Editorial: Laser flare (cell) photometry: 20 years already

Abstract

Two decades ago, Sawa et al. [1] published an article entitled ‘‘New quantitative method to determine protein concentration and cell number in the aqueous in vivo’’ in the Japanese Journal of Ophthalmology. This work represented a milestone in the evolution of measurement of intra-ocular inflammation. The laser flare (cell) photometer (LF(C)P) became commercially available in 1989–1990 and this technology promoted flare from a qualitative parameter to the only quantitative modality we have to measure intraocular inflammation. In 1954, the first grading system of anterior intraocular inflammation using slit-lamp observation of the aqueous humor was proposed by a group of clinicians from the Proctor Foundation and had the merit of standardizing, at least in theory, inflammatory levels in the anterior chamber [2]. Although the system was supposed to set precise standards, it left a lot of space, especially as far as flare was concerned, for interobserver and intra-observer variation, as it was a subjective system based on individual interpretation of slit-lamp findings. As far as aqueous cells were concerned, the system was somewhat more precise as the counting of cells with the slit-lamp is possible to a certain extent, but it remained, nevertheless, semiquantitative at best. In 2004, uveitis specialists from around the world convened in Baltimore following the invitation of a group of American clinicians to decide on a new standardization system for uveitis nomenclature (SUN workshop) and, despite the fact that LFP had been on the market for more than 10 years and its sensitivity and reliability had been proven without question, the SUN workshop took over the Proctor Criteria almost unchanged for the assessment of intraocular inflammation [3]. Laser flare photometry (LFP) basically relies on the same principles as slit-lamp evaluation of flare. As for slit-lamp flare measurement, there is an incoming light beam and the quantity of diffracted light, proportional to the amount of cloudy matter in the aqueous humor (proteins), is measured. However the non-quantifiable polychromatic incident beam of the slit-lamp has been replaced by a quantifiable laser beam in LFP and the measuring device, the subjective human eye, is replaced by an objective photomultiplier–photodetector. Many studies were performed to show the immense superiority of this quantitative and objective method. In this issue a review article on LFP details the different studies that have been performed over the years [4]. Laser flare photometry was, at first, thought to be especially suited for clinical studies on intra-ocular C. P. Herbort (&) Inflammatory and Retinal Eye Diseases, Centre for Ophthalmic Specialized Care (COS), Clinique Montchoisi, Lausanne, Switzerland e-mail: carl.herb@bluewin.ch