Chan Kee Park

Enhanced Depth Imaging Detects Lamina Cribrosa Thickness Differences in Normal Tension Glaucoma and Primary Open-Angle Glaucoma

OBJECTIVEnTo confirm the advantages of the enhanced depth imaging (EDI) mode over the standard mode of the Heidelberg Spectralis spectral domain optical coherence tomography (SD-OCT) for imaging of the lamina cribrosa, and to compare laminar thicknesses of various glaucoma types with or without disc hemorrhage in a similar state of visual field loss.nnnDESIGNnCross-sectional, case-control design.nnnPARTICIPANTSnWe included 137 glaucoma patients and 49 healthy controls.nnnMETHODSnOptic nerve head B-scans were obtained by both the standard and EDI modes of the Spectralis OCT. Laminar thickness was measured at the center of mid-superior, central, and mid-inferior horizontal B-scans. Laminar thickness in patients with normal tension glaucoma (NTG) was compared with that in patients with primary open-angle glaucoma (POAG). To verify the reproducibility of EDI imaging, intraclass correlation coefficients and test-retest variability were calculated from selected B-scans.nnnMAIN OUTCOME MEASURESnLaminar thickness and mean deviation values on standard automatic perimetry.nnnRESULTSnThe EDI OCT imaging showed significantly better intraobserver, interobserver, intravisit, and intervisit reproducibility than those by standard imaging. Laminar thickness in mid-superior, central, and mid-inferior regions was thinner in the POAG and NTG groups than in the normal control group (P<0.001). The mid-superior, central, and mid-inferior regions of the lamina were also significantly thinner in patients with NTG and disc hemorrhage than in those with NTG but no disc hemorrhage.nnnCONCLUSIONSnThe EDI mode of the Heidelberg Spectralis SD-OCT detected differences in the lamina cribrosa by glaucoma type. The lamina cribrosa was thinner in NTG eyes and in NTG eyes with disc hemorrhage.nnnFINANCIAL DISCLOSURE(S)nThe authors have no proprietary or commercial interest in any of the materials discussed in this article.

Retinal ganglion cell death is delayed by activation of retinal intrinsic cell survival program

Neuronal cells undergo apoptosis when deprived of neurotrophic factors due to injury, trauma, or neurodegenerative disease. This study examined cell death in the retina after chronic elevation of intraocular pressure (IOP) in an experimental rat model of human glaucomatous disease. Three episcleral veins on the ocular surface of rats were cauterized. Activation of several cell death programs represented by Fas ligand, FADD (Fas Associated Death Domain/Mort1) and the caspase cascade (caspase-8 and -3) and survival programs represented by phosphorylated protein kinase B (PKB/Akt), Bcl-2 associated death domain (BAD), and cAMP responsive element binding protein (CREB) were examined using immunohistochemistry and Western blotting. Following injury, two major events occurred simultaneously in the retina: activation of programmed cell death pathways and activation of survival mechanisms to maintain the cellular homeostasis of the retina. At the later stage of injury, markers of an activated cell death program appeared to be concentrated in the retinal ganglion cells. In conclusion, we suggest that endogenous cell survival factors triggered at the early stage of injury play a critical role in control of the death or survival of retinal ganglion cells and that the manipulation of this decision phase is one of the therapeutic targets for glaucoma.

Retinal ganglion cell death induced by endoplasmic reticulum stress in a chronic glaucoma model

This study investigated whether endoplasmic reticulum (ER) stress induced retinal ganglion cell (RGC) death in chronic ocular hypertension, one of the RGC death mechanisms, using an experimental glaucoma rat model. Glaucoma was induced in adult male Sprague-Dawley rats by cauterizing three episcleral veins. The intraocular pressure (IOP) remained elevated in the cauterized eyes for the 8-week experiment, whereas it was not elevated in the contralateral control eyes. The average number of RGCs decreased significantly, and TUNEL-positive cells were detected in the ganglion cell layer. In western blotting, Bip, the phosphorylated form of PKR (p-PERK), and C/EBP-homologous protein (CHOP) were significantly expressed at 1 or 2 weeks, and this persisted throughout the 8-week experiment. Phosphorylated eukaryotic initiation factor 2 (p-eIF2alpha) began to increase at 1 week, was sustained through 4 weeks, and decreased slightly at 8 weeks. In cauterized eyes, strong p-PERK and CHOP immunoreactivity was observed in ganglion cells after 8 weeks of IOP elevation. Taken together, in the experimental chronic glaucoma model, ER stress is involved in RGC death, and the PERK-p-eIF2alpha-CHOP pathway plays a role in the RGC apoptosis associated with ER stress. This might be a good therapeutic target to protect RGCs from ER stress injury in glaucoma.

Retinal glial cell responses and Fas/FasL activation in rats with chronic ocular hypertension.

Responses in the retina post injury provoke glial reactions that are not completely understood. This study investigated the reaction of retinal glial cells and the expression and localization of the Fas and Fas-ligand (FasL) in rats with chronic ocular hypertension. Experimental glaucoma was induced in one eye of 60 Sprague-Dawley rats by cauterizing three episcleral vessels. It caused a moderate intraocular pressure (IOP) elevation and significant retinal ganglion cell (RGC) loss for at least 6 weeks in all animals. Immunohistochemical analysis revealed that the expression of GFAP and OX-42 increased in the injured retinae. Fas/FasL immunoreactivity was elevated in the microglia, and we also observed an incremental increase in Fas associated death domain (FADD) immunoreactivity in Müller glial cells and RGCs in the IOP-elevated retinae. The activation of glial cells and upregulation of Fas and FasL suggest that glial cells may contribute to Fas-mediated cell death in the neurodegeneration process of chronic ocular hypertensive retinal insult.

Glial cell response and iNOS expression in the optic nerve head and retina of the rat following acute high IOP ischemia–reperfusion

Acute high IOP ischemia-reperfusion induces the loss of retinal ganglion cells, supporting the hypothesis that the condition of ischemia-reperfusion contributes to the induction and progression of glaucoma. This study investigated morphological changes, glial cell response, and expression of inducible nitric oxide synthase (iNOS) in the optic nerve head and retina of the rat following acute high IOP ischemia-reperfusion. A 60-min ischemic period was administered to the rat eye by raising the IOP, followed by a reperfusion period lasting 2, 5, or 7 days. Histological examination showed that acute high IOP ischemia-reperfusion injury produced optic nerve head and retina damage. In immunohistochemical staining, GFAP and OX-45 were limited to the ganglion cell layer (GCL) or inner nuclear layer (INL) of the control retina and increased to nearly all layers of the retina after acute high IOP ischemia-reperfusion. GFAP and OX-42 were detected at the control optic nerve heads and increased after acute high IOP ischemia-reperfusion. After acute high IOP ischemia-reperfusion, expression of iNOS increased, mostly at the GCL and INL of the retina and at the optic nerve head. Western blot analysis showed that expression of iNOS increased significantly, compared with the control, in the retina and optic nerve head after acute high IOP ischemia-reperfusion. Activation of glial cells and the up-regulation of iNOS may contribute to the damage of the retina and optic nerve head of the rat following acute high IOP ischemia-reperfusion.

Effect of prostaglandin analogues on tear proteomics and expression of cytokines and matrix metalloproteinases in the conjunctiva and cornea.

The purpose of this work was to identify potential tear-film-based proteins and their effect on changes in the conjunctiva and cornea in eyes using prostaglandin (PG) analogues. Recruited subjects were individuals who had used PG for at least 1 year and comparison with eyes of normal controls and timolol using patients were done. Approximately 3-5xa0μL of tears were sampled from both eyes of each subject using glass microcapillaries. Proteomic analysis was done to compare the pooled tear samples from each group by Bradford assay and cytokine arrays. Impression cytology was used to gather mRNA from conjunctival epithelial cells, and target protein mRNA was quantified by PCR. Rabbits treated with PG were scarified, and changes in the corneal stroma were evaluated by immunohistochemical staining and western blot analysis. There were increased levels of IL-1β, IL-6, MMP-1, MMP-3, and MMP-9 and decreased levels of TIMP-1 and TIMP-2 in the tears of PG-treated patients. The mRNA of IL-1β, MMP-1, MMP-3, and MMP-9 was elevated and mRNA of TIMP-1 and TIMP-2 was decreased in the conjunctival epithelial cells. Rabbits treated with PG showed corneal thinning with decreased collagen type I expression. The protein of MMP-1 and MMP-9 was elevated and protein of TIMP-1 was decreased in the rabbit cornea by western blot analysis. Immunohistochemical staining showed elevated expression of MMP-1 and MMP-9 and the decreased expression of TIMP-1 in the corneal stroma. The topical use of PG analogues results in an altered balance between MMPs and TIMPs, which may be triggered by inflammatory cytokines. This results in an increase of matrix degradation and decrease of stromal collagens in the cornea by PG treatments.

Alteration of retinal intrinsic survival signal and effect of alpha2-adrenergic receptor agonist in the retina of the chronic ocular hypertension rat.

The purpose of this study is to examine the retinal expression of intrinsic cell survival molecules and to elucidate the effect of an alpha2-adrenergic receptor agonist in the chronic ocular hypertensive rat model. Chronic ocular hypertension was induced in both eyes of each rat by episcleral vein cauterization. Two five-microliter drops of the selective alpha2-adrenoceptor agonist brimonidine 0.2% (Alphagan; Allergan Inc., Irvine, CA, USA) were topically administered twice daily for up to eight weeks in one eye. The fellow eye received balanced salt solution as a control. Protein and mRNA expression were evaluated at 1, 4, and 8 weeks after injury. Retinal expression of BDNF, Akt, and GFAP was assessed using immunohistochemistry. Retinal levels of mRNA for BDNF, bcl-2, and bcl-xL were determined using semi-quantitative RT-PCR. Retinal ganglion cell (RGC) density was evaluated after retrograde labeling with 4-Di-10-ASP (DiA). A significant decrease in RGC density was observed in ocular hypertensive eyes. Cauterized eyes showed an increase in GFAP expression from one week after injury, and the expression of bcl-2, bcl-xL, and BDNF mRNA was also increased. Treatment of ocular hypertensive eyes with brimonidine resulted in a reduction in RGC loss, a decrease in the level of GFAP immunoreactivity, and an increment in BDNF mRNA and p-Akt expression. Brimonidine appears to protect RGCs from neurodegeneration through mechanisms involving alpha2-adrenergic receptor mediated survival signal activation and up-regulation of endogenous neurotrophic factor expression in the chronic ocular hypertensive rat retina.

Long-term changes in endothelial cell counts after early phacoemulsification versus laser peripheral iridotomy using sequential argon:YAG laser technique in acute primary angle closure.

ObjectiveTo compare the change in endothelial cell counts (ECC) after early phacoemulsification and laser peripheral iridotomy (LPI) using sequential argon:yttrium–aluminum–garnet (YAG) laser technique for the treatment of acute primary angle closure (APAC).MethodsThis was a retrospective chart review, case-control study; 86 APAC patients were enrolled. Sixteen patients who underwent early phacoemulsification with intraocular lens implantation and 32 patients who underwent LPI were matched by propensity score analysis. All subjects underwent a complete ophthalmic examination, including intraocular pressure (IOP) measurements, optic disc examinations, and gonioscopy. ECC were acquired at the center of the cornea with a noncontact specular microscope before treatment, and at 1, 6, 12, and 24xa0months following phacoemulsification or LPI.ResultsThe mean follow-up was 26.1u2009±u20094.7xa0months in the phacoemulsification group and 26.3u2009±u20094.5xa0months in the LPI group. After intervention, the changes in anterior chamber depth and Shaffer grading by gonioscopy were significantly different between groups. ECC were not different before treatment; however, after phacoemulsification or LPI at 12xa0months (2280u2009±u2009320 vs 1993u2009±u2009380xa0cells/mm2) and 24xa0months (2113u2009±u2009333 vs 1880u2009±u2009422xa0cells/mm2), there was a significant difference between the two groups (Pu2009=u20090.040 and Pu2009=u20090.032 respectively). Regression analysis showed that anterior chamber depth at baseline (Pu2009=u20090.041) and intervention modality (phacoemulsification vs LPI; Pu2009<u20090.001) were significantly related to the change in ECC.ConclusionsEarly phacoemulsification showed lower endothelial cell loss than did LPI in the treatment of APAC after a 2-year follow-up. In terms of ECC, early phacoemulsification could be a better intervention modality for APAC.

Changes of the Retina and Intrinsic Survival Signals in a Rat Model of Glaucoma following Brinzolamide and Travoprost Treatments.

Purpose: The purpose of this study is to examine the changes of the retina and the intrinsic survival signals of the retina by brinzolamide (Azopt®) and travoprost (Travatan®) in a rat model of chronic ocular hypertension. Methods: Chronic ocular hypertension was induced by cauterization of three episcleral veins. Terminal deoxynucleotidyl transferase-mediated dUTP-nick end-labeling (TUNEL) staining was performed and the expression of glial fibrillary acidic protein (GFAP) was examined to evaluate changes of retinal ganglion cell (RGC) apoptosis and glial cell activation. Western blot analyses of the bcl-2 family and extracellular signal-regulated kinases (ERK) were done to identify changes of the intrinsic survival signaling pathway in the retina. Results: GFAP expression and TUNEL staining revealed significant decreases in RGC apoptosis and glial cell activation after brinzolamide and travoprost administration; bcl-2 and bcl-xL expression were significantly increased after intraocular pressure elevation and it was further increased with brinzolamide and travoprost treatment. This enhancement of survival signaling may have contributed to the decrease in RGC apoptosis. However, the role of ERK signaling was not significant. Conclusions: Decrease in retinal damage and increased intrinsic survival signals suggests the neuroprotective potential of brinzolamide and travoprost in an animal model of chronic ocular hypertension, but further studies are required.

Contents Vol. 46, 2011

Anatomy, Pathology and Cell Biology A. Prescott, Dundee Biochemistry, Molecular Biology and Molecular Genetics J. Graw, Neuherberg Clinical and Epidemiological Research M. Kojima, Kahoku Cornea and Ocular Surface C. Marfurt, Gary, Ind. Glaucoma H. Th ieme, Mainz Immunology and Microbiology U. Pleyer, Berlin Lens and Cataract S. Varma, Baltimore, Md. Miscellaneous U. Pleyer, Berlin Neuro-Ophthalmology and Vision Sciences P. Aydin, Ankara Ocular Oncology M. Jager, Leiden Physiology, Pharmacology and Toxicology A. Wegener, Bonn Retina and Retinal Cell Biology P. Pereira, Coimbra Editorial Board