Paraxial Ocular Measurements and Entries in Spectral and Modal Matrices: Analogy and Application

Figure 2

Graph of the angle 𝛽−𝛼 in degrees between the principal meridians and the trigonometric factor in irregular astigmatism 𝐹_𝐿 in (8). The curve crosses the horizontal axis at 90°  (𝐹_𝐿=0D) and is an uneven function with respect to 90°: −𝐹_𝐿(90−𝜃)=𝐹_𝐿(90+𝜃). Above 90° the trigonometric factor is positive.