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Cataract extraction following refractive surgery poses special problems for the patient and the surgeon because the corneal change as a result of refractive surgery complicates accurate keratometry, a key element of lens implant power calculation. After laser refractive surgery for myopia, this could result in overestimation of corneal power ...
[1]: 276 The crystalline lens of the human eye is an example of a GRIN lens with a refractive index varying from about 1.406 in the inner core to approximately 1.386 at the less dense cortex. [ 1 ] : 203 Some common mirages are caused by a spatially varying refractive index of air .
A Luneburg lens (original German Lüneburg-Linse) is a spherically symmetric gradient-index lens. A typical Luneburg lens's refractive index n decreases radially from the center to the outer surface. They can be made for use with electromagnetic radiation from visible light to radio waves. For certain index profiles, the lens will form perfect ...
The calculation of glass properties allows "fine-tuning" of desired material characteristics, e.g., the refractive index. [1]The calculation of glass properties (glass modeling) is used to predict glass properties of interest or glass behavior under certain conditions (e.g., during production) without experimental investigation, based on past data and experience, with the intention to save ...
Glasses' Abbe numbers, along with their mean refractive indices, are used in the calculation of the required refractive powers of the elements of achromatic lenses in order to cancel chromatic aberration to first order. These two parameters which enter into the equations for design of achromatic doublets are exactly what is plotted on an Abbe ...
A-scan ultrasound biometry, commonly referred to as an A-scan (short for Amplitude scan), uses an ultrasound instrument for diagnostic testing. [1] A-scan biometry measures the axial length (AL) of the eye prior to cataract surgery in order to assess the refractive power of the intraocular lens that will be implanted.
For common optical glasses, the refractive index calculated with the three-term Sellmeier equation deviates from the actual refractive index by less than 5×10 −6 over the wavelengths' range [5] of 365 nm to 2.3 μm, which is of the order of the homogeneity of a glass sample. [6]
A phakic intraocular lens (PIOL) is an intraocular lens that is implanted surgically into the eye to correct refractive errors without removing the natural lens (also known as "phakos", hence the term). Intraocular lenses that are implanted into eyes after the eye's natural lens has been removed during cataract surgery are known as pseudophakic.