The correspondence of Montesquieu published by the Oxford Foundation informs about visual disorders of the founder of the socio-political science. The examination of his bust's face done by J.B. Lemoyne reveals a divergent squint of the left eye; the one with which he fold that he only could see big objects. This amblyopia was a premature and prolonged embarrassment. During the last ten years of his life, from 1748, date of publication of the Esprit des lois up to his death in 1755 he was blind because of the cataract of the other eye. He has not able to bust in surgery, while the French surgeon Jacques Daviel already proceeded to the extraction of the lens as we do it nowadays.