Acoustic parameters of ocular tissues

doi:10.1016/0301-5629(85)90018-3

Ultrasound in Medicine & Biology

Volume 11, Issue 1, January–February 1985, Pages 157-161

https://doi.org/10.1016/0301-5629(85)90018-3 Get rights and content

Abstract

The sound velocity and the impedance of animal eyes and human eyes are measured by high frequency RF echograms (10 MHz) using a digital computer. The results are compared to literature data from 1955 to 1965, which were obtained with completely different techniques. The pig's eye appears to be a good animal model for the human eye in ultrasonic experiments. The reflectivity levels predicted from the impedance values correspond to known relative reflectivity levels obtained in clinical routine.

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Cited by (38)

A-scan ultrasound in ophthalmology: A simulation tool
2021, Medical Engineering and Physics
In the present study, we developed a computational tool for simulating the ophthalmological applications of A-scan ultrasound, including cataract characterisation and biometry. A-scan biometry is used to measure the axial length (AL) of the eye before cataract surgery to calculate the refractive power of the intraocular lens to be implanted. Errors in the measurement of the AL lead to post-surgical refractive errors. The simulation tool was developed using the k-Wave Matlab toolbox, together with a user-friendly interface developed in Matlab.
Diverse error sources were evaluated. Constant ultrasound speed assumptions may introduce refractive errors of up to 0.6 D; by contrast, probe positioning errors had a lower impact, of up to 0.11 D. The correct identification of the Bruch's membrane is limited not only by axial resolution constraints but also by the low reflection coefficient at the retina/choroid interface. Regarding cataract characterisation, the amplitudes of the echoes reflected at the lens interfaces are sensitive to diverse cataract types and severities, and a more realistic representation could be obtained by using a higher resolution in the eye grid; however, the required computational times would make simulations impracticable when using personal computers. The simulation tool shows good versatility for evaluating diverse aspects of A-scan biometry.
Complementary capabilities of photoacoustic imaging to existing optical ocular imaging techniques
2020, Diabetes and Retinopathy: Volume 2: Computer-Assisted Diagnosis
Since 1886, when the first picture of the human retina was taken, ocular imaging has played a crucial role in the diagnosis and management of ophthalmic diseases. One of the biggest contributors to the advancement of ocular imaging is the adoption of optical imaging techniques. Optical imaging is a method of looking into the body in a noninvasive way, like X-rays. However, unlike radiological imaging techniques that use ionizing radiation, optical imaging uses light and the properties of photons to produce detailed images ranging from structures as small as cells and molecules to structures as large as tissues and organs. There are plenty of advantages of using optical imaging compared to radiological imaging. For one, optical imaging is much safer for patients since it uses nonionizing radiation to excite electrons without causing damage. Additionally, since it is fast and safe, optical imaging can be used to monitor acute and chronic diseases, as well as treatment outcomes. Optical imaging is also useful for imaging soft tissue since different types of tissues absorb and scatter light differently. Finally, optical imaging can advantageously use varying colors of light to see and measure multiple properties of tissues at a time. Therefore, it is no surprise that the optical imaging modalities of fundus photography in the 1920s, scanning laser ophthalmoscope (SLO) imaging in 1981, and optical coherence tomography (OCT) in 1991 have touted a “golden age” in ophthalmic imaging applications. A new technology, photoacoustic imaging, has been shown to have promising features that could make it the next major imaging technique in ophthalmology. Additionally, photoacoustic imaging (PAI) can combine with preexisting optical microscopic imaging modalities to achieve multimodal imaging of the eye. In this chapter, we present a brief overview of fundus photography, SLO, and OCT while discussing the potential of PAI as the next major ocular imaging modality.
The Globe's Eccentric Rotational Axis: Why Medial Rectus Surgery Is More Potent than Lateral Rectus Surgery
2018, Ophthalmology
This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy).
The article tested the assumption during horizontal ductions that tables typically recommend greater lateral rectus than medical rectus surgical doses for horizontal strabismus of any given magnitude. The authors were made aware of a flaw in their analysis, and after re-analyzing MRI data on the ocular center of rotation using the appropriate mathematics acknowledge that the data in Table 2 of the paper are quantitatively inaccurate, and correct only insofar as the ocular rotational axis is in fact different from the geometric center of the globe. This fundamentally undermines the stated attempt to demonstrate that eccentric location of the ocular rotation axis towards the medial rectus and away from the lateral rectus explains the differential effect of medial and lateral rectus muscle procedures.
Measurement of corneal tangent modulus using ultrasound indentation
2016, Ultrasonics
Citation Excerpt :
Ultrasonic methods were reported previously for the measurement of corneal biomechanical properties. Corneal speed of sound can be measured to analyze the corneal properties [21]. Aggregate modulus can be calculated based on the speed of ultrasound to determine the change of corneal mechanical properties [22].
Biomechanical properties are potential information for the diagnosis of corneal pathologies. An ultrasound indentation probe consisting of a load cell and a miniature ultrasound transducer as indenter was developed to detect the force–indentation relationship of the cornea. The key idea was to utilize the ultrasound transducer to compress the cornea and to ultrasonically measure the corneal deformation with the eyeball overall displacement compensated. Twelve corneal silicone phantoms were fabricated with different stiffness for the validation of measurement with reference to an extension test. In addition, fifteen fresh porcine eyes were measured by the developed system in vitro. The tangent moduli of the corneal phantoms calculated using the ultrasound indentation data agreed well with the results from the tensile test of the corresponding phantom strips ( $R^{2} = 0.96$ ). The mean tangent moduli of the porcine corneas measured by the proposed method were 0.089 ± 0.026 MPa at intraocular pressure (IOP) of 15 mmHg and 0.220 ± 0.053 MPa at IOP of 30 mmHg, respectively. The coefficient of variation (CV) and intraclass correlation coefficient (ICC) of tangent modulus were 14.4% and 0.765 at 15 mmHg, and 8.6% and 0.870 at 30 mmHg, respectively. The preliminary study showed that ultrasound indentation could be applied to the measurement of corneal tangent modulus with good repeatability and improved measurement accuracy compared to conventional surface displacement-based measurement method. The ultrasound indentation can be a potential tool for the corneal biomechanical properties measurement in vivo.
Manipulation of intraocular pressure for studying the effects on accommodation
2012, Experimental Eye Research
Citation Excerpt :
The CUB records the time between the peaks and the times were converted to actual distances by multiplication with accepted sound velocities of 1532 m/s for the aqueous and vitreous and 1641 m/s for the lens (van der Heijde and Weber, 1989; Vilupuru and Glasser, 2005). Sound velocities for the pig eyes have been reported to be almost identical to that of human eyes at room temperature (Thijssen et al., 1985) although the sound velocity of the lens can vary with age and is lower in the lens nucleus (Huang et al., 2007). The complete experimental setup is shown in Fig. 2.
A reliable experimental system in which IOP can be manipulated or a rapid IOP change can be induced while simultaneously and continuously measuring IOP and the ocular accommodative changes would be useful for understanding the physiological effect of intraocular pressure (IOP) on the accommodative mechanism. In this study, an IOP perfusion and recording system was developed and tested using 13 enucleated pig eyes. The vitreous chamber of the pig eyes was cannulated with a needle connected to two fluid reservoirs at different heights. One reservoir was set to achieve one of three baseline pressures of 5.5 mmHg, 13.0 mmHg and 20.5 mmHg. The other reservoir was moved to achieve pressures of 1.5 mmHg, 3.0 mmHg, 4.5 mmHg and 6.0 mmHg higher than the baseline pressure. The height differential between the reservoirs determined the amplitude of IOP changes. Rapid IOP changes were induced by switching the reservoirs with a solenoid pinch-valve. Two needles, one each attached to a pressure transducer were inserted into the anterior chamber and vitreous chamber respectively. Custom developed software was used to measure the anterior chamber pressure and vitreous chamber pressure at 80 Hz. A high-resolution continuous A-scan ultrasound biometer (CUB) was used to dynamically measure changes in ocular biometry including anterior chamber depth (ACD), lens thickness (LT) and vitreous chamber depth (VCD) while the vitreous chamber pressure was manipulated. The changes in ACD, LT and VCD were analyzed as a function of the pressure change. Perfusion-induced axial biometric changes were quantified by the slopes of linear regression relationships. Both anterior chamber pressure and vitreous chamber pressure changed relatively systematically with the induced vitreous chamber pressure changes (anterior chamber: y = 0.863x + 0.030, r² = 0.983; vitreous chamber: y = 0.883x + 0.009, r² = 0.981). At perfusion pressures of 5.5, 13.0 and 20.5 mmHg, the slopes for ACD were −5.72, −2.75 and −2.36 μm/mmHg, for LT were −3.31, −1.59 and −1.03 μm/mmHg and for VCD were 19.05, 8.63 and 5.18 μm/mmHg. The system was able to manipulate and monitor IOP while axial biometry changes were recorded. This system will allow the relationship between IOP and accommodation to be studied in non-human primate eyes.
Variance of Speed of Sound and Correlation with Acoustic Impedance in Canine Corneas
2011, Ultrasound in Medicine and Biology
Citation Excerpt :
The CCT (568 ± 68 μm) measured with a clinical pachymeter was comparable to those reported from in vivo studies in canine eyes (Gwin et al. 1982; Gilger et al. 1991) indicating minimal swelling of the corneas. The speed of sound in the canine corneas, 1577 ± 10 m/s, was similar to that in porcine corneas (Thijssen et al. 1985; de Korte et al. 1994; Kampmeier et al. 2000; He and Liu 2009), bovine corneas (Oksala and Lehtinen 1958; Silverman et al. 2009) and human corneas measured postmortem (Rivara and Sanna 1962; Thijssen et al. 1985; de Korte et al. 1994; Ye et al. 1995). This value was lower than what is assumed for human corneas for in vivo measurements, even if the temperature effect is corrected for (the measurements were performed at room temperature while in vivo measurements are done at body temperature) (Thijssen et al. 1985).
The clinical standard for measuring corneal thickness is ultrasound pachymetry that assumes a constant speed of sound. The purpose of this study was to examine the variance of speed of sound and its relationship with acoustic impedance in healthy eyes of canines with a large age span. Corneal speed of sound and acoustic impedance were measured in 34 canine eyes at room temperature (21 ± 1°C). The mean speed of sound was 1577 ± 10 m/s ranging from 1553 to 1594 m/s. There was a strong correlation between speed of sound and acoustic impedance (R = 0.84, p < 0.001). Corneal speed of sound had a small variance in healthy canines over 1-year-old, but was significantly lower in younger canines suggesting an age effect. The strong correlation between corneal speed of sound and acoustic impedance may offer a potential means to noninvasively detect abnormal speed of sound for more accurate corneal thickness estimation.

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Ultrasound in Medicine & Biology

Abstract

References (30)

Studies on refractive elements of human eye by means of ultrasonic echogram

Jap. J. Clin. Ophthal.

In vivo characterization of intraocular membranes

Acoustic properties of the refractive media of the eye

J. Acoust. Soc. Am.

Einführung in die Ophthalmologische Ultraschalldiagnostik

A determination of the velocity of ultrasound in cataractous lenses

Ultrasonography of the Eve and Orbit

Digital computer analysis of time-amplitude ultrasonograms from the human eye. II. Data processing

J. Clin. Ultrasound

Visualizating internal structures of the eye by means of ultrasonics

Compilation of empirical ultrasonic properties of mammalian tissues II

J. Acoust. Soc. Am.

Echoreference standards in ophthalmic ultrasonography

Ultrasound Med. Biol.

An ultrasonic method for outlining the cerebral ventricles

J. Acoust. Soc. Am.

Determination of the velocity of ultrasound in the human lens and vitreous

Acta Ophthal.

Determination of the velocity of ultrasound in the human lens and vitreous

Acta Ophthal.

Post-mortem changes in the rabbit retina

Acta Ophthal.

Applications for spectral analysis in medical ultrasonography

Ultrasonics

Cited by (38)

A-scan ultrasound in ophthalmology: A simulation tool

Complementary capabilities of photoacoustic imaging to existing optical ocular imaging techniques

The Globe's Eccentric Rotational Axis: Why Medial Rectus Surgery Is More Potent than Lateral Rectus Surgery

Measurement of corneal tangent modulus using ultrasound indentation

Manipulation of intraocular pressure for studying the effects on accommodation

Variance of Speed of Sound and Correlation with Acoustic Impedance in Canine Corneas

Clinical supplementAcoustic parameters of ocular tissues

Abstract

Studies on refractive elements of human eye by means of ultrasonic echogram

Jap. J. Clin. Ophthal.

In vivo characterization of intraocular membranes

Acoustic properties of the refractive media of the eye

J. Acoust. Soc. Am.

Einführung in die Ophthalmologische Ultraschalldiagnostik

A determination of the velocity of ultrasound in cataractous lenses

Ultrasonography of the Eve and Orbit

Digital computer analysis of time-amplitude ultrasonograms from the human eye. II. Data processing

J. Clin. Ultrasound

Visualizating internal structures of the eye by means of ultrasonics

Compilation of empirical ultrasonic properties of mammalian tissues II

J. Acoust. Soc. Am.

Echoreference standards in ophthalmic ultrasonography

Ultrasound Med. Biol.

An ultrasonic method for outlining the cerebral ventricles

J. Acoust. Soc. Am.

Determination of the velocity of ultrasound in the human lens and vitreous

Acta Ophthal.

Determination of the velocity of ultrasound in the human lens and vitreous

Acta Ophthal.

Post-mortem changes in the rabbit retina

Acta Ophthal.

Applications for spectral analysis in medical ultrasonography

Ultrasonics

Clinical supplement
Acoustic parameters of ocular tissues