Many spectacles wearers are not even aware of the fact that improper cleaning is hard on their glasses. Take tissues for example: If you use one to clean your lenses, they pick up debris from the lens and scratch it as you clean. These small scratches will eventually wear down the glass causing scratches.
Consequently, your first choice for cleaning your lenses should be micro fibre cloths (e.g. by ZEISS). They remove grease and moisture without scratching your glasses or leaving marks. To regularly clean your glasses, first clean them under running water to remove dust and rough debris. Next, add a a pH-neutral agent to the water and gently dry the lenses with a micro fibre cloth (never rub hard). Tip: Practical tools for your daily eyewear care are special spectacles cleaning supplies (available in spray form or as towelettes, e.g. by ZEISS). These will clean your lenses carefully, thoroughly and have anti-static effects, which helps your glasses stay clear longer because they do not collect as much dust and debris.
Cleaning recommendation: Wash micro fibre cloths at temperatures not to exceed 40 degrees and do not add a fabric softener, as using one could cause your cloth to leave behind streaks the next time you clean your glasses!
Lens coatings with pearl off effects produce similar results (for instance LotuTec by ZEISS), which make it hard for undesirable debris, dust or moisture to get stuck on your lenses. Not only will this cut down the amount of cleaning you need to do significantly; LotuTec also gives your spectacles a longer useful life.
The fact is, scratches are impossible to remove from both plastic and glass lenses, once they are there. Prevention is best. If your glasses get scratched, you should replace them quickly. Although most people believe that the defect is only a cosmetic one, the light is actually diffused by the microfine scratch grooves, which will irritate your eyes.