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Amy Livingston Davis, John Daniel Twelker, Joseph M Miller, Erin M Harvey; Inter-observer and Intra-observer Reliability of Measurements of the Obliquity of Palpebral Fissures. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2739.
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To determine inter-observer and intra-observer reliability of measurements of the obliquity of palpebral fissures.
Subjects were 40 pre-schoolers who attended the Tohono O’odham Early Childhood Headstart program. External photographs of the midface including a centimeter rule sticker attached to the forehead were taken in 40 children. Those images in the form of 35 mm slides were then scanned at a resolution of 5542 X 3766 pixels. Using the ImageJ image processing program (U. S. National Institutes of Health, Bethesda, Maryland, USA, http://rsb.info.nih.gov/ij) the following anatomic landmarks were identified in each of the images: left and right temporal and nasal canthal margins, corneal reflex, and lid margins above and below the corneal reflex. Two observers conducted landmark identification on all subjects, and one of the observers conducted landmark identification a second time on all images. A spreadsheet was used to generate a reference line between the two medial canthi which was then projected toward each lateral canthus. The angle of palpebral fissure obliquity was computed using the line from the medial and lateral canthus and the projected medial canthal line. Intra-observer reliability and inter-observer reliability of right eye measurements were assessed using paired t tests and correlation analysis.
The mean difference between intra-observer measurements (0.29deg (SD 2.10, 95% conf interval of diff -0.38 to +0.96)) and the mean difference between inter-observer measurements (-0.03deg (SD 2.81, 95% conf interval of diff -0.93 to +0.87)) were not statistically significant. Correlation was 0.91 for intra-observer measurements and 0.81 for inter-observer measurements (ps<0.001)
Digital analysis of external midface photographs is a reliable and repeatable procedure for evaluating the obliquity of the palpebral fissures. Future studies will utilize this method to assess the relation between astigmatic axis and the obliquity of palpebral fissure.
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