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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 ...
The correct immersion oil for an objective lens has to be used to ensure that the refractive indices match closely. Use of an oil immersion lens with the incorrect immersion oil, or without immersion oil altogether, will suffer from spherical aberration. The strength of this effect depends on the size of the refractive index mismatch.
where n is the index of refraction of the medium in which the lens is working (1.00 for air, 1.33 for pure water, and typically 1.52 for immersion oil; [1] see also list of refractive indices), and θ is the half-angle of the maximum cone of light that can enter or exit the lens.
Viscosity index. The viscosity index (VI) is an arbitrary, unit-less measure of a fluid's change in viscosity relative to temperature change. It is mostly used to characterize the viscosity-temperature behavior of lubricating oils. The lower the VI, the more the viscosity is affected by changes in temperature.
Index-matching material. In optics, an index-matching material is a substance, usually a liquid, cement (adhesive), or gel, which has an index of refraction that closely approximates that of another object (such as a lens, material, fiber-optic, etc.). When two substances with the same index are in contact, light passes from one to the other ...
The Becke line test is a technique in optical mineralogy that helps determine the relative refractive index of two materials. It is done by lowering the stage (increasing the focal distance) of the petrographic microscope and observing which direction the light appears to move. This movement will always go into the material of higher refractive ...
A gradient-index lens with a parabolic variation of refractive index (n) with radial distance (x). The lens focuses light in the same way as a conventional lens. If the refractive index of a medium is not constant but varies gradually with the position, the material is known as a gradient-index (GRIN) medium and is described by gradient index ...
Total internal reflection fluorescence microscope. A total internal reflection fluorescence microscope (TIRFM) is a type of microscope with which a thin region of a specimen, usually less than 200 nanometers can be observed. TIRFM is an imaging modality which uses the excitation of fluorescent cells in a thin optical specimen section that is ...