You can use a lens cleaner to remove minor scrape on eyeglasses. You can get the lens cleaner from your optometrist or from a CD cleaning kit. But if the scrape is too deep, you may try buffing to remove the scrap but it cannot be removed completely. It only works with minor scrap.
Hey, guy! There! You can drop baby oil on the lenses and rub with the lenses with a piece of soft cloth. But this only works best for minor scrapes. Or you can apply creams which can take scrapes off from sports helmets to remove your scrape. If you couldn't get rid of the scrape and the scrape may affect your vision, you may need to buy a pair of new sunglasses for instead.
I suggest you to ask an optician to remove the scrape for you. If your sunglasses are very expensive, you may damage them or make more scrapes on the lenses. And I have found many suggestions to help remove scratches on sunglasses. You can have a look first. http://www.firmoo.com/answer/question/1898.html