&lt;title&gt;Monte-Carlo simulation of retinal vessel profiles for the interpretation of in-vivo oxymetric measurements by imaging fundus reflectometry&lt;/title&gt;

Hammer, Martin; Leistritz, S.; Leistritz, Lutz; Schweitzer, Dietrich; Thamm, E.; Donnerhacke, Karl‐Heinz

doi:10.1117/12.297857

Cited by 4 publications

(7 citation statements)

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“…Measurements performed by our research group indicate that ␤ is significantly smaller than ␣ for our instrumentation, meaning that single-pass transmission and backscattered light are the dominant collected light path. 27 The Monte Carlo simulation by Hammer et al 20 predicts that the double-pass contribution is significantly smaller than the single-pass contribution for all typical retinal vessel diameters. Choosing a value of ␤ to be 0.10, we can show that the second-order and higher terms of Eq.…”

Section: Negligible Backscattering Approximationmentioning

confidence: 98%

“…The relative magnitudes of single-pass and double-pass transmission are also acutely dependent on the specific geometry of the oximeter apparatus. A Monte Carlo simulation of retinal vessel profiles performed by Hammer et al 20 predicts that the single-pass, double-pass, and backscattered components contribute nearly equally for a 100-m vessel. Single-pass light dominates for smaller ͑25-m͒ vessels, and backscattered light dominates for larger ͑200-m͒ vessels.…”

Section: Light Paths In Retinal Vessel Oximetrymentioning

confidence: 99%

“…It is possible that the double-pass component of the signal collected by a retinal vessel oximeter is negligible ͑i.e., ␤ Ͻ Ͻ ␣͒. The Monte Carlo simulation by Hammer et al 20 predicts that the collected doublepass flux is the smallest component in retinal vessel oximetry and that ⌽ dp may be negligible for vessels larger than ϳ160 m. If the double-pass component can be ignored, then the general oximetry equation, Eq. ͑9͒, can be written as…”

Section: Negligible Double-pass Approximationmentioning

confidence: 99%

“…͑19͒ and ͑20͒ both appear promising for retinal vessel oximetry, both equations contain wavelength-dependent factors that are likely to be functions of fundus reflectivity, and are possibly functions of vessel diameter, retinal position ͑because of varying thickness of the retinal layers͒, and hemoglobin concentration. Monte Carlo simulations of light interaction with the retina 20 should provide a theoretical framework for determining the relationships between these parameters; however, a large database of vessel saturation measurements acquired across a range of known oxygen saturations, hemoglobin concentration, retinal position, fundus pigmentations, and vessel diameters will eventually be required if we are to definitively show calibrated measurements from a retinal vessel oximeter.…”

Section: ͑1͒mentioning

confidence: 99%

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Effect of multiple light paths on retinal vessel oximetry

Smith¹,

Denninghoff²,

Lompado³

et al. 2000

Appl. Opt.

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Techniques for noninvasively measuring the oxygen saturation of blood in retinal arteries and veins are reported in the literature, but none have been sufficiently accurate and reliable for clinical use. Addressing the need for increased accuracy, we present a series of oximetric equations that explicitly consider the effects of backscattering by red blood cells and lateral diffusion of light in the ocular fundus. The equations are derived for the specific geometry of a scanning-beam retinal vessel oximeter; however, the results should also be applicable to photographic oximeters. We present in vitro and in vivo data that suggest the validity of these equations.

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Section: Negligible Backscattering Approximationmentioning

confidence: 98%

Section: Light Paths In Retinal Vessel Oximetrymentioning

confidence: 99%

Section: Negligible Double-pass Approximationmentioning

confidence: 99%

Section: ͑1͒mentioning

confidence: 99%

See 2 more Smart Citations

Effect of multiple light paths on retinal vessel oximetry

Smith¹,

Denninghoff²,

Lompado³

et al. 2000

Appl. Opt.

View full text Add to dashboard Cite

show abstract

“…The basic retinal vessel anatomy, represented by a circular or elliptical blood column coaxially surrounded by a thickness of wall material, has been used to generate cross-sectional profiles (RASSAM et al, 1994;PATEL, 1995;HAMMER et al, 1997).…”

Section: Matched Filtersmentioning

confidence: 99%

Progress towards automated diabetic ocular screening: A review of image analysis and intelligent systems for diabetic retinopathy

Teng

Lefley

Claremont

2002

Med. Biol. Eng. Comput.

165

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Patients with diabetes require annual screening for effective timing of sight-saving treatment. However, the lack of screening and the shortage of ophthalmologists limit the ocular health care available. This is stimulating research into automated analysis of the reflectance images of the ocular fundus. Publications applicable to the automated screening of diabetic retinopathy are summarised. The review has been structured to mimic some of the processes that an ophthalmologist performs when examining the retina. Thus image processing tasks, such as vessel and lesion location, are reviewed before any intelligent or automated systems. Most research has been undertaken in identification of the retinal vasculature and analysis of early pathological changes. Progress has been made in the identification of the retinal vasculature and the more common pathological features, such as small aneurysms and exudates. Ancillary research into image preprocessing has also been identified. In summary, the advent of digital data sets has made image analysis more accessible, although questions regarding the assessment of individual algorithms and whole systems are only just being addressed.

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Dual wavelength retinal vessel oximetry – influence of fundus pigmentation

Hirsch

Cubbidge

Heitmar

2022

Eye

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Background Clinical methods examining oxygenation parameters in humans have been used in many different care settings, but concerns have been raised regarding their clinical utility when assessing people with darker skin pigmentation. While saturation values can be crucial in emergency medicine, they are equally valuable in assessing disease mechanisms and monitoring change in disease progression. Retinal pigmentation varies across individuals and hence, can impact on retinal oxygen parameters. The objective of this study was to quantify and eliminate the impact of retinal pigmentation on retinal vessel oxygen saturation parameters measured in the superficial retinal arterioles and venules. Methods 105 healthy individuals of varying skin colour, iris colour and heritage were included. Following a full eye exam to exclude any ocular abnormality, all participants underwent intraocular pressure, systemic blood pressure measurements and dilated dual wavelength retinal photography. Rotation matrices were employed to minimise the dependency of retinal pigmentation on arterial and venous oxygen saturation measurements determined in a concentric measurement annulus. Results Retinal oxygen saturation in venules showed a linear correlation with retinal pigmentation (y = 0.34 × x + 38.598), whereas arterial saturation followed a polynomial pattern (y = 0.0089 × x2 + 0.7499 × x + 85.073). Both arterial and venous saturation values were corrected using local fundus pigmentation. Pre-correction retinal arterial and venous oxygen saturation were 89.0% (±13.1) and 43.7% (±11.5), respectively, and post- correction values were 94.8% (±8.7) for arteries and 56.3% (±7.0) veins. Conclusions When assessing multi-ethnic cohorts, it is important to consider the impact of pigmentation on imaging parameters and to account for it prior to clinical interpretation.

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<title>Monte-Carlo simulation of retinal vessel profiles for the interpretation of in-vivo oxymetric measurements by imaging fundus reflectometry</title>

Cited by 4 publications

References 0 publications

Effect of multiple light paths on retinal vessel oximetry

Effect of multiple light paths on retinal vessel oximetry

Progress towards automated diabetic ocular screening: A review of image analysis and intelligent systems for diabetic retinopathy

Dual wavelength retinal vessel oximetry – influence of fundus pigmentation

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