Functional, structural, and molecular identification of lymphatic outflow from subconjunctival blebs

Area of Science:

• Ophthalmology
• Anatomy
• Physiology

Background:

• Subconjunctival blebs are crucial for ocular fluid drainage after glaucoma surgery.
• Understanding their outflow pathways is vital for improving surgical outcomes and drug delivery.
• Current knowledge on the precise nature and identity of these pathways remains limited.

Purpose of the Study:

• To investigate and characterize the outflow pathways originating from subconjunctival blebs.
• To determine the histological and molecular identity of these identified pathways.
• To assess the quantitative distribution of these pathways within the bleb structure.

Main Methods:

• Utilized post-mortem porcine, human, and bovine eyes for anatomical study.
• Injected tracers (fluorescein, indocyanine green, dextrans) into the subconjunctival space to visualize outflow pathways.
• Employed optical coherence tomography (OCT), histology, and immunofluorescence for pathway analysis and molecular identification.

Main Results:

• Outflow pathways were successfully visualized in all studied species using various tracers.
• A significantly higher number of pathways were observed in the nasal quadrant compared to the temporal quadrant.
• Histological and immunofluorescence analyses confirmed the lymphatic identity (Prox-1, podoplanin) of the pathways, with no evidence of blood vessel markers (CD31).
• Bicuspid valves, characteristic of lymphatic vessels, were identified within the porcine outflow pathways.

Conclusions:

• Subconjunctival bleb outflow occurs through distinct luminal pathways.
• These pathways are structurally and molecularly identified as lymphatic vessels.
• This finding offers potential for enhanced strategies in glaucoma treatment and ocular drug delivery.