Refractive index distribution and optical properties of the isolated human lens measured using magnetic resonance imaging (MRI)

Jones, Catherine E.; Atchison, David A.; Meder, Roger; Pope, J. H.

doi:10.1016/j.visres.2005.03.008

Cited by 183 publications

(270 citation statements)

References 35 publications

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“…Secondly as pointed out previously [8] "The data were inherently noisy due primarily to the limited sensitivity of the clinical MRI scanner for this type of measurement and the need to minimize scan times to reduce motion artifacts and avoid fatiguing the subject." With the growing availability of clinical MRI systems operating at higher magnetic fields of 7T and above, it should become possible to obtain high resolution refractive index profiles with good signal-to-noise ratio for individual lenses, similar to those that we have obtained ex-vivo [24], particularly with the advent of dedicated receiver coils for eye imaging at these fields.…”

Section: Discussionmentioning

confidence: 74%

Change in human lens dimensions, lens refractive index distribution and ciliary body ring diameter with accommodation

Khan

Pope

Verkicharla

et al. 2018

Biomed. Opt. Express

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Abstract:We investigated changes in ciliary body ring diameter, lens dimensions and lens refractive index distributions with accommodation in young adults. A 3T clinical magnetic resonance imaging scanner imaged right eyes of 38 18-29 year old participants using a multiple spin echo sequence to determine accommodation-induced changes along lens axial and equatorial directions. Accommodation stimuli were approximately 1 D and 5 D. With accommodation, ciliary body ring diameter, and equatorial lens diameter decreased (-0.43 ± 0.31 mm and -0.30 ± 0.23 mm, respectively), and axial lens thickness increased ( + 0.34 ± 0.16 mm). Lens shape changes cause redistribution of the lens internal structure, leading to change in refractive index distribution profiles. With accommodation, in the axial direction refractive index profiles became flatter in the center and steeper near the periphery of the lens, while in the equatorial direction they became steeper in the center and flatter in the periphery. The results suggest that the anatomical accuracy of lens optical models can be improved by accounting for changes in the refractive index profile during accommodation.

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Section: Discussionmentioning

confidence: 74%

Change in human lens dimensions, lens refractive index distribution and ciliary body ring diameter with accommodation

Khan

Pope

Verkicharla

et al. 2018

Biomed. Opt. Express

View full text Add to dashboard Cite

show abstract

“…Regular and enhanced MRI detected differences between normal and cataract lenses in Lizak and colleagues study (10). Other studies show the successful use of MRI for measurement of protein distribution inside the lens and the spatial gradient of refractive index (17,18,(20)(21)(22)(23). Also, some other studies demonstrated that MRI could be used as an effective method to diffusivity mapping of the lens (24)(25)(26).…”

Section: Discussionmentioning

confidence: 99%

Abnormal High Signal Intensity Discovered in Eye Lenses in Routine Brain MRI; Correlation with Ophthalmologist Examination

et al. 2017

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Objectives: The aim of this study was to determine the possible role of brain magnetic resonance imaging (MRI) in cataract detection. Patients and Methods: This study was performed on patients who were referred to Shahid Faghihi hospital with a known disease for brain MRI. Patients were classified in two groups of case and controls. Cases were 44 eyes with abnormal signal of the lens and controls were 88 eyes with normal signal intensity of the lens. All patients underwent an ophthalmological examination and the presence of cataract and intraocular lens (IOL) was assessed in these patients. Average lens signal, average muscle signal, average fat signal, lens to muscle signal ratio, and average lens signal to average fat signal ratio were recorded. Results: The mean of the average lens signal in the case group was significantly higher than controls (370 versus 161, respectively) (P value < 0.0001). Sixteen (36.4%) out of 44 eyes in the case group had cataract, but 48 (54.5%) of 88 eyes in the control group had cataract (P value = 0.049). In the case group, 18.2% had IOL, and this was 6.8% in the controls (P value = 0.046). The mean of the average lens signal in eyes with cataract was 218.5 and in normal eyes, it was 249.1 (P value = 0.36). In eyes with IOL, the mean of the average lens signal was 347.5 and in normal eyes, this was 223.1 (P value = 0.036). Conclusion: Cataract in eyes with abnormal lens signal was significantly lower than eyes with normal lens average signal. The lens signal in eyes with cataract was similar to eyes without cataract. So, average lens signal in brain MRI does not lead to early detection of cataract.

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“…detector elements, it can be shown that ML estimation according to Eq. (3) reduces to nonlinear least-squares fitting between the data and the output of the optical design program: (4) Immediate advantages are that ML estimation is efficient (i.e., unbiased and yields the best possible variance) if an efficient estimator exists, and that it is asymptotically unbiased as more photons are acquired. However, one challenge is that an accurate probability model must be used that includes all sources of randomness (e.g., photon noise and electronic noise) [33] as well as fluctuations of ocular aberrations associated with live imaging of the eye, including the tear film effect.…”

Section: Maximum-likelihood Estimationmentioning

confidence: 99%

“…Accurate determination of optical parameters in normal and abnormal eyes could also be valuable in developing data bases for clinical diagnosis of pathologies, while measurements of ocular surface misalignments would be useful after implantation of intraocular lenses in cataract surgery [1][2][3]. Moreover, knowledge of the refractive index distribution in the lens may be beneficial in optical coherence tomography, which is based on interferometric reflectometry and index changes [4,5]. It could additionally lead to a substantial improvement in retinal imaging.…”

Section: Introductionmentioning

confidence: 99%

“…Of significant interest is the in vivo gradient-index (GRIN) distribution and lenticular geometry of the human crystalline lens as a function of both age and accommodation [3], but this information has been difficult to obtain, and reliable measurements are scarce [4,5,[8][9][10]. While previous studies suggested that aspheric surfaces in the anterior segment and an effective refractive index for the lens are sufficient to model spherical aberration, lack of knowledge regarding the GRIN distribution precludes both the prediction of off-axis aberrations and study of dispersion in the lens, so that experimental data are limited [9].…”

Section: Introductionmentioning

confidence: 99%

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Inverse optical design of the human eye using likelihood methods and wavefront sensing

2008

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We are developing a method for estimating patient-specific ocular parameters, including surface curvatures, conic constants, tilts, decentrations, thicknesses, refractive indices, and index gradients. The data consist of the raw detector outputs from one or more Shack-Hartmann wavefront sensors, and the parameters in the eye model are estimated by maximizing the likelihood. A Gaussian noise model is used to emulate electronic noise, so maximum likelihood reduces to nonlinear least-squares fitting between the data and the output of our optical design program. The Fisher information matrix for the Gaussian model was explored to compute bounds on the variance of the estimates for different system configurations. In this preliminary study, an accurate estimate of a chosen subset of ocular parameters was obtained using a custom search algorithm and a nearby starting point to avoid local minima in the complex likelihood surface.

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Refractive index distribution and optical properties of the isolated human lens measured using magnetic resonance imaging (MRI)

Cited by 183 publications

References 35 publications

Change in human lens dimensions, lens refractive index distribution and ciliary body ring diameter with accommodation

Change in human lens dimensions, lens refractive index distribution and ciliary body ring diameter with accommodation

Abnormal High Signal Intensity Discovered in Eye Lenses in Routine Brain MRI; Correlation with Ophthalmologist Examination

Inverse optical design of the human eye using likelihood methods and wavefront sensing

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