Contact Lenses and Overnight Wear

The tricky bit has been trying to create lenses and hygiene processes which are as safe for the eyes as regular contact lenses.

In the 1980s, an early version of the Acuvue contact lenses was used as a weekly-replacement overnight wear lens. This fell out favour as there was a substantial increase in keratitis - inflammation of the cornea. The search was on for contact lens materials that would let though more oxygen during sleep.

In the last decade new contact lenses have been developed - silicone hydrogel lenses - which transmit more oxygen. They are typically prescribed as a 6-night or 30-night removal, monthly replacement contact lens, and have been successful for overnight wear. However, recent studies have still found that overnight wear carries a higher risk of keratitis, compared with daily or monthly disposable regular contact lenses.