Purpose
The lymphatic system maintains tissue fluid balance and immunity and plays an important role in the pathogenesis of diseases such as tumor metastasis and inflammation. The eye was thought to lack lymphatic vessels except for the conjunctiva. Anatomists such as Arnold (1847) and Teichmann (1861) were the first to visualize and describe the conjunctival lymphatics, respectively. In 1948, Busacca identified a number of anastomosing lymphatics, which penetrated in the orbital cavity nearby the extra-ocular muscles using trypan blue dye. A better understanding of the lymphatic system in the eye can provide the basis for the development of alternative therapeutic strategies for ocular diseases. Lymphography is well explored in other medical specialties such as vascular surgery and oncology. Newer techniques of fluorescence lymphography using indocyanine green (ICG) is being used increasingly. ICG lymphography has been widespread because there is no endogenous fluorescence in the near infrared band (780-1500nm) used for ICG detection and the exam does not cause tissue damage. ICG is approved for hepatic and ophthalmologic applications. In this study we identified conjunctival lymphatic capillaries using lymphography with near-infrared fluorescence.
Methods
A 32-gauge needle was used to inject sterile indocyanine green (0.1mL) subconjuntivaly, in the pretenon’s area 3mm posterior to the limbus of the right eye. The pool of contrast was evaluated by slit lamp biomicroscopy, color photography and multi-modality diagnostic imaging with SPECTRALIS® (Heidelberg Engineering). The exams were performed by the same operator using a preset light intensity. Ophthalmic examination was performed weekly until there was complete contrast absorption.
Results
Small lymph vessels (lymphatic capillaries) were identified and differentiated from blood vessels by multi-modality diagnostic imaging. Meticulous analysis of the ICG lymphography revealed intermittently dilated lymphatic drainage channels underneath the conjunctival blood vessels. No systemic or local side effects were observed following the subconjunctival injection of indocyanine green. The ICG cleared completely from the eye within 4 weeks.
Conclusions
We have identified a minimally invasive method to identify the microanatomy of the conjunctival lymphatic capillaries.
Keywords: 552 imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) •
419 anatomy •
474 conjunctiva