How can they say that lowering one's gaze means that we simply don't look at nakedness and indecency? It is comprehensive, i.e. we don't look at the opposite gender, period. The eyes are the windows of the heart. You don't worry about what you look at, and you will be tested SEVERELY.
"Say to the believing men that they should lower their gaze and guard their private parts; that will make for greater purity for them. Indeed Allaah is well acquainted with all that they do." [an-Nur (24):30]
Whosoever lets his sight roam free will find that he is in a perpetual state of loss and anguish for sight gives birth to love (mahabbah) the starting point of which is the heart being devoted and dependant upon that which it beholds. This then intensifies to become fervent longing (sabaabah) whereby the heart becomes totally dependant and devoted to the (object of its desire). Then this further intensifies and becomes infatuation (gharaamah) which clings to the heart like the one seeking repayment of a debt clings firmly to the one who has to pay the debt. Then this intensifies and becomes passionate love (ishk) and this is a love that transgresses all bounds. Then this further intensifies and becomes crazed passion (shaghafa) and this a love that encompasses every tiny part of the heart. Then this intensifies and becomes worshipful love (tatayyuma). Tatayyum means worship and it is said: tayyama Allaah i.e. he worshipped Allaah.