The normal pH of tears is: March 2007
Ans. D: 7.5 Human tear film/ precorneal film has three distinct layers, from the most outer surface: I. Lipid layer secreted by meibomian glands (or tarsal glands) - coats the aqueous layer; provides a hydrophobic barrier that evaporates and prevents tears spilling onto the cheek. These glands are found among the tarsal plates. Thus, the tear fluid deposits between the eye proper and oil barriers of the lids II. Aqueous layer- secreted by lacrimal gland - promotes spreading of the tear film; promotes the control of infectious agents; promotes osmotic regulation III. Mucous layer- secreted by conjunctival goblet cells - coats the cornea;provides a hydrophilic layer;allows for even distribution of the tear film; covers the cornea
6
6.5
7
7.5