In lensometry, if the single lines come into focus at plano and the triple lines come into focus at -2.00 with the axis at 90 degrees. What is the lens power?

In lensometry, the power of a lens is determined by the focus of the lines observed through the lens when measured. In this scenario, the single lines coming into focus at plano indicate that there is no power along that axis, while the triple lines focused at -2.00 with an axis at 90 degrees indicates the presence of negative lens power along the 90-degree axis.

The term "plano" means that there is no refractive power on that axis, which means that at that position the lens provides a neutral effect on the light. On the other hand, the -2.00 denotes a lens that is a minus lens, which is typically used for nearsightedness (myopia).

When the lens power is expressed in a standard format, it should indicate the power and the orientation of that power. Thus, the -2.00 indicates the strength of the lens power, and “x90” indicates that this power is aligned along the 90-degree meridian. Therefore, the correct representation of the lens power combining both terms is -2.00 at 90 degrees, and since plano was described separately, it can be considered that there is no distance along that meridian.

The notation used in the correct answer