High-Intensity Focused Ultrasound for the Treatment of Infraorbital Fat Protrusion: A Preliminary Case Series

Abstract

Infraorbital fat (IOF) protrusion is a common feature of periorbital aging and is commonly managed with lower blepharoplasty. Although surgical approaches can provide predictable aesthetic outcomes, there remains interest in minimally invasive treatment options for appropriately selected patients. This preliminary case series evaluated the feasibility, short-term tolerability, and clinical outcomes of high-intensity focused ultrasound (HIFU) for the treatment of IOF protrusion. Three Korean patients (two female and one male; mean age, 48 years) underwent HIFU treatment using LinearZ device at focal depths of 4.5 and 9.0 mm following pre-treatment ultrasonography. Each treatment session delivered 0.6 J per shot in DOT mode under local anesthesia. Clinical photographs, patient satisfaction, and Global Aesthetic Improvement Scale (GAIS) scores were assessed three months after the final treatment session. All three patients showed clinically observable improvement in infraorbital bulging and lid-cheek contour, with high patient satisfaction. GAIS scores were 4, 5, and 4, respectively. Treatment was well tolerated, with transient erythema and edema reported and no major adverse events observed during follow-up. Given the very small sample size, absence of a control group, subjective and non-blinded outcome assessment, lack of systematic post-treatment imaging or quantitative fat measurements, and short follow-up, these findings should be considered preliminary and hypothesis-generating. Larger controlled studies incorporating objective outcome measures are warranted to establish efficacy, durability, and optimal treatment parameters of HIFU for IOF protrusion.

Introduction

Among the earliest and most visible signs of facial aging are changes in the eyelids and periorbital region. Aging in this area involves several distinct but interrelated anatomical changes, including skin laxity, orbital septum weakening, and changes in the distribution and position of orbital fat. Over time, weakening of the orbital septum may allow the infraorbital fat (IOF) pads to protrude anteriorly, producing visible infraorbital bulging or “under-eye bags”.¹ A recent three-dimensional computed tomography-based analysis has confirmed that orbital fat protrusion increases with age in East Asian populations, further supporting the structural basis of infraorbital bulging.²

Importantly, IOF protrusion should be distinguished from tear-trough hollowing and periorbital skin laxity. Tear-trough hollowing primarily reflects volume deficiency and age-related changes at the lid-cheek junction, whereas skin laxity reflects changes in the skin and supporting soft tissues.³ These features may coexist and contribute to the overall appearance of the aging lower eyelid but have different anatomical mechanisms and may require different treatment strategies. Lower blepharoplasty remains the standard surgical treatment for prominent IOF, using transcutaneous or transconjunctival approaches to remove or reposition orbital fat, with or without treatment of redundant skin.^1,4,5 Non-surgical approaches such as hyaluronic acid fillers are more commonly used to address volume deficiency associated with tear-trough hollowing rather than to directly treat protruding IOF.⁶ Thus, treatment selection should be based on the predominant anatomical component contributing to the patient’s lower eyelid appearance. High-intensity focused ultrasound (HIFU) has been investigated for several aesthetic applications, including skin tightening and non-invasive adipose tissue reduction.⁷ HIFU delivers focused ultrasonic energy to predetermined tissue depths, producing localized thermal effects while limiting injury to overlying tissues. Experimental studies have suggested that HIFU-mediated thermal injury may promote adipocyte apoptosis and autophagy, whereas other studies have demonstrated effects on collagen and elastin remodeling.⁸ However, these biological effects have primarily been characterized in experimental models or in applications involving other anatomical regions and should not be assumed to demonstrate fat reduction in the infraorbital region.

Clinical evidence specifically addressing HIFU treatment of the lower eyelid remains limited. Pak et al reported improvement in lower eyelid laxity and high patient satisfaction following HIFU treatment in a small clinical study, with no serious treatment-related adverse events.⁹ More recent clinical and systematic reviews have also reported favorable safety and aesthetic outcomes for HIFU in periorbital rejuvenation.¹⁰ However, these studies have primarily evaluated skin tightening or periorbital rejuvenation rather than objective reduction of protruding IOF. Evidence from HIFU studies of subcutaneous adipose tissue suggests that focused ultrasound can produce localized effects in adipose tissue,^8,11 but the extent to which these findings translate to the anatomically constrained and safety-sensitive infraorbital compartment remains uncertain.

The periocular location presents important anatomical considerations because the treatment target lies in close proximity to the globe, orbital septum, infraorbital neurovascular structures, and other orbital contents. Accordingly, treatment depth and energy delivery require careful consideration to minimize unintended exposure of adjacent structures. Pre-treatment ultrasonography can facilitate assessment of IOF thickness and localization, thereby supporting selection of an appropriate focal depth and procedural planning.^12–14

Although HIFU has been investigated for periorbital rejuvenation and for non-invasive adipose tissue reduction in other anatomical regions,^8,9 clinical evidence specifically addressing prominent IOF as a treatment target remains limited. In particular, the feasibility of delivering focused ultrasound to the IOF compartment at predefined depths to improve visible infraorbital bulging has not been well characterized.^8,9 This study therefore presents three cases treated with the LinearZ HIFU device using ultrasound-guided treatment planning and predefined focal depths. We hypothesized that HIFU could be safely applied to the IOF compartment in carefully selected patients and potentially improve infraorbital contour without operative intervention.

Methods

This preliminary case series included three Korean patients (two women and one man; mean age, 48 years) with clinically apparent bilateral IOF protrusion. None had a history of lower eyelid surgery, bleeding disorders, or ocular disease. The ethics committee of the College of Medicine, Soonchunhyang University, Republic of Korea, approved the study and subsequent publication (SCHBC-IRB-2025-12-015). The study was conducted at Maylin Anti-aging Center Ilsan, Seoul, Republic of Korea. We obtained written informed consent from all patients for treatment, publication of case details, and use of clinical photographs.

Pre-treatment diagnostic ultrasonography (GE Healthcare Vscan, Chicago, USA) was performed to assess IOF thickness and location and to guide treatment-depth selection. Figure 1a and b shows the ultrasound transducer location. The mean IOF thickness was approximately 9 mm. Based on these measurements, focal depths of 4.5 and 9.0 mm were selected. Preliminary magnetic resonance imaging (MRI) assessment was performed to evaluate the anatomical relationship between the IOF compartment and the globe.

Figure 1.

(a and b) Diagnostic ultrasound probe position for measurement of IOF thickness using the Vscan handheld ultrasound system. Ultrasound measurements were performed before HIFU treatment to assist treatment planning.

HIFU treatment was performed using the LinearZ system (Jeisys Medical Inc., Seoul, Republic of Korea) in DOT mode. Each shot delivered 0.6 J using a 25-mm treatment line with 1.5-mm spacing. A total of 100 shots were delivered per eye per session, with 50 shots at 9.0 mm and 50 shots at 4.5 mm. The handpiece was moved gently to distribute energy across the treatment area. Local anesthesia was administered using infraorbital and zygomaticofacial nerve blocks. Three treatment sessions were performed at approximately monthly intervals. Figure 2a–c shows the treatment setup and anatomical references. The use of MRI and real-time ultrasound during the procedure helped select the appropriate cartridge.

Figure 2.

(a) HIFU transducer position over the infraorbital region. (b) Sagittal MRI demonstrating the point of maximum IOF thickness. (c) Sagittal MRI demonstrating the point of minimum IOF thickness. MRI was used for pre-treatment assessment of IOF thickness.

Clinical outcomes were assessed three months after the final treatment session using clinical photographs, patient satisfaction, and the Global Aesthetic Improvement Scale (GAIS). GAIS was assessed by non-blinded reviewers. Treatment-related adverse events, including erythema, edema, pain or discomfort, bruising, sensory changes, skin injury, and ocular symptoms, were monitored during treatment and follow-up. No systematic post-treatment ultrasonographic or MRI assessment was performed; therefore, changes in IOF thickness or volume were not quantitatively assessed. Given the small, uncontrolled case-series design, outcomes were summarized descriptively without formal statistical analysis.

Results

Case 1

A 38-year-old female presented with bilateral IOF protuberance and prominent dark circles. Examination confirmed palpable IOF pads (ultrasound-measured thickness ~9 mm). She underwent HIFU as described above. She tolerated treatment with a 4.5 mm depth without pain but experienced mild discomfort during treatment with a 9.0 mm depth cartridge, managed by pausing the procedure briefly. No additional analgesics were required. The treatment was performed in three sessions at monthly intervals. Post-procedural mild edema and erythema resolved spontaneously in a week. After three sessions, under-eye puffiness was noticeably reduced, and the infraorbital groove was softened. At the 3-month follow-up after the final session, she reported being very satisfied with the improvement in the under-eye bags, and the GAIS (Global Aesthetic Improvement Scale) score was 4 (much improved), indicating complete satisfaction. Figure 3 depicts the patient’s treatment results.

Figure 3.

Clinical photographs of Case 1 at baseline and 3 months after the final treatment session show progressive improvement in infraorbital fullness.

Case 2

A 48-year-old female presented with a pronounced lower eyelid fat bulge and infraorbital grooves (tear troughs) and underwent the identical HIFU protocol (Figure 4). She reported no significant pain or adverse effects during treatment. The treatment was performed as described above. After the first session, mild swelling was observed for 5 days. After two additional sessions, the protruding IOF became visibly shallower, and the lid-cheek contour was smoother. At the 3-month follow-up after the final session (Figure 5), she was very satisfied with the reduction in bulging; no complications (hematoma, numbness, or vision changes) occurred, and the GAIS score was 5 (very much improved).

Figure 4.

Clinical photographs of Case 2 at baseline and 3 months after the final HIFU treatment session show a reduction in infraorbital fullness at follow-up.

Figure 5.

Clinical photographs of Case 3 showing frontal views at baseline and 3 months after the final HIFU treatment session, showing improvement in infraorbital contour is shown at follow-up.

Case 3

A 57-year-old male presented with complaints of bilateral under-eye bags and a tired appearance (Figure 5). He had firm IOF pads and thin lower eyelid skin. LinearZ HIFU DOT mode was applied as per protocol. He described moderate discomfort (better controlled by the nerve block) during deeper treatment. Post-procedure edema peaked at 2–3 days and resolved by 7–10 days. At the 3-month follow-up after the final session (Figure 5), his infraorbital fullness was visibly reduced; the tear trough deformity had improved. He was very satisfied, and the GAIS score was 4 (much improved). Throughout, ocular exams remained normal, with no signs of lower eyelid retraction or visual disturbance.

In all cases, the only sequelae were transient edema and erythema; no patient required medications or interventions. All three patients tolerated the sessions well (the longest session lasted ~10 minutes) and did not experience any long-term adverse events during the three-month follow-up period. The outcomes suggested clinically observable improvement in infraorbital fullness and lid-cheek contour with high patient satisfaction. Mean GAIS score was 4.33.

Discussion

This case series provides preliminary evidence that HIFU may improve the clinical appearance of IOF protrusion with an acceptable short-term safety profile. Lower blepharoplasty remains the standard surgical treatment for IOF herniation, with modern transconjunctival techniques offering excellent aesthetic outcomes without visible external scarring in appropriately selected patients.^4,5 However, transconjunctival blepharoplasty is an operative procedure associated with perioperative risks, including hematoma, infection, lower eyelid malposition, and ectropion, as well as a postoperative recovery period.¹⁵ Accordingly, there remains an unmet need for effective minimally invasive treatment options for carefully selected patients who are unwilling or unsuitable to undergo operative intervention. In our experience, HIFU was well tolerated, with only transient erythema and edema, allowing patients to resume normal daily activities shortly after treatment. Therefore, rather than replacing lower blepharoplasty, HIFU may serve as a complementary treatment option for carefully selected patients seeking modest improvement in infraorbital contour with minimal procedural downtime. A recent systematic review also supports the safety and effectiveness of HIFU in the periorbital region.⁷ Pak et al reported significant improvement in infraorbital laxity, high patient satisfaction, and no serious adverse events following HIFU treatment of the lower eyelids.⁹ These findings are consistent with our observations and further support the potential role of HIFU as a minimally invasive option for periorbital rejuvenation.

All three patients demonstrated clinically observable improvement in infraorbital fullness and smoothing of the lid-cheek junction on follow-up photos, without apparent contour irregularity or lower eyelid retraction. These observations are consistent with gradual soft-tissue remodeling following HIFU treatment. Reports from other anatomical regions have also demonstrated that focused ultrasound can produce localized tissue effects while limiting injury to surrounding structures.¹⁶ In the present case series, safety precautions included pre-treatment ultrasonographic assessment of IOF thickness and careful selection of focal depths relative to the orbital rim. No ocular or clinically apparent skin complications were observed during follow-up.

The biological mechanisms underlying HIFU-induced improvement in infraorbital contour are likely multifactorial rather than being attributable to a single pathway. HIFU generates precisely focused thermal coagulation zones that selectively target tissues at predetermined depths while sparing the overlying skin and adjacent structures.¹⁶ Experimental studies suggest that thermal injury to adipocytes may initiate cellular stress responses leading to apoptosis, activation of p53-associated signaling pathways, and autophagy, followed by macrophage-mediated clearance of cellular debris and gradual reduction in adipose tissue volume.^8,17

In parallel, HIFU has been shown to induce collagen denaturation followed by neocollagenesis and elastin remodeling, which may contribute to tissue contraction, improved skin firmness, and enhanced support of the lid-cheek junction alone.^18–20 Consequently, the clinical improvements observed in our patients may reflect a combination of adipose tissue remodeling and soft-tissue tightening, although the relative contribution of these processes cannot be determined from the present study.⁸ The gradual improvement over several weeks is consistent with the time course of these biological processes.¹⁰ However, as this study did not include histologic evaluation or objective post-treatment imaging to quantify changes in fat volume or skin laxity, these mechanisms were not directly demonstrated in our patients and should be regarded as biologically plausible explanations supported by previous experimental and clinical studies.

Although the study yielded positive clinical outcomes, several limitations should be considered when interpreting these findings. First, the very small sample size and absence of a control group preclude meaningful statistical comparisons and substantially limit the generalizability of the findings. Second, the three-month follow-up after the final treatment session provides information on short-term clinical outcomes but is insufficient to establish the long-term durability of the observed improvements or to determine whether additional changes occur with longer follow-up. Third, outcomes were assessed primarily through clinical photographs, patient satisfaction, and GAIS scores, without objective post-treatment quantification of IOF volume or skin laxity. Although pre-treatment ultrasonography was used for treatment planning and measurement of IOF thickness, post-treatment imaging was not systematically performed and therefore could not be used to quantify changes in the fat compartment. In addition, the absence of blinded independent photographic assessment may have introduced photographic and observer-related bias. In addition, patient selection and the subjective nature of patient-reported satisfaction may have contributed to selection and reporting bias. Future prospective studies should incorporate larger controlled cohorts, longer follow-up, standardized photography with blinded independent assessment, and objective imaging or three-dimensional quantitative measurements to determine changes in IOF and soft-tissue laxity and to better establish treatment efficacy, durability, and optimal treatment parameters.

Nevertheless, the uniformly positive outcomes and lack of adverse events are encouraging. To our knowledge, clinical evidence specifically evaluating imaging-guided HIFU treatment at predefined focal depths for IOF protrusion remains limited. The results are supported by prior literature on HIFU in adipose tissue, which shows predictable fat thinning via apoptosis, and by surgical studies that link controlled fat excision with high patient satisfaction.

Conclusion

In this preliminary case series, HIFU treatment using the LinearZ device was feasible and associated with subjective improvement of infraorbital contour in three selected patients. No major adverse events were observed during the three-month follow-up period. Given the small sample size, absence of a control group, relatively short follow-up, and lack of objective post-treatment measurements, these findings should be considered preliminary and hypothesis-generating. HIFU may represent a minimally invasive complementary treatment option for carefully selected patients seeking improvement in lower eyelid contour; however, larger controlled studies incorporating objective outcome measures and longer follow-up are needed to establish efficacy, durability, and optimal treatment parameters.

Ethical Considerations

All patients provided written informed consent for treatment and use of photographs in publication.

Disclosure

The authors declare no conflict of interest for this study.