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Marita P. Feldkaemper, Eva Burkhardt, Frank Schaeffel, Alexandra Marcha Penha; Comparison of A-scan Ultrasound and Low Coherence Interferometry in the Chicken Eye under Different Experimental Conditions. Invest. Ophthalmol. Vis. Sci. 2012;53(14):3439.
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To compare ocular biometry using A-scan ultrasonography (3M Echorule) and low coherence interferometry (Lenstar LS900) in the chicken eye. The purpose of the present study was to analyze the correlations between both techniques and to find out whether the Lenstar might be a feasible method for measurement of retinal and choroidal thickness in the chicken eye.
Two-week old chicks (n=42) were measured. Bland-Altman plots, repeatability and correlation analyses were calculated for both methods. In addition, two week old chicks (n=6) were binocularly treated with +7D lenses and intravitreally injected with saline in one eye and insulin (0.015 nmol Insuman rapid, Aventis, Frankfurt, Germany) in the contralateral eye. Lenstar measurements were taken after four days of lens wear.
There was a high correlation between ultrasonography and low coherence interferometry for anterior chamber depth (ACD), vitreous chamber depth and axial length, but not for lens thickness. Measurments of the Lenstar were more consisten (smaller coefficient of variation). Bland-Altman plots showed that ultrasound provided larger values for all compartments, except for ACD (differences between Echorule and Lenstar -0.11 ± 0.12 mm). Consistent with previous studies, insulin injections in positive lens treated animals increased axial length compared to saline injected eyes. Retinal thickness as measured with the Lenstar significantly increased in the insulin injected animals (insulin vs. saline: 285 ± 17 μm vs. 251 ± 10 μm, paired t-test: p < 0.01). Choroidal thickness could only be measured in some of the chicks.
A high correlation between both instruments was found for three of the four parameters. However, since the absolute values were different, both techniques cannot replace each other. While consistency was better with the Lenstar, a disadvantage is that it can only be used in anesthetized chicks. Retinal thickness increased after insulin injections as measured with the Lenstar.
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