Contact lenses are a popular alternative to corrective eyewear. They can be worn full-time or part-time for sports and recreation. The two main categories are soft (or gel) lenses and rigid gas permeable (RGP) lenses. Soft lenses are more popular and available in various formats to correct far-sightedness, near-sightedness, and astigmatism. RGP lenses have an important role in certain types of astigmatism and with fitting irregular corneal surfaces. All contact lenses touch eye tissue, and as such are a medical device that must be professionally fit, including training for proper handling and for important hygiene considerations.