The LASH Contact Lens Study is a prospective longitudinal study of silicone hydrogel (SH) contact lens wearers who sleep in their lenses for up to 29 consecutive nights (30 days) of continuous wear (CW), with monthly disposal. Up to 207 healthy nearsighted or farsighted patients with minimal or no astigmatism and no contraindications to CW lens use will be followed for 1 year. The primary outcome measure is the time to development of a corneal inflammatory event (CIE) as defined by slit lamp findings and patient symptoms. The main exposure of interest is corneal staining. Other key exploratory variables include bacterial contamination of study lenses and inflammatory mediators found in the tear film.