Papers by CHAHIRA MILOUDI
Notre objectif a été d'analyser l'influence de la variabilité spatio-temporelle de la réf... more Notre objectif a été d'analyser l'influence de la variabilité spatio-temporelle de la réflectance des cônes sur le comptage des cônes par imagerie à haute résolution par optique adaptative plein champ, et de proposer des méthodes pour pallier ces difficultés. La première partie des travaux porte sur l'étude de la variabilité temporelle des cônes. Nous avons confirmé la présence d'un phénomène de scintillement des cônes à une fréquence au moins égale à celle de notre système d'acquisition. Nous avons proposé une procédure d'analyse d'images incluant restauration par déconvolution myope, recalage rigide, fusion d'images pour la construction de cartographies de cônes. Nous avons montré que dans le cas des sujets sains, la procédure de fusion d'image permet de rapprocher la mesure de la densité des cônes des références histologiques. La directionalité de la réflectance des cônes est appelée effet Stiles-Crawford optique. Nous en avons identifié une no...
Adaptive Optics and Wavefront Control in Microscopy and Ophthalmology (AOMICRO), 2015
Investigative Ophthalmology & Visual Science, 2015
Notre objectif a ete d'analyser l'influence de la variabilite spatio-temporelle de la ref... more Notre objectif a ete d'analyser l'influence de la variabilite spatio-temporelle de la reflectance des cones sur le comptage des cones par imagerie a haute resolution par optique adaptative plein champ, et de proposer des methodes pour pallier ces difficultes. La premiere partie des travaux porte sur l'etude de la variabilite temporelle des cones. Nous avons confirme la presence d'un phenomene de scintillement des cones a une frequence au moins egale a celle de notre systeme d'acquisition. Nous avons propose une procedure d'analyse d'images incluant restauration par deconvolution myope, recalage rigide, fusion d'images pour la construction de cartographies de cones. Nous avons montre que dans le cas des sujets sains, la procedure de fusion d'image permet de rapprocher la mesure de la densite des cones des references histologiques. La directionalite de la reflectance des cones est appelee effet Stiles-Crawford optique. Nous en avons identifie une no...
Investigative Ophthalmology & Visual Science, 2015
Investigative Opthalmology & Visual Science, 2015
The purpose of this study was to describe a previously unreported manifestation of the optical St... more The purpose of this study was to describe a previously unreported manifestation of the optical Stiles-Crawford effect (oSCE) in normal eyes. METHODS. In a cohort of 50 normal subjects, the directional reflectance of cones in the retinal periphery was explored by flood-illuminated adaptive optics (FIAO) and optical coherence tomography (OCT). RESULTS. In 32 eyes (64%), off-axis FIAO images of the retinal periphery (~15-208 from the fovea) showed variably sized patches of hyporeflective dots (called here negative mosaic) coexisting with hyperreflective (positive) cones. In nine cases, shifting the entry pupil toward the optical axis restored the positive cone mosaic, with a point-by-point correspondence between positive and negative mosaics. Rods remained hyperreflective around negative and positive cones. These changes were paralleled by changes of the OCT reflectance of the cone outer segment tips and, to a lesser extent, of the inner/outer segment limit. CONCLUSIONS. By en face FIAO imaging of the retina, the contrast of cones over rods may be strongly dependent on the entry pupil to such an extent that their reflectance is lower than that of rods. We hypothesized that the negative cone mosaic aspect results from the differential Stiles-Crawford effect of cones and rods. Cone reflectance by en face FIAO parallels the reflectance from the cone outer segment tip line and to a lesser extent of the inner/outer segment limit by OCT. Taking this into account, the oSCE is of importance for the interpretation of high-resolution images of photoreceptors. (ClinicalTrials.gov number, NCT01546181.
2014 International Workshop on Computational Intelligence for Multimedia Understanding (IWCIM), 2014
Adaptive optics (AO) fundus imaging is an optoelectronic technique allowing an improvement of an ... more Adaptive optics (AO) fundus imaging is an optoelectronic technique allowing an improvement of an order of magnitude of lateral resolution of retinal images. Currently, its main applications in ophthalmology span from photoreceptor to retinal pigment epithelial cells and vessels, each of them being affected by specific diseases. Technological and image processing improvements are expanding the scope of its medical applications. Here we will review some of the current and envisioned applications of AO in clinical practice.
Retina, 2015
Background: In healthy fundi, glistening whitish dots (so-called Gunn's dots) can often be seen, ... more Background: In healthy fundi, glistening whitish dots (so-called Gunn's dots) can often be seen, especially in young subjects. They are commonly attributed to the reflectance of Müller cell's footplates. However, despite their potential interest as biomarkers of retinal diseases, Gunn's dots have received little attention in the scientific literature. Methods: Scanning laser ophthalmoscope reflectance imaging and adaptive optics infrared flood imaging were performed in 18 healthy subjects (age range, 18-58 years) to analyze the localization, density, and shape of Gunn's dots. Results: Gunn's dots were more easily observed in the midperipheral retina along temporal vessels, although in two subjects, they could be detected in the macula. The reflectance of Gunn's dots showed a strong directional variability, which paralleled that of the inner limiting membrane. The mean (±SD) diameter of Gunn's dots was 13.3 mm (±3.5). Their density peaked at 120 per square millimeter and decreased with age to become barely detectable after 50 years. Conclusion: Gunn's dots are highly anisotropic structures close to the inner limiting membrane. The density, size, and age-related decline are closer to the characteristics of hyalocytes than those of Müller cells. Further studies are necessary to progress in the determination of their origin and interest as biomarkers of retinal diseases.
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Papers by CHAHIRA MILOUDI