Spherical aberration in relation to visual performance in contact lens wear
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The optical characteristics of the vertebrate crystalline lens are reviewed in terms of environmental concerns and spherical aberration. Lens shape and relative size are determined by such factors as whether the eye is to be used in air or water and whether it is to be used under scotopic or photopic conditions. The continued growth of the lens through life can be related to whether the lens exhibits positive or negative spherical aberration. In general, spherical aberration, as measured using a split laser beam method with excised lenses, is minimized in species with life histories indicating superior resolution ability. In addition, lens optical quality, as indicated by zonular differences in focal length, deteriorates with lens age. Finally, the measurement of spherical aberration may be used to monitor lens integrity during lens culture experiments.
Scotopic vision
Coma (optics)
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To determine the ocular spherical aberration after using preoperative corneal spherical aberration guided aspheric IOL selection for cataract surgery.Twenty-six eyes of cataract patients were scheduled for cataract surgery with aspheric IOL implantation based on preoperative corneal spherical aberration (SA) measured by Galilei corneal topography. The target postoperative total wavefront spherical aberration was zero. Three types of LOL were used in this study: TecnisZA9003 (Abbott Medical Optics Inc) with spherical aberration of -0.27 microm; Acrysof LQ SN60WF (Alcon Inc.) with spherical aberration of -0.20 microm and B&L Akreos with zero spherical aberration. Ocular spherical aberration was measured with a Wave Light machine 3 months postoperatively to demonstrate the total ocular spherical aberration.The preoperative mean corneal spherical aberration in the 3 groups was 0.351 +/- 0.08, 0.181 +/- 0.04, and 0.056 +/- 0.03 microns respectively. All 26 eyes of 26 patients completed the 3-month follow-up visit. Postoperative ocular spherical aberration of the 3 groups were: TecnisZA9003 (10 eyes) +0.023 +/- 0.011 microm; Acrysof IQ SN60WF (11 eyes) +0.045 +/- 0.018 microm; and B&L Akreos (5 eyes) +0.018 +/- 0.008 microm. These values were significantly lower than the predicted values in the Tecnis and Akreos groups and there was no correlation between the actual postoperative ocular spherical aberration and the predicted ocular spherical aberration in all groups.The implantation of an aspheric intraocular lens based on preoperative corneal spherical aberration is effective in reducing total ocular spherical aberration and improving visual function.
Intraocular lenses
Spherical model
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This paper deals with the problem of replacing a thin lens by a thick lens with approximately the same properties as the thin lens. Equations enabling the calculation of the parameters of a thick lens that has the same focal length and the same value for one of the Seidel aberration coefficients (either the Seidel aberration coefficient of spherical aberration or the Seidel aberration coefficient of coma) as the thin lens are derived. A comparison of the proposed method for calculating the parameters of the thick lens with existing methods is given in examples. Further, the problem of replacing a thick lens made of optical glass with a given refractive index by another thick lens with a different refractive index but with the same focal length and the same Seidel aberration coefficient of spherical aberration is investigated.
Coma (optics)
Thin lens
Chromatic aberration
Simple lens
Optical aberration
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Gradient index rod lenses have been successfully applied to imaging systems and micro-optical circuits in electro-optical systems. When the rod lens is used as a light-focusing micro device such as a pick-up lens in the video disk, a high numerical aperture (NA) is necessary in order to get a small focused spot. NA of the rod lens is determined by the quadratic gradient constant g of the refractive-index profile, the diameter, and the length of the lens. However, NA can be changed by making an end surface spherical even if those parameters are made constant. On the other hand, the spherical surface has the minus spherical aberration, so it becomes possible to compensate the plus aberration of the rod lens by the spherical surface. 1)
Gradient-index optics
Numerical aperture
Aperture (computer memory)
Simple lens
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Most municipalities require that police officer applicants have a minimum level of uncorrected visual acuity. The primary basis for the uncorrected acuity standards is that an officer can have spectacles forcibly removed and would need a minimum level of vision to continue performing his/her duties. This article discusses the pros and cons of allowing contact lens wearers to bypass the uncorrected visual acuity standard. Although there are several factors that can make the contact lens wearer a less desirable recruit, a good contact lens wearer who doesn't meet the uncorrected standard could safely and efficiently perform the duties of a police officer. It is recommended that a municipality may consider waiving the uncorrected visual acuity standard for a good contact lens wearing candidate. Suggested guidelines for implementing this policy are discussed.
Officer
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Purpose: The present study was conducted to investigate the actual condition of circle lens wear and the differences caused by the pigmentation in blinking rate, non-invasive tear break-up time (NIBUT), and lens surface between circle and soft contact lens wear during clinical application. Methods: Eighty subjects were surveyed to know the actual condition of wearing circle lens. Blink rate, NIBUT of 20 subjects in twenties were measured after separately wearing soft contact lens and circle lens for 5 days. Their lens surfaces were also observed by scanning electron microscope. Results: Fifty percent of circle lens wearers answered that major reason for changing circle lens was discomfort and 67% of answerers wore circle lens more than 6 hours a day. The tendency of increased blink rates in both wearers of circle and soft contact lens at 30 minutes later when tear film stabilized and 3 hour after lens wearing was shown on the 1st, 3rd and 5th day with expanding wearing time. Especially at 3 hours after lens wearing on the 3rd and 5th day, the difference of blink rates was statistically different in circle lens wear and soft contact lens wear. The NIBUTs of soft contact lens wearers and circle lens wearers were 6.0 and 3.7 secs, respectively, at 30 min later on 1st day and were significantly different. NIBUTs of soft contact lens wearers and circle lens wearers were also statistically different 3 hrs after lens wearing on the 1st day and the similar pattern of NIBUTs was shown on the 3rd and 5th day. The roughness of both surfaces in soft contact lens and front surface in circle lens was same. However, pigmented front surface of circle lens was rougher and uneven. Conclusions: As the results, the circle lens wearers might feel discomfort in clinical application since the difference in lens surface of circle lens would change lens wettability during wearing. The difference by tinting contact lens was shown from the result, which could help better wearing circle lens.
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Among the optical equipments spherical surface lens has been used widely today. But this kind of lens forms big aberration easily. Non-spherical surface lens can get rid of the spherical surface lens' shortcoming and will be highly valuable. This article gives some optical surfaces and lens that have no spherical aberration, with this type of lens can raise the quality of formation that images by optical equipments and simplify their structure inside.
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This paper reports results of the first test of a unipotential electron lens whose end electrodes are electron-transparent foils. This lens is unusual among electrostatic unipotential lenses in that it can have negative values for both its focal length and third-order spherical aberration coefficient. Preliminary measurements of these quantities have been made on a foil lens and are compared with theoretical values. Some of the practical limitations in using foils as lens elements are considered, and a potential use for this lens as part of a spherical aberration corrected doublet is discussed.
Electrostatic lens
Electron optics
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