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Boss Daniel, Pavel Zakharov, Andrew Nolan, Michael C Mrochen; Eye motion compensation for accurate ocular biometry with a combined Purkinje mirror imaging (PMI) and optical low coherence reflectometry (OLCR) system.. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):1967.
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© ARVO (1962-2015); The Authors (2016-present)
Successful cataract surgery relies on accurate preoperative ocular biometric measurements based on which an appropriate intraocular lens (IOL) can be calculated. One important ocular parameter required to design a correct IOL is the axial length of the eye.<br /> Over the last years, optical low coherence reflectometry (OLCR) has become the standard of care for axial length measurements in cataract surgery due to its high precision and accuracy.<br /> However, because of the finite scanning time in OLCR, eye motions occurring during the measurement can induce motion artefacts. A simultaneous measurement of the eye position would allow to compensate for eye motion artefacts in OLCR and hence improve the accuracy of measured axial length.
A combined Purkinje mirror imaging (PMI) and OLCR setup was developed. The PMI modality allows for accurate anterior segment biometry. Additionally, the eye tracking capability of PMI allows to register eye motions during an OLCR measurement.<br /> To verify the eye motion compensations with PMI, a model eye was mounted onto translational stages and typical eye motion sequences were applied while OLCR measurements were performed.
Figure 1A shows a reconstructed OLCR envelope signal from a model eye with interference peaks at the anterior and posterior corneal surface (P1,P2), anterior and posterior lens surface (P3,P4) and the retina (RET). Figure 1B shows a 2-D plot of 26 consecutive OLCR scans that were obtained while an eye motion sequence was applied. A zoom-in on aligned interference peaks reveals that axial length differs between different scans due to uncompensated eye motion. After the signal was re-interpolated using PMI tracked eye position, scans show good alignment. (cf. Figure 1C).
By using a combined PMI/OLCR modality, eye motion artefacts in the OLCR signal could be compensated, improving thereby the reproducibility of axial length measurement. The proposed method for motion compensation could be applied to other devices such as optical coherence tomography for which eye motion compensation is critical.
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