Purchase this article with an account.
Ken Marion, Moritz Niemeyer, Srinivas R Sadda, Vikas Chopra; Dynamic Analysis on the Effects of Lighting Variation on Anterior Chamber Angle Metrics with Cirrus Spectral Domain Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4838.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
To evaluate the impact of variations in ambient lighting conditions on the reproducibility and reliability of novel Schwalbe’s Line-based anterior chamber angle (ACA) metrics using the Cirrus spectral domain optical coherence tomography instrument.
The inferior irido-corneal angles of 25 normal eyes were imaged twice with the Cirrus SD-OCT under light-meter controlled conditions at five different light levels (measured with a light meter at camera/eye interface), as well as with and without the corneal illumination (CI) function. Thus in total, each eye was imaged 20 times for a total of 500 assessments. Schwalbe’s line angle opening distance (SL-AOD) and Schwalbe’s line trabecular-iris-space area (SL-TISA) were graded twice by masked, certified graders at the Doheny Imaging Reading Center using customized ImageJ grading software. Percent differences in measurements from the brightest to darkest ambient light levels (with or without CI) were computed. Intra- and inter-grader reproducibility was evaluated at each lighting level by absolute mean difference (AMD), absolute error (AE), mean percent difference (MPD), coefficient of variation (CV), intra-class correlation coefficient (ICC), spearman correlation (R2), and Bland-Altman plots.
With the CI function ON, decreasing the ambient light level from 1.0 to 0.0 foot-candles decreased the average SL-AOD measurement from 394µm+/-137µm to 356µm+/-137µm (MPD 10.71%) and the average SL-TISA measurement from 297µm2+/-114µm2 to 261µm2+/-109µm2 (MPD 13.7%). With the CI function OFF, the average SL-AOD measurement decreased from 366µm+/-136µm to 329µm+/-122µm (MPD 10.9%) and the average SL-TISA measurement from 271µm2+/-113µm2 to 234µm2+/-98µm2 (MPD 15.8%). Intra- and inter-grader results showed excellent reproducibility at each light level with and without CI. Bland-Altman plots of all comparisons did not demonstrate any apparent bias, with similar repeatability at various SL-AOD and SL-TISA values.
Anterior chamber angle morphometrics are exquisitely sensitive to changes in ambient illumination and even the illumination generated by the OCT instrument. These findings highlight the importance of strictly controlling lighting conditions when studying anterior chamber geometry.
This PDF is available to Subscribers Only