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The aim of an accurate intraocular lens power calculation is to provide an intraocular lens (IOL) that fits the specific needs and desires of the individual patient. The development of better instrumentation for measuring the eye's axial length (AL) and the use of more precise mathematical formulas to perform the appropriate calculations have significantly improved the accuracy with which the ...
Vertex distance is the distance between the back surface of a corrective lens, i.e. glasses (spectacles) or contact lenses, and the front of the cornea. Increasing or decreasing the vertex distance changes the optical properties of the system, by moving the focal point forward or backward, effectively changing the power of the lens relative to ...
The CoC size of 0.025 mm for this format appears in Jacobson's Photographic Lenses Tutorial, [1] and the 1730 in his 1996 Photographic Lenses FAQ. [2] Jacobson derived the 0.025 mm CoC number from analysis of the Zeiss Triotar lens DoF markings on the Rollei B35 (see photo). The manual for the Rollei B35 also states 0.025 mm CoC for its ...
Fresnel equations calculator FreeSnell – Free software computes the optical properties of multilayer materials. Thinfilm – Web interface for calculating optical properties of thin films and multilayer materials (reflection & transmission coefficients, ellipsometric parameters Psi & Delta).
Pre-operative measurements, including corneal curvature, axial length, and white-to-white measurements are used to estimate the required power of the IOL. These methods include several formulae, including Hagis, [32] Hoffer Q, [32] Holladay 1, [32] Holladay 2, [32] and SRK/T. [33] Free online calculators use similar input data. [32]
For example, on the Minox LX focusing dial there is a red dot between 2 m and infinity; when the lens is set at the red dot, that is, focused at the hyperfocal distance, the depth of field stretches from 2 m to infinity. Some lenses have markings indicating the hyperfocal range for specific f-stops, also called a depth-of-field scale. [3]
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35 mm equivalent focal lengths are calculated by multiplying the actual focal length of the lens by the crop factor of the sensor. Typical crop factors are 1.26× – 1.29× for Canon (1.35× for Sigma "H") APS-H format, 1.5× for Nikon APS-C ("DX") format (also used by Sony, Pentax, Fuji, Samsung and others), 1.6× for Canon APS-C format, 2× for Micro Four Thirds format, 2.7× for 1-inch ...