Hycosan Extra Hycosan Extra is double the strength of Hycosan & four times more viscous but still with minimal blurring of vision. This increase in viscosity increases the duration of action, making it ideal for more severe cases of dry eye & a great alternative to eye ointments during the day. As with the rest of the Hycosan range, Hycosan Extra is preservative free & is compatible with all contact lenses. Hycosan Extra uses the unique, patented COMOD system to deliver a preservative free eye drop that is sterile for 6 months after first opening. This also ensures that just a single calibrated drop is dispensed per click to ensure accurate dosing & less wastage.