Phacoemulsification with Toric intraocular lens (IOL) implantation is the main surgery for curing cataracts with astigmatism. During this surgery, accurate astigmatic axis alignment of the toric IOL is crucial for the postoperative astigmatism correction effect. Automatic cyclotorsion identification through computer-assisted navigation can help guide doctors to quickly and accurately align the axis without markers. However, navigation can be easily hampered by illumination variation, instrument intervention, and inconspicuous biomarkers during surgery. Moreover, existing advanced methods are difficult to balance alignment accuracy and real-time performance. To address these challenges, we propose a toric IOL navigation framework based on learnable keypoint matching. The framework detects dense and reliable keypoint features in frames through a self-supervised lightweight neural network, and then uses semantic filtering and keypoint matching to complete the inter-frame cyclotorsion alignment estimation. During navigation, the keyframe is updated and inserted in real-time according to the matching quality to overcome accumulated alignment errors and potential abnormal matching. The framework was tested using a self-developed surgical dataset. Test results show that compared with other advanced methods, our framework achieves the lowest alignment error (0.71°) on a lowconfiguration computer, with a processing speed of 26.3 FPS, and can adapt to non-ideal surgical scenarios such as strong intervention, low texture, and weak illumination.
We give a discussion on the evolution properties of the finite array Airy beams (FAAB) in the misaligned slab system constituting of right handed materials (RHMs) and double negative materials (DNMs) on the basis of the light transfer matrix and the generalized Huygens-Fresnel integral equation. The beam intensity distribution on several observation plane and its side transmission view are investigated numerically with different misaligned parameters, which is beneficial to precise discussion of this beam transmitting in the misaligned optical model because the mishap is inevitable more or less in practical optical system design and manufacture. Moreover, we theoretically put forward a kind of Fabry-Perot resonator to detect Na2CO3 solution concentration based on the derived misaligned conclusions, the influence of curvature radius on the emerging beam’s evolution characteristics is discussed, the empirical formulae between FAAB’s normalized peak intensity and Na2CO3 solution concentration are derived by using the fit linear analysis in misaligned and aligned sensors, respectively. It is hoped that the related method and design philosophy can be applied in the environmental monitoring, medical care and public health chemical synthesis and so on.
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