As excessive cleaning of the lenses may damage the anti-reflective coating, do not clean the lenses frequently. In most cases blowing dust off is sufficient. Finger prints should be removed as soon as possible.
To clean:
1. Remove dirt from the lens surface by blowing with clean air before using cotton wool to wipe the lens surface.
2. Soak cotton wool with 96% isopropyl alcohol or commercial lens cleaner containing more than 30% isopropyl alcohol. Twist it to remove excess liquid
3. Clean the lens one time only and discard the cotton wool. Use new cotton wool each time.