Occlusion of the meibomian glands with a keratinized sheet can occur in blepharitis.Historically, the rule with blepharitis cases was that a third were caused by Staphylococcus, another third by seborrhea, and the final third were from a combination of Staph and seborrhea, mixed with causes such as Demodex folliculorum mites, Pityrosporum ovale, or fungi.