Opto-mechanical artificial eye with accommodative ability.

The purpose of this study was to describe the design and characterization of a new opto-mechanical artificial eye (OMAE) with accommodative ability. The OMAE design is based on a second-pass configuration where a small source of light is used at the artificial retina plane. A lens whose focal length can be changed electronically was used to add the accommodation capability. The changes in the OMAE's aberrations with the lens focal length, which effectively changes the accommodative state of the OMAE, were measured with a commercial aberrometer. Changes in power and aberrations with room temperature were also measured. The OMAE's higher-order aberrations (HOAs) were similar to the ones of the human eye, including the rate at which fourth-order spherical aberration decreased with accommodation. The OMAE design proposed here is simple, and it can be implemented in an optical system to mimic the optics of the human eye

Fundus topographical distribution patterns of ocular toxoplasmosis

BACKGROUND: To establish topographic maps and determine fundus distribution patterns of ocular toxoplasmosis (OT) lesions. METHODS: In this retrospective study, patients who presented with OT to ophthalmology clinics from four countries (Argentina, Turkey, UK, USA) were included. Size, shape and location of primary (1°)/recurrent (2°) and active/inactive lesions were converted into a two-dimensional retinal chart by a retinal drawing software. A final contour map of the merged image charts was then created using a custom Matlab programme. Descriptive analyses were performed. RESULTS: 984 lesions in 514 eyes of 464 subjects (53% women) were included. Mean area of all 1° and 2° lesions was 5.96±12.26 and 5.21±12.77 mm2, respectively. For the subset group lesions (eyes with both 1° and 2° lesions), 1° lesions were significantly larger than 2° lesions (5.52±6.04 mm2 vs 4.09±8.90 mm2, p=0.038). Mean distances from foveola to 1° and 2° lesion centres were 6336±4267 and 5763±3491 µm, respectively. The majority of lesions were found in temporal quadrant (p<0.001). Maximum overlap of all lesions was at 278 µm inferotemporal to foveola. CONCLUSION: The 1° lesions were larger than 2° lesions. The 2° lesions were not significantly closer to fovea than 1° lesions. Temporal quadrant and macular region were found to be densely affected underlining the vision threatening nature of the disease

Examining In Vivo Changes in Lamina Cribrosa in Non-human Primates with Experimental Glaucoma

Glaucoma is a disease that results in the degeneration of retinal ganglion cell axons and the death of retinal ganglion cells (RGCs). It is one of the leading causes of permanent blindness worldwide. Clinical examinations currently in practice are limited in their ability to detect glaucoma prior to loss of RGC axons. The main goal of this work is to characterize early changes in the optic nerve head of monkeys with experimental glaucoma (EG) using in vivo and non-invasive methods to better understand the mechanisms behind glaucoma. In vivo images of the lamina cribrosa were acquired using a spectral domain optical coherence tomography and an adaptive optics scanning laser ophthalmoscope (AOSLO). We transformed 2D AOSLO images onto a 3D anterior lamina cribrosa surface (ALCS) and computed the 3D morphometry of the ALCS. Using principal component analysis (PCA), we estimated the predominant local ALCS beam orientation directly from raw grayscale in vivo images without the need for binary segmentation. Subsequently, we developed an automated method to segment the lamina cribrosa pores using level sets. Our 3D transformation method provides a better representation of the ALCS from in vivo images. Following 3D transformation, mean pore area increased by 5.1 ± 2.0% in 11 normal eyes and 16.2 ± 5.9% in 4 glaucomatous eyes due to the increased curvatures. Our PCA technique yielded small errors in local orientation (0.2 ± 0.2◦) when tested on synthetic data, accurately determined local beam orientation and was repeatable in control eyes over time. In addition, automated segmentation of pore boundaries using level sets method was comparable to manual segmentation (sensitivity = 83%, specificity = 95%) and yielded repeatable values over time. In conclusion, the PCA beam orientation and level sets segmentation methods can be used to accurately and objectively detect and track in vivo changes in lamina cribrosa microarchitecture during the progression of EG.Computer Science, Department o

Comparison of confocal and non-confocal split-detection cone photoreceptor imaging

Quadrant reflectance confocal and non-confocal scanning light ophthalmoscope images of the photoreceptor mosaic were recorded in a subject with congenital achromatopsia (ACHM) and a normal control. These images, captured with various circular and annular apertures, were used to calculate split-detection images, revealing two cone photoreceptor contrast mechanisms. The first contrast mechanism, maximal in the non-confocal 5.5-10 Airy disk diameter annular region, is unrelated to the cone reflectivity in confocal or flood illumination imaging. The second mechanism, maximal for confocal split-detection, is related to the cone reflectivity in confocal or flood illumination imaging that originates from the ellipsoid zone and/or inner-outer segment junction. Seeking to maximize image contrast, split-detection images were generated using various quadrant detector combinations, with opposite (diagonal) quadrant detectors producing the highest contrast. Split-detection generated with the addition of adjacent quadrant detector pairs, shows lower contrast, while azimuthal split-detection images, calculated from adjacent quadrant detectors, showed the lowest contrast. Finally, the integration of image pairs with orthogonal split directions was used to produce images in which the photoreceptor contrast does not change with direction.</jats:p