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glass

 [glas]
1. a hard, brittle, often transparent material, usually consisting of the fused amorphous silicates of potassium or sodium, and of calcium, with silica in excess.
2. a container, usually cylindrical, made from this material.

glass

(glas),
A transparent substance composed of silica and oxides of various bases.
[A.S. glaes]

glass

crystallophobia, hyalophobia.

glass

(glas)
A transparent substance composed of silica and oxides of various bases.
[A.S. glaes]

glass

1. Material from which lenses and optical elements may be made. It is hard, brittle and lustrous and usually transparent. It is produced by fusing sand (silica) at about 1400ºC with various oxides (potassium, sodium, etc.) and other ingredients such as lead oxide, lime, etc. Glass may be produced in various colours by the addition of different substances (e.g. metal oxides). 2. A lens. See annealing; feathers; lens blank; strain; stria; surfacing.
absorption glass Glass which transmits only a certain portion of the incident light, the rest being absorbed.
Bagolini's glass A plano lens on which fine parallel striations have been grooved. It produces a slight reduction in acuity but a punctate light source observed through this lens appears as a streak of light orientated at 90º from the striations. Two such lenses placed in front of the eyes with the striations oriented 90º apart are used to detect sensory and motor anomalies such as, retinal abnormal correspondence, suppression, etc. Syn. Bagolini's lens; Bagolini's striated glass. See Bagolini lens test.
cobalt-blue glass See cobalt lens.
crown glass Glass characterized by low dispersion. The most commonly used crown glass in ophthalmic lenses, called ophthalmic crown or spectacle crown, has a refractive index n = 1.523 and a constringence or V-value of 59. There are other types of crown glass (e.g. dense barium crown n = 1.623, V-value 56; fluor crown n = 1.485, V-value 70). See doublet; triplet.
glass cutter A tool with a diamond-tipped edge or hard steel to cut glass.
depolished glass See ground glass.
glass eye See glass eye.
flint glass Glass containing lead or titanium besides the usual ingredients and having a high dispersion (example: Tital, V-value 31) compared with crown glass and a high refractive index (n = 1.701). It is, however, a softer and heavier material than crown. It is used in ophthalmic lenses of high power as it can be made much thinner than a crown glass lens of the same power. See doublet; high index lens; triplet.
ground glass Glass that has been ground with emery, sandblasted or etched with fluoric acid to give it a matt surface. Such glass is usually translucent but not transparent. Syn. depolished glass. See frosted lens.
magnifying glass See magnifying lens.
opal glass A white or milky translucent glass used to diffuse light.
photochromic glass See photochromic lens.
safety glass 1. Glass that has been ground and polished and then heated just below its softening point and rapidly cooled. Such treatment renders the glass highly resistant to fracture, and breakage causes it to crumble rather than shatter. Safety glass can also be produced chemically. In this process the lens is immersed in a molten salt bath (e.g. 99.5% potassium nitrate and 0.5% silicic acid at a temperature of 470ºC for some 16 hours). The lens surface thus becomes compressed as larger potassium ions replace the smaller sodium ions which are in the glass. Chemically strengthened lenses have greater impact resistance and can be made thinner than air-tempered glass lenses. However, when broken the fragments of the chemically strengthened lenses are not as blunt as those of air-tempered glass lenses. Syn. toughened glass. 2. Non-shatterable laminated glass used in automobiles and goggles. See safety lens; polariscope; industrial spectacles.
toughened glass See safety glass.
Wood's glass See Wood's light.

glass

(glas)
A transparent substance composed of silica and oxides of various bases.
[A.S. glaes]

Patient discussion about glass

Q. My myopic son is wearing power glasses. Are there any other nutritional supplements to support eye sight? My myopic son is wearing power glasses from the age of 2 years. His power is not very high yet but the rate of his eye power is doubling every year. Doctor had given him some medicines and had told him to have lots of carrots. We are giving him carrot juice every day. But soon he stopped taking it for some months. But he is having juice now but I wish to know are there any other nutritional supplements to support eye sight?

A. eating carrots can help people who suffers from vitamin A or beta-carotene deficiency. which leads to poor night vision. but that's it. there is no reason to eat tremendous amounts of carrots, there are food supplements that will help you achieve it without becoming orange. anyway, getting too much vitamin A can be toxic.
here is a "snopes" about it-
http://www.snopes.com/food/ingredient/carrots.asp

More discussions about glass
References in periodicals archive ?
Sabic contributed its Lexan PC glazing materials, advanced coatings technology, and engineering design expertise The concept's rear window utilizes Sabic's Exatec E9000 plasma coating for glasslike scratch and UV resistance.
The Softlips Cube is a dome-shape balm in a sleek, glasslike design that combines function and style, filling a gap as the lipstick/cosmetics and lip balm segments converge.
Unlike the inexpensive and plentiful limestone, which is porous and somewhat roughly textured, the ultra expensive Corinthian granite has a glossy, almost glasslike surface that is extremely slippery when wet, which it will be pretty much all the time given the constant mist and spray given off by the mighty Cataracts.
In our study, translucent zones remained unstained when a water-based marking pen was used, thus revealing a glasslike structure with crossed lamellae (Kobayashi 1976, Nishida et al.
Below -30[degrees]C, their elasticity decreased exponentially, approaching values close to glasslike, i.e.
In the case of the remaining penetrations (designated as numbers 2-7), it was possible to observe very intense covering of both face and root with a glasslike layer of manganese, silicon, and aluminium oxides.
One of the most major changes In the standard of care is that, in the '80s, dental hygienists wanted to prepare a smooth root surface and would root plane until the root was "glasslike." Now, we are taught to remove biofilm and calculus, but not to the extreme of removing many layers of cementum from the root surface.
Busch and Kenseth both called the race ''treacherous,'' pointing to the combination of a repave last year and Goodyear's new ''multi-zone'' tires that made it seem as if they were skating across a smooth, glasslike surface most of the afternoon.
02 European plastics producer Raatz creates visual effects with its glasslike Acrylic Couture Cancello.
Much of that money goes toward construction of a plant to convert the underground waste into glasslike logs for safe, secure storage.
Slack, "Glasslike heat conduction in high-mobility crystalline semiconductors," Physical Review Letters, vol.
The conditions - a combination of Pirelli opting for the harder two of the four dry compounds available and the glasslike nature of the new track - resulted in all three sessions proving hectic.