BACKGROUND: Loss of skin elasticity due to redundancy of the upper eyelid (dermatochalasis) and falling of the upper eyelid border to a lower position (blepharoptosis) are often the earliest signs of facial aging. Upper eyelid blepharoplasty is an effective procedure to establish a good eyelid position, and is the most common facial cosmetic procedure [1]. When performing upper eyelid blepharoplasty, eyelid symmetry is essential for a satisfactory surgical outcome. Even if not possible, every surgeon tries to achieve complete symmetry when performing aesthetic eyelid surgery [2]. Several previous studies by surgeons with > 10 years of experience reported how preoperative incision markings should be made to achieve satisfactory surgical outcomes and excellent surgical results for upper eyelid blepharoplasty [3-7]. However, none of these studies investigated naturally occurring asymmetry when applying a preoperative design for upper blepharoplasty incision markings. During the preoperative design step, we noticed certain asymmetric tendencies. We therefore characterised these differences to ensure a more effective preoperative design for upper blepharoplasty incision markings for both eyelids. METHODS: This retrospective study examined 22 patients who underwent bilateral upper blepharoplasty surgery resulting from senile dermatochalasis and/or blepharoptosis. The initial preoperative incision design markings were drawn with the patient sitting upright. Then, with the patient in a supine position, preoperative design photographs were taken. We measured medial canthal excision angle (MCA), maximal lid excision height (MLH), maximal lid excision width (MLW), peak point angle, and peak point distance and compared measurements between both upper eyelids designs using Image J software. RESULTS: The mean MCA for the right side (30.68 ± 10.16°) was significantly different to that for the left side (35.39 ± 13.82°; p < 0.001). The mean MLH for the right side (1.17 ± 0.24 cm) was significantly different to that for the left side (1.24 ± 0.25 cm; p = 0.002). The mean MLW for the right side (0.72 ± 0.19 cm) was significantly different to that for the left side (0.77 ± 0.21 cm; p = 0.011). The mean peak point angle for the right side (15.67 ± 5.09°) was significantly different to that for the left side (18.11 ± 5.49°; p = 0.001). The mean peak point distance for the right side (2.41 ± 0.31°) was significantly different to that for the left side (2.22 ± 0.28 cm; p = 0.001). CONCLUSION: In upper blepharoplasty, the preoperative incision marking design measurements of the left side were significantly greater than those of the right side. The symmetry can therefore be maximised by including the asymmetries in the preoperative design.