Collector Channel Dynamics: OCT Capture of Real-time Pressure-dependent Changes in Lumen Area in Ex Vivo Normal and Glaucomatous Eyes

Abstract

Purpose : 1. To determine whether OCT imaging can detect dynamic collector channel (CC) motion in human eyes. CC entrance closure in glaucoma or disruption with surgery may impact distal resistance. 2. To determine if Schlemm’s canal (SC) & CC motion differ in normal & glaucoma eyes. Slower responses reflect different tissue properties.

Methods : 13 quadrants from 3 ex vivo normal & 4 glaucomatous eyes (Age 80.3 ± 9.4, Sex 5F/2M, W4/O3) were maintained in media to optimize tissue properties1. Quadrants were immersed in media and a cannula was inserted into Schlemm’s canal (SC) by a micromanipulator. The cannula was connected to a valve switchable between 2 reservoirs to generate pressure changes from 0-30 mm Hg & 30-0 mm Hg. Pressure-dependent tissue motion was imaged by a very high-resolution OCT technique2,3. SC & CC response evaluation by Image J & videos (https://youtu.be/DliJ9fICfDg).

Results : 22 CC from 13 quadrants were identified & imaged. Pressure-induced TM movement with synchronous SC & CC lumen enlargement was observed at each identified lumen location. Lumen dimension change (Δ) reflects the movement of collagenous structures surrounding SC & CC. Both SC & CC area Δs occurred more rapidly in normal than in glaucoma eyes (see SC & CC normalized areas & responses to IOP Δs) (Fig. 1); SC & CC area rebound was present in glaucoma tissues reflective of surrounding tissue properties. In one glaucoma eye, SC was narrow with the TM attached to SC wall at a CC entrance; the TM motion Δ was slower than in other eyes (Fig. 2 & videos).

Conclusions : OCT imaging detected dynamic synchronous SC & CC lumen area Δs in human eyes. Pressure-dependent CC lumen configuration Δs suggest CC may act as regions of distal resistance. SC & CC motion occurred more slowly and tissue rebound was present in glaucoma tissues consistent with altered properties vs. normals. Novel aspects include: 1) a recovery technique to restore normal TM responses in ex vivo human eyes, 2) high-resolution OCT imaging of the outflow system during static or dynamic transtrabecular pressure changes. CC motion and differences in tissue response times in normal and glaucoma eyes warrant further study.

References 1. IOVS 1988;29: p90 2. JBO 2014;19:106013. 3. IOVS 2017;58: p4809.



References
1. IOVS 1988;29:p90
2. JBO 2014;19:106013.
3. IOVS 2017;58:p4809.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.

 

Dynamic SC & CC Responses

 

OCT Images: 0 & 30 mm SC Pressure