Most custody transfer flow meters fall into one of four categories: ∗∗ Centipoise (cP) = Specific Gravity × Centistokes (cSt).įor measurement since the 1930s however, in the last 10–15 years, other technologies have emerged that can offer improved cost/benefit ratios, depending on the viscosity and temperature of the fluid and the required accuracy of the meter. Typical Viscosity in cP ∗∗ degrees F (degrees C) By referring to the table, we find the conversion factor to be 2.09 (10 −3). To convert absolute or dynamic viscosity from one set of units to another, locate the given set of units in the left-hand column and multiply the numerical value by the factor shown horizontally to the right under the set of units desired.Īs an example, suppose a given absolute viscosity of 2 P is to be converted to slugs/foot second. The apparent dose-response of the CMC preparations with regard to staining suggests that CMC has a direct and protective effect on ocular surface integrity.∗ Pound f = Pound of Force † Pound m= Pound of Mass Conclusion: These clinical data indicate that a mid-viscosity 1% CMC artificial tear may have enhanced benefit for dry eye patients over conventional low-viscosity products, without compromising patient acceptability. The acceptability and preference survey indicated that a large percentage of patients found the mid-viscosity tear no more blurring than low-viscosity tears in practical use, and that it generally required less frequent application than previously-used tear preparations. Results: Both treatment groups (low- and mid-viscosity tears)experienced a significant reduction compared to baseline in staining and symptom scores at day 7 (p<0.001), and the mid-viscosity group experienced a further reduction in staining at day 30 (p<0.01). In a further study, 465 current users of a variety of artificial tear products were given either the mid-viscosity tear or one of several current low-viscosity tears, and surveyed for acceptability and preference over the preparation they used previously.
Patients were assessed at days 7 and 30 for signs and symptoms of dry eye, including corneal and conjunctival staining and a standardized symptom survey. All subjects used a conventional artificial tear (Visine Tears, Pfizer) for 2 weeks prior to the study. Methods: 103 subjects with mild to moderate dry eye were given either a low-viscosity 0.5% CMC artificial tear (Refresh Tears, Allergan) to use 4 times a day for 1 month. This study has investigated the clinical performance of this product. Recently, a new mid-viscosity dry eye drop (60-90 cps) has been introduced, which has been formulated with a unique mixture of mid- and high-molecular weight carboxymethylcellulose (CMC). Viscosities of most common dry eye products have been either low (<10 cps) or very high (≷300 cps). Many of these demulcents are polymers which may be prepared from a range of molecular weights at various concentrations, resulting in a specific viscosity.
Purpose: Current dry eye treatments are primarily lubricant eye drops containing one or more recognized opthalmic demulcents.
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