Correction of Primary Multiple Upper Eyelid Folds by Three Mini-Incision Upper Blepharoplasty and Simultaneous Orbital Fat Pad Repositioning in East Asians.

BACKGROUND: This study aims to assess the feasibility and efficacy of a three mini-incision upper blepharoplasty combined with simultaneous orbital fat pad repositioning for correcting primary multiple upper eyelid folds in East Asians. METHODS: A retrospective analysis of 75 patients who underwent three mini-incision double-eyelid blepharoplasty in conjunction with orbital fat pad repositioning for the correction of multiple upper eyelid folds between January 2018 and January 2022 was conducted. During the surgery, the lateral extension of the central upper eyelid fat mass was anchored medially to the upper medial eyelid via three small skin incisions. Postoperative follow-up was carried out to evaluate the improvement in multiple upper eyelid folds, and patient satisfaction was measured. RESULTS: The follow-up period ranged from 6 to 36 months, with an average of 12 months. Post-surgery, the multiple fold lines were completely resolved in 71 patients (95%), while relapse occurred in 4 patients (5%). The overall satisfaction rate was 88%. CONCLUSIONS: The three mini-incision double-eyelid blepharoplasty combined with simultaneous orbital fat repositioning is an effective method for correcting primary multiple upper eyelid folds. This technique presents a novel alternative for patients with primary multiple eyelid folds, particularly those who are hesitant to undergo a full-incision double-eyelid procedure. LEVEL OF EVIDENCE IV: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Correction of Sunken Upper Eyelid in Asian Blepharoplasty Based on Anatomical and Histological Study of Orbital Fat Fascia Flap.

OBJECTIVES: To explore the clinical application of orbital fat fascia flap in the correction of sunken upper eyelid in Asian blepharoplasty based on anatomical and histological research. METHODS: Observe the histological structure of the orbital fat and its fascia vascularity through cadaver anatomy and histological sections of 10 cadavers. Based on the anatomical and histological characteristics of orbital fat, 36 patients with mild to moderate sunken upper eyelids were corrected by transposition of orbital fat fascia flap with preservation of fascia vascular pedicle. During the operation, the lateral part of the central cellulite of orbital fat was separated longitudinally and transferred to the sunken place to correct the sunken upper eyelid. RESULTS: Anatomy and histology show that the orbital fat was located between the anterior layer of the levator aponeurosis and the posterior layer of the orbital septum and was separated into fat lobules by many fibrous septa. The blood vessels move forward from back to front along the orbital fat interlobular septum, and the blood vessels in the capsule below the orbital fat are abundant. Clinical results showed that the shape of the sunken upper eyelid was significantly improved in 35 cases after correction with this method during the postoperative follow-up from 9 months to 18 months. The mean sunken depth improved from 6.2mm (±1.0 mm) preoperatively to 2.2mm (±0.9 mm) at the last follow-up with a statistical significance. And only 1 case had partial depression in the unilateral eyelid and received autologous granular fat transplantation with satisfactory postoperative results. CONCLUSION: The transposition of orbital fat fascia flap with longitudinal separation and preservation of fascia vascular pedicle can better correct the sunken upper eyelid during blepharoplasty, and the long-term effect is stable, which is worthy of clinical promotion. LEVEL OF EVIDENCE IV: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

The Origin and Course of the Blood Supply to the Lower Eyelid Orbital Fat: Anatomical Study and Clinical Significance.

PURPOSE: The aim of this study is to investigate the origin and course of the orbital fat arterial supply in the lower eyelid using traditional anatomy and three-dimensional computed tomography (CT). METHODS: Twenty-seven cadaver heads were infused with mercury sulfide contrast media through the ophthalmic artery, maxillary artery, transverse facial artery, and facial artery. CT images were obtained after contrast agent injection, three-dimensional CT scans were reconstructed, and the cadaver heads were dissected. RESULTS: Forty-five qualified hemifaces showed that the orbital fat arterial supply in the lower eyelid originates primarily from the inferomedial muscular trunk (IMT) of the ophthalmic artery and the orbital branch of the infraorbital artery. The medial branch of the IMT terminated at the medial fat pad (35.6%) or the orbital floor (64.4%). The lateral branch terminated at the inferior oblique (IO) muscle (28.9%) or the central and lateral fat pads (17.8%). In 53.3%, the lateral branch extended to the anterior part of the lateral fat pad and terminated in the orbital wall or the zygomaticoorbital foramina. The orbital branch of the infraorbital artery coursed between the orbital floor and the orbital fat, providing supply to the IO muscle, inferior rectus (IR) muscle, nasolacrimal duct, and orbital fat. CONCLUSION: This study elucidated the origin and course of the orbital fat arterial supply in the lower eyelid, which may help to avoid reducing the blood supply of the orbital fat pedicles during surgery. LEVEL OF EVIDENCE IV: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Effect of retrobulbar prostaglandin analog injection on orbital fat in rats.

PURPOSE: Periorbital fat atrophy is a known side effect of topical prostaglandin analogs (PA). This side effect may have implications in the treatment of diseases like thyroid orbitopathy. In this in vivo study we aimed to evaluate the effects of retrobulbar injection of three different PAs on orbital fat. METHODS: Eighteen adult male Wistar-albino rats were divided into three groups of six animals. 0.1 ml of 0.03% bimatoprost, 0.005% latanoprost, or 0.005% travoprost was injected into the right orbits and saline was injected into the left orbits, as controls. Both orbits were exenterated after 3 weeks. Histological cross-sections were analyzed using ImageJ image analysis software. Intraconal adipocyte density was calculated. RESULTS: There was no significant difference in the adipocyte density between the PA injected orbits and the control side in each of the three groups. When calculations from all three groups were analyzed together, again the difference in the adipocyte density between the PA injected orbits and the control side was not significant. CONCLUSION: No significant fat atrophy was noted in this rat model three weeks after retrobulbar injection of PAs. To evaluate retrobulbar injection of PA as a potential therapy for orbital diseases with fat proliferation, in vivo studies in different animal models, higher concentrations of PA, or longer follow-up duration are required.

The relationship between ethmoidal foramina and orbital fat herniation.

BACKGROUND: The aims of this study are to determine the incidence and more frequent localizations of orbital fat tissue herniation accompanying dehiscences in the medial orbital wall and to investigate the relationship between orbital fat tissue herniations and the anterior and posterior ethmoidal foramina. METHODS: One thousand two hundred patients who had undergone computed tomography with a preliminary diagnosis of sinusitis and who had no previous facial, orbital, paranasal sinus surgeries or history of trauma were retrospectively analyzed. The localization of the ethmoidal foramina and orbital fat tissue herniations were marked. In patients with orbital fat tissue herniation, the relationship between the localization of orbital fat tissue herniation and the anterior and posterior ethmoidal foramina was investigated. RESULTS: The incidence of orbital adipose tissue herniation in our study was 7.9%. Of the 98 herniations on the bilateral medial orbital wall, 60 were in zone 3, and the most common herniation site was zone 3. A statistically significant difference was noted between the localization zone of the anterior ethmoidal foramen and the localization zones of orbital fat tissue herniations (Fisher's exact test, p < 0.001). DISCUSSION: Zone 3 is the weakest area of the medial orbital wall, and zone 3 is the most prone to herniation of fat tissue. The association of orbital fat tissue herniations with the anterior ethmoidal foramen is extremely common. Being cognizant of this finding may help a surgeon better estimate the anatomical view to be met before functional endoscopic sinus surgery as well as to minimize the risk of possible orbital complications, especially anterior ethmoidal artery injury.

The relationship between ethmoidal foramina and orbital fat herniation.

Background/aim: The aims of this study are to determine the incidence and more frequent localizations of orbital fat tissue herniation accompanying dehiscences in the medial orbital wall and to investigate the relationship between orbital fat tissue herniations and the anterior and posterior ethmoidal foramina. Material and methods: One thousand two hundred patients who had undergone computed tomography with a preliminary diagnosis of sinusitis and who had no previous facial, orbital, paranasal sinus surgeries or history of trauma were retrospectively analyzed. The localization of the ethmoidal foramina and orbital fat tissue herniations were marked. In patients with orbital fat tissue herniation, the relationship between the localization of orbital fat tissue herniation and the anterior and posterior ethmoidal foramina was investigated. Results: The incidence of orbital adipose tissue herniation in our study was 7.9%. Of the 98 herniations on the bilateral medial orbital wall, 60 were in zone 3, and the most common herniation site was zone 3. A statistically significant difference was noted between the localization zone of the anterior ethmoidal foramen and the localization zones of orbital fat tissue herniations (Fisher's exact test, p < 0.001). Conclusion: Zone 3 is the weakest area of the medial orbital wall, and zone 3 is the most prone to herniation of fat tissue. The association of orbital fat tissue herniations with the anterior ethmoidal foramen is extremely common. Being cognizant of this finding may help a surgeon better estimate the anatomical view to be met before functional endoscopic sinus surgery as well as to minimize the risk of possible orbital complications, especially anterior ethmoidal artery injury.

Extraocular muscle expansion after deep lateral orbital wall decompression: influence on proptosis reduction and its predictive factors.

PURPOSE: To examine the relationship between extraocular muscle expansion and proptosis reduction (Δproptosis) in patients with thyroid eye disease who underwent deep lateral orbital wall decompression and to analyze the factors that contribute to extraocular muscle expansion. METHODS: This retrospective, observational study included 133 sides from 77 patients with thyroid eye disease. The cross-sectional areas of the greater wing of the sphenoid bone (trigone), extraocular muscles, and superior ophthalmic vein were measured on computed tomographic images. Variables influencing Δproptosis were analyzed using multivariate linear regression analyses with stepwise variable selection. Predictive factors for the rate of postoperative increase in the cross-sectional extraocular muscle areas (Δextraocular muscle) were analyzed using the same statistical method. RESULTS: The amount of orbital fat removed (P < 0.001) and rate of Δlateral rectus muscle (P < 0.001) were positively and negatively correlated with Δproptosis, respectively (r = 0.425; adjusted r2 = 0.168; P < 0.001). The cross-sectional trigone area (P < 0.001) was positively correlated with the rate of Δlateral rectus muscle, whereas the preoperative cross-sectional lateral rectus muscle area (P < 0.001) and amount of orbital fat removed (P = 0.036) were negatively correlated with the rate of Δlateral rectus muscle (r = 0.551; adjusted r2 = 0.288; P < 0.001). CONCLUSION: Lateral rectus muscle expansion was negatively correlated with proptosis reduction and proved to be predictable before surgery. The results of this study will help predict proptosis reduction after deep lateral orbital wall decompression and to preoperatively plan additional orbital bony and fat decompression.

Herniation of orbital fat through the inferior orbital fissure and into the infratemporal fossa: a cadaveric case report and review.

Orbital fat herniation is primarily in a subconjunctival location. However, herniation through the inferior orbital fissure (IOF) has been scantly reported. Here, we report a cadaveric case of herniation of orbital fat through the inferior orbital fissure and into the infratemporal fossa. The cadaver's orbital anatomy and orbital fat herniation were found during routine dissection. The details of this case are reported. We also discuss anatomical variations of the inferior orbital fissure as well as the related vascular and nervous system structures related to orbital fat herniation. This is a rare case of a cadaver with this anatomical abnormality.

Post-traumatic enophthalmos secondary to orbital fat atrophy: a volumetric analysis.

PURPOSE: To investigate via volumetric analysis whether orbital fat atrophy occurs in late post-traumatic enophthalmos. METHODS: An IRB-approved retrospective cohort study identified patients with diagnoses of both orbital fracture and enophthalmos with a CT orbits >3 months after injury. Exclusion criteria were surgical repair, other orbital disease or surgery, adjacent sinus disease, and an abnormal contralateral orbit. Images were analyzed using OsiriX imaging software (v.9.0.2, Pixmeo, Switzerland). Total orbital volume and orbital fat volume for the fractured and normal contralateral orbits were measured via three-dimensional volume rendering assisted region-of-interest computation. Enophthalmos was measured radiographically. Paired samples t-tests were used to compare orbital fat and total orbital volumes between the fractured and normal contralateral orbits. RESULTS: Thirteen patients met the inclusion criteria. The numbers of patients with each fracture pattern were floor (4), medial wall (4), floor/medial wall (3), zygomaticomaxillary complex (floor+lateral wall) (1), zygomaticomaxillary complex+medial (inferior/medial/lateral walls) (1). Mean time from injury to CT scan was 21.8 ± 16.3 months. Comparing the fractured and normal contralateral orbits, there was a statistically significant decrease in orbital fat volume (mean difference 0.9 ml (14.2%), p = .0002) and increase in total orbital volume (mean difference 2.0 ml (7.0%), p = .0001). One ml orbital volume change was responsible for 0.83 mm enophthalmos. CONCLUSIONS: In addition to an increase in total orbital volume, orbital fat loss occurs with late post-traumatic enophthalmos due to unrepaired fractures. This suggests correction of bony change alone may be insufficient in some cases, and the use of custom implants may compensate for fat atrophy.

Damage to the inferior oblique muscle branch of the oculomotor nerve: a complication during orbital fat decompression.

PURPOSE: To present patients who suffered damage to the inferior oblique muscle branch of the oculomotor nerve during orbital fat decompression. METHODS: This study was a retrospective chart review of all patients who underwent orbital decompression surgery between April 2009 and June 2016 by the authors. RESULTS: Among 414 sides from 226 consecutive patients who underwent orbital decompression, the inferior oblique muscle branch was injured in two sides (0.5%) of two patients. Both patients showed hypotropia and incyclotropia immediately after surgery. Within 6 months of injury, ocular deviation on primary gaze had mostly resolved after conservative treatment. None of the patients underwent strabismus surgery. Postoperative computed tomographic images demonstrated that the affected branch was indistinct 3-4 mm posterior to the inferior oblique muscle. CONCLUSIONS: This report indicates that injury to the inferior oblique muscle nerve branch can occur at a point posterior to the inferior oblique muscle during orbital fat decompression; however, the resulting ocular deviation improves considerably within 6 months of injury.

Autoantibody against aldehyde dehydrogenase 2 could be a biomarker to monitor progression of Graves' orbitopathy.

PURPOSE: This study surveyed the novel autoantigens expressed in the orbital fat tissue of patients with Graves' orbitopathy (GO) and explored the possibility of the autoantibodies against novel autoantigens as biomarkers for GO. METHODS: We used immuno-proteomic methods to survey novel autoantigens expressed in the orbit fat tissue of GO patients and confirmed by enzyme-linked immunosorbent assay (ELISA). RESULTS: One protein spot (aldehyde dehydrogenase 2 (ALDH2)) revealed high reactivity with the GO serum than did the healthy control serum and was further verified by ELISA. We found that the plasma anti-ALDH2 antibody level was increased in GO patients compared to healthy control donors. In addition, anti-ALDH2 antibody level was correlated with GO activity classified by clinical activity score(r = 0.588, p < 0.001, using Pearson's correlation). CONCLUSIONS: These increased levels of anti-ALDH2 antibody in GO serum suggested that ALDH2 could attribute target autoantigen in GO, and anti-ALDH2 autoantibody might serve as a biomarker for GO and help to predict disease activity.

Orbital fat regeneration following hormonal treatment of metastatic breast carcinoma.

Enophthalmos in the setting of breast cancer metastatic to the orbit results primarily from the disease pathogenesis, or secondary to treatment effects. Orbital volume restoration and fat regeneration following endocrine treatment monotherapy has not been previously reported. A 76- year-old previously healthy female presented with progressive right enophthalmos secondary to metastatic lobular breast carcinoma. Treatment with an aromatase inhibitor (letrozole) resulted in tumor regression and orbital fat restoration with a corresponding improvement in orbital volume and enophthalmos on clinical exam. The patient is alive on continued letrozole with no progressive disease ten years after diagnosis. This case illustrates the resilience of orbital soft tissues and ability of orbital fat to regenerate in face of breast cancer metastasis. We hypothesize that endocrine monotherapy, and avoidance of radiation therapy, allowed for differentiation of remaining orbital stem cells, and facilitated the fat regenerative process.

Comparison of Morphology of Adipose Body of the Orbit and Subcutaneous Fat in Humans.

We compared histological structure of the orbital and subcutaneous adipose tissue. Quantitative morphometry showed that the mean diameter of adipocytes and their volume density in the orbital adipose tissue were significantly lower than in the subcutaneous fat, while volume density of vessels and elements of the connective tissue in the orbital adipose tissue was higher. Previously known and revealed here differences in the structure of orbital and subcutaneous adipose tissue do not answer the question, whether subcutaneous adipose tissue can be used for replacement of the orbital tissue deficit.

Orbital fat volume in the inferolateral quadrant in Japanese: a guide for orbital fat decompression without injury to the oculomotor nerve.

PURPOSE: The inferior oblique muscle branch of the oculomotor nerve is susceptible to injury during orbital fat removal from the inferolateral quadrant of the orbit. Understanding the amount of removable orbital fat volume in this quadrant may be helpful in achieving maximum fat decompression without causing nerve injury. The aim of this study was to calculate the orbital fat volume in the inferolateral quadrant using computed tomographic (CT) images. METHODS: In this retrospective, observational study, contiguous 1-mm coronal CT images were obtained from 53 sides (30 patients). The cross-sectional areas of the orbital fat in the inferolateral quadrant were measured from the level just behind the inferior oblique muscle to the orbital apex. The cross-sectional areas reached the inferior oblique muscle branch medially, the lateral orbital wall laterally, the inferior edge of the lateral rectus muscle superiorly, and the orbital floor inferiorly. An integrated value between the cross-sectional areas and the CT slice thickness was calculated. RESULTS: The mean orbital fat volume in the inferolateral quadrant was 3.9 ± 1.4 mL (range: 1.3-7.0 mL). Multiple regression analysis demonstrated a significant relationship between orbital fat volume and Hertel exophthalmometry measurement (adjusted r 2 = 0.101; P = 0.012), although the thickness of the lateral and inferior recti muscles was deleted from the regression equation by stepwise process. CONCLUSIONS: The orbital fat volume in the inferolateral quadrant can serve as a guide for orbital fat removal without causing injury to the inferior oblique muscle nerve branch.

Absence of chromosomal abnormalities in herniated orbital fat.

AIMS: Lipomatous tumours of the orbit are rare, and can sometimes be difficult to characterize. Herniated orbital fat is thought to be a reactive process, but its presentation can mimic a lipomatous tumour such as an atypical lipomatous tumour or spindle cell/pleomorphic lipoma. Genetic studies to determine if it is indeed a reactive process rather than an adipocytic neoplasm have not been performed. METHODS AND RESULTS: Four samples of herniated orbital fat were reviewed clinically, histopathologically and immunohistochemically. Array comparative genomic hybridization (aCGH) was used to search for genome-wide copy number alterations within the tumours. Histological evaluation revealed that all four tumours contained collections of adipocytes surrounded by fibrous septae. Lochkern cells and floret-like multinucleated giant cells were present, consistent with herniated orbital fat. CD34 was positive in all tumours. Staining for MDM2 and CDK4 was negative. ACGH analysis demonstrated no copy number alterations. CONCLUSIONS: Herniated orbital fat may share some histopathological features with lipoma and atypical lipomatous tumour, but the absence of copy number gains or losses is consistent with the impression that herniated orbital fat is a reactive process. Genetic analysis may be another method to help differentiate herniated orbital fat from a lipomatous orbital tumour when the diagnosis is in question.

[Enophthalmos secondary to an orbital varix]. / Enoftalmos unilateral por várice orbitaria.

The enophthalmos is a rare cause of consultation in medical practice. The majority of cases are due to orbital space enlargement of traumatic origin. We report the case of a 63 year old patient with progressive enophthalmos of the left eye, with twelve years of evolution. Ophthalmologic examination revealed the presence of a marked enophthalmos on the left side, which improved significantly with Valsalva maneuvers. A CT scan and an MRI of the orbit allowed diagnosing uncomplicated orbital varices. Orbital varices are rare and usually manifest by episodes of intermittent exophthalmos. However, on rare occasions, repeated distension and collapse can lead to progressive enophthalmos by orbital fat atrophy.

Evaluation of the Treatment Effects of Conditioned Medium from Human Orbital Adipose-Derived Stem Cells in a Corneal Alkali Burn Rabbit Model.

Purpose: This study aimed to evaluate the effects of a new treatment-conditioned medium from human orbital adipose-derived stem cells (OASC-CM)-on corneal recovery after alkali burns in a rabbit model. Methods: The corneal alkali burn rabbit model was established and treated with OASC-CM, conditioned medium from human abdominal subcutaneous adipose-derived stem cells (ABASC-CM), and fresh control culture medium (con-CM) three times a day for 7 days, respectively. Subsequently, the treatment effects were evaluated and compared through clinical, histological, immunohistochemical, and cytokine evaluations. Results: Clinically, OASC-CM alleviated corneal opacity and edema and promoted recovery of corneal epithelium defect. Histologically and immunohistochemically, OASC-CM inhibited neovascularization, conjunctivalization, and immuno-inflammatory reaction, while promoting corneal regeneration and rearrangement. Increased secretion of interleukin-10 and inhibited protein levels of cluster of differentiation 45, interferon-γ, and tumor necrosis factor-α were observed in the alkali-burned cornea after OASC-CM treatment, which might be the relevant molecular mechanism. Conclusions: OASC-CM showed significant effects on the recovery of rabbit corneal alkali burns and eliminated immunological and ethical limitations, representing a new option for corneal wound treatment.

Correction of severe upper-eyelid sunken deformity in Asians by double-eyelid procedure and combination of orbital fat pad repositioning and autologous fat transplantation: a one-year follow-up study of 79 cases.

Background: Nowadays, people's pace of life continues to rapid up, and many bad habits will accelerate the aging of the eye periphery, and patients with sunken upper eyelids are to be found in younger people. In young Asians, single eyelids are often accompanied by upper eyelid depression, so correcting the upper eyelid depression during blepharoplasty becomes a higher challenge for plastic surgeons. Current surgical methods for upper eyelid depression include three major categories: tissue repositioning, injection and filling, and combined use. According to grades 1 and 2 are mild or moderate upper eyelid sunken. The sunken can be well corrected only by repositioning the orbital fat pad, while the correction effect for severe upper eyelid sunken in grades 3 and 4 is Poor, need to be used in combination to achieve the desired effect. Purpose: The authors sought to determine whether, for patients with single eyelids and severe upper eyelid depression of grades 3 and 4, combined with orbital fat pad repositioning and autologous fat transplantation during blepharoplasty, an aesthetic and youthful blepharoplasty can be achieved. Methods: This study included 79 patients with single eyelids and severe upper eyelid depression of grades 3 and 4 who received treatment between June 2020 and July 2022. All patients underwent double eyelid surgery plus orbital fat repositioning and autologous fat grafting. Results: After a minimum follow-up period of 1 year, overall patient satisfaction was 92%. The recurrence rate within the first year was 6% and the complication rate was 5%. Conclusion: This combined surgery may be an option for young Asians with single eyelids and severe upper eyelid depression. In this study, the surgery resulted in natural-looking double eyelids and younger-looking eye sockets in most patients. A combination of different surgical methods based on the patient's preoperative condition is critical to achieving long-term correction.

Giant cell angiofibroma or localized periorbital lymphedema?

Giant cell angiofibroma represents a rare soft tissue neoplasm with a predilection for the orbit. We recently encountered a mass removed from the lower eyelid of a 56-year-old female that histopathologically resembled giant cell angiofibroma. The process consisted of haphazardly arranged CD34-positive spindled and multinucleated cells within an edematous, densely vascular stroma. However, the patient had recently undergone laryngectomy and radiotherapy for a laryngeal squamous cell carcinoma. A similar mass had arisen on the contralateral eyelid, and both had developed several months post-therapy. Lymphedema of the orbit can present as tumor-like nodules and in some cases may share histopathologic features purported to be characteristic of giant cell angiofibroma. A relationship between giant cell angiofibroma and lymphedema has not been established, but our case suggests there may be one. The potential overlap of these two conditions should be recognized, as should other entities that may enter the differential diagnosis.

In Vivo Effects of Prostaglandin Analogues Application by Topical Drops or Retrobulbar Injections on the Orbital Fat of a Rat Model.

PURPOSE: To assess the in vivo effects of bimatoprost 0.03% (Lumigan®) on the orbital fat in a rat model. METHODS: Twenty rats were randomly divided into two groups: bimatoprost was administrated to the right eye by topical drops (group 1) or retrobulbar injection (group 2), and saline was administrated to the left eye by similar administration routes (controls). Four weeks later, all rats were sedated and euthanized, both orbits exenterated, and thin sections through the intraconal orbital fat were obtained. RESULTS: Average adipocyte cell count was significantly lower in the bimatoprost treated orbits (drops or retrobulbar injection, 29.5 vs. 67.5 cells per slide in the control globes, p=0.046). Fat cells were not detected in 9/20 (45%) bimatoprost treated orbits     . CONCLUSIONS: Orbits treated with bimatoprost by drops or retrobulbar injection demonstrated significant decrease in adipocytes cell count compared with controls. Bimatoprost could be an effective treatment for inactive thyroid eye disease.