Mast cells: Cells that initiate allergic reactions by releasing histamines and other pro-inflammatory mediators in the presence of allergens.

Histamine: A pro-inflammatory mediator released by mast cells in the presence of allergens. Histamine causes the red, watery, itchy eyes associated with ocular allergies.

Disappearing or transient preservative: A common additive found in artificial tears, this is an agent that rapidly degenerates into oxygen and water when it contacts the tear film.

Fairness to Contact Lens Consumer Act: A new law enacted in February 2004 that requires all eyecare practitioners to release a patient's contact lens prescription immediately after fitting. For details, download a free PDF from

Corneal reshaping therapy: An alternative vision correction therapy that uses a series of reverse geometry contact lenses to correct myopia.