Search results
Results From The WOW.Com Content Network
PL is an abbreviation for plano or plain, meaning no prescription; PD or IPD Pupillary Distance or Interpupillary Distance, respectively. It is the distance between pupil centers. BVD Back vertex distance is the distance between the back of the spectacle lens and the front of the cornea (the front surface of the eye). This is significant in ...
The term "optometry" comes from the Greek words ὄψις (opsis; "view") and μέτρον (metron; "something used to measure", "measure", "rule").The word entered the language when the instrument for measuring vision was called an optometer, (before the terms phoropter or refractor were used).
Vision of humans and other organisms depends on several organs such as the lens of the eye, and any vision correcting devices, which use optics to focus the image.. The eyes of many animals contains a lens that focuses the light of its surroundings onto the retina of the eye.
The cup-to-disc ratio (often notated CDR) is a measurement used in ophthalmology and optometry to assess the progression of glaucoma. The optic disc is the anatomical location of the eye's "blind spot", the area where the optic nerve leave and blood vessels enter the retina. The optic disc can be flat or it can have a certain amount of normal ...
The RNFL formed by the expansion of the fibers of the optic nerve; it is thickest near the optic disc, gradually diminishing toward the ora serrata.. As the nerve fibers pass through the lamina cribrosa sclerae they lose their medullary sheaths and are continued onward through the choroid and retina as simple axis-cylinders.
The approximate field of view of an individual human eye (measured from the fixation point, i.e., the point at which one's gaze is directed) varies by facial anatomy, but is typically 30° superior (up, limited by the brow), 45° nasal (limited by the nose), 70° inferior (down), and 100° temporal (towards the temple).
The visual system is the physiological basis of visual perception (the ability to detect and process light).The system detects, transduces and interprets information concerning light within the visible range to construct an image and build a mental model of the surrounding environment.
Higher Abbe numbers mean a better lens material, and lower Abbe numbers result in the presence of chromatic aberration (i.e., color fringes above/below or to the left/right of a high contrast object), especially in larger lens sizes and stronger prescriptions (beyond ±4.00D). Generally, lower Abbe numbers are a property of mid and higher index ...