ballast

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ballast

(bal'ăst),
1. Material of doubtful value itself used to stabilize something (for example, maritime practice). 2. Something largely without intrinsic value.
Farlex Partner Medical Dictionary © Farlex 2012

ballast 

Additional weight of material incorporated in a part of a contact lens to maintain it in a given orientation (Fig. B1). This is often provided by giving prismatic power to the lens (prism ballast lens).
Fig. B1 Truncated and prism-ballasted toric contact lensenlarge picture
Fig. B1 Truncated and prism-ballasted toric contact lens
Millodot: Dictionary of Optometry and Visual Science, 7th edition. © 2009 Butterworth-Heinemann
References in periodicals archive ?
In November 2011, The Department of Energy (DOE) issued new rules regulating the efficiency of fluorescent lamp ballasts, which take effect on November 14, 2014.
For example, HPS lamps for use on mercury vapor lamp ballasts that operate at 10 percent lower power have been described in the literature (Ravi and others 1993).
STMicroelectronics has introduced a new family of power MOSFETs for use in high-efficiency power supplies for products such as LCD monitors, televisions and energy-saving lamp ballasts.
International Rectifier introduced the IRS2168D fully integrated and protected high-voltage integrated circuit (HVIC) for advanced electronic linear fluorescent lamp ballasts which incorporate active power factor correction (PFC).