Dry eye is one of the most common conditions encountered

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					Clinical                                                        .
                                                       Jeffrey P Gilbard MD and Dennis Pardo OD

      Lubricant eye drops
      The electrolyte factor
                                                                                                       terms of their electrolyte composition.
                                                                                                       Some have little or no electrolyte content,
               ry eye is one of the most common conditions encountered

                                                                                                       and even those companies that make a
               by eyecare professionals. The literature suggests that                                  serious attempt to duplicate the electrolyte
               about 14% of adults over 40 experience ocular dryness                                   balance of healthy tears only approximate
               and discomfort. The prevalence among contact lens                                       these concentrations.
       wearers is even higher, given that typical wearers are older, use                                  In an independent clinical study8,
       multipurpose solutions or wear continuous wear lenses1-3.                                       TheraTears™ was shown to restore
                                                                                                       conjunctival goblet cells in dry eye seen
     One of the mainstays of addressing these              Published studies have shown that           after LASIK vision correction surgery.
     common issues is the use of topical               electrolytes such as potassium are critical     Patients were treated with the TheraTears
     lubricants. The marketplace, however, is          to the maintenance of normal conjunctival       solution at least four times a day and, at
     crowded with lubricant eye drops or               goblet-cell density. Other important            night, one drop of a 1% CMC solution
     comfort drops. So, the question arises:           electrolytes in the tear film include           was applied. Controls were treated with a
     apart from viscosity and the presence or          sodium, calcium, magnesium and                  preservative-free balanced salt solution. At
     absence of a preservative, are all drops          bicarbonate (four concentrations,               one week and one month, respectively,
     similar? And if not, what are the                 see Table 1).                                   87.5% and 100% of TheraTears-treated
     differences?                                                                                      patients were free of dry eye symptoms,
        This article discusses one difference that     Imbalance and toxicity                          while only 12.5% and 20% of control-
     appears to have significant bearing on            Conversely, an imbalance of electrolytes in     treated patients were symptom free. When
     providing discernable relief – the amount         the tear film is associated with what can       the authors looked at goblet cell density by
     and ratio of electrolytes in lubricant eye        be called ‘electrolyte imbalance toxicity’.     impression cytology after one month of
     drops.                                            For example, toxicity caused by                 treatment, the TheraTears solution was
                                                       preservative-free sodium chloride solution      shown to significantly restore conjunctival
     Maintaining the balance                           has been demonstrated in rabbit eyes and        goblet-cell density while treatment with
     The ocular surface epithelium is unique in        in tissue culture4-6.                           preservative-free control did not.
     that it does not have a blood supply. It              The toxicity caused by an electrolyte          Two subsequent studies9,10 found that
     derives its electrolytes and oxygen from the      imbalance causes the same changes that          patients who started using TheraTears
     tear film. The tear film, in other words, is a    are seen in dry eye disease, i.e. increased     about one week before LASIK surgery saw
     vital fluid and, as such, the electrolyte         corneal epithelial cell desquamation and        better faster, and felt more comfortable
     balance of that fluid is crucial for              loss of conjunctival goblet-cell density. The   than those who did not.
     biological function. If serum electrolytes        signs and symptoms of electrolyte
     are out of balance, for example, the              imbalance toxicity are therefore                Summary
     consequences can be deadly, so the                indistinguishable from those of dry eye.        Peer-reviewed studies and other clinical
     electrolyte balance in Lactated Ringers               The good news is that using better-         studies have shown that matching the
     (used as a serum substitute) must match           balanced lubricant eye drops helps to           electrolyte balance of the human tear film
     that of real serum. Similarly, the                restore the ocular surface. In the 1980s,       allows for an increase in conjunctival
     electrolytes in the balanced salt solution        Wilson, O’Leary and Bachman found they          goblet-cell density. If your patients are not
     used intraocularly during eye surgery must        could decrease the corneal desquamation         getting satisfactory results from their
     match those of the aqueous humour. The            caused by preservative-free sodium              lubricant eye drops, electrolyte imbalance
     same reasoning applies to the tear film, in       chloride by adding certain electrolytes to      could be part of the problem.
     that the electrolytes in eye drops need to        the solution7.
     match those of the tear film.                                                                     About the authors
         In our research, we found that unless         Electrolytes as a catchphrase                   Dr. Jeffrey Gilbard is an ophthalmologist
     an eye drop had an electrolyte balance that       Given the importance of electrolytes to the     who began his research program on dry
     precisely matched that of the human tear          health of the ocular surface, it is not         eye in 1976 as a medical student at
     film, there was a loss of conjunctival            surprising that many companies now              Columbia University. He developed the
     goblet cells (conjunctival goblet-cell            compete by touting the electrolyte              tear osmolarity test for dry eye and has
     density is a very sensitive indicator of          composition of their products. However,         since written over 40 original articles,
     ocular surface health, and goblet cells           all formulations are different, especially in   reviews and book chapters on dry-eye
     provide the natural lubrication for the                                                           disease. He is a Clinical Assistant Professor
     ocular surface)4.                                                                                 of Ophthalmology at Harvard Medical
                                                                                                       School and Founder & CEO of Advanced
           Electrolyte          Concentration                                                          Vision Research. Dr. Dennis Pardo is a
                                (mMol/Litre)                                                           graduate of The New England College of
                                                                                                       Optometry. After completing a Primary
           Sodium (Na)          132
                                                                                                       Care Residency he joined the Faculty at
           Potassium (K)        24                                                                     NEWENCO as an Associate Clinical
           Bicarbonate (HCO2)   32.8                                                                   Professor. Dr. Pardo also holds a Master’s
           Calcium (Ca)         0.8                                                                    degree in Public Health from Yale
                                                                                                       University School of Medicine. As Director
           Magnesium (Mg)       0.61                                                                   of Professional Relations for Advanced
                                             Table 1                                                   Vision Research, Dr. Pardo lectures
                    Normal electrolyte concentration                                                   extensively on dry eye topics to eye care
                                     in human tears8                                                   professionals and optometry students.

     Reprinted from OT (Optometry Today/Optics Today) July 15, 2005

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