Aqueous outflow - A continuum from trabecular meshwork to episcleral veins

Teresia Carreon, Elizabeth van der Merwe, Ronald L. Fellman, Murray Johnstone, Sanjoy K. Bhattacharya

Research output: Contribution to journalReview articlepeer-review

125 Scopus citations


In glaucoma, lowered intraocular pressure (IOP) confers neuroprotection. Elevated IOP characterizes glaucoma and arises from impaired aqueous humor (AH) outflow. Increased resistance in the trabecular meshwork (TM), a filter-like structure essential to regulate AH outflow, may result in the impaired outflow. Flow through the 360° circumference of TM structures may be non-uniform, divided into high and low flow regions, termed as segmental. After flowing through the TM, AH enters Schlemm's canal (SC), which expresses both blood and lymphatic markers; AH then passes into collector channel entrances (CCE) along the SC external well. From the CCE, AH enters a deep scleral plexus (DSP) of vessels that typically run parallel to SC. From the DSP, intrascleral collector vessels run radially to the scleral surface to connect with AH containing vessels called aqueous veins to discharge AH to blood-containing episcleral veins. However, the molecular mechanisms that maintain homeostatic properties of endothelial cells along the pathways are not well understood. How these molecular events change during aging and in glaucoma pathology remain unresolved. In this review, we propose mechanistic possibilities to explain the continuum of AH outflow control, which originates at the TM and extends through collector channels to the episcleral veins.

Original languageEnglish (US)
Pages (from-to)108-133
Number of pages26
JournalProgress in Retinal and Eye Research
StatePublished - Mar 1 2017


  • Basement membrane: turnover and stability
  • Collector channels
  • Continuum hypothesis
  • Deep scleral plexus
  • Distal outflow
  • Glaucoma
  • Mechanosensing
  • Segmental outflow
  • Trabecular meshwork
  • schlemm's canal

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems


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