Hwan Heo

A Selective Inhibitor of Drp1, Mdivi-1, Increases Retinal Ganglion Cell Survival in Acute Ischemic Mouse Retina

PURPOSE To determine whether acute intraocular pressure (IOP) elevation alters dynamin-related protein 1 (Drp1) as well as whether a selective inhibitor of Drp1, mdivi-1, can block apoptotic cell death and subsequently increase retinal ganglion cell (RGC) survival in ischemic mouse retina. METHODS C57BL/6 mice received injections of mdivi-1 (50 mg/kg) or vehicle, and then transient retinal ischemia was induced by acute IOP elevation. RGC survival was measured after FluoroGold labeling. Drp1 and glial fibrillary acidic protein (GFAP) protein expression and distribution were assessed at 12 hours after ischemia-reperfusion by Western blot and immunohistochemistry. Apoptotic cell death was assessed by TUNEL staining. RESULTS Drp1 and GFAP protein expression was significantly increased in the early neurodegenerative events (within 12 hours) of ischemic mouse retina. Mdivi-1 treatment blocked apoptotic cell death in ischemic retina, and significantly increased RGC survival at 2 weeks after ischemia. In the normal mouse retina, Drp1 is expressed in the ganglion cell layer (GCL) as well as the inner plexiform layer, the inner nuclear layer (INL), and the outer plexiform layer (OPL). In the GCL, Drp1 immunoreactivity was strong in RGCs. While Drp1 protein expression was increased in the GCL of vehicle-treated ischemic retina at 12 hours. Mdivi-1 treatment did not change this increase of Drp1 protein expression but significantly decreased GFAP protein expression. CONCLUSIONS These findings suggest that altered Drp1 activity after acute IOP elevation may be an important component of a biochemical cascade leading to RGC death in ischemic retina.

A nationwide population-based study of low vision and blindness in South Korea.

PURPOSE To investigate the prevalence and associated risk factors of low vision and blindness in the Korean population. METHODS This cross-sectional, population-based study examined the ophthalmologic data of 22,135 Koreans aged ≥5 years from the fifth Korea National Health and Nutrition Examination Survey (KNHANES V, 2010-2012). According to the World Health Organization criteria, blindness was defined as visual acuity (VA) less than 20/400 in the better-seeing eye, and low vision as VA of 20/60 or worse but 20/400 or better in the better-seeing eye. The prevalence rates were calculated from either presenting VA (PVA) or best-corrected VA (BCVA). Multivariate regression analysis was conducted for adults aged ≥20 years. RESULTS The overall prevalence rates of PVA-defined low vision and blindness were 4.98% and 0.26%, respectively, and those of BCVA-defined low vision and blindness were 0.46% and 0.05%, respectively. Prevalence increased rapidly above the age of 70 years. For subjects aged ≥70 years, the population-weighted prevalence rates of low vision, based on PVA and BCVA, were 12.85% and 3.87%, respectively, and the corresponding rates of blindness were 0.49% and 0.42%, respectively. The presenting vision problems were significantly associated with age (younger adults or elderly subjects), female sex, low educational level, and lowest household income, whereas the best-corrected vision problems were associated with age ≥ 70 years, a low educational level, and rural residence. CONCLUSIONS This population-based study provides useful information for planning optimal public eye health care services in South Korea.

Megalopapilla in children: a spectral domain optical coherence tomography analysis.

To compare various optic nerve head (ONH) parameters and peripapillary retinal nerve fibre layer (pRNFL) thickness between megalopapilla cases and normal control using spectral domain optical coherence tomography (SD‐OCT) in children.

Mangiferin Protects Retinal Ganglion Cells in Ischemic Mouse Retina via SIRT1

Abstract Purpose: To investigate whether mangiferin can increase the viability of retinal ganglion cells (RGCs) in ischemic mouse retina, and to determine the possible mechanism of neuroprotection. Methods: C57BL/6J mice underwent constant elevation of intraocular pressure for 60 min and received saline or mangiferin (30 mg/kg) intraperitoneally once daily until sacrifice. HIF-1α, GFAP and SIRT1 expression was assessed at 1, 4, and 7 days after retinal ischemia. Bax and Bcl-2 expression was also analyzed at 1 and 4 days. RGC survival was assessed by labeling flat-mounted retinas with Brn3a at 2 weeks after retinal ischemia. The effect of co-treatment with mangiferin and sirtinol (SIRT1 inhibitor) was also evaluated. Results: The expression of HIF-1α and GFAP was upregulated in saline-treated retinas within 7 days after ischemia. Mangiferin treatment suppressed this upregulation. The expression of SIRT1 was downregulated in saline-treated ischemic retinas. This downregulation was reversed by mangiferin treatment, resulting in a significant difference from saline-treated ischemic retinas. In mangiferin-treated ischemic retinas, Bax expression was downregulated, whereas Bcl-2 expression was upregulated in comparison with saline-treated ischemic retinas. Mangiferin treatment protected ischemic retinas against RGC loss. Treatment of sirtinol decreased the neuroprotective effect of mangiferin. Conclusions: Our findings suggest that mangiferin has a neuroprotective effect on RGC through downregulation of HIF-1a and GFAP, and upregulation of SIRT1 in ischemic mouse retinas. We suggest that mangiferin might be a potential neuroprotective agent against RGC loss under oxidative stress.

Investigation of spark gap discharge in a regime of very high repetitition rate

It is our interest to design and develop a high power pulser system employing microplasma discharge in a spark gap system. The type of discharge generates short electric pulses capable of both the characteristics of high repetition rate and fast rise time. Such a switch pulser has wide applications in the industry. An efficient electrical discharge in the spark gap is very important for the switching operation. The regime of operation utilizes the residual plasma in the inter pulse recovery of the spark gap to increase the repetition rate. Therefore, the mechanisms of the discharge in a controlled manner, such as the plasma discharge by the arc channel, the dielectric recovery process as well as residual plasma in the post arc period are of great importance to ensure the high repetition rate. The aforementioned mechanisms are established through optimization of the circuit element parameters such as the electrode geometry, the gap distance, the gas pressure, the gas type as well as the applied voltage and current ratings.

Clinical features of superficial and deep peripapillary microvascular density in healthy myopic eyes

Purpose To evaluate the clinical features of peripapillary microvasculature in myopic eyes and investigate the association between the superficial and deep peripapillary microvascular density and the myopic optic disc characteristics. Materials and methods This cross-sectional study included one hundred and fifty healthy myopic eyes with β-peripapillary atrophy (β-PPA). Ovality index, degree of optic disc rotation, and the area of β-PPA were measured. Superficial and deep peripapillary microvascular density was measured using optical coherence tomography angiography. Logistic regression analysis was performed to look for the factors associated with peripapillary microvascular reduction. Results The mean superficial peripapillary microvascular density was 62.14 ± 5.47%; 33 (22.0%) participants were found to have decreased microvascular density. Increased axial length (p < 0.001) and decreased average peripapillary retinal nerve fiber layer thickness (p = 0.027) were associated with the superficial peripapillary microvascular reduction. The mean deep peripapillary microvascular density was 73.76 ± 4.02%; 26 (17.33%) participants were found to have decreased microvascular density. Larger ovality index (p = 0.028) and more inferiorly rotated optic disc (p = 0.021) were associated with the deep peripapillary microvascular reduction. Conclusions Axial elongation was significantly associated with microvascular reduction in the superficial peripapillary retina, whereas it was not associated with deep peripapillary microvascular reduction. The deep peripapillary microvascular density was independently associated with myopic optic disc characteristics such as ovality index and optic disc rotation.

Design and evaluation of water Blumlein pulse generator

We designed and tested a water filled Blumlein pulse generator. For the purpose of repetitive operation, we used a gas spark switch and high voltage transformer. The pulse generator was tested an aqueous resistor dummy load. When the load resistance was matched with the pulse generators impedance, we obtain about up to 200 kV voltage pulse.

Association between meibomian gland dysfunction and compliance of topical prostaglandin analogs in patients with normal tension glaucoma

Purpose The aim of this study was to investigate the association between tear film and meibomian gland parameters in patients with normal tension glaucoma (NTG), who underwent topical prostaglandin analog (PGA) monotherapy, and medication compliance. Methods Ocular surface disease index (OSDI), Schirmer’s test, tear film break-up time (TBUT), keratoepitheliopathy (KEP) score with fluorescein, and meibomian gland parameters were assessed in 45 eyes of 45 patients with NTG (NTG group), who received topical PGA monotherapy for more than 1 year. The results were compared to those of 40 eyes of 40 normal subjects (control group). Medication compliance was assessed by an 8-item Morisky Medication Adherence Scale (MMAS-8). Multiple logistic regression analysis was used to identify the factors associated with medication compliance. Results There was a significant difference in OSDI (P = 0.043), Schirmer’s test (P < 0.001), TBUT (P < 0.001), KEP score (P = 0.015) and all meibomian gland parameters (all P < 0.001) between two groups. When the NTG group was divided into compliant and non-compliant groups based on the scores of MMAS-8, 30 (75%) patients were classified into the compliant group. Multiple logistic regression analysis revealed that the lid margin score (OR, 0.256; 95% CI, 0.072–0.908, P = 0.035), meibum score (OR, 0.144; 95% CI, 0.023–0.915, P = 0.04), and meibo score (OR, 0.344; 95% CI, 0.140–0.845, P = 0.02) were significant factors associated with compliance in patients with NTG. The meibomian gland parameters showed a negative correlation with medication compliance (all P < 0.005). Conclusions Malfunction of the meibomian glands can be an important clinical finding associated with compliance of PGA monotherapy in patients with NTG.

Prevalence and Factors Associated with the Use of Eye Care Services in South Korea: Korea National Health and Nutrition Examination Survey 2010–2012

Purpose To estimate the factors and prevalence of eye care service utilization in the South Korean population. Methods This cross-sectional, population-based study included data from 22,550 Koreans aged ≥5 years who participated in the Korea National Health and Nutrition Examination Survey from 2010 to 2012. For people aged 5 to 11 years (young children), information was based on self-reports of contact with eye care service in the past year; for people aged ≥12 years (older population), the information was based on the self-reported lifetime contact with eye care service. Univariate and multivariate logistic regression analyses of the complex sample survey data were performed. Results The prevalence of eye care service use in young children during the past year was 61.1% (95% confidence interval, 58.1%–64.1%), while that in the older population during their lifetime was 73.5%. Subjects aged 7 to 11 years were more likely to have had an eye examination in the past year than subjects aged 5 to 6 years (odds ratio, 3.83; 95% confidence interval, 2.37–6.19). Multivariate logistic regression analysis indicated that higher monthly household income, being a National Health Insurance holder, and having private health insurance were related to more frequent use of eye care services in young children. For the older population and women, those living in an urban area and those with a best-corrected visual acuity less than 20 / 40 in the worse-seeing eye were more likely to have had an eye examination during their lifetime. Low education level was associated with low lifetime use of eye care services in the older population. Conclusions There are sociodemographic disparities with use of eye care services in South Korea. This population-based study provides information that is useful for determining different intervention programs based on sociodemographic disparities to promote eye care service utilization in South Korea.

Analysis of Clinical Factors Associated with Retinal Morphological Changes in Patients with Primary Sjögren's Syndrome

Purpose To investigate clinical factors associated with abnormal retinal morphologies in patients with primary Sjögrens syndrome (pSS). Methods One-hundred-thirty patients with pSS who underwent immunoserological tests, minor salivary gland biopsies, and optical coherence tomography examinations were retrospectively analyzed. Risk factors for abnormally reduced peripapillary retinal nerve fiber layer (pRNFL) and macular ganglion cell–inner plexiform layer (mGCIPL) thicknesses were evaluated, as well as the correlation between clinical factors and pRNFL and mGCIPL thicknesses. Results Anti-Sjögrens syndrome type B (SSB) antibody positivity (P = 0.048) was identified as a risk factor associated with abnormally reduced pRNFL thickness, and anti-SSB positivity (P = 0.005) and erythrocyte sedimentation rate (ESR) level (P = 0.031) were identified as risk factors associated with an abnormally reduced mGCIPL thickness as revealed by multivariate logistic regression analysis. There was a significant negative correlation between anti-SSB antibody levels and the thickness of pRNFL and mGCIPL. The thicknesses of pRNFL and mGCIPL were significantly reduced in anti-SSB–positive eyes when compared to anti-SSB–negative eyes (P < 0.05). However, histopathologic grading was not associated with the pRNFL and mGCIPL thicknesses. Conclusion Anti-SSB antibody positivity and ESR levels may be useful for predicting an abnormally reduced pRNFL or mGCIPL thickness in patients with pSS. Our results may provide clinical evidence to substantiate the association between aberrant autoimmunity and inner retinal changes in patients with pSS.