Laser flare-cell photometer: principle and significance in clinical and basic ophthalmology

Abstract

A slit-lamp examination is an indispensable and essential clinical evaluation method in ophthalmology, but, it is qualitative subjective. To complement its weaknesses in making a quantitative evaluation of flare intensity and number of cells in the aqueous humor in the eye, we invented the laser flare-cell photometer in 1988. The instrument enables a non-invasive quantitative evaluation of flare intensity and number of cells in the aqueous with good accuracy and repeatability as well as maneuverability equal to slit-lamp microscopy. The instrument can elucidate the pathophysiology in the blood-aqueous barrier (BAB) function in a variety of ocular disorders. The accuracy of the instrument makes it possible to investigate not only the pathophysiology of intraocular disorders but also the effects of various drugs and surgical procedures in BAB. The instrument does not only lighten the burden on patients in clinical examinations and study but it also helps minimize the sacrifice of experimental animals and improves the reliability of the results by minimizing inter-individual variations through its good repeatability. Here I shall relate how the instrument has been applied to clinical and basic studies in ophthalmology and what novel knowledge its application contributed to pathophysiology in ophthalmology.

Ocular Spot Fluorometer Equipped With a Lock-In Amplifier for Measurement of Aqueous Flare

“…The breakdown of the blood–aqueous barrier (BAB) and the appearance of inflammatory cells in the anterior chamber (A/C) are the hallmarks of uveitis. 1–3 The collapse of BAB results in the release of serum proteins into A/C. The inflammatory cells and proteins scatter light (i.e., Tyndall effect) giving rise to aqueous flare.…”

“…The inflammatory cells and proteins scatter light (i.e., Tyndall effect) giving rise to aqueous flare. 1,3 One conventional approach to scoring the severity of uveitis is based on grading the intensity of aqueous flare using slit-lamp biomicroscopy as per Standard Uveitis Nomenclature (SUN) scoring system. 4 According to SUN classification, the aqueous flare is graded 0 in the absence of any notable flare, 1+ for faint flare, 2+ for moderate flare (iris and lens details clear), 3+ for marked flare (iris and lens details are hazy), and 4+ for intense flare (fibrin in the aqueous humor).…”

“…4 The scoring system, albeit subjective, is frequently employed in the clinical management of uveitis. 1,3–5 The subjective nature of SUN scoring leads to significant intra- and interobserver variability. Moreover, the grading does not offer sufficient granularity (i.e., subdivisions between 0 to 1+, 1+ to 2+, and 2+ to 3+) that would be essential for evaluation of the efficacy of drugs or modalities of drug delivery toward the treatment of uveitis.…”

Flaremetric evaluation of blood-aqueous barrier breakdown in diabetic patients after phacoemulsification and intraocular lenses with or without heparin-coated surface implantation

“…This phenomenon is featured by influx of serum proteins and inflammatory cells into the aqueous humour of anterior and posterior chamber as a consequence of BAB breakdown. In the aqueous of anterior chamber these elements can be detected quantitatively using laser flare photometry [5].…”

Instrument-based Tests for Measuring Anterior Chamber Cells in Uveitis: A Systematic Review

“…LFCP became available in 1988 and uses the light scattering properties of AC particles to quantify the concentration of inflammatory materials in the aqueous humor. It has been primarily validated as a tool for measuring AC flare, 10 the cloudy appearance given to the aqueous during inflammation, however several models also have the ability to count AC cells. AS-OCT provides cross-sectional scans of the AC and can capture cells in aqueous humor as hyper-reflective dots.…”