Twice-Daily Systane Complete Versus Four-Times-Daily Thealoz Duo for Dry Eye Disease

The goal of this clinical trial is to learn whether a twice-daily dosing schedule of Systane Complete eye drops works as well as a four-times-daily dosing schedule of Thealoz Duo eye drops to treat dry eye disease in adults. The main questions it aims to answer are: * Does twice-daily Systane Complete provide similar improvement in dry eye symptoms, measured by the Ocular Surface Disease Index (OSDI), compared with four-times-daily Thealoz Duo after 30 days of treatment? * How do the treatments affect tear film stability, tear production, and damage to the surface of the eye? Researchers will compare Systane Complete (used twice a day) to Thealoz Duo (used four times a day) to see if the simpler dosing schedule maintains similar benefits for symptoms and eye surface health. Participants will be adults with mild to moderate dry eye disease who are seen in an outpatient eye clinic. They will be randomly assigned to one of the two treatment groups. All participants will use their assigned eye drops in both eyes for 30 days and will attend clinic visits at the start of the study and after 30 days. At each visit, participants will complete the OSDI questionnaire and undergo standard eye tests, including tear break-up time, Schirmer test, and grading of surface staining on the eye.

Inclusion Criteria: * Adults (≥18 years of age) with mild to moderate dry eye disease (DED). * Ocular Surface Disease Index (OSDI) score between 13 and 32 at baseline. * At least one abnormal objective test of ocular surface dysfunction, defined as one or more of the following: * Schirmer test result \< 10 mm in 5 minutes (without anesthesia), or * Tear break-up time (TBUT) \< 10 seconds, or * Ocular surface staining graded between stages 1 and 3 according to the Oxford scale. * Best-corrected visual acuity of 20/200 or better in both eyes. * Able to provide written informed consent and comply with study procedures and scheduled visits. Exclusion Criteria: * Pregnancy or breastfeeding. * Participation in another clinical trial or prior participation in the present study. * Best-corrected visual acuity worse than 20/200 in either eye. * Active ocular disease including conjunctivitis, blepharitis, keratitis, ocular trauma, ocular surface scarring, corneal ulcers, neurotrophic keratitis, bullous keratopathy, or neoplastic disease of the ocular surface. * Glaucoma or eyelid disorders that affect normal eyelid function. * Advanced dry eye disease requiring second-line TFOS DEWS II therapy. * Ocular surgery within the previous 3 months. * Contact lens use within 15 days prior to enrollment. * Known hypersensitivity to any component of the study medications. * Substance dependence within the previous 2 years. * Systemic conditions that could increase the risk of study participation or interfere with interpretation of study outcomes, as judged by the investigators. * Women of childbearing potential not using stable contraceptive methods for at least 30 days prior to enrollment and throughout the study duration.