488 research outputs found
In vivo laser Doppler holography of the human retina
The eye offers a unique opportunity for non-invasive exploration of
cardiovascular diseases. Optical angiography in the retina requires sensitive
measurements, which hinders conventional full-field laser Doppler imaging
schemes. To overcome this limitation, we used digital holography to perform
laser Doppler perfusion imaging of the human retina in vivo with near-infrared
light. Wideband measurements of the beat frequency spectrum of optical
interferograms recorded with a 39 kHz CMOS camera are analyzed by short-time
Fourier transformation. Power Doppler images and movies drawn from the zeroth
moment of the power spectrum density reveal blood flows in retinal and
choroidal vessels over 512 512 pixels covering 2.4 2.4 mm
on the retina with a 13 ms temporal resolution.Comment: 5 pages, 5 figure
Pulsatile microvascular blood flow imaging by short-time Fourier transform analysis of ultrafast laser holographic interferometry
We report on wide-field imaging of pulsatile microvascular blood flow in the
exposed cerebral cortex of a mouse by holographic interferometry. We recorded
interferograms of laser light backscattered by the tissue, beating against an
off-axis reference beam with a 50 kHz framerate camera. Videos of local Doppler
contrasts were rendered numerically by Fresnel transformation and short-time
Fourier transform analysis. This approach enabled instantaneous imaging of
pulsatile blood flow contrasts in superficial blood vessels over 256 x 256
pixels with a spatial resolution of 10 microns and a temporal resolution of 20
ms.Comment: 4 page
Enhancement of Optical Coherence Tomography Images of the Retina by Normalization and Fusion
This paper describes an image processing method applied to Optical Coherence Tomography (OCT) images of the retina. The aim is to achieve improved OCT images from the fusion of sequential OCT scans obtained at identical retinal locations. The method is based on the normalization of the acquired images and their fusion. As a result, a noise reduction and an image enhancement are reached. Thanks to the resulting improvement in retinal imaging, clinical specialists are able to evaluate more efficiently eyes pathologies and anomalies. This paper presents the proposed method and gives some evaluation results
Twisted partial actions of Hopf algebras
In this work, the notion of a twisted partial Hopf action is introduced as a
unified approach for twisted partial group actions, partial Hopf actions and
twisted actions of Hopf algebras. The conditions on partial cocycles are
established in order to construct partial crossed products, which are also
related to partially cleft extensions of algebras. Examples are elaborated
using algebraic groups
Clinical and cost-effectiveness of internal limiting membrane peeling for patients with idiopathic full thickness macular hole. Protocol for a Randomised Controlled Trial : FILMS (Full-thickness macular hole and Internal Limiting Membrane peeling Study)
Background: A full-thickness macular hole (FTMH) is a common retinal condition associated with impaired vision. Randomised controlled trials (RCTs) have demonstrated that surgery, by means of pars plana vitrectomy and post-operative intraocular tamponade with gas, is effective for stage 2, 3 and 4 FTMH. Internal limiting membrane (ILM) peeling has been introduced as an additional surgical manoeuvre to increase the success of the surgery; i.e. increase rates of hole closure and visual improvement. However, little robust evidence exists supporting the superiority of ILM peeling compared with no-peeling techniques. The purpose of FILMS (Fullthickness macular hole and Internal Limiting Membrane peeling Study) is to determine whether ILM peeling improves the visual function, the anatomical closure of FTMH, and the quality of life of patients affected by this disorder, and the cost-effectiveness of the surgery.
Methods/Design: Patients with stage 2–3 idiopathic FTMH of less or equal than 18 months duration (based on symptoms reported by the participant) and with a visual acuity ≤ 20/40 in the study eye will be enrolled in this FILMS from eight sites across the UK and Ireland. Participants will be randomised to receive combined cataract surgery (phacoemulsification and intraocular lens implantation) and pars plana vitrectomy with postoperative intraocular tamponade with gas, with or without ILM peeling. The primary outcome is distance visual acuity at 6 months. Secondary outcomes include distance visual acuity at 3 and 24 months, near visual acuity at 3, 6, and 24 months, contrast sensitivity at 6 months, reading speed at 6 months, anatomical closure of the macular hole at each time point (1, 3, 6, and 24 months), health related quality of life (HRQOL) at six months, costs to the health service and the participant, incremental costs per quality adjusted life year (QALY) and adverse events.
Discussion: FILMS will provide high quality evidence on the role of ILM peeling in FTMH surgery.
Trial registration: This trial is registered with Current Controlled Trials ISRCTN number 33175422 and Clinical Trials.gov identifier NCT00286507.Chief Scientist Office, Scotland (project ref no CZH/4/235), NHS GrampianPeer reviewedPublisher PD
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