Optimization of the open-loop liquid crystal adaptive optics retinal imaging system

Ningning, Kong; Li, Chao; Mao, Xia; Li, Dayu; Qi, Yunfeng; Li, Xuan

doi:10.1117/1.jbo.17.2.026001

Cited by 12 publications

(10 citation statements)

References 31 publications

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“…The voltage applied to the pixels controls the refractive index, and the advantage is that higher speeds can be obtained. LC devices require the use of linearly polarised light [56]; Kong et al [57], however, recently described an open loop ophthalmic AO system in which the uncorrected polarisation component is used by the wavefront sensor. A limitation of LC devices is the relatively limited dynamic range when using the device to correct ocular aberrations.…”

Section: Wavefront Correcting Technologymentioning

confidence: 99%

Adaptive Optics Technology for High-Resolution Retinal Imaging

Lombardo

Serrao

Devaney

et al. 2012

Sensors

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Adaptive optics (AO) is a technology used to improve the performance of optical systems by reducing the effects of optical aberrations. The direct visualization of the photoreceptor cells, capillaries and nerve fiber bundles represents the major benefit of adding AO to retinal imaging. Adaptive optics is opening a new frontier for clinical research in ophthalmology, providing new information on the early pathological changes of the retinal microstructures in various retinal diseases. We have reviewed AO technology for retinal imaging, providing information on the core components of an AO retinal camera. The most commonly used wavefront sensing and correcting elements are discussed. Furthermore, we discuss current applications of AO imaging to a population of healthy adults and to the most frequent causes of blindness, including diabetic retinopathy, age-related macular degeneration and glaucoma. We conclude our work with a discussion on future clinical prospects for AO retinal imaging.

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Section: Wavefront Correcting Technologymentioning

confidence: 99%

Adaptive Optics Technology for High-Resolution Retinal Imaging

Lombardo

Serrao

Devaney

et al. 2012

Sensors

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“…The designed FOV is 1°, which is less than the isoplanatic patch diameter. For avoiding the light spots on the wavefront sensor being too big to result in detection error, a shutter with a hole can be positioned in the illumination path [37]. Two light sources with different size of illumination area can also be adopted.…”

Section: Resultsmentioning

confidence: 99%

Flood-illuminated adaptive optics ophthalmoscope with a single curved relay mirror

Liu¹,

Qi²,

Zheng³

et al. 2013

Photon. Res.

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For decreasing light loss and diminishing the aberrations of the optical system, an open-loop adaptive optics (AO) system for retinal imaging in vivo is introduced. Taking advantage of the ability of young human eyes to accommodate, there was only one single curved mirror to make the pupil of the eye conjugate with the wavefront corrector and the wavefront sensor. A liquid crystal spatial light modulator (LC-SLM) was adopted as the wavefront corrector because the LC-SLM can be made in a small size to match the sensor. To reduce a pair of lenses or focusing mirrors, the wavefront corrector and sensor are positioned in the noncommon path. The system adopts open-loop control and the high-precision LC-SLM guarantees the effectiveness of the AO system. The designed field of view is 1°on the retina (about 300 μm). The image quality was simulated with different mirror surface types, including circular, parabolic, and hyperbolic. A hyperbolic mirror with conic constant −1.07, which is close to −1, could best eliminate the aberrations. Theoretical analysis showed that the optical throughput of this system was at least 22.4% higher than that of a standard transmission AO system. In a practical experiment, a parabolic mirror was positioned in the optical path. Images of the cone photoreceptors and the capillary vessels were obtained successfully. This system simplifies the optical setup in comparison to the commonly used 4F systems while still guaranteeing the effectiveness of AO to correct the ocular aberrations.

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“…Modern retinal microscopic imaging technologies make it possible to noninvasively acquire high-resolution retinal images [3,4] . However, non-uniform illumination, low contrast of thin vessels and background noises make it a challenging task to diagnose diseases.…”

Section: Introductionmentioning

confidence: 99%

“…When f ∇ is small, the energy function is dominated by the first item of formula (4) and result in a slowly changing vector field. However, when f ∇ is large enough, the energy function is dominated by the second item of formula(4) and result in f g ∇ ≈ . The GVF can be acquired by solving the following Euler equations:…”

mentioning

confidence: 98%

A novel retinal vessel extraction algorithm based on matched filtering and gradient vector flow

Mao

2013

SPIE Proceedings

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The microvasculature network of retina plays an important role in the study and diagnosis of retinal diseases (age-related macular degeneration and diabetic retinopathy for example). Although it is possible to noninvasively acquire high-resolution retinal images with modern retinal imaging technologies, non-uniform illumination, the low contrast of thin vessels and the background noises all make it difficult for diagnosis. In this paper, we introduce a novel retinal vessel extraction algorithm based on gradient vector flow and matched filtering to segment retinal vessels with different likelihood. Firstly, we use isotropic Gaussian kernel and adaptive histogram equalization to smooth and enhance the retinal images respectively. Secondly, a multi-scale matched filtering method is adopted to extract the retinal vessels. Then, the gradient vector flow algorithm is introduced to locate the edge of the retinal vessels. Finally, we combine the results of matched filtering method and gradient vector flow algorithm to extract the vessels at different likelihood levels. The experiments demonstrate that our algorithm is efficient and the intensities of vessel images exactly represent the likelihood of the vessels.

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Optimization of the open-loop liquid crystal adaptive optics retinal imaging system

Cited by 12 publications

References 31 publications

Adaptive Optics Technology for High-Resolution Retinal Imaging

Adaptive Optics Technology for High-Resolution Retinal Imaging

Flood-illuminated adaptive optics ophthalmoscope with a single curved relay mirror

A novel retinal vessel extraction algorithm based on matched filtering and gradient vector flow

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