The clinical gold standard for deriving vertical prism prescriptions is the patient's vertical associated phoria (The relieving prism to bring a vertical fixation disparity to zero). It is generally accepted that the most accurate device used to measure fixation disparity at nearpoint is the Sheedy disparometer. However, the Sheedy disparometer is relatively large, expensive and not currently manufactured. These factors may make measurements of vertical associated phorias less appealing and accessible to practitioners. This study evaluated the vertical associated phoria measurements of twenty non-asthenopic subjects with measurable vertical phorias. Vertical associated phoria measurements were made using the Sheedy disparometer and a unique inexpensive anaglyphic vertical fixation disparity test composed of a card with a specifically designed red and green image and a pair of standard anaglyphic glasses for the patient to wear. Both tests at 40 em and were administered in an equally randomized order. The results indicate that vertical associated phoria measurements with the anaglyphic test are statistically equivalent to the Sheedy disparometer (mean difference = 0.00; p= value >0.9999). Based on this study, this inexpensive anaglyphic card can be used to confidently derive an accurate vertical associated phoria value for vertical prism prescriptions. Other clinical considerations are discussed.
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