Fig. 4

Sub-group vector analysis of refractive astigmatism according to type of IOL in G1. Refractive astigmatism was converted to vector notations by using equations by Fourier analysis (J0 = −(C/2)*cos2θ, J45 = −(C/2)*sin2θ (C = minus cylinder power of refractive errors, θ = cylinder axis of refractive errors, J0 < 0 against the rule astigmatism, J0 > 0 with the rule astigmatism, J45 accounts for oblique astigmatism), x axis = J0, y axis = J45). All types of toric IOLs showed clustering of dots toward (0, 0), postoperatively. Front-toric IOL: A = preoperative, B = postoperative, Back-toric IOL: C = preoperative, D = postoperative, Bi-toric: E = preoperative, F = postoperative. IOL = intraocular lens, G1 = normal corneal astigmatism group