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G. M. Notz, K. C. Dimiceli, M. Stahl, T. W. Wilson, A. V. Levin; Corneal Diameter Analysis Using External Photography. Invest. Ophthalmol. Vis. Sci. 2010;51(13):6307.
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Measuring corneal diameter with calipers has been the gold standard.The purpose of this study is to evaluate the accuracy of twotechniques to measure corneal diameter: standard calipers andcorneal rings versus digital photography.
We developed a corneal diameter model card which included precisecircles of corresponding diameter in millimeter and a rulerfor control. Pediatric and adult patients were measured usingcalipers. Diameters were also recorded for the corneal ringwhich most closely approximates the dimension of the limbuswhen held in front of cornea. Digital photographs were takenwith model cards held at the plane of the cornea. Corneal diameterwas measured comparing corneal images to standard circles andthe control ruler. Data was de-identified and separated suchthat the caliper and ring measurements and photographic measurementswere recorded by separate investigators at separate times inorder to prevent bias.
Statistical analysis has been initiated. We have compared caliperand ring measurements experimentally and ruler and model cardcircles photographically. 100% of photographic measurementsbetween ruler and model card circles are within 0.5mm of eachother, 95% CI [88%-100%]. 87% of experimental caliper and cornealring measurements are within 0.5mm, 95% CI[69%-96%]. N= 30.
Initial results demonstrate that our external photographic designis accurate when comparing ruler and model card circle measurements.Using external photography could facilitate accurate and moreeasily obtainable corneal measurements in young or uncooperativepatients.
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