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Longitudinal profile of retinal ganglion cell damage assessed with blue-light confocal scanning laser ophthalmoscopy after ischaemic reperfusion injury
  1. C K S Leung1,2,
  2. J D Lindsey1,
  3. L Chen2,
  4. Q Liu1,
  5. R N Weinreb1
  1. 1
    Hamilton Glaucoma Center, Department of Ophthalmology, University of California, San Diego, La Jolla, California, USA
  2. 2
    Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Shatin, Hong Kong, PR China
  1. Dr R N Weinreb, Hamilton Glaucoma Center, University of California, San Diego, La Jolla, CA 92093-0946, USA; weinreb{at}eyecenter.ucsd.edu

Abstract

Aim: To longitudinally investigate retinal ganglion cell (RGC) expression of Thy-1, a cell-surface glycoprotein specifically expressed in RGCs, with a blue-light confocal scanning laser ophthalmoscope, following retinal ischaemia induced by acute elevation of intraocular pressure.

Methods: A blue-light confocal scanning laser ophthalmoscope (bCSLO, 460 nm excitation and 490 nm detection) was used to image Thy1-cyan fluorescent protein (CFP) mice before and weekly for 4 weeks after transiently elevating the intraocular pressure to 115 mm Hg for 45 min (n = 4) or 90 min (n = 5) to induce ischaemic injury. Corresponding retinal areas before and after the intraocular pressure (IOP) elevation, during the period of ischaemic reperfusion, were compared, and the fluorescent spots (Thy-1 expressing RGCs) were counted. The longitudinal profile of CFP-expressing RGCs was modelled with a linear regression equation. The spatial distribution of RGC damage was analysed in the superior, nasal, inferior and temporal quadrants of the retina.

Results: No significant change was found at 4 weeks after 45 min of IOP elevation (n = 4, p = 0.465). The average RGC densities before and 4 weeks after IOP elevation were 1660 (SD 242) cells/mm2 and 1624 (209) cells/mm2, respectively. However, significant loss of CFP-expressing RGCs was detected at 1 week following 90 min of IOP elevation (n = 5, p<0.001). After this initial RGC loss, no significant change was detected subsequently. The proportion of RGC fluorescence remaining was variable and ranged from 14.5% to 79.5% at 4 weeks after the IOP elevation. The average RGC densities before and 4 weeks after IOP elevation were 1443 (162) cells/mm2 and 680 (385) cells/mm2, respectively. Diffuse loss of fluorescent RGCs was observed in the spatial distribution analysis.

Conclusions: The longitudinal profile of Thy-1 expressing RGC fluorescence loss after ischaemic injury is non-progressive and unrelated to the duration of reperfusion.

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Footnotes

  • Competing interests: RW received research instruments from Heidelberg Engineering.

  • Funding: Supported in part by National Eye Institute Grants EY11008 (JDL) and EY014661 (JDL)

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