Parabolic light fixtures became popular towards the end of the 20th century when more and more offices had CRT computer monitors. These fixtures do a great job at reducing the amount of glare that is visible on these older screens. A parabolic fixture uses a grid of louvers to shield the lamps inside the fixture when viewed at a slight angle. The louvers are specially designed so that the full intensity of the lamp inside is not reflected directly at the room occupants.
To this day, many facility managers prefer the look of parabolic light fixtures over newer center basket or architectural troffers. These certainly were a step up from the prismatic lay-in, but other options are available now that can enhance the beauty of the space. The parabolic fixture is a work-hourse in the billions of square feet of office space in the country as a large percentage of that stock is lit with these fixtures.
These fixtures, which can also be called deep cell parabolic troffers, are typically available in various configuratons. You will notice that the names reference the number of cells the fixture has. This is the total number of squares in the grid of louvers. For example, an 18-cell parabolic 2x4 troffer has 18 squares that allow light to exit the fixture. These are arranged in 3 columns and 6 rows (3 x 6 = 18). When matching fixtures in an existing space, it's important to look for a fixture that has the same number of cells.
Parabolic fixtures are now available with LED T8 as a light source or even integrated LED arrays. Newer LED-based parabolic fixtures have options for a semi-transparent lens to be inserted above the louvers that softens the light coming from the LED arrays. This reduces any discomfort that room occupants might have when looking directly up into the fixtures.