Prof. Wallace Chamon Profile

Prof. Wallace Chamon

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Publications (3)

Proceedings Article | 4 October 2023 Poster + Paper

Comparison between histogram of oriented gradients and convolutional features for keratoconus detection using corneal curvature maps

Lucas Orlandi de Oliveira, Felipe Marques de Carvalho Taguchi, Renato Feijó Evangelista, André Orlandi de Oliveira, Edson Shizuo Mori, Jarbas Caiado de Castro Neto, Wallace Chamon

Proceedings Volume 12675, 1267513 (2023) https://doi.org/10.1117/12.2677521

KEYWORDS: Feature extraction, Histograms of oriented gradient, Eye models, Education and training, Diseases and disorders, Visualization, Machine learning, Tomography, Performance modeling, Neurons

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Proceedings Article | 19 June 2015 Paper

Evaluation of eye tissue elasticity by means of sound propagation speed measuring in vivo

Joao Crispim, Adriano Bogar, Norma Allemann, Jarbas C. Neto, Wallace Chamon

Proceedings Volume 9531, 95310W (2015) https://doi.org/10.1117/12.2179598

KEYWORDS: Cornea, Optical coherence tomography, Tissues, Crystals, Eye, In vivo imaging, Ultrasonography, Ultrasonics, Tissue optics, Statistical analysis

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Introduction: To date, it has never been demonstrated the propagation sound speed in human corneas and lens in vivo. With the advent of Optical Coherence Tomography (OCT), it became possible to determine the dimensions of the ocular tissues without the interference of sound propagation speed and to use this information to define the real propagation sound speed for each patient and individualized structure. Aim: To determine the sound propagation speed in the cornea and lens from patients that theoretically exhibits differences in tissue elasticity (normal corneas and keratoconus, corneas of young and elderly patients, in addition to clear crystalline lens from young and elderly patients with cataract). Then, relate the determined velocity in each group with the expected tissue elasticity of the cornea and lens. Methods: We studied 100 eyes from 50 patients: 50 with keratoconus and no cataract and 50 with cataract and no corneal changes. All patients measured corneal and lens thickness by ultrasound methods (Ultrasonic Biomicroscopy - UBM and Ultrasonic Pachymetry - USP) and by OCT (RTVue®, Lenstar® and Visante®), then were divided into 2 groups: Group 1 (Cornea) analyzed the central corneal thickness (UBM, USP, RTVue®, Visante®, Lenstar®); Group 2 (Lens) analyzed the axial thickness of the lens (UBM and Lenstar®). Based on standard ultrasonic speed from USP (1640 m/s) and UBM (1548 m/s), we calculated the real sound propagation speed in each tissue. Results: Based on USP, the corneal sound speed on control group (1616 m/s) was faster than on keratoconus group (1547 m/s) (P < 0.0001). Based on UBM, the lens sound speed on cataract group (1664 m/s) was faster that on control group (1605 m/s) (P < 0.0001). Discussion: It is known that sound propagates faster in materials with lower elasticity. We found that the sound speed on keratoconic corneas (high elasticity) was slower and on cataract lens (lower elasticity) was faster than normal corneas and lens in vivo.

Proceedings Article | 26 February 2014 Paper

Elastography methods applicable to the eye

Altaf Khan, Soledad Cortina, Wallace Chamon, Thomas Royston

Proceedings Volume 8946, 89460B (2014) https://doi.org/10.1117/12.2037364

KEYWORDS: Cornea, Elastography, Wave propagation, Eye, Tissues, Doppler effect, Finite element methods, Vibrometry, 3D modeling, Motion measurement

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