eco-. (iːkəu) prefix. concerned with living things in relation to their environment. the eco-system.

Cylindrical lensOptics

Pearl No. 6: In cataract surgery, targeting emmetropia has a greater effect on Snellen acuity outcome than manipulating spherical aberration. Thus, surgeons should first optimize their formulas for IOL power calculation before adjusting spherical aberration. Aspheric IOLs improve the quality of vision by providing greater contrast sensitivity, not by increasing Snellen acuity. An increase in spherical aberration away from 0.00 causes a decrease in contrast sensitivity.4

by AL Pettersson · 2008 · Cited by 49 — Spherical aberration is by definition rotationally symmetric [6] and varies markedly within the population with a mean of about 0.1 ± 0.1 μm with a 6 mm pupil [ ...

Even multi-lens objectives are often called photographic lenses. In a few cases (e.g. of some tele objectives), they also contain mirrors. Important Parameters ...

Pearl No. 4: Measurements of spherical aberrations of the anterior corneal surface have found the average value to be 0.27 μm with a large standard deviation of 0.10 μm. Due to this variation, the value should be measured for each individual patient.3

Pearl No. 1: The wavefront characteristics of light can be described in mathematical terms using different systems, including Zernike polynomials and Fourier analysis. Using Zernike polynomials, sphere (defocus) and cylinder (astigmatism) describe the two higher-order aberrations (HOAs) that we measure with phoropters. These aberrations account for approximately 83% of the magnitude of the wavefront of light. Spherical aberration and coma are the next most significant HOAs. Spherical aberration describes the amount of bending that occurs as light passes through a refracting surface, such as the cornea, and compares the relative position of the focal points for the peripheral and central light beams. Positive spherical aberration occurs when the peripheral rays are focused in front of the central rays; this value is expressed in microns.

In the field of optometry, cylindrical lenses are crucial for subjective refraction tests. A cross cylinder, which combines two cylindrical lenses with equal strength but opposite power, is often used to diagnose astigmatism. This tool helps in assessing both the strength and axis of the astigmatic power, ensuring accurate prescriptions for corrective eyewear. Beyond medical applications, cylindrical lens optics are also employed in laser systems, imaging, and optical data storage, showcasing their versatility and importance in modern technology.

Pearl No. 7: Using aspheric IOLs improves driving safety due to improved contrast sensitivity. This is particularly evident on nighttime simulation testing, in which up to a 45-foot advantage in stopping distance at 55 mph (88.51 km/hr) can be achieved.5

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Cataract & Refractive Surgery Today Global | Europe Edition delivers cutting-edge information to cataract and refractive surgeons. CRST Global | Europe Edition promotes continuing education by covering such topics as surgical pearls, complications management, technological advances, and practice management. MORE ABOUT CRSTG | Europe Edition »

The Triton line scan camera is ideal for a wide range of high-speed applications such as continuous inspection of paper, plastic, and metal manufacturing.

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Pearl No. 9: The clearest image is provided when the total spherical aberration value for the eye is 0.00. Most of the effect of targeting this value is seen in nighttime lighting conditions (Figure 3).6

Pearl No. 12: Negative aspheric IOLs have a slightly higher power centrally. For a 20.00 D lens, this power can be 0.50 D greater and, thus, provides some pseudoaccommodative effect. This is one explanation for increased near vision in patients implanted with aspheric IOLs.

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Cylindrical lenses are specialized optical components used primarily to correct astigmatism, a common refractive error in the eye. Unlike spherical lenses, which have the same curvature in all directions, cylindrical lenses have curvature in only one direction. This unique property allows them to focus light into a line rather than a point, making them ideal for applications requiring precise control over light direction and focus. OST Photonics, a leader in cylindrical optics, offers high-quality cylindrical lenses designed to meet various optical needs.

Pearl No. 8: The impact of spherical aberration is dependent on pupil size. For practical purposes, spherical aberration comes into play when pupils are greater than 4 mm; thus, it has the most impact under mesopic or scotopic conditions and in younger patients. Older individuals may have large pupils, so pupils should be measured for each patient if aspheric IOLs are to be used.

Used to provide focusing power in one section only. For illumination or detection of light from line sources. Also used for the anamorphic compression of beams and images.

Jan 1, 2024 — FOV is measured in degrees and tells you how much area a camera can capture. Wide-angle lenses cover more area but with less detail. Telephoto ...

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Pearl No. 3: In the human eye, HOAs come primarily from the anterior corneal surface and the lens; other sources are the posterior corneal surface and the retina. In an aphakic eye, the anterior corneal surface accounts for 98% of wavefront changes. Small-incision (less than 2.8 mm) cataract surgery causes minimal changes in the spherical aberration of the eye and, for practical terms, can be considered to have no effect.2

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Cylindrical lenses are utilized for astigmatism correction in the eye and rangefinders, inducing astigmatism by elongating a point of light into a line. They find extensive application in barcode scanning, projection optics systems, laser measurement systems, and holography. Ost Photonics offers cylindrical lenses in plano-concave or plano-convex configurations.

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Sep 21, 2022 — ... 1x magnification. For tactical work, the LPVO should be stored or carried on 1x power. This allows the shooter to react the fastest to ...

George H.H. Beiko, BM, BCh, FRCSC, is an Assistant Professor of Ophthalmology at McMaster University and a Lecturer at the University of Toronto, Canada. Dr. Beiko states that he is a consultant to Abbott Medical Optics Inc. He may be reached at e-mail: george.beiko@ sympatico.ca.

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Dec 30, 2020 — Crystal clear focus on any task Trades and craftspeople understand the value of magnification. Whether you're into ceramics, leather, ...

Pearl No. 5: The presence of spherical aberrations can cause glare and halo around lights. The greater the degree of spherical aberration, the greater amount of halo that is induced (Figure 2).

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Pearl No. 14: Tilt and decentration affect the performance of aspheric IOLs. Aspheric lenses must be decentered more than 0.8 mm and tilted more than 10° before all effect is lost.8

Pearl No. 10: Refractive error can compensate for residual spherical aberration. Positive spherical aberration causes a myopic shift, and negative spherical aberration causes a hyperopic shift in refraction. Although refractive error is independent of pupil size, spherical aberration is dependent on pupil size; for small pupils, it can be negligible, but for larger pupils it is significant in its effect. Thus, refractive error will compensate for spherical aberration at larger pupil sizes but will introduce defocus at smaller pupil sizes (Figure 4). This information can be used to customize results for individual patients based on the choice of aspheric IOL.7

Pearl No. 13: Corneal spherical aberration and Q value are not the same thing. Spherical aberration describes how a wavefront deviates from the ideal after passing through a refracting surface. In actuality, it is a measure of the effect a surface has on light and is measured in microns. The Q value describes the refracting surface and is a measure of the shape of a surface; it has no units. The shape of a surface does affect spherical aberration. An ideal spherical surface has a Q value of 0.00. A prolate surface has a negative Q value; a parabola is a prolate surface that eliminates all spherical aberration and has a Q value of -0.50. The human cornea has an average Q value of -0.26; it would require a value of -0.52 to eliminate all spherical aberration. The Q value of a young adult crystalline lens is -0.25; thus, the combined value for a young phakic eye results in elimination of spherical aberration. As the lens ages, the Q value changes, and after age 40 is 0.00. With a perfect single refracting surface such as an ellipse, keratometry and Q value could be used to calculate the spherical aberration of that surface. For a corneal Q value of -0.26 and average keratometry of 44.00 D, the calculated spherical aberration is 0.18 μm. The average measured spherical aberration of the cornea is 0.27 μm because the cornea has a complex surface that is steeper centrally. Common aspheric IOLs correct the average theoretical corneal spherical aberration, the average measured corneal spherical aberration, or do not influence it.

Use the adjective mechanical to describe something related to machinery or tools. If your car breaks down on the same day that your watch stops, ...

Pearl No. 2: The wavefront of the human eye can be measured using wavefront analyzers such as Shack- Hartmann systems and Tracey aberrometers (iTRACE; Tracey Technologies, Corp.). Corneal topographers can measure the front surface of the cornea (Figure 1), and this data can be transformed to determine the HOAs of the cornea. By convention, corneal spherical aberration is measured at 6 mm.1

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Pearl No. 15: Leaving spherical aberration (positive or negative) in the optical system improves depth of focus, but at the cost of loss of contrast vision. Current strategies involve targeting up to -0.30 to -0.40 µm of spherical aberration in one eye, so as to increase depth of focus without significantly affecting Snellen acuity.