Experimental demonstration of ray-rotation sheets.

We have built microstructured sheets that rotate, on transmission, the direction of light rays by an arbitrary, but fixed, angle around the sheet normal. These ray-rotation sheets comprise two pairs of confocal lenticular arrays. In addition to rotating the direction of transmitted light rays, our sheets also offset ray position sideways on the scale of the diameter of the lenticules.

Experimental demonstration of ray-optical refraction with confocal lenslet arrays.

We observe imaging through windows comprising pairs of confocal lenslet arrays that have different focal lengths but that are otherwise identical. Image space is stretched in the longitudinal direction only. Such windows are examples of METATOYs, optical components that can change light-ray direction in ways that appear wave-optically forbidden.

Measured double-pass intensity point-spread function after adaptive optics correction of ocular aberrations.

The double-pass intensity point-spread function was recorded in four subjects using a monochromatic source emitting at 543 nm, through a 6.7-mm diameter pupil i) at the fovea after adaptive optics correction of the ocular aberrations, ii) at the fovea without adaptive optics correction, and iii) at 2 degrees of eccentricity with adaptive optics correction. The half-width at half-maximum of the double-pass point-spread function was narrower after correction of the ocular aberrations.

Regulation of subfoveal choroidal blood flow in age-related macular degeneration.

Purpose: To assess the capability of the subfoveal choroidal circulation to regulate its blood flow in response to an acute increase in ocular perfusion pressure in the eyes of healthy elderly persons or of subjects with neovascular age-related macular degeneration (AMD).

Methods: Changes of subfoveal choroidal blood velocity (ChBVel), volume (ChBVol), and flow (ChBF) induced by isometric exercise were determined using laser Doppler flowmetry (LDF) in 19 young healthy volunteers (group 1), 24 elderly healthy volunteers with mild macular pigment distribution changes (group 2), and 23 subjects with subfoveal classic neovascularization caused by AMD (group 3).

Results: Isometric exercise induced significant increases in mean ocular perfusion pressure (PPm) of 19.

Visually evoked hemodynamical response and assessment of neurovascular coupling in the optic nerve and retina.

The retina and optic nerve are both optically accessible parts of the central nervous system. They represent, therefore, highly valuable tissues for studies of the intrinsic physiological mechanism postulated more than 100 years ago by Roy and Sherrington, by which neural activity is coupled to blood flow and metabolism. This article describes a series of animal and human studies that explored the changes in hemodynamics and oxygenation in the retina and optic nerve in response to increased neural activity, as well as the mechanisms underlying these changes.

Flicker-evoked response measured at the optic disc rim is reduced in ocular hypertension and early glaucoma.

Purpose: To determine in patients with ocular hypertension (OHT) or early glaucoma (EOAG) the change in blood flow measured at the neuroretinal rim of the optic disc in response to a 15-Hz diffuse green luminance flicker, a stimulus that activates predominantly the ganglion cell magnocellular pathway.

Methods: Thirteen patients with EOAG, 29 with OHT, and 16 age-matched control subjects, all with excellent fixation, were examined. Blood flow (F(onh)) at the neuroretinal rim of the optic disc was continuously monitored by laser Doppler flowmetry before and during exposure to a 15-Hz, 30 degrees field green luminance flicker.

Temporal dynamics and magnitude of the blood flow response at the optic disk in normal subjects during functional retinal flicker-stimulation.

Near-infrared laser Doppler flowmetry was applied in 15 normal volunteers to record the time course and magnitude of changes in the velocity (Vel), volume (Vol) and flow (F) of blood and tissue reflectance (R) at the optic disk in response to 40 and 50 s of increased retinal neural activity. This activity was evoked by diffuse luminance flicker of the retinal posterior pole. After 20 s of flicker, the group averages of Vel, Vol, and F were significantly higher than at baseline (pre-flicker) by 12, 24 and 38%.

Flicker-evoked changes in human optic nerve blood flow: relationship with retinal neural activity.

Purpose: Visual flicker induces a response in human optic nerve blood flow (F(onh)) and inner retinal activity, as assessed by laser Doppler flowmetry and electroretinogram (ERG), respectively. In this study the relationship was examined between the flicker-evoked changes in F(onh) (RF(onh)) and ERG when various parameters of the stimulus were varied.

Methods: In five normal observers (mean age, 41; range, 25-62 years) F(onh) and ERG were recorded simultaneously in response to pure red (R) or pure green (G) flicker, as well as heterochromatic R-G flicker (30 degrees field at the posterior pole).

Relationship of blood flow changes of the human optic nerve with neural retinal activity: a new approach to the study of neuro-ophthalmic disorders.

Background: The relationship between the flicker-evoked changes in optic nerve blood flow (F onh ) and neural retinal activity was investigated by laser Doppler flowmetry and electroretinogram (ERG), respectively.

Material And Methods: In five normal subjects F onh was continuously recorded before, during and after exposure to green flicker modulation (30 degrees field at the posterior pole), at different levels of mean illuminance between 0.9 and 13.