But, in the world to come, the soul also needs "eyes" לחזות בנועם ה', to be able to see the glory of Hashem, and 'ears' to hear the words of Hashem teaching Torah in Gan Eden. One who during his lifetime is not careful to guard his sense of sight, instead permitting himself to look at what the Torah forbids, will be like a blind man in the Olam Ha'emes - unable to gaze upon the light of Hashem.
Just like someone whose eyes are damaged, he will not be able to see through the light of his neshama, because his neshama's eyes were injured. The degree of the injury to his eyes will be proportional to the level of his self-abandonment.
When one realises that due to falling for the momentary pleasure that the Yetzer Hora has fed him, he has corrupted his eyes and darkened them, drawing down a spirit of טומאה upon them, he will suffer tremendous bitterness and regret.
The Chofetz Chaim adds that although the above is true to all bodily functions, special care should be taken to safeguard the eyes from temptation, as they are the gateway to the yetzer hora. As our Chachomim say, "עין רואה ולב חומד וכלי המעשה גומרין", "The eye sees, the heart desires and the instruments of action consummate." Therefore, we must be extra vigilant in guarding our sense of sight, as the eyes have the power to corrupt the neshama more than any other bodily function, all of them acting upon what his eyes have begun.
(שמירת הלשון פרק ל)