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B. Antona, E. Gonzalez, F. Barra, A. Barrio, I. Sanchez; Repeatability and Agreement in the Horizontal Ocular Deviation Measurements. Invest. Ophthalmol. Vis. Sci. 2009;50(13):3825.
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Clinical measurement of the ocular deviation (OD) is an important part of the optometric exam. In order to demonstrate if a significant change in the OD has occurred, it is important to determine the degree of repeatability of this measurement. The aim of the present study was to compare the measurements of OD determined by using one objective clinical method, the cover test (CT) and three different subjective clinical methods including the von Graefe method (VG), the Maddox rod test (MD) and the modified Thorington method (TH). These techniques differ in terms of either the method using to dissociate the eyes or the vergence components stimulated. The hypothesis was that the degree of repeatability of the four methods could be quite different and that the four techniques could not be interchangeable.
The OD was measured on two separate occasions in 61 visually normal subjects with a mean age of 19.7 years (range 18 to 32 years). In each method, all measurements were recorded by the same examiner. The repeatability of the tests and the agreement between tests was estimated by using the statistical method of Bland and Altman. We determined the mean difference (MD), the standard deviation of the differences (SD) and the 95% limits of agreement, i.e. the range over which 95% of values would be predicted to lie (MD ± 1.96·SD).
The 95% limits of agreement for the horizontal ocular deviation were: Far distance (6 m): CT: ±1.17Δ; VG: ±3.98Δ and MD: ±4.53Δ. Near distance (40 cm): CT: ±3.18Δ; VG: ±9.26Δ; MD: ±8.27Δ and TH: ±6.52Δ. The CT presented the best intra-examiner repeatability, with the smaller 95% interval of agreement. Comparing different techniques, the interval between the 95% limits of agreement correspond to substantial differences, always higher than ±4.35Δ. The highest interval corresponds to the comparison of CT with MD at near (±7.50Δ). OD measurements always showed better repeatability and better agreement at far vision than at near, probably because of the lower variability of accommodative response at far vision.
From the point of view of its intra-examiner repeatability, the cover test and the modified Thorington method were the recommended techniques to measure ocular deviation. The level of agreement observed between the four techniques was such that their interchangeable use in clinical practice is not recommended.
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