Effect of tears and tear residues on worn etafilcon and polymacon disposable contact lenses on the adhesion of Pseudomonas aeruginosa.

Abstract

Pseudomonas aeruginosa (Pa) ulcerative keratitis is the most severe complication of contact lens wear. The highest incidence of infection occurs with extended-wear hydrogel contact lenses, compared with daily-wear hydrogel lenses and with rigid gas-permeable lens wear.1–6 Corneal infection in contact lens users is believed to be initiated by the adhesion of the microorganism to the lenses.7–9 The microorganisms can then be transferred to the contact lens-compromised cornea when the immunological defense mechanism of the ocular surface is blocked by the wearing of the lens.10,11 In normal eyes, without a contact lens, blinking and the normal flow of tears cleanse the cornea of surface debris, desquamated epithelial cells, air polluters, and microorganisms. The mucoid component of the tears inhibits bacterial binding to the cornea surface. Enzymes and immunoglobulins in the tear fluid also protect the cornea against microorganisms.12 Polymorphonuclear leukocytes (PMN) released from the palpebral conjunctiva to the tears destroy invading microorganisms.13 However, hydrogel contact lenses that allow minimum tear exchange over the cornea interfere with all these lines of defense of the ocular surface.14 Also, with some of the available hydrogel lenses during daily-wear, and with all hydrogel lenses under the closed eye during sleep, the cornea becomes more vulnerable to microorganism invasion, due to the hypoxic stress induced by the lenses on the corneal epithelium.10,15,16