Purpose: Prospective study to evaluate the anti-inflammatory efficacy of isotonic seawater solution on metalloproteinase 9 (MMP-9) levels in the tears of patients with dry eye disease (DED). Methods: A total of 50 patients were included, with the following dry eye criteria in both eyes: InflammaDry ® test initially positive, ocular surface disease index (OSDI) score ≥ 12 and <33, tear film breakup time (TBUT) ≤ 10 seconds, Shirmer I test result ≤ 10 mm/5 minutes, corneal staining ≥ 1. Additionally, all the patients selected corresponded to a dry eye type 2-3 severity degree-mild and moderate-Dry Eye Workshop Study (DEWS) classification. The InflammaDry test is used to measure levels of MMP9 at the beginning and the end of the study. All patients were treated exclusively with isotonic seawater solution 5 times a day for 3 weeks. Results: The InflammaDry test was positive in 100% of the patients (n = 50) and in 100% (n = 100) of the eyes before treatment. In 14 (28%) patients the test became negative in both eyes, and in 15 (30%)