A Protocol and Literature Review for Indocyanine Green in the Assessment of Periorbital and Facial Lymphatics

Introduction

Lymphatic channels and their drainage pathways play a critical role in oculofacial conditions including eyelid festoons, filler-associated edema and persistent postoperative edema. However, studies regarding the lymphatic channels and the modalities available to image lymphatics in the periorbital area are limited.

Indocyanine green (ICG) is a widely used imaging compound. It is a water-soluble dye that fluoresces in the near-infrared region with a short half-life.¹ The expanded use of open intra-operative imaging devices using ICG now includes sentinel lymph node dissection, surgical anastomosis perfusion studies, limb lymphedema and tissue flap perfusion.^2-4

Advancement in imaging devices have made real-time ICG lymphography a feasible and accessible method to assess lymphatics. In this study, the authors highlight a novel injection protocol to study eyelid and facial lymphatics and review the associated literature within this region.

Methods

A prospective clinical study was conducted from 2021 – 2022 on patients undergoing oculoplastic procedures. This study was approved by the Institutional Review Board of the University of Illinois at Chicago.

Subcutaneous injection of 0.03 – 0.06 mg of ICG was given in the pretarsal orbicularis of the upper or lower eyelid within the medial 1/3 or lateral 2/3 of the eyelid to visualize the lymphatic drainage. Fluorescent images were captured in real-time with video using the SPY PHI System (Stryker, Kalamazoo, MI) or EleVision IR Platform (Medtronic, Minneapolis, MN) continuously over a 30-minute period in a dark room. The number of eyelid lymphatic channels and transit time to facial landmarks were analyzed.

A review of ICG in lymphography in line with the Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines was performed. A PubMed/MEDLINE search was executed in January 2023 using the terms: “(ICG OR indocyanine green) AND (lymphography) AND (eyelid OR face OR periorbita OR eye OR facial)”, “(ICG OR indocyanine green) AND (lymphatics) AND (facial OR face OR eyelid).” Titles and abstracts were reviewed independently. Articles were excluded if they had no extractable clinical data, were not relevant to facial lymphatics or ICG or were not written in English.

Results

Twelve eyelid injections (10 patients) were performed. A 0.03 mg dose of ICG allowed for optimal periorbital lymphatic and lymph node mapping without excessive background fluorescence. Facial lymphatic mapping transit times varied. Lymphatic mapping of the medial eyelid traveled to the submandibular node. Lymphatic mapping of the lateral eyelid traveled to the preauricular node. Two eyelid lymphatic channels were mapped on the upper eyelid (n=7 patients). One to two eyelid lymphatic channels were mapped on the lower eyelid (n=2 patients). Adverse events included temporary subcutaneous green tissue staining and injection site pain.

A total of 33 abstracts were identified on literature review, with 8 duplicates and 15 non-eyelid or facial lymphography articles. Ten abstracts, published between 2011-2021, were included.^5-14 Studies assessed the use of ICG in the evaluation of the facial lymphatics of healthy participants (n=5 patients)⁵ and eyelid (n=3 patients),⁶ conjunctival lymphatic vessels (n=1 patient),⁷ Morbihan’s disease (n=1 patient),⁸ facial lymphedema following tumor resection and radiation for head and neck cancers (n=2 patients),⁵ post-face transplant (n=1 patient),⁹ post-facial flap placement (n=18 patients),¹⁰ and guided sentinel lymph node biopsies for periocular conjunctival melanoma (n=4 patients),¹¹ eyelid melanoma (n=1 patient),¹¹ and midface Merkel cell carcinoma (n=1 patient).¹² Two animal studies were identified using monkeys assessing eyelid lymphatics following a face transplant (n=9 primate models)¹³ and porcine animals assessing lymphatic flow following bleb creation (n=11 porcine models).¹⁴ Two studies compared ICG lymphography to Technectium-99m-labeled lymphoscintigraphy.^11,12

The amount injected of ICG ranged from 0.25 – 6.25 mg with volumes that varied between 0.05–1.5 mL. Monitoring protocols of lymphatics drainage included still and video images. Screening intervals ranged from 5-minute intervals every 30 minutes, or 10-minute intervals every 60 minutes, with total recording time of 3 hours. Image capturing devices included Confocal Scanning Laser Ophthalmoscope, Photodynamic Eye and Photodynamic Eye II Hamamatsu Photonics and Life-cell SPY Elite Imaging. One paper did not report their injection protocol and three papers did not report their monitoring protocol.

All studies were able to visualize the lymphatics. Outcomes measured included qualitative analysis of lymphatic flow to nodal drainage pathways, monitoring of lymphostasis, dermal back flow, lymphatic velocity and the ability to identify sentinel lymph nodes.

Limitations included the small sample size and wide variety in protocol. No studies included quantification data of the relative ICG fluorescence.

Discussion

In this study, the authors highlight a novel protocol for the real-time visualization and assessment of periorbital lymphatics using ICG. The number of eyelid lymphatic channels, travel time, and drainage to the respective lymph nodes were captured. This protocol highlights the ability to visualize the intricate eyelid lymphatic pathways.

Limited modalities are currently available to assess lymphostasis. While computed tomography and magnetic resonance imaging can capture tissue edema, high resolution imaging is required to capture abnormal lymphatic channels.¹⁵ Lymphoscintigraphy is an alternative modality; however, it is more invasive, requires an injection of a radiotracer, is not easily accessible and may prove difficult to interpret, thereby limiting its use.^16,17 ICG lymphography allows ease of lymphatics visualization in real-time, uses a mobile camera and lacks of exposure to radiotracers.

Periorbital and facial lymphatics have been successfully captured in both animal and human studies.^5-14 A wide range of pathology has been described including ocular, eyelid and facial lymphedema. Many of these studies are qualitative, describing the presence of lymphatic flow. However, Yamamoto et al described the linear lymphatic pathways and distinct patterns of dermal backflow described as splash, starburst, and diffuse.⁶ As more patients undergo periorbital and facial lymphography, formal nomenclature may be necessary.

ICG lymphography can be utilized to assess clinical outcomes. In the case of Morbihan’s disease, ICG evaluated facial edema immediately following blepharoplasty with lymphaticovenous anastomosis and one year later, illustrating resolution of lymphoedema.⁸ When studying the regeneration of the lymphatic pathways following allographic facial transplantation distinct lymphatic pathways were readily visualized once the lymphedema improved.⁹ ICG lymphography may be an important tool when studying disease states and treatment outcomes of periorbital and facial lymphedema.

Within the literature, a range of protocols were described. The total ICG injection amount ranged from 0.5 – 6.25 mg given subcutaneously, and volumes varied between 0.05 – 0.2 mL.^5-14 Within the author’s protocol, the optimal injection amount was 0.03 mg with a volume of 0.05 mL. Subcutaneous green tissue staining typically resolved within two days at lower concentrations and lasted a week at higher concentrations. The temporary persistence of ICG within the eyelid should be taken into consideration in the aesthetic patient population undergoing ICG lymphography for diagnostic purposes.

Limitations of this study include the small number of subjects and its qualitative nature. The protocol evolved throughout the study to optimize variables such as the machine type, camera focal distance, amount of ICG injected, and atmospheric lighting. However, based on the preliminary results, the authors would advocate for injection of 0.03 mg of ICG with 0.05 mL volume subcutaneously within the eyelid in a dark room.

In conclusion, this study demonstrates ICG’s ability to visualize the eyelid and facial lymphatics. There is a growing literature utilizing ICG to study lymphatics within this region. Further studies are needed to study normal anatomy and disease states such as monitoring lymphedema following aesthetic injectables, festoons, and prolonged post-surgical edema.

Disclosure
This Project was supported by the NIH Grant P30EY001792, Research to Prevent Blindness Unrestricted Departmental Grant, Manhattan Eye Foundation and the Illinois Society for the Prevention of Blindness Grant.

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