The proposed study is a prospective, open-label, unicentric, phase IV clinical trial.

This study is design to find new efficacy biomarkers for IKERVIS® (1mg/mL ciclosporin) eye drops after 1 and 3 month after initiation of therapy. Additionally, this study intends to investigate whether IKERVIS® will help patients to better overcome situations of desiccating stress by exposing them to an adverse controlled environment (ACE) and analyzing both clinical and molecular parameters.

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.