Ocular Biomechanics and Biotransport

Ethier, C. Ross; Johnson, Mark; Ruberti, Jeff

doi:10.1146/annurev.bioeng.6.040803.140055

Cited by 257 publications

(200 citation statements)

References 120 publications

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“…As Ethier et al (24) stated, material properties of the cornea are heterogeneous, highly anisotropic, nonlinear, and viscoelastic. In a broad review, Torres et al (25) described CCT and corneal collagen fiber density as the most important intrinsic factors determining corneal biomechanics.…”

Section: Discussionmentioning

confidence: 99%

Ability of corneal biomechanical metrics and anterior segment data in the differentiation of keratoconus and healthy corneas

Fontes¹,

Ambrósio²,

Jardim³

et al. 2010

Arq. Bras. Oftalmol.

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Purpose: To evaluate the sensitivity, specificity, and test accuracy of corneal biomechanical metrics and anterior segment data in differentiating keratoconus from healthy corneas. Methods: Comparative case series. Patients with and without keratoconus (gender and age-matched) were submitted for complete eye examinations including corneal hysteresis (CH) and corneal resistance factor (CRF) as measured by the Ocular Response Analyzer and anterior segment data as gathered through Pentacam assessments. The anterior segment data measurement included average central keratometric readings (K-Ave), corneal astigmatism (CA), central corneal thickness (CCT), anterior chamber depth (AC depth) and corneal volume (CV). All parameters were assessed, compared and analyzed. A receiver operating characteristic (ROC) curve was used to identify the best cutoff point by which to maximize the sensitivity and specificity of discriminating keratoconus from normal corneas for each data category. Results: Seventy seven eyes from forty three patients (24 male, 19 female) with keratoconus and eighty six eyes from forty three (24 male, 19 female) healthy controls were enrolled. ROC curve analysis showed poor overall predictive accuracy for all studied parameters in differentiating keratoconus from normal corneas. The highest sensitivity (79.2%) was obtained for both AC depth and CH (cutoff points 3.22 mm and 9.39 mmHg respectively). The best specificity (89.5%) and test accuracy (80.34%) were obtained for CA (cutoff point of 2.2 D). Conclusion: When considered together, studied parameters showed statistical differences between groups. However, when considered independently they presented low sensitivity, specificity and test accuracy in differentiating keratoconus from healthy corneas. Keywords: Cornea; Corneal diseases; Corneal topography; Biomechanics; Keratoconus. RESUMOObjetivo: Avaliar a sensibilidade, especificidade e acurácia de parâmetros biomecânicos e anatômicos do segmento anterior isolados na diferenciação de córneas saudáveis e com ceratocone. Métodos: Estudo tipo série de casos comparativa. Pacientes com ceratocone e controles saudáveis foram pareados (idade e sexo) e submetidos a exame oftalmológico completo, incluindo avaliação biomecânica (ORA) e tomográfica (Pentacam). Ceratometria central média, astigmatismo corneano, espessura corneana central, profundidade da câmara anterior, volume corneano, CH e CRF foram estabelecidos, avaliados e comparados. Curvas ROC (Receiver operating characteristic) foram utilizadas para identificar o melhor valor de corte que apresentasse a maior sensibilidade e especificidade na discriminação entre ceratocone e córneas saudáveis para cada dado estudado. Resultados: Setenta e sete olhos de 43 pacientes com ceratocone (24 homens e 19 mulheres) e 86 olhos de pacientes saudáveis (24 homens e 19 mulheres) foram incluídos no estudo. Curvas ROC mostraram baixa acurácia na predição do diagnóstico de ceratocone em todos os parâmetros isolados estudados. Maior sensibilidade encontrada foi 79,...

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Section: Discussionmentioning

confidence: 99%

Ability of corneal biomechanical metrics and anterior segment data in the differentiation of keratoconus and healthy corneas

Fontes¹,

Ambrósio²,

Jardim³

et al. 2010

Arq. Bras. Oftalmol.

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“…2A ). Unhindered transport across BrM of nutrients to and metabolites from the RPE is essential for normal vision by the photoreceptors ( 1,2 ). It has been instructive for us to analogize BrM, a wall of a capillary bed, to the intima of a large artery, due to its position between diffusion barriers, thickening throughout adulthood, and extracellular matrix composition ( 3, 4 ) (see below).…”

Section: Epidemiology and Risk Factorsmentioning

confidence: 99%

Apolipoprotein B-containing lipoproteins in retinal aging and age-related macular degeneration

Curcio

Johnson

Huang

et al. 2010

Journal of Lipid Research

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169

145

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“…Here we measured Brillouin scattering from the intact eye, to our knowledge for the first time, suggesting the possibility of in vivo biomechanical studies of the crystalline lens and cornea. Measuring their viscoelastic properties non-invasively with micrometre-scale resolution would greatly enhance our ability to understand their roles in a variety of ocular problems, such as presbyopia 29 , and to improve cornea tissue bonding and cataract surgery 30 . Further improving extinction, for example by cascading more VIPA stages, should make it possible to visualize and monitor the biomechanical properties of other tissues in situ at the cellular level.…”

mentioning

confidence: 99%

Confocal Brillouin microscopy for three-dimensional mechanical imaging

2007

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Acoustically induced inelastic light scattering, first reported in 1922 by Brillouin 1 , allows noncontact, direct readout of the viscoelastic properties of a material and has widely been investigated for material characterization 2 , structural monitoring 3 and environmental sensing 4 . Extending the Brillouin technique from point sampling spectroscopy to imaging modality 5 would open up new possibilities for mechanical imaging, but has been challenging because rapid spectrum acquisition is required. Here, we demonstrate a confocal Brillouin microscope based on a fully parallel spectrometer-a virtually imaged phased array-that improves the detection efficiency by nearly 100-fold over previous approaches. Using the system, we show the first cross-sectional Brillouin imaging based on elastic properties as the contrast mechanism and monitor fast dynamic changes in elastic modulus during polymer crosslinking. Furthermore, we report the first in situ biomechanical measurement of the crystalline lens in a mouse eye. These results suggest multiple applications of Brillouin microscopy in biomedical and biomaterial science.The mechanical properties of biological tissues and biomaterials are closely related to their functional abilities 6 , and thus play significant roles in many areas of medicine. For example, coronary arteries hardened by calcification can cause heart problems, mechanically weakened bones resulting from osteoporosis represent a serious orthopaedic concern, and the stiffness of the extra-cellular matrix influences drug delivery and cell motility 7 . As such, the ability to measure mechanical properties non-invasively in vivo at the microscopic (cellular) scale would have a wide range of biomedical applications, as well as uses in material science and engineering 8,9 .Conventional mechanical tests, such as dynamic mechanical analysis and rheometry, require mechanical forces to be applied to samples through contact and, although accurate and comprehensive, they are therefore not well suited to in situ high-resolution measurements. Miniaturized mechanical methods have become increasingly sophisticated 10 , but they are still limited to surface measurement. Elastography is a promising technique used to extract mechanical information from structural deformation images 11 ; however, sensitivity to the assumed stress distribution and physiological motion limit spatial resolution and measurement precision. Acoustic techniques, such as ultrasound and acoustic microscopy, are non-invasive and can offer microscopic resolution. However, these techniques tend to be effective only for Spontaneous Brillouin scattering is an inelastic scattering process arising from inherent density fluctuations, or acoustic phonons, in the medium (Fig. 1a). Brillouin spectroscopy measures spectral changes upon scattering, providing direct information on the phonon's properties that are closely related to the viscoelastic properties of the medium (see Methods). Previously, Brillouin spectroscopy has been used successfully to me...

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Ocular Biomechanics and Biotransport

Cited by 257 publications

References 120 publications

Ability of corneal biomechanical metrics and anterior segment data in the differentiation of keratoconus and healthy corneas

Ability of corneal biomechanical metrics and anterior segment data in the differentiation of keratoconus and healthy corneas

Apolipoprotein B-containing lipoproteins in retinal aging and age-related macular degeneration

Confocal Brillouin microscopy for three-dimensional mechanical imaging

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