It is narrated from Hazrat Saeed bin Musayyib that a man injured another man's eye, causing partial loss of his vision. This case was brought before Hazrat Ali (may Allah be pleased with him). He ordered that one of the man's eyes be covered and that he walk while holding an egg, and the man kept looking until his vision was completely gone. Then a mark was placed at that spot. Saeed bin Musayyib states that when the man looked with his other eye, they found it to be normal. So Ali (may Allah be pleased with him) said: Give him compensation for the loss of vision in proportion to the damage compared to the other eye.