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K.N. Dalton, R. Rogers, L. Jones; Physical Properties of Multi–Purpose Contact Lens Solutions . Invest. Ophthalmol. Vis. Sci. 2006;47(13):89.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the physical properties of commercially available multi–purpose contact lens solutions (MPS) .
The osmolality (Advanced Instruments Model 3320 osmometer), pH (VWR SB20 pH meter), viscosity (ViscoLab 3000 viscometer) and surface tension (Cahn DCA–322) of various contact lens MPS were measured at room temperature. Viscosity measurements were also taken at 34°C. The solutions examined were Alcon’s Opti–Free Express (OFX), AMO’s Complete Moisture Plus (COM) and Ultracare (UC), B&L’s ReNu MultiPlus (RNU) and Sensitive Eyes (SE) and CIBA–Vision’s AOSept® (AO), Clear Care (CC), SoloCare Aqua (SC) and SoftWear saline (SWS). The peroxide systems were measured before and after neutralisation.
The osmolality values indicated that several solutions were hypo–osmotic compared with tears, with typical values in the area of 285 to 310mOsm/Kg. Significantly lower values were obtained with OFX, at 225 mOsmol/Kg, while significantly higher values were found for unneutralised UC (945mOsm/Kg), AO (1325 mOsm/Kg), and CC (1319 mOsm/Kg). Post–neutralization, the osmolality decreased for all three peroxide–based solutions. The pH of most solutions was close to neutral (range 7.00 to 7.36), the exceptions being the peroxide systems prior to neutralisation (AO at 6.40, CC at 6.53, and UC at 3.33), neutralised AO (6.66) and CC (6.76), and OFX (7.82). The average viscosity of most solutions at room temperature fell within a range of 0.95 to 1.26 mPa.s, the exception being COM, which had a markedly higher viscosity of 3.02 mPa.s. At 34°C, the average viscosity of most solutions fell within a range of 0.70 to 0.83 nPa.s, except COM, which had a viscosity of 1.92 mPa.s. The surface tension values for the MPS differed markedly. AO (unneutralized and neutralized) and unneutralized UC were similar in surface tension to SWS, around 67 mN/m, while the other MPS exhibited surface tensions around 40 mN/m. The exceptions were OFX (31.2 mN/m) and SC (35.1 mN/m).
This study details many physical properties not readily available from manufacturers and indicates that they vary significantly among MPS. These characteristics may partly explain the reason some patients exhibit such strong preferences for certain care systems.
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