Accuracy of cornea and lens biometry using anterior segment optical coherence tomography

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 $[mean±standarddeviation(SD)]d1$ by $+62±4μm$ and $d2$ by $+4±88μm$. The improved scheme reduces $d1$$(−0.4±4μm)$ and $d2$$(0±49μm)$ errors while also reducing $d3$ errors from $+218±90$ (uncorrected) to $+14±123μm$ (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 $0±23μm$, respectively, with the improved scheme. Those of the anterior and posterior lens surfaces reached $+2±22$ and $+11±71μm$, 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.