April 2014
Volume 55, Issue 13
Free
ARVO Annual Meeting Abstract  |   April 2014
Visualization of Aqueous Humor Dynamics upon Chronic Ocular Hypertension and Hypotensive Drug Treatment using Gadolinium-enhanced MRI
Author Affiliations & Notes
  • Leon C Ho
    Neuroimaging Laboratory, Department of Radiology, University of Pittsburgh, Pittsburgh, PA
    Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong, China
  • Ian P Conner
    Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA
  • Chi-wai Do
    School of Optometry, The Hong Kong Polytechnic University, Hong Kong, China
  • Seong-Gi Kim
    Neuroimaging Laboratory, Department of Radiology, University of Pittsburgh, Pittsburgh, PA
    Center for Neuroscience Imaging Research, Institute for Basic Science (IBS), Dept. of Biological Science, SKKU, Suwon, Republic of Korea
  • Ed X Wu
    Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong, China
  • Gadi Wollstein
    Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA
  • Joel S Schuman
    Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA
  • Kevin C Chan
    Neuroimaging Laboratory, Department of Radiology, University of Pittsburgh, Pittsburgh, PA
    Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA
  • Footnotes
    Commercial Relationships Leon Ho, None; Ian Conner, None; Chi-wai Do, None; Seong-Gi Kim, None; Ed Wu, None; Gadi Wollstein, None; Joel Schuman, Zeiss, Inc. (P); Kevin Chan, None
  • Footnotes
    Support None
Investigative Ophthalmology & Visual Science April 2014, Vol.55, 2902. doi:
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      Leon C Ho, Ian P Conner, Chi-wai Do, Seong-Gi Kim, Ed X Wu, Gadi Wollstein, Joel S Schuman, Kevin C Chan; Visualization of Aqueous Humor Dynamics upon Chronic Ocular Hypertension and Hypotensive Drug Treatment using Gadolinium-enhanced MRI. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2902.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract
 
Purpose
 

While current clinically approved glaucoma treatments target at altering aqueous humor (AH) dynamics to lower elevated intraocular pressure (IOP), the contributions of imbalanced AH dynamics to the pathogenesis of ocular hypertension (OHT) and glaucoma are not fully elucidated. This study used a small-molecular-weight MRI contrast agent, gadolinium (Gd) to mimic AH and visualize AH dynamics in rats upon microbead (MB)-induced OHT or ocular hypotensive drug treatments.

 
Methods
 

8 Sprague-Dawley rats were injected with a mixture of 10 and 15μm MB into the right (R) anterior chamber (AC) to block aqueous outflow (AO) and induce sustained OHT for 2 weeks. 18 additional normotensive rats were topically applied to R eye with 0.005% latanoprost (Lat; n=6), 0.5% timolol maleate (Tim; n=6) and 0.2% brimonidine tartrate (BT; n=6) 1hr before MRI to lower IOP by facilitating AO, suppressing aqueous inflow (AI) and both respectively. Gd-DTPA was intraperitoneally injected to each rat, and T1-weighted images (30s each) were continuously acquired for 2hr in a 9.4 Tesla MRI scanner. 3 weeks later, saline was applied to R eyes of 2 rats from each drug group as sham control (Sal; n=6) and Gd-MRI was repeated. The MRI signal time course, initial increase rate (IIR) of Gd signal, peak signal intensity (PI) and time to peak (TP) in AC and vitreous body (VB) were computed.

 
Results
 

Right before MRI, the mean % IOP changes of treated R eye relative to untreated left (L) eye were 100%, -29%, -27%, -36% and -4% for MB, Lat, Tim, BT and Sal groups (p<0.05 except Sal). IOP increase by AO reduction in MB gave higher IIR & PI and shorter TP in R than L AC (p<0.05), whereas IOP decrease by AO increase in Lat or AI reduction in Tim gave opposite Gd-MRI patterns to MB (p<0.05 for Lat; p=0.06-0.2 for Tim). For BT, both L and R AC showed lower IIR, higher PI and longer TP than other groups (p<0.05). Only MB had higher PI in R than L VB (p<0.05). No Gd-MRI difference was found between both eyes in Sal, whereas IIR in L AC was slightly higher in Lat and Tim than MB and Sal (p=0.09-0.16).

 
Conclusions
 

IIR, PI and TP in Gd-MRI may reflect altered AH dynamics quantitatively upon OHT or anti-glaucoma drug treatments. The drastic Gd-MRI changes in BT and the slight changes in untreated AC of Lat and Tim may also draw attention to the systemic effects of topical hypotensive drugs on AH dynamics.

     
Keywords: 552 imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • 427 aqueous • 420 anterior chamber  
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