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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.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

glass

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

glass

crystallophobia, hyalophobia.
Farlex Partner Medical Dictionary © Farlex 2012

glass

(glas)
A transparent substance composed of silica and oxides of various bases.
[A.S. glaes]
Medical Dictionary for the Health Professions and Nursing © Farlex 2012

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.
Millodot: Dictionary of Optometry and Visual Science, 7th edition. © 2009 Butterworth-Heinemann

glass

(glas)
A transparent substance composed of silica and oxides of various bases.
[A.S. glaes]
Medical Dictionary for the Dental Professions © Farlex 2012

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
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Earlier this year, Samsung showcased a 55-inch glassless 3D TV prototype at the Flat Panel Display show in China.
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In seconds, the gunmen broke through the wooden slats of the glassless windows and entered the house.
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Durafet III Glassless pH electrode eliminates problems commonly associated with traditional glass electrodes, such as fragility, poor response and frequent replacement.
But now, the lodgings of the poor sometimes seem more stable than the palaces, where you can often look through glassless windows and see the sky because the roofs were blown off in 1943, and the owners have never had the will or money to restore them.