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Michael Stock, David Salvay, Kisha Piggott, Bradley Shoss, Susan M Culican; Obtaining Lissamine Green 1% Solution for Clinical Use. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):5744.
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© ARVO (1962-2015); The Authors (2016-present)
With new compounding pharmacy laws, the only economically feasible approach to using lissamine is through dye-impregnated strips. This research aims to determine the concentration of lissamine that can be obtained using a single commercially-available lissamine strip. With the optimal vital staining requiring 1% concentration of lissamine we sought to obtain this concentration using supplies in an ordinary ophthalmology clinic.
A standard curve was generated using compounded lissamine green 1% solution. Three different serial dilutions were made with preservative-free artificial tears (PFATs), basic salt solution (BSS), and proparacaine. Serial dilutions were measured by a sphectrophotometer at a wavelength of 633 micrometers. A single lissamine strip was wetted with 50 microliters (equivalent of 1 drop).This was done with each of the 3 solvents. Dilution series were made from each of these and tested. Using the standard curves, the concentrations were calculated. Next, combinations of number of strips, amount of solvent, and absorption time in a microcentrifuge tube were performed. Serial dilutions of these combinations were measured with an aim of attaining a 1% solution. Combinations that produced 1% solutions were reproduced and re-measured. Cost analyses were then performed to select the most economical method.
Single lissamine strips wetted with any of the solvents produced a 0.17%±0.05% (95% confidence interval) lissamine solution (PFATs 0.10%±0.02%, BSS 0.18%±9.2%, and proparacaine 0.21%±7.5%). This is at least a 5-fold weaker concentration than the optimal for vital staining. Combinations of 4 strips in 200 microliters (4 drops) for 1 minute and 2 strips in 200 microliters for 5 minutes were both found to reach concentrations of 1%. Cost analysis shows the 2 strip/ 4 drops/ 5 minutes method to cost $0.67 and 4 strips/ 4 drops/ 1 minute method $1.27.
Use of a single lissamine strip leads to suboptimal concentrations for vital staining. With only the addition of disposable microcentrifuge tubes to the clinical setting, ophthalmologists can make 1% solutions of lissamine. This solution is both more economical as well as in compliance with both state and national compounding laws.
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