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The Abbe number is a measure of the dispersion of a transparent material, with high values indicating low dispersion. It is used in lens design and classification of glasses, and can be calculated from the refractive indices at different wavelengths.
A corrective lens is a device that improves visual perception by correcting refractive errors. Learn about the different types of corrective lenses, such as glasses, contact lenses, intraocular lenses, and their prescriptions, uses, and advantages.
Learn how to determine the power of intraocular lens (IOL) for cataract surgery using different methods and formulas. The web page explains the factors affecting IOL power calculation, such as axial length, corneal power, estimated lens position and anterior chamber constant.
Cataract surgery is the removal of the natural lens of the eye that has developed a cataract, an opaque or cloudy area. The eye's natural lens is usually replaced with an artificial intraocular lens (IOL) implant. Learn about the causes, symptoms, diagnosis and methods of cataract surgery.
Clear lens extraction is a surgical procedure to remove the clear lens of the eye and replace it with an intraocular lens. It is used to correct refractive errors, treat glaucoma and prevent cataract.
A phakic intraocular lens (PIOL) is a surgical implant to correct high refractive errors without removing the natural lens. Learn about the types, uses, advantages, disadvantages, complications and contraindications of PIOLs.
A progressive lens is a corrective lens used in eyeglasses to correct presbyopia and other disorders of accommodation. It has a gradient of increasing lens power from top to bottom, and can provide clear vision at different distances. Learn about its history, design, advantages, disadvantages and adaptation.
Memorial in Jena, Germany to Ernst Karl Abbe, who approximated the diffraction limit of a microscope as = , where d is the resolvable feature size, λ is the wavelength of light, n is the index of refraction of the medium being imaged in, and θ (depicted as α in the inscription) is the half-angle subtended by the optical objective lens (representing the numerical aperture).