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Structural Confirmation of Lymphatic Outflow from Subconjunctival Blebs of Live Human Subjects
Jong Yeon Lee1,2, Gad Heilweil1, Phuc Le1
1Doheny Eye Institute and Stein Eye Institute, Department of Ophthalmology, David Geffen School of Medicine, University of California, Los Angeles, USA.
Purpose:
To uncover the mechanism of subconjunctival outflow in human patients.
Design:
Cross-sectional study.
Subjects/Participants And/Or Controls:
Fifteen subjects receiving subconjunctival anesthesia prior to intravitreal injection for routine clinical care.
Methods:
Anterior segment OCT (AS-OCT) was performed in patients with various instances of conjunctival edema or subconjunctival fluid. Other subjects received a subconjunctival mixture of 0.005% indocyanine green and 2% lidocaine. After subconjunctival injection of the tracer/anesthetic mixture, blebs and associated outflow pathways were angiographically imaged and the time for appearance recorded. The pattern and structure of outflow pathways were studied using AS-OCT. Angiographic and AS-OCT results were compared to trabecular/conventional outflow imaging which demonstrates veins.
Main Outcome Measures:
Ocular surface lymphangiography and AS-OCT images.
Results:
AS-OCT of the conjunctiva in a normal eye demonstrated thin non-edematous conjunctiva with absent intraconjunctival lumens or subconjunctival fluid. Subjects with a history of trabeculectomy, subconjunctival drug injection, or chemosis demonstrated thickened conjunctiva and intraconjunctival luminal pathways that contained valve-like structures. Tracer-based studies in patients demonstrated blebs with irregular subconjunctival bleb-related outflow patterns that arose in a time-dependent fashion. These angiographic pathways were luminal on OCT, sausage-shaped, and contained intraluminal valve-like structures. This was in contrast to trabecular/conventional outflow imaging where pathways were classically Y-shaped, of even-caliber, and lacked valve-like structures.
Discussion:
Outflow pathways were seen in cases of conjunctival edema and after subconjunctival tracer injection. These pathways were lymphatic based upon pattern and structural study. Better understanding of bleb-related lymphatic outflow may lead to improved bleb-requiring glaucoma surgeries and subconjunctival drug delivery.
