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A study on the effects and visibility of low-order aberrations on laser beams with orbital angular momentum
摘要： Laguerre–Gaussian-like laser beams have been proposed for driving experiments with high-intensity lasers. They carry orbital angular momentum and exhibit a ring-shaped intensity distribution in the far field which make them particularly attractive for various applications. We show experimentally and numerically that this donut-like shape is extremely sensitive to off-axis wavefront deformations. To support our claim, we generate a Laguerre–Gaussian-like laser beam and apply a selection of common low-order wavefront aberrations. We investigate the visibility of those wavefront deformations in the far field. Under use of established tolerance criteria, we determine the thresholds for the applied aberration and compare the findings with simulations for verification.
关键词： tolerance criteria,Laguerre–Gaussian-like laser beams,orbital angular momentum,far field,wavefront aberrations
更新于2025-09-19 17:13:59
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Optical and neural anisotropy in peripheral vision
摘要： Optical blur in the peripheral retina is known to be highly anisotropic due to nonrotationally symmetric wavefront aberrations such as astigmatism and coma. At the neural level, the visual system exhibits anisotropies in orientation sensitivity across the visual field. In the fovea, the visual system shows higher sensitivity for cardinal over diagonal orientations, which is referred to as the oblique effect. However, in the peripheral retina, the neural visual system becomes more sensitive to radially-oriented signals, a phenomenon known as the meridional effect. Here, we examined the relative contributions of optics and neural processing to the meridional effect in 10 participants at 08, 108, and 208 in the temporal retina. Optical anisotropy was quantified by measuring the eye’s habitual wavefront aberrations. Alternatively, neural anisotropy was evaluated by measuring contrast sensitivity (at 2 and 4 cyc/deg) while correcting the eye’s aberrations with an adaptive optics vision simulator, thus bypassing any optical factors. As eccentricity increased, optical and neural anisotropy increased in magnitude. The average ratio of horizontal to vertical optical MTF (at 2 and 4 cyc/deg) at 08, 108, and 208 was 0.96 6 0.14, 1.41 6 0.54 and 2.15 6 1.38, respectively. Similarly, the average ratio of horizontal to vertical contrast sensitivity with full optical correction at 08, 108, and 208 was 0.99 6 0.15, 1.28 6 0.28 and 1.75 6 0.80, respectively. These results indicate that the neural system’s orientation sensitivity coincides with habitual blur orientation. These findings support the neural origin of the meridional effect and raise important questions regarding the role of peripheral anisotropic optical quality in developing the meridional effect and emmetropization.
关键词： peripheral retina,anisotropy,wavefront aberrations,neural adaptation,adaptive optics
更新于2025-09-11 14:15:04
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Intrastromal crosslinking in post-LASIK ectasia
摘要： We describe a case of early post-LASIK ectasia detected in the first 6 months after surgery. The patient was treated by means of intrastromal corneal crosslinking under the flap, without de-epithelialization, which resulted in a positive outcome. At the time of writing, 2 years after the procedure, the patient remained free of progression.
关键词： Keratomileusis, laser in situ,Adult,Case reports,Corneal wavefront aberrations,Corneal stroma,Astigmatism,Postoperative complications,Cross-linking reagent,Refractive surgical procedures,Humans,Female
更新于2025-09-09 09:28:46
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Impact of higher-order aberrations on depth-of-field
摘要： It is well known that depth-of-focus (DOF) is influenced by optical factors (such as pupil size and monochromatic aberrations). However, neural factors such as blur sensitivity and defocus adaptation may play an important role on the extent of DOF. A series of experiments were conducted to study if optical or neural factors are most pertinent in explaining the variability of DOF across subjects. An adaptive optics system with a black and white target, a 3.8-mm artificial pupil, and a subjective criterion (based on objectionable blur) were used to measure depth of field ([DOFi]; DOF computed in the object space) in 11 participants, after at least 6 min of adaptation. This was done under three conditions: (a) with their own higher order aberrations (HOA); (b) after correction of their monochromatic HOA; and (c) after altering the HOA pattern for some participants to reflect the HOA pattern measured for a different participant. Natural DOFi and DOFi after HOA correction were positively correlated (R2 ? 0.461), but a significant decrease in DOFi (21% on average) was found after HOA correction (p ? 0.042). Effect of HOA on the intersubject variability of DOFi was 3.9 times smaller than the effect of the image neural processing. This study shows that DOFi depends on both optical and neural factors, but the latter seems to play a more important role than the former.
关键词： depth of focus,visual optics,wavefront aberrations,depth of field,physiological optics
更新于2025-09-09 09:28:46
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Repeatability and Reproducibility of Anterior Segment Measurements in Normal Eyes Using Dual Scheimpflug Analyzer
摘要： Objectives: To assess the repeatability and reproducibility of anterior segment measurements including aberrometric measurements Materials and Methods: Three repeated consecutive measurements were taken by two independent examiners. The following were evaluated: total corneal power and posterior corneal power, corneal higher-order wavefront aberrations (6.0 mm pupil), pachymetry at the central, paracentral, and peripheral zones, and anterior chamber depth (ACD). Repeatability was assessed by calculating the within-subject standard deviation (Sw), precision (Pr), repeatability (Rep), and intraclass correlation coefficient (ICC). Reproducibility was evaluated by Bland-Altman analysis. Results: Thirty eyes of 30 patients were included. The best ICC values were for corneal pachymetry and ACD. For both observers, acceptable ICC was also achieved for the other parameters, the only exceptions being posterior corneal astigmatism and total high order aberration. The 95% LoA (Limits of Agreement) values for all measurements showed small variability between the two examiners. Conclusion: The Galilei system provided reliable measurements of anterior segment parameters. Therefore, the instrument can be confidently used for routine clinical use and research purposes.
关键词： wavefront aberrations,interobserver repeatability,Galilei,intraobserver
更新于2025-09-04 15:30:14