Efficacy and Safety of Ikervis Under Controlled Environmental Conditions Environment

Inclusion Criteria: * Age \> 18 years. * Diagnosis of DED with Severe Keratitis who have not improved despite regular use of tear substitutes by an ophthalmologist, at least 2 months previously. * Not stable (as defined by the two items below) under at least 2 months of constant and regular use of artificial tears (at least 4 drops a day) * Fluorescein corneal staining ≥ 2 (Oxford scale) in both eyes. * DEQ-5 \> 6 points * Use of at least 4 times daily of an ocular artificial tears. * Any concomitant medication that may affect DED, ocular surface condition or vision, must have a start date at least 3 months prior to baseline and dosage is not expected to change during the study. * Best corrected visual acuity (BCVA) of at least 0.1 logMar at 6 meters with each eye. * Signature of written informed consent form and data protection form. Exclusion Criteria: * Known allergy or sensitivity to the study product(s) or its components. * Any ocular pathology other than DED. * History of severe ocular inflammation other than that due to DED or infection in the 6 previous months to the study inclusion. * Any ocular surgery or trauma that may affect corneal sensitivity and/or normal tear distribution in the 6 previous months or any ocular or systemic surgery or procedure planned during the study duration that may affect the study as assessed by principal investigator. * History of refractive surgery in the previous 18 months. * Contact lens use in the ONE previous month to study inclusion and during the duration of the study. * Use of any ocular topical medication for pathologies other than DED. * Use of any other ocular topical medication for DED other than artificial tears during the last ONE (steroids) or THREE months (ciclosporine, tacrolimus) . * Any uncontrolled severe systemic disease that may affect the eye (except for Sjögren's syndrome) * The start date of any systemic medication that may affect DED, ocular surface condition or vision is \< 3 months prior to baseline or a change in dosage is anticipated during the study. * Occlusion of the lacrimal puncta either surgically or with plugs within one month prior to study, or anticipated use of the same during the study. * Pregnancy or breastfeeding. * Current enrolments in an investigational drug or device study or participation in such a study within 30 day of entry into this study at baseline.