Artificial Tears

The number of artificial tear preparations available over the counter is overwhelming (Tables 5-1 and 5-2). This is evidenced by a single glance at the shelf in the local pharmacy. Artificial tears contain various components and different combinations of buffers, tonicity agents, polymers, and occasionally preservatives and vitamins.

The major therapeutic component in artificial tears is the water-soluble polymer. These agents determine the viscosity (thickness) of the artificial tear solution and aid in tear stabilization. They include methylcellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methylcellulose, carboxymethylcellulose, and polyvinyl alcohol. Electrolytes help to maintain pH and tonicity of the solution. Examples of pH buffers include boric acid, sodium bicarbonate, sodium borate, hydrochloric acid, sodium citrate, sodium hydroxide, and sodium prosphate. Tonicity agents include dextran, dextrose, potassium chloride, propylene glycol, and sodium chloride.

Table 5-1

Partial List of Nonpreserved Artificial Tears (Brand Names)

Bion Tears Celluvisc Hypotears PF Refresh Plus Refresh Endura Tears Naturale Free Theratears

Table 5-2

Selected Preserved Artificial Tears (Brand Names)

AKWA Tears Aquasite Computer Eye Drops Genteal Hypotears Moisture Eyes Nutra-Tears Rhoto Zi Systane Tears Naturale Forte Viva Drops Visine Tears

Preservatives are included in multi-dose preparations of artificial tears, decreasing the risk of bacterial contamination. Benzalkonium chloride, EDTA, and Polyquaternium-1 are some of the common preservatives used in artificial tear preparations. Due to the likelihood of developing a preservative-related toxicity, solutions with preservatives must be used with some precautions, if used on a frequent basis.

There are a few artificial tear preparations with added vitamins and antioxidants. For example, Viva Drops® add vitamin A to their preparation while Nutratear® contains vitamin B12. Some studies suggest that vitamin supplementation is of benefit in treating severe dry eye and other forms of keratitis, including superior limbal keratoconjunctivitis. Theratears® has a patented electrolyte balance that exactly matches that of natural human tears. This formulation may prove to have additional benefits to the corneal and conjunctival health of the dry eye patient.

The frequency of administration is dependent upon the severity of the condition. The drops may be instilled as infrequently as once or twice daily or as often as every hour, as necessary. To prevent preservative toxicity, it is recommended that nonpreserved artificial tear solutions be used if drops are prescribed for more than 3 or 4 times daily use. Nonpreserved artificial tears, however, are not as convenient due to their single-dose containers and increased expense.

Table 5-3

Selected Lubricating Agents in Order of Increasing Viscosity (Brand Names)

Hypotears Refresh Tears Plus Tears Naturale Bion Tears Ocucoat Celluvisc

Adapted from data obtained from Storz Ophthalmics, St. Louis, Mo.

A beneficial development has been the introduction of the "disappearing" preservatives in artificial tear solutions. On contacting the eye, the preservative is converted to dilute hydrogen peroxide, which then changes into water and oxygen within a minute of contacting the eye. The cornea is much less likely to develop preservative toxicity with this short contact time. The advantage is the benefits of nonpreserved tears with the convenience, safety, and value of a preserved solution. Commercially available products such as Genteal® have been a welcome addition to the artificial tear market.

Viscosity is another property of artificial tears that must be considered. Viscosity varies among the various tear preparations available (Table 5-3). More viscous solutions promote longer contact time and increased therapeutic benefits. The disadvantage of viscous tear solutions is their tendency to blur vision temporarily; the more viscous the solution, the more blurred the vision.

Clinicians have developed elaborate programs to determine the appropriate viscosity for a given patient and condition. These programs are usually some sort of subjective single-elimination tournament with the winner determined after a period of up to 6 weeks. Patients may get frustrated with the length, expense, and time involved in the program. It may be best to give the patient a set frequency and send him or her home with multiple samples of varying viscosity. The patient should then find the tear he or she prefers and use it. The patient might also be given information regarding the pros and cons of the different drops based on their makeup, viscosity, and cost.

In addition to administration by drops, there have been a few products introduced that deliver the solution as a spray mist. Though these products have gained a following by some patients, they have not yet achieved widespread popularity by patients or physicians in the therapeutic treatment of dry eye.

The extraocular use of viscoadherent and viscoelastic agents in the treatment of dry eye has also been advocated. Marketed under the name Ocucoat®, hydroxypropyl methylcellulose is available as a viscous artificial tear. Also, sodium hyaluronate has been applauded by some clinicians for its ability to promote tear film stability, although it is not available as an artificial tear preparation at the time of this publication.

There are varying clinical opinions on the best agent and program in treating dry eye with artificial tears. Patients often get confused and frustrated with the many options, chronic and frequent drop use, expense, and inconvenience. These aspects should be discussed with the patient at the office visit to ensure proper compliance and, ultimately, successful treatment of the condition.

Lastly, many patients often use ocular decongestants to soothe dry eyes. These drops "get the red out" but have minimal contact time with the eye, provide little lubrication, and can actually

Table 5-4

Selected Ophthalmic Lubricating Ointments (Brand Names)

Preserved

AKWA Tears Ointment Hypotears Ointment Lacri-lube SOP

Refresh PM Tears Renewed make the eye more red and dry, if used frequently. Inform all dry eye patients that they should stay away from these drops. These ocular decongestants do have a place (as will be discussed in the upcoming chapter), but that place is not in the treatment of dry eye.

There has been some research and clinical study looking at the use of viscoelastic agents extraocularly in the treatment of dry eye. Marketed under the name Ocucoat®, hydroxymethyl-cellulose is now available as a viscous artificial tear. Sodium hyaluronate has been applauded by some for its ability to promote tear film stability, but not all agree with this assessment.

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Responses

  • Zach
    Are viva eye lubricating drops available in local pharmacy?
    2 years ago

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