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Abbe number. In optics and lens design, the Abbe number, also known as the V-number or constringence of a transparent material, is an approximate measure of the material's dispersion (change of refractive index versus wavelength), with high values of V indicating low dispersion. It is named after Ernst Abbe (1840–1905), the German physicist ...
On February 2, 2023, the CDC advised people to stop using EzriCare Artificial Tears and said that the eye drops were contaminated. The P. aeruginosa strain had been found in 55 people across 12 states as of January 31, resulting in one death and vision loss in five people. A recall was ordered for EzriCare Artificial Tears, which later included ...
One must bear in mind that the human eye itself has an Abbe number V d ≈ 50.2 so the expensive, high-end optical glass types mentioned above have little value for central vision; however, the wearer's view through the side of a glass lens is not comparable to central vision through the eye: Low dispersion glass definitely makes optically ...
Varilux. Varilux is a brand name belonging to Essilor International, a producer of corrective lenses. The first version of the lens was invented by Bernard Maitenaz and released in 1959, and was the first modern progressive lens to correct presbyopia. The progressive lens is characterized by correcting near, intermediate and far vision.
The Food and Drug Administration compiled a list of over-the-counter eye drops to avoid. 27 eye drops from retailers in California can cause vision loss, FDA warns. See the recall
Saiff’s scenario — including his confusion — is prevalent. And with 4.1 million Americans turning 65 this year — a record number — the decision is front and center in many households ...
Progressive lenses are corrective lenses used in eyeglasses to correct presbyopia and other disorders of accommodation. They are characterised by a gradient of increasing lens power, added to the wearer's correction for the other refractive errors. The gradient starts at the wearer's distance prescription at the top of the lens and reaches a ...
An optical instrument is said to be diffraction-limited if it has reached this limit of resolution performance. Other factors may affect an optical system's performance, such as lens imperfections or aberrations, but these are caused by errors in the manufacture or calculation of a lens, whereas the diffraction limit is the maximum resolution ...