Biomedical subjects

Hyeong Gon Yu

Publications and source records attributed to Hyeong Gon Yu.

17 recordsLinked to original sources

PubMed2007

Factors influencing refractive outcomes after combined phacoemulsification and pars plana vitrectomy: results of a prospective study.

PURPOSE: To evaluate the factors influencing the refractive outcomes of combined phacoemulsification, foldable intraocular lens (IOL) implantation, and pars plana vitrectomy (PPV). SETTING: Department of Ophthalmology, Seoul National University Hospital, Seoul, Korea. METHODS: One hundred fifty-four consecutive patients who had combined phacoemulsification, IOL implantation, and PPV between September 2001 and August 2004 were enrolled in a prospective study. Refractive, keratometric, and axial length measurements were performed preoperatively and 4 months postoperatively. The factors influencing the postoperative refractive outcomes were analyzed. RESULTS: The mean refractive prediction error (ie, actual minus predicted spherical equivalent [SE]) was -0.06 diopters (D) +/- 0.75 (SD). In long eyes (preoperative axial length more than 24.5 mm), the mean predicted SE and actual SE were -0.81 +/- 0.76 D and -1.24 +/- 0.79 D, respectively; the difference was significantly different (P = .001, paired t test). Patients with a preoperative visual acuity worse than 5/200 and those with preoperative foveal detachment had a significant postoperative myopic shift (P = 0.024 and P = 0.002, respectively; paired t test). Postoperative refractive error was not influenced by the intraocular air or gas tamponade during surgery (P = 0.336, paired t test). CONCLUSIONS: The combined surgery included a small biometric error that was within the tolerable range in most cases. However, myopic shifts developed in patients with long axial lengths, poor preoperative visual acuity, and the preoperative presence of foveal detachment.

Adult↗

PubMed2006

Phacotrabeculectomy with mitomycin C in patients with uveitis.

PURPOSE: To evaluate the safety and efficacy of combined phacoemulsification, intraocular lens implantation, and trabeculectomy with mitomycin C for the management of uveitic complications. DESIGN: Retrospective case-control study. METHODS: We conducted a retrospective review of the records of 23 consecutive eyes with chronic noninfectious uveitis (uveitic group) and 43 nonuveitic eyes (control group) that had received primary phacotrabeculectomy. Mitomycin C was used in all the uveitic eyes. Considering the high preoperative intraocular pressure (IOP) of the uveitic group, nonuveitic eyes that had a preoperative IOP of >or=20 mm Hg or that had been given two or more medications were included in the control group. All patients were followed for at least one year. The main outcome measures were postoperative vision, IOP control, complications, and acute uveitis relapse rates. RESULTS: Visual outcome of the uveitic group was similar to the control group. In the uveitic group, the success rate of IOP control (91.3% at one year, 84.8% at two years) was favorable but was significantly lower than in the control group (P = .0423). Complications were comparable between the groups. Primary surgical failure in the uveitic group was associated with the postoperative acute uveitis attack. In the uveitic group, the acute uveitis attack rate showed no change after surgery (P = .283). CONCLUSION: With adequate inflammation suppression, phacotrabeculectomy with mitomycin C is an effective and safe therapeutic option for the management of secondary cataract and glaucoma in uveitic eyes. A lower surgical success rate of the uveitic group might be attributable to the postoperative inflammation recurrence.

Acute Disease↗

PubMed2006

Intraocular cytokine environment in active Behçet uveitis.

PURPOSE: To determine cytokine profiles in aqueous humor and peripheral blood from patients with Behçet uveitis. DESIGN: Prospective, experimental, and case-control study. METHODS: Aqueous humor and peripheral blood samples from 24 patients with Behçet uveitis, 28 patients with other causes of endogenous uveitis, and 20 healthy subjects after uncomplicated cataract surgery were obtained. Cytokines (interferon gamma (IFN-gamma), interleukin [IL]-2, IL-4, IL-10, IL-12, IL-15, and tumor necrosis factor alpha (TNF-alpha)) were measured by enzyme-linked immunosorbent assay and compared between the uveitis groups. RESULTS: Aqueous interferon gamma (IFN-gamma) levels were higher in patients with Behçet uveitis in contrast to higher concentrations of IL-4 in patients without Behçet uveitis. Aqueous levels of tumor necrosis factor alpha (TNF-alpha) were higher in patients with Behçet uveitis than in patients without Behçet uveitis. Aqueous and serum IL-10 were detected in all patients without Behçet uveitis, but were below detection limits in all patients with Behçet uveitis. Furthermore, IL-15 was exclusively increased in the aqueous humor of Behçet uveitis. The aqueous IL-2 or IL-12 levels were similar regardless of the presence of Behçet uveitis. CONCLUSIONS: Our results showed that an extreme Th1 polarization, a high proinflammatory condition, a low immunosuppressive status, and the presence of natural killer (NK) or CD8+ T cell-activating cytokine were unique features in aqueous humor with Behçet uveitis, suggesting that different immunopathogenic mechanisms may be involved in the ongoing intraocular inflammation of Behçet uveitis.

Adult↗

PubMed2006

Differential expression of vitreous proteins in proliferative diabetic retinopathy.

PURPOSE: To identify vitreous proteins that were differentially expressed in patients suffering from proliferative diabetic retinopathy with active neovascularization. METHODS: The vitreous samples of 15 active proliferative diabetic retinopathy patients were analyzed by two-dimensional gel electrophoresis and mass spectrometry, and the results were compared with those from age-matched patients with macular hole. RESULTS: Twenty-five protein spots were identified in the two-dimensional gel electrophoresis gels. Eight proteins (pigmented epithelium derived factor, serine protease inhibitor, apolipoprotein A-IV precursor, prostaglandin-H2 D-isomerase, a(1)-antitrypsin precursor, ankyrin repeat domain 15 protein, alpha2-HS-glycoprotein, and beta V spectrin) in the 25 spots were expressed significantly differently between the macular hole and proliferative diabetic retinopathy patients (p value < 0.05). Five proteins were upregulated in the proliferative diabetic retinopathy patients, and three were downregulated (p value < 0.05). CONCLUSIONS: We constructed vitreous protein profiles for proliferative diabetic retinopathy patients and identified eight candidate proteins believed to be involved in the pathogenesis of proliferative diabetic retinopathy.

Aged↗

PubMed2006

Combined low dose cyclosporine and prednisone down-regulate natural killer cell-like effector functions of CD8brightCD56+ T cells in patients with active Behçet uveitis.

PURPOSE: To investigate the changes of effector-related phenotypic markers and the natural killer (NK)-like effector functions of CD8(bright)CD56+ T cells in patients with Behçet uveitis after combined cyclosporine and prednisone (Cs/Pd) treatment. METHODS: Ten patients with active Behçet panuveitis and 10 healthy controls were prospectively recruited in this study. The effector-related surface markers (CD27, CD62L, CD11b, HLA-DR, CD94, NKG2D), chemokine receptors (CXCR1, CXCR3, CCR4, CCR5), and intracellular perforin of circulating CD8(bright)CD56+ T cells were determined by flow cytometric analysis before and after two months' treatment. NK-like cytotoxicity of ex vivo CD8(bright)CD56+ T cells against K562 was measured by standard 51Cr release assay. RESULTS: The expression levels of effector-related molecules on CD8(bright)CD56+ T cells normalized after treatment. The expression levels of CXCR1 and CCR5 were down-regulated on CD8(bright)CD56+ T cells after treatment. The amounts of preformed intracellular perforin of CD8(bright)CD56+ T cells were reduced to the normal levels. Furthermore, the NK-like cytolytic capacities of CD8(bright)CD56+ T cells were decreased after treatment. CONCLUSIONS: Our results suggest that the combined Cs/Pd treatments in active Behçet uveitis may downregulate the NK-like effector functions of CD8(bright)CD56+ T cells.

Adult↗

PubMed2006

A phacovitrectomy with a clear corneal incision for a full-thickness macular hole.

PURPOSE: To describe the results of a pars plana vitrectomy, combined with phacoemulsification, using a sutureless, superotemporal, clear corneal incision for patients with a macular hole. METHODS: This study reviewed the records of 22 patients (22 eyes) who underwent a phacoemulsification with the insertion of an acrylic intraocular lens, using a 3.2 mm superotemporal clear corneal incision and a pars plana vitrectomy with an internal limiting membrane peeling in one session, for the treatment of a macular hole. RESULTS: All 22 patients had their macular holes closed using the combined surgical procedures. The mean preoperative visual acuity was 0.086, and the mean postoperative visual acuity was 0.173. This improvement was statistically significant (paired Student's t-test, p < 0.05). No patients developed posterior capsular opacity, retinal detachment, or a cystoid macular edema. The surgically induced astigmatism (SIA) was 0.808 diopters (0.808 +/- 0.761) two months after surgery. CONCLUSIONS: Combining cataract surgery with vitrectomy can achieve visual rehabilitation in the early postoperative period without requiring post-vitrectomy cataract surgery. A sutureless clear corneal incision, used in this procedure, can minimize the SIA and promote postoperative wound healing. If sutureless, transconjunctival, pars plana vitrectomy can be used more widely in the future, then the simplified, combined cataract surgery using a small clear corneal incision will also become more common, hence decreasing operation time, and hastening postoperative recovery.

Adult↗

PubMed2005

CD8brightCD56+ T cells are cytotoxic effectors in patients with active Behcet's uveitis.

Behçet's uveitis, characterized by chronic recurrent uveitis and obliterating retinal vasculitis, frequently causes bilateral blindness. Intraocular infiltration of TCRalphabeta+CD8brightCD56+ cells was a distinct feature in Behçet's uveitis. However, phenotypic natures and effector functions of the cells have remained elusive. This study was conducted to determine phenotypic and functional characteristics and cytotoxic mechanisms of CD8brightCD56+ T cells in Behçet's uveitis. CD11b+CD27-CD62L- phenotypes of CD8brightCD56+ T cells were increased in patients with active Behçet's uveitis compared with inactive Behcet's patients and normal controls. Interestingly, CD45RAdimCD45RO- phenotypes were expanded, and CD94 expression was markedly up-regulated in contrast to the down-regulation of NKG2D. Furthermore, these subsets were polarized to produce IFN-gamma and contained high amounts of preformed intracellular perforin while exclusively expressing surface FasL upon PI stimulation. Moreover, the cytolytic functions of freshly isolated CD8brightCD56+ T cells were up-regulated against both K562 (NK-sensitive) and Raji (NK-resistant) cells, which were effectively inhibited by perforin inhibitor (concanamycin A). Their cytolytic activity against HUVECs was also increased and was effectively suppressed by Fas ligand inhibitor (brefeldin A) and partly by perforin inhibitor. Furthermore, cytolytic functions of PMA and ionomycin-stimulated CD8brightCD56+ T cells against HUVECs were greatly enhanced, by pretreatment of recombinant human IFN-gamma on HUVECs. Therefore, CD8brightCD56+ T cells in Behçet's uveitis are characterized by cytotoxic effector phenotypes with functional NK receptors and function as strong cytotoxic effectors through both Fas ligand-dependent and perforin-dependent pathways.

Adult↗

PubMed2005

Anatomical and functional characteristics in atrophic maculopathy associated with spinocerebellar ataxia type 7.

PURPOSE: To assess the anatomic and functional characteristics in a Korean family with spinocerebellar ataxia type 7-associated atrophic maculopathy. DESIGN: Observational case report. METHODS: Three patients in a family underwent funduscopic examination, fluorescein angiogram, full-field electroretinogram (ERG), electro-oculogram, and optical coherence tomography (OCT). Macular functions were assessed using multifocal ERG and scanning laser ophthalmoscope (SLO) microperimetry. RESULTS: Both eyes showed bull's eye configuration and cone-rod dystrophy phenotype. OCT revealed that retinal thinning extended outside the visibly atrophic lesions. Multifocal ERG demonstrated that amplitudes from the six ring segments were reduced in a centrifugal pattern. SLO microperimetry showed that fixations were unstable and shifted superior to the atrophic lesions. The areas of functional deficits were greater than those of anatomic deficits. CONCLUSIONS: Macular functions were severely depressed in atrophic maculopathy associated with spinocerebellar ataxia type 7 in both the visibly atrophic areas and the areas without visible atrophy in a centrifugal pattern.

Adult↗

PubMed2005

Vitrectomy for persistent panuveitis in Behçet's disease.

PURPOSE: To determine whether vitrectomy is safe and effective for the management of vitreoretinal complications in Behçet's patients with persistent panuveitis. METHODS: Patients who had undergone therapeutic vitrectomy for Behçet's panuveitis were reviewed retrospectively. Those patients who had shown persistent uveitis despite maximum medical therapy were included. Surgical outcomes were measured by an improvement in vision of 0.3 logarithm of minimum angle of resolution, acute relapse rates, and postoperative complications. RESULTS: Twenty-one patients with a mean postoperative follow-up of 30 months were identified. For almost all patients visual acuity and inflammatory control were significantly improved after vitrectomy. However, patients with optic disc neovascularization (NVD) showed no improvement in their vision or inflammatory control. The postoperative rise of intraocular pressure was frequently associated with intravitreal triamcinolone acetonide injections. CONCLUSIONS: Our study suggests that vitrectomy may be both safe and effective for the management of vitreoretinal complications in Behçet's patients with persistent uveitis. Patients with NVD, however, may have poor outcomes.

Adult↗

PubMed2005

Down-regulation of IFN-gamma-producing CD56+ T cells after combined low-dose cyclosporine/prednisone treatment in patients with Behçet's uveitis.

PURPOSE: To investigate the effects of combined low-dose cyclosporine and prednisone (Cs/Pd) treatment on circulating CD56+ T cells in patients with Behçet's uveitis. METHODS: Ten patients with Behçet's uveitis and 10 healthy control subjects were prospectively recruited. The patients were treated with Cs/Pd for 2 months. Phenotypic and functional changes in circulating CD56+ T cells were assayed before and after treatment. CD56+ T-cell subsets were determined by flow cytometric analysis with monoclonal antibodies for CD3, CD4, CD8, CD56, pan gammadelta TCR, and Valpha24. The absolute numbers of cells in the lymphocyte subsets were calculated. Cytokine (IFN-gamma, IL-4, and IL-10) expressions were measured by ELISA and by intracellular cytokine staining. RESULTS: The proportions of CD56+ T cells, specifically CD8highCD56+ and CD56+gammadelta T-cell subsets, were significantly higher in active Behçet's uveitis but normalized after treatment, whereas the total T-lymphocyte count and the absolute numbers of CD56- T cells were unaffected by treatment. The levels of IFN-gamma and IL-4 were elevated in aqueous humor and serum in Behçet's uveitis (P < 0.001), whereas IL-10 was not detected. After treatment, serum IL-4 levels markedly increased (P < 0.001), and IFN-gamma production by circulating CD56+ T cells was then suppressed. IL-4 and -10 production by CD56+ T cells was increased by treatment, but in contrast, minimal changes were found in CD56- T cells. CONCLUSIONS: The results imply that Cs/Pd treatment for Behçet's uveitis selectively affects the population of and the cytokine expression in CD56+ T cells, but without significant changes in CD56- T cells, and that IFN-gamma-producing CD56+ T cells are the central pathogenic immune cells in Behçet's uveitis.

Adult↗

PubMed2005

Subretinal inflammatory myofibroblastic tumor: clinicopathological findings.

PURPOSE: To present a case of inflammatory myofibroblastic tumor which was manifested as an idiopathic subretinal mass without underlying pathology. METHODS: The subretinal mass was surgically excised and evaluated histopathologically. Fluorescein angiography and optical coherence tomography were performed pre- and post-operatively. RESULTS: The mass was histologically composed of lymphoplasma cell infiltration and fibrous proliferation without microorganisms or malignant cells. Immunohistochemistry for smooth muscle actin revealed myofibroblasts as a major cellular component. Preoperative optical coherent tomography showed that the lesion was contiguous to the retina while inducing foveal detachment. Postoperatively, the fovea was attached with visual recovery, and the subretinal lesion did not recur during the follow up. CONCLUSIONS: Inflammatory myofibroblastic tumors may be included in the differential diagnoses of subretinal masses.

Adult↗

PubMed2004

Phacoemulsification and foldable intraocular lens implantation combined with vitrectomy and silicone oil tamponade for severe proliferative diabetic retinopathy.

PURPOSE: To determine the clinical outcomes of phacoemulsification and foldable intraocular lens (IOL) implantation combined with primary vitrectomy and silicone oil tamponade to treat severe proliferative diabetic retinopathy (PDR). SETTING: Department of Ophthalmology, Seoul National University College of Medicine, and Seoul Artificial Eye Center, Seoul National University Hospital Clinical Research Institute, Seoul, Korea. METHODS: The results of combined cataract surgery and silicone oil injection in 20 eyes (20 patients) were retrospectively analyzed. All patients had tractional or tractional-rhegmatogenous retinal detachment and clinically significant lens opacities; none had previous intraocular surgery. An acrylic foldable IOL was implanted in the capsular bag or ciliary sulcus. RESULTS: Primary anatomic success was achieved in 90% of eyes. Functional success was attained in 60% of eyes after a mean follow-up of 7.6 months. The postoperative visual acuity improved in 60% of patients, was unchanged in 20%, and was worse in 20%. Silicone oil was removed in 80% of patients without complications after a mean of 3.4 months. The mean absolute value of the difference between the predicted refraction and postoperative refraction was 0.74 diopter (D) (range 0.03 to 1.74 D). CONCLUSION: Phacoemulsification and foldable IOL implantation combined with primary vitrectomy and silicone oil tamponade was performed safely with favorable anatomic and visual outcomes in eyes with severe PDR.

Adult↗

PubMed2004

Long-term effect of plasmin on the vitreolysis in rabbit eyes.

The aim was to investigate the proteolytic activity of plasmin and its long-term complications. Plasmin was injected into the vitreous cavity of rabbits' eyes. Slit lamp biomicroscopy and electroretinography were performed. Rabbits were serially sacrificed at four months, and globes fixated and prepared for light and transmission electron microscopy. In both the plasmin-injected and control eyes, electroretinography showed a transient decrease in the amplitude, but this recovered to the baseline level in a week. Under the light microscope, the plasmin-treated eyes had a smooth retinal surface, implying separation of the vitreous cortex from the retina. In the control eyes, the collagen fibers remained on the retinal surface. By transmission electron microscopy, the plasmin-treated eyes showed a vitreous-free retinal surface, but no vitreoretinal separation was observed in the control eyes. Plasmin induces a cleavage between the vitreous and the internal limiting membrane, with no long-term complications, so may be a useful pharmacologic adjunct to vitrectomy.

Animals↗

PubMed2004

A case of atypical progressive outer retinal necrosis after highly active antiretroviral therapy.

This is a report of an atypical case of progressive outer retinal necrosis (PORN) and the effect of highly active antiretroviral therapy (HAART) on the clinical course of viral retinitis in an acquired immunodeficiency syndrome (AIDS) patient. A 22-year-old male patient infected with human immunodeficiency virus (HIV) presented with unilaterally reduced visual acuity and a dense cataract. After cataract extraction, retinal lesions involving the peripheral and macular areas were found with perivascular sparing and the mud-cracked, characteristic appearance of PORN. He was diagnosed as having PORN based on clinical features and was given combined antiviral treatment. With concurrent HAART, the retinal lesions regressed, with the regression being accelerated by further treatment with intravenous acyclovir and ganciclovir. This case suggests that HAART may change the clinical course of PORN in AIDS patients by improving host immunity. PORN should be included in the differential diagnosis of acute unilateral cataract in AIDS patients.

AIDS-Related Opportunistic Infections↗

PubMed2003

Transscleral fixation of a foldable intraocular lens in aphakic vitrectomized eyes.

PURPOSE: To evaluate the clinical outcomes of transscleral fixation of a foldable intraocular lens (IOL) in eyes that had pars plana lensectomy combined with pars plana vitrectomy for severe vitreoretinal disease. SETTING: Seoul National University Hospital, Seoul, Korea. METHODS: The medical records of 21 patients who had a transscleral fixation of a foldable IOL after previous vitrectomy combined with lensectomy for severe posterior segment pathology were reviewed. The underlying vitreoretinal diseases were complicated proliferative diabetic retinopathy (n = 9), proliferative vitreoretinopathy (n = 5), traumatic retinal detachment (n = 3), intraocular foreign body (n = 2), and uveitic retinal detachment (n = 2). The postoperative best corrected visual acuity (BCVA) was compared with the preoperative BCVA. Autorefractometry and keratometry measurements and central endothelial cell counts were evaluated 1 day preoperatively and 6 months postoperatively. RESULTS: The mean age of the patients was 54.5 years. The preoperative aphakic period ranged from 2 to 22 months. The visual acuity reached the preoperative BCVA by 2 months after surgery and was better than the preoperative BCVA at 6 months (P =.006) and at the final visit (P =.003). Six months postoperatively, the mean myopic shift by cycloplegic autorefractometry was -1.0 diopter (D) and the mean scalar shift in surgically induced keratometric cylinder, 1.0 D. The mean central corneal endothelial loss at 6 months was 6.7% (range 2.4% to 22.2%). The only vitreoretinal complications were a transient vitreous hemorrhage and a reopened macular hole that was reattached after fluid-gas exchange. CONCLUSION: Transscleral fixation of a foldable IOL was safe and led to favorable visual outcomes in aphakic vitrectomized eyes with previous severe vitreoretinal disease.

Adult↗

PubMed2003

A new rapid and non-radioactive assay for monitoring and determining the proliferation of retinal pigment epithelial cells.

AlamarBlue is used to induce color and fluorescence in the microenvironment of activated cells. The alamarBlue assay was studied to determine if it could be used as a method of evaluating the number of retinal pigment epithelial (RPE) cells. A series of two-fold dilutions of RPE cells were placed into 96-well culture plates. The alamarBlue was added to the culture media after attaching the cells. The absorbance and fluorescence were measured consecutively at various intervals over a period of 24 hr. Cell viability were evaluated by means of the trypan blue exclusion method and flow cytometry using a combination of propidium iodide and annexin V was done to prove the safety of alamarBlue assay to the cells. Both the absorbance and the fluorescence had a linear relationship with the number of RPE cells. Exposing the RPE cells to alamarBlue was not detrimental to the cells. In conclusion, the alamarBlue assay constitutes a one-step, extremely simple, reproducible, economical and non-toxic procedure for evaluating the number of viable RPE cells.

Cell Count↗

PubMedDate not supplied

Photodynamic therapy with verteporfin for juxtafoveal choroidal neovascularization in serpiginous choroiditis.

The authors describe a patient who underwent successful photodynamic therapy with verteporfin for juxtafoveal choroidal neovascularization complicated by serpiginous choroiditis. A 41-year-old woman presented with decreased vision and metamorphopsia in her right eye, which was diagnosed as a recurrence of serpiginous choroiditis at the first visit. Within a month, visual acuity had diminished to 20/1000 despite immunosuppressive treatment. At that time, indocyanine green angiography and optical coherence tomography revealed choroidal neovascularization in the juxtafoveal area. Photodynamic therapy with verteporfin was administered twice, after which juxtafoveal choroidal neovascularization regressed and her visual acuity improved to 20/20.

Adult↗