Diurnal variation of ocular hysteresis in normal subjects: relevance in clinical context

Laiquzzaman, Mohammad; Bhojwani, Rajan; Cunliffe, I A; Shah, Sunil

doi:10.1111/j.1442-9071.2006.01185.x

Cited by 99 publications

(68 citation statements)

References 24 publications

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“…Kida et al (26) , and Laiquzzaman et al (27) found that CH remained almost constant throughout the day, whereas CCT and intraocular pressure showed statistically significant variations (higher values during the nocturnal period) in young adults. The small number of patients in both studies might restrict their findings to these specific populations.…”

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.

View full text Add to dashboard Cite

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“…In another study, an increase in CCT values was seen at night but corneal viscoelasticity did not change. 15 This is explained because of the change in hydration state, which can be said for dry-eye syndrome too. Karadayı et al 17 showed that the CCT in dry eyes increases rapidly after application of artificial tears.…”

Section: Discussionmentioning

confidence: 99%

“…According to Laiquzzaman et al 15 CH of normal subjects have the same values in both eyes, so right and left eyes were taken in one group. Diurnal variation of CH was evaluated and it was seen that CH values were steady within 24 h. 15,16 The mean CH value was calculated by three consecutive measurements taken in 5 min. CH was 10.56±0.25 mm Hg in the dry-eye group and 10.34±0.26 mm Hg in the normal population.…”

Section: Discussionmentioning

confidence: 99%

Corneal hysteresis in patients with dry eye

Fırat

Doğanay

2011

Eye

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“…38 Among these parameters, CH is the one that has been most evaluated in previous studies and is considered an indicator of the viscoelastic properties of the cornea. 31 CH is weakly correlated with CCT, is almost constant throughout the day, 39 and seems unassociated with refractive error or axial length. 40,41 ORA measurements show good within-session repeatability in normal volunteers.…”

Section: Perkins Handheld Tonometer (Medtronic Solan Jacksonville Fmentioning

confidence: 99%

Modalities of Tonometry and their Accuracy with Respect to Corneal Thickness and Irregularities

Moraes

Prata

Liebmann

et al. 2008

Journal of Optometry

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Recent advances in tonometry have led to the development of a number of devices with differing clinical applications. Their role in cases of abnormal corneal thickness and surface irregularities is particularly important, as inaccurate estimation of the true intraocular pressure (IOP) in such cases may lead to suboptimal evaluation. The purpose of the present review was to evaluate the accuracy of the most widely used devices in cases of corneal thickness and surface irregularities, based on a survey of the published literature. The analysis was based on a Medline search focusing mainly on papers that have evaluated the devices' accuracy with respect to corneal thickness and irregularities. Nine device types (Goldmann tonometer, Tono-Pen, Perkins tonometer, Ocular Response Analyzer, non-contact tonometer, pneumatonometer, I-Care rebound tonometer, Pascal dynamic contour tonometer (DCT) and Phosphene tonometer) were described in detail. Moreover, the physical principles and major utility of each tonometer were compared. Each of the many different commercially available tonometers has specific advantages and disadvantages. New non-invasive technologies are getting closer to a precise estimation of the true IOP. However, among all tonometers, none is highly accurate when both corneal thickness and surface irregularities are present. Fifty years after its development, Goldmann tonometry remains the gold standard to which all other devices are compared. RESUMENAvances recientes en el campo de la tonometría han propiciado el desarrollo de diversos dispositivos con diferentes aplicaciones clíni-cas. Resulta de particular importancia el papel que juegan en el caso de espesores corneales anormales o en presencia de irregularidades en la superficie de la córnea, puesto que, en esos casos, una medida imprecisa de la presión intraocular (PIO) real puede traer como consecuencia una valoración incorrecta del caso. El objetivo de esta revisión es evaluar el grado de precisión de los dispositivos más utilizados hoy en día en casos en los que existen irregularidades en la superficie de la córnea o en el espesor corneal. Para ello, se llevó a cabo una búsqueda de datos entre los artículos publicados. El análisis estuvo basado en una búsqueda bibliográfica realizada dentro de Medline, centrándose principalmente en aquellos artícu-los científicos que habían estudiado el grado de precisión del dispositivo en función del espesor corneal del paciente y de la presencia o no de irregularidades corneales. Se describen en detalle nueve tipos de dispositivos: tonómetro de Goldmann, Tono-Pen, tonómetro de Perkins, Ocular Response Analyzer, tonómetro sin contacto, neumotonómetro, tonómetro de rebote I-Care, tonómetro de contorno dinámico Pascal y tonómetro de fosfeno. Además, se presentan de forma comparada los principios físicos en los que está basado cada tonómetro y las situaciones en las que cada uno resulta de mayor utilidad. Cada uno de los distintos tonómetros disponibles en el mercado presenta ventajas y desventajas respecto...

show abstract

Diurnal variation of ocular hysteresis in normal subjects: relevance in clinical context

Cited by 99 publications

References 24 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

Corneal hysteresis in patients with dry eye

Modalities of Tonometry and their Accuracy with Respect to Corneal Thickness and Irregularities

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