhile, Estragon wonders whether "Pozzo" is the right name to use. He maintains that they will eventually hit on the right name if they call out different names. This is a bizarre turn of events. However, it highlights Pozzo's fear, which is seemingly universal in nature.
Estragon's calling out of the names "Cain" and "Abel" is significant. So is his pronouncement that Pozzo is "all humanity." Cain and Abel, the cherished first sons of Adam and Eve, initiated the world's first sibling conflict . And, according to the Bible, Cain committed the first murder on earth. Brotherly love was destroyed by envy, thus resulting in the world's first tragedy.
Similarly, Pozzo's departure from objectivity in act 1 to confusion and emotional disarray in act 2 represents a sort of tragedy. It is Pozzo who, through his blindness, draws attention to our powerlessness over time and our mortality.
As the exchange continues, Vladimir demands to know when Pozzo became blind. The latter answers that he woke up one day "as blind as Fortune." Dissatisfied with the answer, Vladimir persists. This prompts Pozzo to blow up. He furiously declares that the blind have no notion of time:
Pozzo (suddenly furious). Have you not done tormenting me with your accursed time! It's abominable! When! When! One day, is that not enough for you, one day he went dumb, one day I went blind, one day we'll go deaf, one day we were born, one day we shall die, the same day, the same second, is that not enough for you? (Calmer.) They give birth astride of a grave, the light gleams an instant, then it's night once more.
Pozzo's diatribe draws attention to the fact that people are born in darkness and have no notion of time when they take their first breath on earth. Although they live for a time, they have no power over the length of their existence. Seemingly, the "light gleams for an instant" and then it's "night once more." In death, there is only darkness, and they have little power to determine this progression of their existence.
In this way, Pozzo's blindness can be viewed as a somatic reaction to his overwhelming feelings of powerlessness.