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Genis Cardona, Joan Gispets, Míriam Verdú, Carme Serés; Modification Of The Van Herick Technique For Objective Assessment Of The Anterior Chamber Angle. Invest. Ophthalmol. Vis. Sci. 2011;52(14):6271.
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The purpose of this study was to determine the influence of peripheral corneal thickness (PCT) on a modification of the Van Herick technique for objective assessment of the anterior chamber angle (ACA).
The Van Herick technique (Van Herick, Shaffer & Schwartz, Am J Ophthalmol, 1969) has been traditionally employed as a non-contact alternative to gonioscopy to estimate the ACA by comparing the width of the cornea with the width of the anterior chamber or dark area (DA). Temporal slit-lamp optic section images of 82 eyes (ages 21 to 38 years) were captured and the width of the cornea and DA were measured via digital image analysis. The ratio of these values was used to classify eyes as having open (grades 3 & 4) or closed (grades 1 & 2) ACAs. Scheimpflug photography (Pentacam, Oculus, Inc.) was used to determine PCT and ACA of the same eyes, applying a cut-off value of 29.5 degrees (Hong et al, Yonsei Med J, 2009) as threshold for angle closure.
Objective image analysis revealed 8% closed and 92% open ACAs. Scheimpflug image ACAs and PCT ranged from 28 to 59 degrees (9% closed angle; 91% open angle) and from 516 to 709 µm, respectively. Although differences between objective and Scheimpflug ACAs were not statistically significant, probably as a result of the higher incidence of open ACAs in our sample, a total of 6 patients with a Scheimpflug ACA < 29.5 degrees were incorrectly classified as open angle with the objective Van Herick assessment. Width of DA and PCT were not correlated (r=-0.17; p=0.116), thus suggesting that, given the encountered disparity in PCT, comparison of the width of the DA with the width of the optic section may lead to frequent errors in the assessment of ACAs. A moderate association was found between Scheimpflug ACAs and width of DA (r=0.41; p<0.001).
The results of this study suggest that even if the Van Herick technique may benefit from image analysis, the objective measurement of the width of the DA may permit a better estimation of ACA by preventing the influence of the high intersubject variability in PCT. Some more work with a wider sample, including more closed angle eyes, is necessary.
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