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Imaging Glaucomatous Damage Across the Temporal Raphe
摘要： PURPOSE. To image and analyze anatomical differences at the temporal raphe between normal and glaucomatous eyes using adaptive optics scanning laser ophthalmoscopy (AOSLO) and optical coherence tomography (OCT), and to relate these differences to visual ?eld measurements. METHODS. Nine glaucomatous eyes of 9 patients (age 54–78 years, mean deviation of visual ?eld [MD] (cid:2)5.03 to (cid:2)0.20 dB) and 10 normal eyes of 10 controls (age 54–81, MD (cid:2)1.13 to t1.39 dB) were enrolled. All the participants were imaged in a region that was centered approximately 98 temporal to the fovea. The size of imaging region was at least 108 vertically by 48 horizontally. The raphe gap, de?ned as the distance between the superior and inferior retinal nerve ?ber layer (RNFL) bundles, was measured. A bundle index was computed to quantify the relative re?ectivity and density of the nerve ?ber bundles. We also measured thickness of the ganglion cell complex (GCC) and RNFL. RESULTS. The raphe gap was larger in glaucomatous eyes than control eyes. Speci?cally, eight glaucomatous eyes with local averaged ?eld loss no worse than (cid:2)3.5 dB had larger raphe gaps than all control eyes. The bundle index, GCC thickness, and RNFL thickness were on average reduced in glaucomatous eyes, with the ?rst two showing statistically signi?cant differences between the two groups. CONCLUSIONS. Structural changes in the temporal raphe were observed and quanti?ed even when local functional loss was mild. These techniques open the possibility of using the raphe as a site for glaucoma research and clinical assessment.
关键词： visual ?eld,OCT,raphe,glaucoma,adaptive optics
更新于2025-09-04 15:30:14
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Accommodation Responds to Optical Vergence and Not Defocus Blur Alone
摘要： To determine whether changes in wavefront spherical curvature (optical vergence) are a directional cue for accommodation. Nine subjects participated in this experiment. The accommodation response to a monochromatic target was measured continuously with a custom-made adaptive optics system while astigmatism and higher-order aberrations were corrected in real time. There were two experimental open-loop conditions: vergence-driven condition, where the deformable mirror provided sinusoidal changes in defocus at the retina between (cid:2)1 and t1 diopters (D) at 0.2 Hz; and blur-driven condition, in which the level of defocus at the retina was always 0 D, but a sinusoidal defocus blur between (cid:2)1 and t1 D at 0.2 Hz was simulated in the target. Right before the beginning of each trial, the target was moved to an accommodative demand of 2 D. Eight out of nine subjects showed sinusoidal responses for the vergence-driven condition but not for the blur-driven condition. Their average (6SD) gain for the vergence-driven condition was 0.50 (60.28). For the blur-driven condition, average gain was much smaller at 0.07 (60.03). The ninth subject showed little to no response for both conditions, with average gain <0.08. Vergence-driven condition gain was significantly different from blur-driven condition gain (P ? 0.004). Accommodation responds to optical vergence, even without feedback, and not to changes in defocus blur alone. These results suggest the presence of a retinal mechanism that provides a directional cue for accommodation from optical vergence.
关键词： accommodation,vergence,defocus blur,adaptive optics,dynamic accommodation
更新于2025-09-04 15:30:14
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Metasurface with pull
摘要： Using light to manipulate small particles has proven an indispensable tool for ‘tweezing’, sorting and force measurements. To achieve effective optical traps with high ‘stiffness’, researchers often go to great lengths to tailor light fields, for example by using holographic elements. Now, Aliaksandra Ivinskaya and colleagues from Russia, the USA, the UK and Israel predict that small particles can be manipulated using a plane wave of light and a simple flat surface of an anisotropic media supporting hyperbolic modes. Their hyperbolic metamaterial is composed of metal and dielectric layers and is potentially less affected by losses and offers more broadband capability than purely plasmonic approaches. In their theoretical study a small dielectric sphere near a hyperbolic metamaterial is considered. The particle is sufficiently small to provide the required momentum to excite both surface plasmon and bulk hyperbolic waves from incident plane waves. Strong optical pulling forces were predicted over the 400–800 nm wavelength range thanks to the broadband high density of states of hyperbolic modes.
关键词： metasurface,hyperbolic modes,plasmon,nano-optics,optical manipulation
更新于2025-09-04 15:30:14