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Analysis of Variation of Orbital Soft Tissue by a Novel Method in Magnetic Resonance Imaging

Summary: Accurate evaluation of the orbital soft tissue is essential when conducting surgery to remove excess lower eyelid fat. However, the eyelid puffiness decreases in the supine-position intraoperatively and when magnetic resonance imaging is performed preoperatively, compared with the standing/sitting-position in which patients are commonly examined. We investigated the orbital soft tissue difference between standing/sitting and supine positions. The study was conducted on six patients with an average age of 58.5 years. Anterior soft tissue and adipose tissue of eyeball axis, anterior adipose tissue in front of the infraorbital margin, total adipose tissue, and horizontal and vertical orbital positions were determined. Statistical examination by t test showed that soft tissue and adipose tissue, except for total adipose tissue, were significantly reduced in the supine-position compared with the standing/sitting-position. There was a significant difference in eye position only in the vertical direction. Anterior adipose tissue in front of the infraorbital margin, which is important during lower eyelid surgery, appeared 17.5% lower in the supine-position than in the standing/sitting-position. It is necessary to consider this postural discrepancy during the surgical management of lower eyelid fat.

S urgical intervention for lower eyelid sagging and bagginess is a common procedure. 1 To operate on the upper and lower eyelids, dissecting the soft tissue around the eye is essential for dermatological/plastic surgeons. 1 Patients typically complain of eyelid puffiness when standing or sitting. However, the eyelid puffiness is reduced in the supine-position, such as during the surgery, due to the postural variation exhibited by the anatomy of the orbital soft tissue. Some reports have recommended magnetic resonance imaging (MRI) for illustrating soft tissue in the orbital region. 2,3 Nevertheless, even if preoperative evaluation by ultrasound or MRI is performed, the droopy eyelids and the puffiness of soft tissue, which are apparent while the patient is standing or sitting, are masked during the surgery wherein the patient is in the supine-position.
In the present study, we aimed to investigate for the first time, to the best of our knowledge, the changes in the orbital soft tissue between the near-standing-position (60 degree head-up) and the supine-position by taking an MRI. (See figure 1, Supplemental Digital Content 1, which displays the two-microcoil method for magnetic resonance imaging. Two microcoils were used to sandwich the eyes in position with a 60 degree head-up state. http:// links.lww.com/PRSGO/B873.)

Participants
The study was performed on six patients with lower eyelid sagging (12 eyelids) who visited Kobe University Hospital between August 2019 and June 2021. The participants did not have specific diseases such as collagen disease and thyroidism, and consisted of two men and four women with an average age of 58.5 years (range, 51-65 years). The institutional review board approved the study design, and informed consent was obtained from the participants.  Summary: Accurate evaluation of the orbital soft tissue is essential when conducting surgery to remove excess lower eyelid fat. However, the eyelid puffiness decreases in the supine-position intraoperatively and when magnetic resonance imaging is performed preoperatively, compared with the standing/sitting-position in which patients are commonly examined. We investigated the orbital soft tissue difference between standing/sitting and supine positions. The study was conducted on six patients with an average age of 58.5 years. Anterior soft tissue and adipose tissue of eyeball axis, anterior adipose tissue in front of the infraorbital margin, total adipose tissue, and horizontal and vertical orbital positions were determined. Statistical examination by t test showed that soft tissue and adipose tissue, except for total adipose tissue, were significantly reduced in the supineposition compared with the standing/sitting-position. There was a significant difference in eye position only in the vertical direction. Anterior adipose tissue in front of the infraorbital margin, which is important during lower eyelid surgery, appeared 17.5% lower in the supine-position than in the standing/sitting-position. It is necessary to consider this postural discrepancy during the surgical management of lower eyelid fat.

Analysis of Variation of Orbital Soft Tissue by a Novel Method in Magnetic Resonance Imaging
Case RepoRt

PRS Global Open • 2022
Imaging A 1.5-Tesla MRI was used (Achieva1.5, Philips Medical Systems, Best, the Netherlands). The microcoil was positioned over the eyes of the supine patient. However, this produced a poor-quality image in the standing-position. Therefore, two microcoils with a diameter of 10 cm each were used on either side of the eyes, effectively sandwiching them, and the images were taken in near-standing-position while the head was rotated 60 degrees (Supplemental Digital Content 1, http://links.lww.com/PRSGO/B873). The T1-weighted images were taken using the following parameters: TR/TE: 146/13 ms, turbo factor: 7, the number of signals averaged 1 in sagittal planes. The orbital soft tissue was measured on the images using the AZE Virtual Place software (AZE Ltd., Tokyo, Japan).
Tissue quantification was performed according to the method described by Sean Darcy et al, 4  Individual differences are present in terms of the shape and size of the eyeball. Therefore, the sagittal section of the eye was determined based on the optic nerve, and the rate of fat change, not the amount, was calculated.

Statistical Analysis
Two-sided t test was used for statistical analyses, and statistical significance was considered at a P value less than 0.05.

RESULTS
The two-microcoil method achieved a high resolution, which enabled the quantification and comparison of the soft tissue and adipose tissue around the eyes (Supplemental Digital Content 2, http://links.lww. com/PRSGO/B874). The yellow frame shown on the slide is anterior adipose tissue in front of the infraorbital margin (Supplemental Digital Content 2, http:// links.lww.com/PRSGO/B874). Based on the t test, soft tissue and adipose tissue, except for total adipose tissue, were significantly reduced in the supine-position compared with the standing/sitting-position (Table 1). There was a significant difference in the orbital position only in the vertical direction ( Table 1). The changes between the near-standing-position (60 degree headup) and supine-position are shown in Table 1 and Supplemental Digital Content 2 (http://links.lww. com/PRSGO/B874). The mean value of anterior soft tissue of the lower eyeball axis decreased from 178.0 ± 32.94 to 163.75 ± 33.07 mm 2 (change = -14.25, change rate = 92.0%, P < 0.01). The mean value of anterior adipose tissue of the eyeball axis decreased from 81.17 ± 18.68 to 71.25 ± 15.96 mm 2 (change = -9.92, change rate = 87.8%, P < 0.01). The mean value of anterior adipose tissue in front of the infraorbital margin, which requires treatment during lower eyelid sagging surgery, decreased from 62.5 ± 16.06 to 51.58 ± 14.32 mm 2 (change = -10.92, change rate = 82.5%, P < 0.01). The mean value of total adipose tissue decreased from 532.6 ± 63.14 to 518.5 ± 64.09 mm 2 (change = -14.1, change rate = 97.4%, not significant). The mean value of horizontal positions of the orbit changed from 8.67 ± 1.42 to 8.83 ± 1.33 mm (change = 0.16, change rate = 101.8%, not significant). The mean value of Table 1

DISCUSSION
This study emphasized two critical lessons by quantifying the soft tissue and adipose tissue around the eye in near-standing-position (60 degree head-up) and in supine-position.
First, the two-microcoil method, with a 60 degree headup position, provided high-quality resolution images with MRI.
Second, anterior adipose tissue in front of the infraorbital margin, which is essential during lower eyelid surgery, appeared 17.5% lower supine-position (at the time of surgery) than near-standing-position (60 degree headup) (at the time of examination).
It is important to note that this study was limited by a small sample size. Therefore, it is necessary to conduct the next survey in each gender as well as in each age group because of the reported increase of lower eyelid fat with aging. 4 Further long-term studies are also needed.

CONCLUSIONS
Some surgeons may obtain good clinical results by removing slightly more fat than expected during surgery and completing the surgery with a concave shape instead of a flattened shape. This study presents supportive data that suggests consideration of the discrepancy between the positions is necessary to manage the lower eyelid fat surgically.