Answer :
Final answer:
To convert a lens prescription from positive cylinder form to negative cylinder form, subtract the cylinder power from the sphere power and rotate the axis by 90 degrees. The correct negative cylinder form for a -5.00/+2.00 x 140 lens is -3.00/-2.00 x 50.
Explanation:
The subject of the question involves converting a lens prescription from positive cylinder form to negative cylinder form. In optics, prescription glasses can have their cylinder power expressed either in positive or negative terms, which relate to the way the lens is constructed to correct for astigmatism. This involves a detailed understanding of how lenses are described in terms of their power (diopters), axis (orientation of the astigmatism correction), and whether the lens is concave or convex.
To convert from a + cylinder to a - cylinder, you subtract the cylinder power from the sphere power and rotate the axis by 90 degrees. Given a lens described as -5.00/+2.00 x 140, we subtract +2.00 from -5.00 to get -7.00 for the sphere. The cylinder remains the same magnitude but becomes negative, resulting in -2.00.
Next, we adjust the axis by 90 degrees: 140 degrees - 90 degrees equals 50 degrees. Therefore, the correct answer is -3.00/-2.00 x 50, which matches with option b.
