Anterior chamber cell grading by optical coherence tomography

Abstract

Purpose: To quantify cells in the ocular anterior chamber (AC) by optical coherence tomography (OCT).

Methods: A time-domain anterior segment OCT system was used to image latex microsphere suspensions in vitro and the AC of uveitis and normal subjects in vivo. The OCT scan pattern, consisting of 2- and 4-mm-diameter concentric circular scans, was divided into central, superior, and inferior regions. A computer algorithm was developed to automatically identify particles in OCT images. A uveitis specialist used slit-lamp biomicroscopy to grade the AC cells on a scale of 0 to 4+.

Results: Latex microspheres and ac cells were visualized as reflective spots in oct images. OCT latex microsphere concentration measurements were highly correlated to known particle concentrations (r = 1.000) and had an efficiency of 0.72. in 30 nongranulomatous and 12 granulomatous eyes, the OCT cell counts correlated well with slit-lamp grades in all three regions (Spearman's rho coefficient: >0.63). The average OCT cell count was 3.7 cells/grade in nongranulomatous eyes and 2.0 cells/grade in granulomatous eyes. OCT revealed significant amounts of inferior AC cells in 5 of 16 quiescent uveitis eyes (mean ± SD: 19.9 ± 7.4 cells). OCT captured rare cells in normal eyes (1.1 ± 1.1 cells centrally).

Conclusions: OCT provided quantitative information on AC inflammatory cells. The OCT cell counts correlated well with clinical grading, and particles in the inferior AC that were missed by slit-lamp examination were detected by OCT. OCT could be a valuable tool for the diagnosis and management of anterior uveitis.

Conflict of interest statement

Disclosure: Y. Li, Carl Zeiss Meditec, Inc. (F); C. Lowder, None; X. Zhang, None; D. Huang, Carl Zeiss Meditec, Inc. (F, C, R), Optovue, Inc. (I, R), P

Figures

Figure 1.

OCT scan pattern for imaging the anterior chamber of the eye. (A) Concentric circular scans of 2- and 4-mm diameters were overlaid on a charge-coupled device image. (B) Data from the central, superior, and inferior regions were analyzed.

Figure 2.

In vitro experiment. (A) OCT images of the latex microsphere suspension in a cuvette. (B) 4-Connected pixel connectivity. (C) Plot of the OCT-measured particle concentration versus latex microsphere concentration.

Figure 3.

In vivo OCT images acquired with the “AC grading” scan pattern. (A) A normal example with no anterior chamber cells. (B) A nongranulomatous case with slit-lamp cell grade of 0.5+. Anterior chamber cells in the OCT image (circles) and in the magnified panel (arrows). A keratic precipitate (chevron) was present on the corneal endothelium in the central region. (C) A granulomatous case with slit-lamp cell grade of 2+. (D) A pigmentary case with pigment granules in the anterior chamber. (E) An abnormal quiescent uveitis case with cells in the inferior region.

Figure 4.

Bar plots of OCT cell counts versus slit-lamp cell grades. (A) Nongranulomatous eyes. (B) Granulomatous eyes.

Figure 5.

Bar plot of OCT cell counts in normal and quiescent uveitis cases.

Figure 6.

Illustration of the thermally driven aqueous humor circulation in the AC. (Diagram of the anterior chamber eye, courtesy: National Eye Institute, National Institutes of Health, Bethesda, MD.)