• Keratoconjunctivitis sicca (KCS) results from a deficiency of the precorneal tear film in which either an inadequate quantity or deficient quality of tears are produced.
  • The precorneal tear film is composed of 3 layers:
    • Inner mucin layer: adheres the tear film to the cornea
    • Middle aqueous layer: provides corneal nutrition and waste removal
    • Outer lipid layer: prevents evaporation of the tear film
  • Quantitative deficiency involves the aqueous layer, which is produced by the orbital and nictitating membrane (NM) lacrimal glands.
  • Qualitative deficiency involves the mucin layer, which is produced by conjunctival goblet cells, or the lipid layer, which is produced by meibomian glands.

Sign in to continue reading this article

Not registered? Create an account for free to read full articles on

To access full articles on, please sign in below.

Busy? Sign in Faster. Sign into with your social media account.
Up Next