As you know the main contents of vodka is alcohol and water, then there's nothing serious about it. The main element of alcohol is Ethanol; it's a kind of mild and organic solvent. It may bring you a little irritating feeling when it gets into your eyes. Please wash it with clean water thoroughly and immediately. No serious hurt will be caused by it, so please don’t worry. Alkali will do harm to your eyes more than acid material. Ethanol is belonged to weak acid fields. If it remains just in a second with a bit splash, there will be no question with timely water washing. However, if strong discomfort exists, or find some hurt in your eyes, you must promptly go to a doctor.