<unk> usage Overview Although<unk>  are used to mimic or supplement the roles of the<unk> film and contain water, electrolytes, and certain polymers, they do not contain the biologically active components found in naturally-produced<unk> . Moreover,<unk>  often contain chemicals that are not present in naturally-produced<unk> . Preparations can contain carboxymethyl cellulose, polyvinyl alcohol, hydroxypropyl methylcellulose (a.k.a. HPMC or hypromellose), hydroxypropyl cellulose and hyaluronic acid (a.k.a. hyaluronan, HA). With preservatives Preparations can also contain preservatives in order to prolong usage and avoid bacterial contamination. Preservatives include benzalkonium chloride (BAK), ethylenediaminetetraacetic acid (EDTA), purite, chlorobutanol, sodium perborate, thiomersal, disodium edetate, and oxychloro complex (SOC). Preservatives can be toxic and cause damage to the corneal epithelium. For instance, high concentrations of benzalkonium chloride (BAK) can cause cytotoxicity, cause cell lysis, and reduce<unk> and mucin production. Patients should limit their use of<unk>  with preservatives to less than four to six times a day. If<unk>  need to be utilized more than four to six times a day, a preservative-free formulation should be used. Preservative-free Preservative-free<unk>  formulations are indicated for patients who cannot tolerate<unk> formulations with preservatives, patients who are using<unk>  more than four to six times a day, and patients who are using multiple topical eye drops with preservatives. Preservative-free eye drops are found in single vials. However, single unit-dose<unk>  without preservatives are more expensive than bottled<unk>  with preservatives. Some patients confuse over the counter drops that contain tetrahydrozoline (i.e. Visine®), a vasoconstrictor, with<unk> . Desensitization can occur with extended usage of drops containing tetrahydrozoline.
Artificial tears
Bionic contact lens
Whitfield's ointment
Topical steroid
Contact lens
Fundal massage
Eyelid revision
Laser thermal keratoplasty