Publications by authors named "Han Sang Park"

23 Publications

  • Page 1 of 1

Real-time measurement of intraocular pressure variation during automatic intravitreal injections: An ex-vivo experimental study using porcine eyes.

PLoS One 2021 26;16(8):e0256344. Epub 2021 Aug 26.

Department of Mechanical Engineering, POSTECH, Pohang, Korea.

Purpose: To measure needle insertion force and change in intraocular pressure (IOP) in real-time during intravitreal injection (IVI). The effects of needle size, insertion speed, and injection rate to IOP change were investigated.

Methods: Needle insertion and fluid injection were performed on 90 porcine eyeballs using an automatic IVI device. The IVI conditions were divided according to needle sizes of 27-gauge (G), 30G, and 33G; insertion speeds of 1, 2, and 5 mm/s; and injection rates of 0.01, 0.02, and 0.05 mL/s. Insertion force and IOP were measured in real-time using a force sensor and a pressure transducer.

Results: The peak IOP was observed when the needle penetrated the sclera; the average IOP elevation was 96.3, 67.1, and 59.4 mmHg for 27G, 30G, and 33G needles, respectively. An increase in insertion speed caused IOP elevation at the moment of penetration, but this effect was reduced as needle size decreased: 109.8-85.9 mmHg in 27G for 5-1 mm/s (p = 0.0149) and 61.8-60.7 mmHg in 33G for 5-1 mm/s (p = 0.8979). Injection speed was also related to IOP elevation during the stage of drug injection: 16.65 and 11.78 mmHg for injection rates of 0.05 and 0.01 mL/s (p < 0.001).

Conclusion: The presented data offers an understanding of IOP changes during each step of IVI. Slow needle insertion can reduce IOP elevation when using a 27G needle. Further, the injection rate must be kept low to avoid IOP elevations during the injection stage.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0256344PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8389368PMC
August 2021

Impact of Model for End-Stage Liver Disease allocation system on outcomes of deceased donor liver transplantation: A single-center experience.

Ann Hepatobiliary Pancreat Surg 2021 Aug;25(3):336-341

Department of Surgery, Seoul National University College of Medicine, Seoul, Korea.

Backgrounds/aims: From June of 2016, the Model for End-Stage Liver Disease (MELD)-based allocation system replaced the Child- Turcotte-Pugh (CTP) score-based system for organ allocation liver in Korea. The aim of this study was to analyze changes in outcomes and arising issues before and after the implementation of the MELD system.

Methods: From June 2014 to June 2018, 129 patients were selected from recipients who underwent deceased donor liver transplantation (DDLT) in Seoul National University Hospital. Pediatric cases were excluded. According to the allocation system, patients were divided into two groups (52 in the MELD group and 77 in the CTP group).

Results: MELD scores of the two groups differed significantly (37.8 ± 2.0 in the MELD group vs. 31.0 ± 8.2 in the CTP group; = 0.001). The etiology of patients was changed for liver transplantation. The proportion of alcoholic liver cirrhosis increased in the era of the MELD allocation system. However, proportions of hepatitis B related liver cirrhosis and hepatocellular carcinoma were decreased. Six-month mortality rate of the MELD group was 25.0%, which was higher than that (11.7%) of the CTP group ( = 0.022). The 90-day complication rate was significantly higher in the MELD group than in the CTP group (11.5% vs. 2.6%; = 0.040).

Conclusions: When the MELD allocation system was used to distribute livers to severely ill patients, it resulted in poorer outcomes after surgery and higher proportion of alcoholic cirrhosis. Thus, it is necessary to adjust the MELD allocation system so that outcomes after DDLT could be improved.
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http://dx.doi.org/10.14701/ahbps.2021.25.3.336DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8382855PMC
August 2021

Multiple-Session Subthreshold Micropulse Laser Therapy for Exudative Perifoveal Vascular Anomalous Complex: a case report.

Retin Cases Brief Rep 2021 Jul 16. Epub 2021 Jul 16.

Department of Ophthalmology, Kyungpook National University Hospital, Kyungpook National University School of Medicine, Daegu, South Korea.

Purpose: To report a case of exudative perifoveal vascular anomalous complex treated with a 532 nm subthreshold micropulse laser unresponsive to intravitreal injections.

Methods: A case report.

Results: A 65-year-old woman presented with blurred vision in left eye for 1 month. An isolated perifoveal aneurysm surrounded by retinal hemorrhages and hard exudates was revealed in fundus examination and optical coherent tomography showed a round lesion with a hyperreflective wall, subretinal fluid, and an intraretinal cyst. She was diagnosed with exudative perifoveal vascular anomalous complex and received 4 intravitreal injections. However, her best-corrected visual acuity decreased and an aneurysmal lesion with macular edema persisted for approximately 6 months. We applied 3 sessions of 532 nm subthreshold micropulse laser therapy around the aneurysm because the intravitreal injection treatment was ineffective. Since the last session, macular edema was disappeared and the involuted lesion remained substantially stable without recurrence and her best-corrected visual acuity improved without visual field defect.

Conclusion: To our knowledge, this is the first report of a successful subthreshold micropulse laser treatment for an exudative perifoveal vascular anomalous complex lesion and it could be a safe and effective method for the patient unresponsive to intravitreal injections.
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http://dx.doi.org/10.1097/ICB.0000000000001181DOI Listing
July 2021

Long-Term Effect of Silicone Oil Tamponade for Postoperative and Posttraumatic Bacterial Endophthalmitis.

J Ophthalmol 2021 1;2021:6658281. Epub 2021 Feb 1.

Department of Ophthalmology, School of Medicine, Kyungpook National University, Daegu 41944, Republic of Korea.

Purpose: To compare clinical features and microbial profiles, treatment outcomes, and prognostic factors of the eyes between postoperative and posttraumatic bacterial endophthalmitis after pars plana vitrectomy (PPV) with silicone oil (SO) tamponade.

Methods: Overall, 57 eyes of 57 patients who diagnosed exogenous bacterial endophthalmitis and underwent PPV with SO tamponade between 2000 and 2019 were reviewed. Causative microorganisms, culture positivity, change of mean best-corrected visual acuity (BCVA), and course of treatment were investigated between postoperative and posttraumatic groups, and relevant factors were analyzed according to the final BCVA.

Results: The mean BCVA change was not significantly different between groups. The positive rate of microorganisms was significantly higher in the postoperative group. The mean time to surgery over 48 hours, initial BCVA worse than hand motion, and additional surgery after initial vitrectomy were correlated with poor final BCVA worse than 20/200. There was significantly achieved final BCVA 20/200 or better in the and group than the and group.

Conclusion: PPV with SO tamponade may be an effective surgical treatment strategy for exogenous bacterial endophthalmitis. Final visual outcomes were not significantly different between postoperative and posttraumatic groups, and the mean time to surgery, initial visual acuity, additional surgery, and type of microorganism are significantly related to visual prognosis.
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http://dx.doi.org/10.1155/2021/6658281DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7870316PMC
February 2021

Spatial scanning of a sample with two-dimensional angle-resolved low-coherence interferometry for analysis of anisotropic scatterers.

Biomed Opt Express 2020 Aug 20;11(8):4419-4430. Epub 2020 Jul 20.

Department of Biomedical Engineering, Duke University, Durham, NC 27708, USA.

Angle-resolved low-coherence interferometry (a/LCI) measures depth-resolved angular scattering for cell nuclear morphology analysis. 2D a/LCI, developed to collect across two scattering planes, is currently limited by the lack of spatial scanning. Here we demonstrate 2D a/LCI scanning across a three-dimensional volume using an image rotation scheme and a scanning mirror. Validation using various optical phantoms demonstrated excellent scatterer size determination over a 7.5 mm linear range, for a total accessible area of ∼44 mm. Measurements from anisotropic scatterers allowed accurate determination of sizes and computation of aspect ratios. This scanning system will facilitate analysis of scatterer structure across wider tissue areas.
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http://dx.doi.org/10.1364/BOE.398052DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7449733PMC
August 2020

Development of Contact Lens-Shaped Crosslinked Amniotic Membranes for Sutureless Fixation in the Treatment of Ocular Surface Diseases.

Transl Vis Sci Technol 2020 05 15;9(6):12. Epub 2020 May 15.

Bio-Medical Institute, Kyungpook National University Hospital, Daegu, Republic of Korea.

Purpose: To develop a new method of manufacturing contact lens-shaped crosslinked amniotic membranes (AMs) using glutaraldehyde (GA) and dialdehyde starch (DAS) as crosslinking agents.

Methods: Amniotic membranes were placed on a curved plastic mold and crosslinked with either 4.5% DAS or 1% GA, after which their physical properties and biological safety were evaluated.

Results: The tensile strength of the GA- and DAS-crosslinked samples was much increased compared with that of normal AMs. Neither crosslinking process affected AM transparency. Although the GA-crosslinked AM showed better enzymatic resistance, its physiological structure was severely damaged after the crosslinking process. On the other hand, compared with the GA-crosslinked AM, the DAS-crosslinked AM showed higher growth factor concentrations and better biocompatibility, similar to normal AMs. In addition, the DAS-crosslinked AM was effective in the recovery of corneal epithelial wounds and was well maintained over 3 days without decentration or degradation on the ocular surface in human subjects.

Conclusions: Contact lens-shaped AMs were successfully prepared with crosslinking agents. Crosslinking with DAS did not affect the structural properties or biological activity of the AMs, and the improved mechanical properties helped the AM to maintain its curved shape. This crosslinking method allowed us to transplant AMs into patients' eyes without sutures.

Translational Relevance: Sutureless fixation of contact lens-shaped AMs would be very convenient and safe for the treatment of corneal surface disease.
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http://dx.doi.org/10.1167/tvst.9.6.12DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7408872PMC
May 2020

Subthreshold Micropulse Yellow Laser (577 nm) for Idiopathic Macular Telangiectasia Type 1 Resistant to Intravitreal Injection.

Korean J Ophthalmol 2020 04;34(2):168-169

Department of Ophthalmology, Kyungpook National University School of Medicine, Daegu, Korea.

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http://dx.doi.org/10.3341/kjo.2019.0071DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7105782PMC
April 2020

Incidence and treatment outcomes of secondary epiretinal membrane following intravitreal injection for diabetic macular edema.

Sci Rep 2020 01 17;10(1):528. Epub 2020 Jan 17.

Department of Ophthalmology, Kyungpook National University School of Medicine, Daegu, 41944, Korea.

The purpose of this study was to investigate the incidence of secondary epiretinal membrane (ERM) after intravitreal injection and the effect of ERM on visual acuity and central macular thickness (CMT) in patients with diabetic macular edema (DME). We included 147 eyes of 95 patients over 18 years old who were diagnosed with DME from 2012 to 2016, treated with intravitreal injection, and followed-up more than 24 months. Mean CMT in the ERM group was significantly thicker than in the non-ERM group after 9, 12, 18, and 24 months. Secondary ERM developed in 9.5% of patients during follow-up. Compared to other agents, the incidence of secondary ERM was significantly higher after intravitreal injection of dexamethasone implant. Among patients in the ERM group, the mean decrease of CMT between pre-injection and 2 weeks post-injection was significantly less after secondary ERM formation than before ERM formation. Secondary ERM formation was significantly associated with the number of intravitreal injections and the use of dexamethasone implant. Therefore, secondary ERM develops more frequently as the number of intravitreal injections increases and after intravitreal dexamethasone implant injection. The therapeutic effects of intravitreal injections for DME patients decrease after secondary ERM formation.
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http://dx.doi.org/10.1038/s41598-020-57509-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6969073PMC
January 2020

Quantitative phase imaging of erythrocytes under microfluidic constriction in a high refractive index medium reveals water content changes.

Microsyst Nanoeng 2019 2;5:63. Epub 2019 Dec 2.

1Department of Biomedical Engineering, Duke University, Durham, NC 27708 USA.

Changes in the deformability of red blood cells can reveal a range of pathologies. For example, cells which have been stored for transfusion are known to exhibit progressively impaired deformability. Thus, this aspect of red blood cells has been characterized previously using a range of techniques. In this paper, we show a novel approach for examining the biophysical response of the cells with quantitative phase imaging. Specifically, optical volume changes are observed as the cells transit restrictive channels of a microfluidic chip in a high refractive index medium. The optical volume changes indicate an increase of cell's internal density, ostensibly due to water displacement. Here, we characterize these changes over time for red blood cells from two subjects. By storage day 29, a significant decrease in the magnitude of optical volume change in response to mechanical stress was witnessed. The exchange of water with the environment due to mechanical stress is seen to modulate with storage time, suggesting a potential means for studying cell storage.
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http://dx.doi.org/10.1038/s41378-019-0113-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6885519PMC
December 2019

Collagen immobilization on ultra-thin nanofiber membrane to promote endothelial monolayer formation.

J Tissue Eng 2019 Jan-Dec;10:2041731419887833. Epub 2019 Nov 14.

Bio-Medical Institute, Kyungpook National University Hospital (KNUH), Daegu, South Korea.

The endothelialization on the poly (ε-caprolactone) nanofiber has been limited due to its low hydrophilicity. The aim of this study was to immobilize collagen on an ultra-thin poly (ε-caprolactone) nanofiber membrane without altering the nanofiber structure and maintaining the endothelial cell homeostasis on it. We immobilized collagen on the poly (ε-caprolactone) nanofiber using hydrolysis by NaOH treatment and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/sulfo--hydroxysulfosuccinimide reaction as a cost-effective and stable approach. NaOH was first applied to render the poly (ε-caprolactone) nanofiber hydrophilic. Subsequently, collagen was immobilized on the surface of the poly (ε-caprolactone) nanofibers using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/sulfo--hydroxysulfosuccinimide. Scanning electron microscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, and fluorescence microscopy were used to verify stable collagen immobilization on the surface of the poly (ε-caprolactone) nanofibers and the maintenance of the original structure of poly (ε-caprolactone) nanofibers. Furthermore, human endothelial cells were cultured on the collagen-immobilized poly (ε-caprolactone) nanofiber membrane and expressed tight junction proteins with the increase in transendothelial electrical resistance, which demonstrated the maintenance of the endothelial cell homeostasis on the collagen-immobilized-poly (ε-caprolactone) nanofiber membrane. Thus, we expected that this process would be promising for maintaining cell homeostasis on the ultra-thin poly (ε-caprolactone) nanofiber scaffolds.
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http://dx.doi.org/10.1177/2041731419887833DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6856979PMC
November 2019

Shear Modulus Measurement by Quantitative Phase Imaging and Correlation with Atomic Force Microscopy.

Biophys J 2019 08 12;117(4):696-705. Epub 2019 Jul 12.

Duke University, Department of Biomedical Engineering, Durham, North Carolina.

Many approaches have been developed to characterize cell elasticity. Among these, atomic force microscopy (AFM) combined with modeling has been widely used to characterize cellular compliance. However, such approaches are often limited by the difficulties associated with using a specific instrument and by the complexity of analyzing the measured data. More recently, quantitative phase imaging (QPI) has been applied to characterize cellular stiffness by using an effective spring constant. This metric was further correlated to mass distribution (disorder strength) within the cell. However, these measurements are difficult to compare to AFM-derived measurements of Young's modulus. Here, we describe, to our knowledge, a new way of analyzing QPI data to directly retrieve the shear modulus. Our approach enables label-free measurement of cellular mechanical properties that can be directly compared to values obtained from other rheological methods. To demonstrate the technique, we measured shear modulus and phase disorder strength using QPI, as well as Young's modulus using AFM, across two breast cancer cell-line populations dosed with three different concentrations of cytochalasin D, an actin-depolymerizing toxin. Comparison of QPI-derived and AFM moduli shows good agreement between the two measures and further agrees with theory. Our results suggest that QPI is a powerful tool for cellular biophysics because it allows for optical quantitative measurements of cell mechanical properties.
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http://dx.doi.org/10.1016/j.bpj.2019.07.008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6712492PMC
August 2019

Invited Article: Digital refocusing in quantitative phase imaging for flowing red blood cells.

APL Photonics 2018 Nov 2;3(11). Epub 2018 Oct 2.

Department of Biomedical Engineering, Duke University, Durham, North Carolina 27708, USA.

Quantitative phase imaging (QPI) offers high optical path length sensitivity, probing nanoscale features of live cells, but it is typically limited to imaging just few static cells at a time. To enable utility as a biomedical diagnostic modality, higher throughput is needed. To meet this need, methods for imaging cells in flow using QPI are in development. An important need for this application is to enable accurate quantitative analysis. However, this can be complicated when cells shift focal planes during flow. QPI permits digital refocusing since the complex optical field is measured. Here we analyze QPI images of moving red blood cells with an emphasis on choosing a quantitative criterion for digitally refocusing cell images. Of particular interest is the influence of optical absorption which can skew refocusing algorithms. Examples of refocusing of holographic images of flowing red blood cells using different approaches are presented and analyzed.
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http://dx.doi.org/10.1063/1.5043536DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6561492PMC
November 2018

Weakly supervised lesion localization for age-related macular degeneration detection using optical coherence tomography images.

PLoS One 2019 5;14(4):e0215076. Epub 2019 Apr 5.

Department of Information and Communication Engineering, Daegu Gyeongbuk Institute of Science & Technology (DGIST), Daegu, Republic of Korea.

Age-related macular degeneration (AMD) is the main cause of irreversible blindness among the elderly and require early diagnosis to prevent vision loss, and careful treatment is essential. Optical coherence tomography (OCT), the most commonly used imaging method in the retinal area for the diagnosis of AMD, is usually interpreted by a clinician, and OCT can help diagnose disease on the basis of the relevant diagnostic criteria, but these judgments can be somewhat subjective. We propose an algorithm for the detection of AMD based on a weakly supervised convolutional neural network (CNN) model to support computer-aided diagnosis (CAD) system. Our main contributions are the following three things. (1) We propose a concise CNN model for OCT images, which outperforms the existing large CNN models using VGG16 and GoogLeNet architectures. (2) We propose an algorithm called Expressive Gradients (EG) that extends the existing Integrated Gradients (IG) algorithm so as to exploit not only the input-level attribution map, but also the high-level attribution maps. Due to enriched gradients, EG can highlight suspicious regions for diagnosis of AMD better than the guided-backpropagation method and IG. (3) Our method provides two visualization options: overlay and top-k bounding boxes, which would be useful for CAD. Through experimental evaluation using 10,100 clinical OCT images from AMD patients, we demonstrate that our EG algorithm outperforms the IG algorithm in terms of localization accuracy and also outperforms the existing object detection methods in terms of class accuracy.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0215076PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6450633PMC
January 2020

Short-duration multiple-session subthreshold micropulse yellow laser (577 nm) for chronic central serous chorioretinopathy: results at 3 years.

Eye (Lond) 2019 05 4;33(5):819-825. Epub 2019 Jan 4.

Retina Center, Nune Eye Hospital, Daegu, Republic of Korea.

Objectives: To review the 3-year follow-up results of subthreshold micropulse yellow laser (SMYL) delivered by a short-duration multiple-session method for treatment of chronic central serous chorioretinopathy (CSC).

Methods: A total of 27 eyes from 27 patients with chronic CSC available for 3 years of follow-up were enrolled in this retrospective and interventional study. Patients were treated with 577-nm SMYL photocoagulation at a 15% duty cycle over multiple sessions, with low power ranging from 200 to 400 mW that was increased in 100 mW increments according to resolution of subretinal fluid at monthly follow-up. Laser titration was not performed. A treatment duration of 20 ms rather than the conventional duration (100-300 ms) was applied over the area of retinal pigment epithelium leakage and all areas of serous retinal detachment, including the fovea.

Results: The mean follow-up period was 3.7 ± 0.8 years (range, 3-6 years). A total of 22 out of 27 eyes (81.5%) including six cases of recurrence during the follow-up period exhibited complete resolution of subretinal detachment at final follow-up, whereas only five eyes (15.5%) had either a partial or null response to SMYL treatment. The baseline best-corrected visual acuity was 0.26 ± 0.24 logarithm of the minimum angle of resolution (logMAR), which was improved to 0.08 ± 0.15 logMAR at 1-year (p = 0.005) and 3-year (p = 0.01) follow-up. The central macular thickness at baseline was 389.6 ± 103.4 μm, which was changed to 197.2 ± 40.0 μm (p < 0.001) at 1-year follow-up, 196.4 ± 40.2 μm (p < 0.001) at 3-year follow-up.

Conclusion: Short-duration multiple-session SMYL therapy may be effective for long-term treatment of chronic CSC.
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http://dx.doi.org/10.1038/s41433-018-0309-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6707150PMC
May 2019

Automated Detection of P. falciparum Using Machine Learning Algorithms with Quantitative Phase Images of Unstained Cells.

PLoS One 2016 16;11(9):e0163045. Epub 2016 Sep 16.

Department of Biomedical Engineering, Duke University, Durham, North Carolina, United States of America.

Malaria detection through microscopic examination of stained blood smears is a diagnostic challenge that heavily relies on the expertise of trained microscopists. This paper presents an automated analysis method for detection and staging of red blood cells infected by the malaria parasite Plasmodium falciparum at trophozoite or schizont stage. Unlike previous efforts in this area, this study uses quantitative phase images of unstained cells. Erythrocytes are automatically segmented using thresholds of optical phase and refocused to enable quantitative comparison of phase images. Refocused images are analyzed to extract 23 morphological descriptors based on the phase information. While all individual descriptors are highly statistically different between infected and uninfected cells, each descriptor does not enable separation of populations at a level satisfactory for clinical utility. To improve the diagnostic capacity, we applied various machine learning techniques, including linear discriminant classification (LDC), logistic regression (LR), and k-nearest neighbor classification (NNC), to formulate algorithms that combine all of the calculated physical parameters to distinguish cells more effectively. Results show that LDC provides the highest accuracy of up to 99.7% in detecting schizont stage infected cells compared to uninfected RBCs. NNC showed slightly better accuracy (99.5%) than either LDC (99.0%) or LR (99.1%) for discriminating late trophozoites from uninfected RBCs. However, for early trophozoites, LDC produced the best accuracy of 98%. Discrimination of infection stage was less accurate, producing high specificity (99.8%) but only 45.0%-66.8% sensitivity with early trophozoites most often mistaken for late trophozoite or schizont stage and late trophozoite and schizont stage most often confused for each other. Overall, this methodology points to a significant clinical potential of using quantitative phase imaging to detect and stage malaria infection without staining or expert analysis.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0163045PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5026369PMC
August 2017

Hemoglobin consumption by P. falciparum in individual erythrocytes imaged via quantitative phase spectroscopy.

Sci Rep 2016 Apr 18;6:24461. Epub 2016 Apr 18.

Dept. of Biomedical Engineering, Duke University, Durham, NC 27708, US.

Plasmodium falciparum infection causes structural and biochemical changes in red blood cells (RBCs). To quantify these changes, we apply a novel optical technique, quantitative phase spectroscopy (QPS) to characterize individual red blood cells (RBCs) during the intraerythrocytic life cycle of P. falciparum. QPS captures hyperspectral holograms of individual RBCs to measure spectroscopic changes across the visible wavelength range (475-700 nm), providing complex information, i.e. amplitude and phase, about the light field which has interacted with the cell. The complex field provides complimentary information on hemoglobin content and cell mass, which are both found to dramatically change upon infection by P. falciparum. Hb content progressively decreases with parasite life cycle, with an average 72.2% reduction observed for RBCs infected by schizont-stage P. falciparum compared to uninfected cells. Infection also resulted in a 33.1% reduction in RBC's optical volume, a measure of the cells' non-aqueous components. Notably, optical volume is only partially correlated with hemoglobin content, suggesting that changes in other dry mass components such as parasite mass may also be assessed using this technique. The unique ability of QPS to discriminate individual healthy and infected cells using spectroscopic changes indicates that the approach can be used to detect disease.
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http://dx.doi.org/10.1038/srep24461DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4834482PMC
April 2016

Comparative clinical study of conjunctival toxicities of newer generation fluoroquinolones without the influence of preservatives.

Int J Ophthalmol 2015 18;8(6):1220-3. Epub 2015 Dec 18.

Department of Ophthalmology, Kyungpook National University, School of Medicine, Daegu 700-721, Korea.

Aim: To compare the conjunctival epithelial toxicities of three newer-generation fluoroquinolones without preservatives.

Methods: In a prospective, randomized, double blind comparative study, 47 eyes of 47 patients with a primary pterygium were enrolled, and divided randomly into three groups (levofloxacin 0.5%, gatifloxacin 0.3%, and moxifloxacin 0.5%). After pterygium surgery with the same conjunctival autograft technique, each patient maintained a regimen with a randomly assigned fluoroquinolone eye drop. Patients were examined every other day after surgery until the epithelium had completely healed. Photos were taken and used to measure the area of residual epithelial defects. Conjunctival healing time and speed (initial defect area/healing time (mm(2)/d) compared in each group using Kruskal-Wallis tests.

Results: There were no significant differences in mean age, gender, and conjunctival defect size of the donor site between these groups. However, the mean of conjunctival healing time and speed were statistically different in each group. The mean of conjunctival epithelial healing time was 8.93±2.69d (levofloxacin group), 10.31±2.96d (gatifloxacin group), and 13.50±4.10d (moxifloxacin group), P=0.006. The mean conjuctival epithelial healing speed was 6.18±1.39 mm(2)/d (levofloxacin group), 5.52±1.68 mm(2)/d (gatifloxacin group), and 4.40±1.30 mm(2)/d (moxifloxacin group), P=0. 003.

Conclusion: Without the influence of preservatives, levofloxacin and gatifloxacin might be less toxic to the regeneration of conjunctival epithelial cells and cause a faster conjunctival wound healing relative to moxifloxacin.
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http://dx.doi.org/10.3980/j.issn.2222-3959.2015.06.26DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4651893PMC
December 2015

Influence of defocus on quantitative analysis of microscopic objects and individual cells with digital holography.

Biomed Opt Express 2015 Jun 11;6(6):2067-75. Epub 2015 May 11.

Department of Biomedical Engineering and Fitzpatrick Institute for Photonics, Duke University, Durham NC 27708, USA.

Digital holography offers a unique method for studying microscopic objects using quantitative measurements of the optical phase delays of transmitted light. The optical phase may be integrated across the object to produce an optical volume measurement, a parameter related to dry mass by a simple scaling factor. While digital holography is useful for comparing the properties of microscopic objects, especially cells, we show here that quantitative comparisons of optical phase can be influenced by the focal plane of the measurement. Although holographic images can be refocused digitally using Fresnel propagation, ambiguity can result if this aspect is not carefully controlled. We demonstrate that microscopic objects can be accurately profiled by employing a digital refocusing method to analyze phase profiles of polystyrene microspheres and red blood cells.
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http://dx.doi.org/10.1364/BOE.6.002067DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4473744PMC
June 2015

Short-term efficacy of subthreshold micropulse yellow laser (577-nm) photocoagulation for chronic central serous chorioretinopathy.

Graefes Arch Clin Exp Ophthalmol 2015 Dec 26;253(12):2129-35. Epub 2015 Feb 26.

Nune Eye Hospital, 18-21F LIG Bldg, 2397, Dalgubeol-daero, Suseong-gu, Daegu, Republic of Korea.

Purpose: To investigate the short-term efficacy of subthreshold micropulse yellow laser photocoagulation in the treatment of chronic central serous chorioretinopathy (CSC).

Methods: A retrospective case series study was performed from April 2012 to June 2014 at Nune Eye Hospital. A total of ten eyes of ten chronic or chronic recurrent CSC patients received subthreshold micropulse yellow laser photocoagulation with a 15 % duty cycle at a reduced energy level from the micropulse laser test burn. Laser exposure time was 20 ms, and the spot diameter was 100 μm. Patients were followed up at the authors' hospital for at least 3 months.

Results: Mean age of patients was 43.9 years. The baseline best-corrected visual acuity was 0.21 ± 0.21 logarithm of the minimum angle of resolution (logMAR), which was improved to 0.055 ± 0.093 logMAR (p = 0.020) at the  3-month follow-up and 0.035 ± 0.063 logMAR (p = 0.012) at final follow-up. Central macular thickness at baseline was 349.2 ± 53.2 μm, which was changed to 250.7 ± 28.8 μm (p = 0.009) at the 3-month follow-up and 261.2 ± 38.31 μm (p = 0.009) at final follow-up.

Conclusions: Subthreshold micropulse yellow laser photocoagulation showed short-term efficacy in treating chronic CSC without retinal damage. However, prospective, randomized, and comparative large-scale studies are needed to evaluate the efficacy and safety of this treatment.
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http://dx.doi.org/10.1007/s00417-015-2965-7DOI Listing
December 2015

Clinical characteristics of polypoidal choroidal vasculopathy associated with chronic central serous chorioretionopathy.

Korean J Ophthalmol 2012 Feb 14;26(1):15-20. Epub 2012 Jan 14.

Department of Ophthalmology, Kyungpook National University Hospital, Daegu, Korea.

Purpose: To investigate the clinical characteristics of polypoidal choroidal vasculopathy (PCV) associated with chronic central serous chorioretinopathy (CSC).

Methods: We retrospectively reviewed the medical records of 246 PCV patients (283 eyes) between July 2004 and August 2009 and investigated the clinical characteristics of the PCV patients who had specific fundus findings of chronic CSC.

Results: Among PCV patients, 13 eyes (4.6%) of 13 PCV patients (5.3%) had fundus findings of chronic CSC. All of the PCV lesions had a solitary polyp located outside the atrophic retina, predominantly in the macular area (84.6%), most showed an exudative pattern (69.2%) and there were a few that showed a hemorrhagic pattern (30.8%). All of the lesions were smaller than 1 disc diameter. Most of the PCV lesions (76.9%) were cured with less than two treatments in a short period of 6.4 ± 1.9 months; however, visual acuity deteriorated (61.5%) or was not changed (30.8%) in most of the cases.

Conclusions: The PCV associated with chronic CSC had several clinical features such as a small exudative retinal lesion with a solitary polyp and frequent involvement of the macular area. Even though there was poor visual outcome due to the atrophic change, all of the PCV lesions were easily resolved in a short period with a simple treatment course and no recurrence.
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http://dx.doi.org/10.3341/kjo.2012.26.1.15DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3268163PMC
February 2012

Intravitreal bevacizumab injection for persistent serous retinal detachment associated with Vogt-Koyanagi-Harada disease.

Graefes Arch Clin Exp Ophthalmol 2011 Jan 6;249(1):133-6. Epub 2010 Aug 6.

Department of Ophthalmology, School of Medicine, Kyungpook National University, Daegu, South Korea.

Background: To introduce a case of Vogt-Koyanagi-Harada (VKH) disease in which the serous retinal detachment (SRD), refractory to the systemic steroid therapy, was resolved in a short time after an intravitreal injection of bevacizumab.

Methods: Interventional case report to show the effect of bevacizumab for the SRD in a VKH patient.

Results: A 42-year-old woman, diagnosed with VKH disease, showed decreased visual acuities and multiple SRDs in both eyes. The best-corrected visual acuity (BCVA) was FC 30 cm in both eyes. On optical coherence tomography (OCT), multiple SRDs were confirmed. On OCT, the height of SRD in the central fovea area was 1119 μm in the right eye and 1151 μm in the left eye. After high-dose steroid treatment for 5 weeks, the SRD in the left eye was completely resolved, however, the SRD in the right eye was persisted. At the time, the height of SRD in the right eye was 884 μm and the BCVA was 0.1. For the treatment of persistent SRD causing a decreased visual acuity despite a long-term high-dose course of systemic steroid therapy, an intravitreal injection of 1.25 mg bevacizumab was performed for the right eye, following an informed consent. One week later, there was fast and complete reabsorption of multiple SRDs in the right eye. The retinal thickness in the foveal area was measured to be 189 μm by OCT and the BCVA was improved to 0.7.

Discussion: An intravitreal injection of bevacizumab combined with systemic steroid in VKH is expected to shorten the time for the persistent presence of SRD and to prevent the permanent visual impairment.
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http://dx.doi.org/10.1007/s00417-010-1477-8DOI Listing
January 2011

Fibrin glue-assisted augmented amniotic membrane transplantation for the treatment of large noninfectious corneal perforations.

Cornea 2009 Feb;28(2):170-6

Department of Ophthalmology, Kyungpook National University School of Medicine, Daegu, South Korea.

Purpose: To evaluate and report the efficacy of fibrin glue (FG)-assisted augmented amniotic membrane transplantation (AMT) in patients with large corneal perforations.

Methods: In a retrospective case series, 10 patients with corneal perforations more than 2 mm in diameter were treated with "FG-assisted augmented AMT." A 5- or 7-ply "augmented amniotic membrane" (AM) was constructed by applying FG to each sheet of AM to repair the corneal perforation. The augmented AM was designed 0.5 mm larger than the diameter of the perforation. The augmented AM was transplanted onto the perforation site with 10-0 nylon suture. If needed, additional overlay AM was sutured on top.

Results: The mean ulceration diameter was 2.7 +/- 0.95 mm (range, 2-5 mm). All patients retained their own globes after the procedure and had well-formed deep anterior chambers, and 90% of patients showed complete epithelialization over the AM. The mean reepithelialization time was 14.9 +/- 4.9 days (range, 10-24 days). No eyes showed evidence of infection or recurrent corneal melting during the follow-up period.

Conclusions: FG-assisted augmented AMT was easily performed for repairing large corneal perforations. This surgical method was very helpful in stabilizing the wound in the early postoperative period.
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http://dx.doi.org/10.1097/ICO.0b013e3181861c54DOI Listing
February 2009

Effect of experimental scleral shortening on axial length of the rabbit eye.

Korean J Ophthalmol 2005 Jun;19(2):101-5

Department of Ophthalmology, Kyungpook National University College of Medicine, Daegu, Korea.

Purpose: To evaluate the change of axial length (AL), intraocular pressure (IOP), and corneal astigmatism after scleral shortening with scleral invagination in the rabbit eye.

Methods: The authors performed scleral shortening (3 mm) with scleral invagination in two groups of 6 eyes each: 180 degrees (group 1) and 360 degrees (group 2).

Results: Average AL shortening was more prominent in group 2 (0.5 +/- 0.17 mm) than in group 1 (0.37 +/- 0.29 mm), but the difference was not statistically significant. IOP increased immediately after the procedure and was maintained at a high level through 2 months postoperatively. Induced corneal astigmatism was more prominent in group 1 than in group 2. The difference was statistically significant in group 1 (p<0.05) but not in group 2.

Conclusions: In the scleral shortening with scleral invagination procedure, a large amount of scleral invagination resulted in more shortening of axial length, but there was more corneal astigmatism in 180-degree invagination of the sclera than in 360-degree. Further research is required to determine the effect of the extent of scleral invagination on the change of these values.
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http://dx.doi.org/10.3341/kjo.2005.19.2.101DOI Listing
June 2005
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