Inflammation and Blood–Aqueous Barrier Disruption
We agree with Drs. Laurell and Zetterström that laser flare photometry provides an indirect measure of the anterior chamber inflammatory response. In a study comparing the laser flare-cell meter and fluorophotometry in assessing the BAB after cataract surgery, Shah and coauthors1 found that although both techniques measure different parameters, both were able to document the integrity or breakdown of the BAB. Fluorophotometry was useful in documenting the integrity or breakdown of the BAB, but the laser flare meter appeared to be more sensitive in quantifying subtle changes in barrier function to large proteins. As the BAB recovers, reduction in the apparent size of tight junctions results in not only a decrease in protein concentration in the anterior chamber, but also a relative reduction in higher MW proteins. These changes would be expected to have a relatively greater effect on flare, as measured by laser photometry, than on the anterior chamber concentration of a small molecule such as fluorescein, which would not be as sensitive to changes in tight junction size above a certain threshold value. Therefore, laser photometry is more useful for detecting sequential change in BAB function, whereas fluorophotometry is more sensitive in detecting when the BAB has fully recovered.
Both laser flare photometry and fluorophotometry are highly sensitive methods of measuring anterior chamber inflammation. Minute differences in flare levels documented by either technique may therefore not have significant relevance at the clinical level. Laser flare photometry still has the advantage over fluorophotometry in being rapid, reproducible, totally noninvasive, and relatively easy to use. It is therefore an important and useful tool for large-scale clinical trials.
Soon-Phaik Chee FRCS(G)
Seng-Ei Ti FRCS(Ed)
Donald T.H. Tan FRCS(G)
© 2000 by Lippincott Williams & Wilkins, Inc.
1. Shah SM, Spalton DJ, Allen RJ, Smith SE. A comparison of the laser flare cell meter and fluorophotometry in assessment of the blood-aqueous barrier. Invest Ophthalmol Vis Sci 1993; 3124-3130