There is a long list of causes of dry eye syndrome, including ocular surface conditions (e.g., blepharitis, meibomian gland dysfunction), ocular surgical history (e.g., corneal transplantation, refractive surgery), inflammatory conditions (e.g., allergies), hormone imbalance (e.g., thyroid hormones, sex hormones), environment (e.g., dry weather, contact lens over-wearing, smoking), neurological conditions (e.g., trigeminal nerve palsy, infrequent blinking), medication (e.g., anti-histamines), and systemic disease (e.g., Sjogren's syndrome, diabetes mellitus) [19]. This evidence concerns the gene TG and Sjogren syndrome.