Optical properties of conjunctiva, sclera, and the ciliary body and their consequences for transscleral cyclophotocoagulation: erratum

Nemati, Babak; Rylander, H. G.; Welch, Ashley J.

doi:10.1364/ao.36.000416

Cited by 5 publications

(7 citation statements)

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“…Note that a single refractive index can be applied to create an acceptable image registration for both the inner scleral wall and the ciliary pigmented epithelium (Figure 5c). Previously publications have reported the index of refraction or scaling factor for rabbit sclera and ciliary body to be 1.41 and 1.38, respectively 25–26. Bovine muscle tissue and human cardiac muscle were also reported to have a refractive index of 1.38 27–28.…”

Section: Methodsmentioning

confidence: 99%

“…Although there are estimates of the appropriate refractive index for the sclera/ciliary body in the published literature,25–26 it is not currently an option to incorporate this refractive index into measurements made with the calipers in the Visante software. Thickness measurements were obtained at 1 mm, 2 mm, and 3 mm posterior to the sclera spur (Figure 6) using calipers in the Visante software as previously described 10.…”

Section: Methodsmentioning

confidence: 99%

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Semiautomatic Extraction Algorithm for Images of the Ciliary Muscle

Kao¹,

Richdale²,

Sinnott³

et al. 2011

Optometry and Vision Science

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Purpose To development and evaluate a semi-automatic algorithm for segmentation and morphological assessment of the dimensions of the ciliary muscle in Visante™ Anterior Segment Optical Coherence Tomography images. Methods Geometric distortions in Visante images analyzed as binary files were assessed by imaging an optical flat and human donor tissue. The appropriate pixel/mm conversion factor to use for air (n = 1) was estimated by imaging calibration spheres. A semi-automatic algorithm was developed to extract the dimensions of the ciliary muscle from Visante images. Measurements were also made manually using Visante software calipers. Interclass correlation coefficients (ICC) and Bland-Altman analyses were used to compare the methods. A multilevel model was fitted to estimate the variance of algorithm measurements that was due to differences within- and between-examiners in scleral spur selection versus biological variability. Results The optical flat and the human donor tissue were imaged and appeared without geometric distortions in binary file format. Bland-Altman analyses revealed that caliper measurements tended to underestimate ciliary muscle thickness at 3 mm posterior to the scleral spur in subjects with the thickest ciliary muscles (t = 3.6, p < 0.001). The percent variance due to within- or between-examiner differences in scleral spur selection was found to be small (6%) when compared to the variance due to biological difference across subjects (80%). Using the mean of measurements from three images achieved an estimated ICC of 0.85. Conclusions The semi-automatic algorithm successfully segmented the ciliary muscle for further measurement. Using the algorithm to follow the scleral curvature to locate more posterior measurements is critical to avoid underestimating thickness measurements. This semi-automatic algorithm will allow for repeatable, efficient, and masked ciliary muscle measurements in large datasets.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Semiautomatic Extraction Algorithm for Images of the Ciliary Muscle

Kao¹,

Richdale²,

Sinnott³

et al. 2011

Optometry and Vision Science

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“…Experimentally measured absorption and scattering coefficients of the conjunctival epithelium (Nemati et al. , ) are approximated by least‐squares polynomial fits as

{italicμ}_{a}^{normalCE} = A_{1} {italicλ}^{4} + A_{2} {italicλ}^{3} + A_{3} {italicλ}^{2} + A_{4} λ + A_{5}

where A 1 = 5.76328 × 10 −13 A 2 = −5.05681 × 10 −9 , A 3 = 1.09816 × 10 −5 A 4 = −0.00905007, A 5 = 2.607, and

{italicμ}_{S}^{normalCE} = B_{1} {italicλ}^{5} + B_{2} {italicλ}^{4} + B_{3} {italicλ}^{3} + B_{4} {italicλ}^{2} + B_{5} λ + B_{6}

where B 1 = 2.63396 × 10 −13 , B 2 = −2.81535 × 10 −10 , B 3 = −1.10282 × 10 −6 , B 4 = 0.00236644, B 5 = −1.62947, and B 6 = 392.569. Here, the absorption and scattering fit errors, R 2 , are 0.98 and 0.9, respectively.…”

Section: Methodsmentioning

confidence: 99%

“…To find a k , the equation for a fit in matrix notation, M fit = Λ a , is solved for a given set of n experimental data points ( λ i , μ i ) and the solution vector a is calculated as, a = (Λ T Λ ) −1 Λ T M fit (Nemati et al. , ).…”

Section: Methodsmentioning

confidence: 99%

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Combined reflectance spectroscopy and stochastic modeling approach for noninvasive hemoglobin determination via palpebral conjunctiva

et al. 2014

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A combination of stochastic photon propagation model in a multilayered human eyelid tissue and reflectance spectroscopy was used to study palpebral conjunctiva spectral reflectance for hemoglobin (Hgb) determination. The developed model is the first biologically relevant model of eyelid tissue, which was shown to provide very good approximation to the measured spectra. Tissue optical parameters were defined using previous histological and microscopy studies of a human eyelid. After calibration of the model parameters the responses of reflectance spectra to Hgb level and blood oxygenation variations were calculated. The stimulated reflectance spectra in adults with normal and low Hgb levels agreed well with experimental data for Hgb concentrations from 8.1 to 16.7 g/dL. The extracted Hgb levels were compared with in vitro Hgb measurements. The root mean square error of cross‐validation was 1.64 g/dL. The method was shown to provide 86% sensitivity estimates for clinically diagnosed anemia cases. A combination of the model with spectroscopy measurements provides a new tool for noninvasive study of human conjunctiva to aid in diagnosing blood disorders such as anemia.

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Dynamic Optical Coherence Elastography of the Anterior Eye: Understanding the Biomechanics of the Limbus

Zvietcovich

Nair

Singh

et al. 2020

Invest. Ophthalmol. Vis. Sci.

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Purpose Currently, the biomechanical properties of the corneo-scleral limbus when the eye-globe deforms are largely unknown. The purpose of this study is to evaluate changes in elasticity of the cornea, sclera, and limbus when subjected to different intraocular pressures (IOP) using wave-based optical coherence elastography (OCE). Special attention was given to the elasticity changes of the limbal region with respect to the elasticity variations in the neighboring corneal and scleral regions. Methods Continuous harmonic elastic waves (800 Hz) were mechanically induced in the sclera near the corneo-sclera limbus of in situ porcine eye-globes ( n = 8). Wave propagation was imaged using a phase-sensitive optical coherence tomography system (PhS-OCT). The eyes were subjected to five different IOP-levels (10, 15, 20, 30, and 40 mm Hg), and spatially distributed propagation velocities were calculated along corneal, limbal, and scleral regions. Finite element analysis (FEA) of the same regions under the same excitation conditions were conducted for further validation of results. Results FEA demonstrated that the stiffness of the heterogeneous cornea-limbus-sclera transition can be characterized by phase velocity measurements of the elastic waves produced at 800 Hz in the anterior eye. Experimental results revealed that the wave speed in the limbus ( c L = 6.5 m/s) is between the cornea ( c c = 2.9 m/s) and sclera ( c s = 10.0 m/s) at a physiological IOP level (15 mm Hg) and rapidly increases as the IOP level is increased, even surpassing the wave speed in the sclera. Finally, the change in elastic wave speed in the limbus (Δ c L ∼18.5 m/s) was greater than in the cornea (Δ c c ∼12.6 m/s) and sclera (Δ c s ∼8.1 m/s) for the same change in IOP. Conclusions We demonstrated that wave-based OCE can be utilized to assess limbus biomechanical properties. Moreover, experimental evidence showed that the corneo-scleral limbus is highly nonlinear compared to the cornea and sclera when the eye-globe is deformed by an increase of IOP. This may suggest that the limbus has enough structural flexibility to stabilize anterior eye shape during IOP changes.

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Optical properties of conjunctiva, sclera, and the ciliary body and their consequences for transscleral cyclophotocoagulation: erratum

Abstract: Corrections are given to the reported [Appl. Opt. 35, 3321 (1996)] units of the absorption and scattering coefficients mu (a) and mu (s), respectively. The corrections pertain to two figures, several tables, and the text describing results.

Cited by 5 publications

References 1 publication

Semiautomatic Extraction Algorithm for Images of the Ciliary Muscle

Semiautomatic Extraction Algorithm for Images of the Ciliary Muscle

Combined reflectance spectroscopy and stochastic modeling approach for noninvasive hemoglobin determination via palpebral conjunctiva

Dynamic Optical Coherence Elastography of the Anterior Eye: Understanding the Biomechanics of the Limbus

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