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We assess the accuracy of the Visante anterior segment optical coherence tomographer (AS-OCT) and present improved formulas for measurement of surface curvature and axial separation. Measurements are made in physical model eyes. Accuracy is compared for measurements of corneal thickness (d₁) and anterior chamber depth (d₂) using-built-in AS-OCT software versus the improved scheme. The improved scheme enables measurements of lens thickness (d₃) and surface curvature, in the form of conic sections specified by vertex radii and conic constants. These parameters are converted to surface coordinates for error analysis. The built-in AS-OCT software typically overestimates [mean±standard  deviation(SD)]d₁ by +62±4  µm and d₂ by +4±88µm. The improved scheme reduces d₁ (−0.4±4  µm) and d₂ (0±49  µm) errors while also reducing d₃ errors from +218±90 (uncorrected) to +14±123  µm (corrected). Surface x coordinate errors gradually increase toward the periphery. Considering the central 6-mm zone of each surface, the x coordinate errors for anterior and posterior corneal surfaces reached +3±10 and 0±23  µm, respectively, with the improved scheme. Those of the anterior and posterior lens surfaces reached +2±22 and +11±71  µm, respectively. Our improved scheme reduced AS-OCT errors and could, therefore, enhance pre- and postoperative assessments of keratorefractive or cataract surgery, including measurement of accommodating intraocular lenses.

©2007 Society of Photo-Optical Instrumentation Engineers