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ABSTRACT: PURPOSE: To present a computerized method of measuring binocular alignment using a selective wavelength filter and an infrared camera and to validate the efficacy of automated image analysis compared to the gold standard prism and alternate cover test (PCT). METHODS: A prospective observational pilot study was performed on 30 subjects with intermittent exotropia, 30 subjects with esotropia, and 30 orthotropic subjects who were able to cooperate with the PCT. Two independent ophthalmologists examined the angle of deviation using the PCT. Full-face images were obtained with an infrared camera while a selective wavelength filter was placed in front of either eye. Images were analyzed using the 3D Strabismus Photo Analyzer. Interobserver variability, test-retest reliability and correlation between the angles of deviation were determined of both methods. RESULTS: The 95% limit of agreement of interobserver variability was ±4.8 PD for the PCT and ±4.3 PD for the selective wavelength filter analysis. The 95% limit of agreement of test-retest reliability between the PCT and selective wavelength filter analysis was ±8.5 PD. Results of the PCT and selective wavelength filter analysis showed a strong positive correlation (R= 0.900, P < 0.001). CONCLUSIONS: Infrared images acquired with a selective wavelength filter can detect the latent components of strabismus and automated image analysis showed excellent agreement with the standard PCT. This automated method is an accurate and reliable tool for measuring ocular deviation with minimal observer dependency.
Investigative ophthalmology & visual science 03/2013; · 3.43 Impact Factor
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So Hyun Bae,
Jeong-Hwan Che, Jong-Mo Seo,
Joonsoo Jeong,
Eui Tae Kim,
Seung Woo Lee,
Kyo-in Koo,
Gregg J Suaning,
Nigel H Lovell,
Dong-Il Dan Cho,
Sung June Kim,
Hum Chung
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ABSTRACT: The purpose of our study is to evaluate the biocompatibility of various polymers used as microelectrode arrays (MEAs) in retinal prostheses through in vitro cytotoxicity testing following a standardized
Three types of polymer-based MEAs were examined: silicone-based platinum, polyimide-based gold and liquid crystal polymer (LCP)-based gold MEAs. The silicone/platinum MEAs were fabricated by a Nd:YAG laser, polyimide/gold MEAs by a semiconductor manufacturing technique, and LCP/gold MEAs by laser micromachining and thermal-bonding process. All experimental procedures followed the International Organization for Standardization (ISO) 10993-5. To obtain the extracts of specimens, 4 g of each type of MEA were eluted by culture media, MEM, for 24 hours. Then, several diluents of extracts, including the original extracts, were applied to a cultured-cell monolayer, L929 fibroblasts. The morphologic changes of cells were analyzed by microscope after 24 and 48 hours of incubation. The quantitative evaluations of cell viability were performed by MTT assay after 24 hours of incubation.
The microscopic evaluations revealed that extracts from polymer-based MEAs did not induce morphologic changes or reduction of cells compared with control irrespective of concentrations of extracts. The MTT assay showed high viability values of approximately 80 to 130% regardless of diluted ratio of extracts from polymer-based MEAs. None of the polymers demonstrated a significant reduction of cell viability when compared with control.
All types of polymer-based MEAs, including silicone/platinum, polyimide/gold, and LCP/gold MEAs, meet the criteria of biocompatibility guided by international standards, ISO 10993-5.
Investigative ophthalmology & visual science 03/2012; 53(6):2653-7. · 3.43 Impact Factor
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ABSTRACT: The principal objective of this study was to evaluate the protective effect of cysteamine against the oxidative stress-induced cell death of human corneal endothelial cells.
In this study, human corneal endothelial cells (HCECs) were cultured according to a previously published method. With treatment of 0 mM or 5 mM of tert-butyl hydroperoxide (tBHP) with various concentrations (0-50 mM) of cysteamine, reactive oxygen species (ROS) production was measured using an oxidation-sensitive fluorescent probe, and dichlorofluorescein diacetate (DCFH-DA) methods. Cell viability was assayed via the Cell Counting Kit-8 method. The levels of cellular glutathione were also assessed enzymatically with glutathione reductase using a commercial glutathione assay kit (Cayman Chemical, USA).
This study showed that cysteamine reduced 2',7'-dihydrodichlorofluorescein oxidation and increased glutathione. Cysteamine significantly inhibited tBHP-induced ROS production. Cysteamine-treated cells evidenced higher viability relative to the controls at 5 mM tBHP, and cysteamine also effectively protected HCECs against ROS-induced cell death via an increase in intracellular glutathione.
Our data indicate that cysteamine was not toxic at low concentrations and, at high concentrations, protects HCECs against oxidative injury-mediated cell death via the inhibition of ROS production, although cysteamine is toxic in cells at high concentrations without oxidative stress.
Current eye research 10/2011; 36(10):910-7. · 1.51 Impact Factor
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ABSTRACT: To evaluate the efficacy of a computerized optokinetic nystagmus (OKN) test in detecting visual acuity (VA) of >20/200.
This was a combined retrospective and prospective, noninterventional study. In phase I of the study, data from 168 eyes of 154 subjects who underwent the computerized objective VA test using OKN responses at Seoul National University Bundang Hospital were reviewed and reanalyzed, and a table for predicting the range of subjective VA for each step of objective VA was made. From the table, the cutoff value for detecting VA of >20/200 was determined. In phase II of the study, the distribution of subjective VA according to each objective VA step was determined for 80 eyes of 40 subjects at Seoul Veteran's Hospital. The sensitivity and the specificity of our cutoff value were evaluated in the two groups.
No significant difference was found in the distribution of subjective VA according to objective VA steps between the two groups. For the subjects in phase I of the study, the sensitivity of our cutoff value was 91.7% and the specificity was 88.3%. For patients in phase II of the study, the sensitivity of our cutoff was 86% and the specificity was 96.7%.
This study shows that an objective VA test using OKN responses can be effective in predicting real VA and detecting VA of >20/200.
Investigative ophthalmology & visual science 08/2011; 52(10):7492-7. · 3.43 Impact Factor
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ABSTRACT: To evaluate the efficacy of a computerized optokinetic nystagmus (OKN) test for determination of objective visual acuity (VA) at distance in patients with various ocular diseases.
This is a prospective, non-interventional study that included 85 eyes of 71 patients with one or more ocular pathologies. Study patients were classified into group C (39 eyes of 30 patients with central visual damage), group P (24 eyes of 20 patients with peripheral visual defect) and group M (22 eyes of 21 patients with media opacity). Objective distance VA was measured with OKN induction and suppression methods, and the correlation between the objective and subjective VA at distance was evaluated using linear regression analysis. Mean subjective VAs were compared among each objective VA step and among the three groups.
Significant correlation was found between subjective distance VA and objective VA determined by both OKN induction and suppression methods in all three groups and in overall patients. In overall patients, the mean subjective VA was significantly different in several objective VA steps (Welch's ANOVA, p < 0.001 for induction and suppression methods). No significant difference in subjective VA among the three groups was found in any objective VA step.
Our objective VA test using OKN induction and suppression methods can be useful in estimating distance VA in patients with various ocular diseases.
Albrecht von Graæes Archiv für Ophthalmologie 05/2011; 249(9):1379-85. · 2.17 Impact Factor
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ABSTRACT: In this paper, a novel microelectrode array (MEA), with varying arrowhead shapes, is fabricated and evaluated for retinal prostheses. The proposed MEA has a total of 199 arrowhead-shaped microelectrodes, with heights ranging from 42 to 123.5 μm. This height variation allows each microelectrode to contact the spherical eyeball conformably and to approach the stimulation target retinal cells very closely. The fabricated MEAs are implanted in rabbit eyes. The physical contact of the MEA is evaluated using optical coherent tomography (OCT) images, which show that the implanted MEA makes an excellent conformal contact with the spherically shaped retinal layers. These OCT images also exhibit good biocompatibility of the implanted MEA. The evaluation results show that the proposed MEA has a high potential for clinical applications. Our ongoing project is aimed at clinical application in three years. [2010-0037].
Journal of Microelectromechanical Systems 03/2011; · 2.10 Impact Factor
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ABSTRACT: There has been no report about hereditary and clinical features of retinitis pigmentosa (RP) in Koreans. To evaluate these, data were collected from 365 RP patients including age, gender, visual acuity (VA), spherical equivalent (SE) of refractive errors, funduscopic findings, color vision test, visual field score (VFS) obtained from Goldmann perimetry, and the inheritance patterns from pedigrees. Simplex RP was the most common inheritance pattern (61.9%); followed by autosomal recessive RP (17.3%), autosomal dominant RP (12.1%) and X-linked recessive RP (8.8%). Myopia was the most common refractive errors (77.5%) including 16.1% of high myopia. The most common cataract type was posterior subcapsular cataract (25.8%). Observed retinal findings included changes of retinal pigment epithelium (88.8%), bony spicule-like pigmentation (79.7%), attenuation of retinal vessel (76.2%), waxy disc pallor (12.6%), golden ring around optic disc (2.2%), epiretinal membrane (0.8%) and cystoid macular edema (0.5%). Corrected VA and refractive errors did not show any significant difference between the inheritance patterns. VFS was significantly worse in autosomal recessive RP than in autosomal dominant RP. Color vision defect was noted in 66.1% on Hardy-Rand-Rittlers color vision test. In conclusion, Korean RP patients have the indigenous hereditary and clinical features as well as the ordinary ones.
Journal of Korean medical science 06/2010; 25(6):918-23. · 0.84 Impact Factor
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ABSTRACT: The objective measurement of the visual acuity is one of the most important issues in ophthalmology clinics, and the optokinetic
nystagmus (OKN) can be a good candidate for this purpose. In this paper, an eyeglasses-based electrooculogram (EOG) for the
detection of the OKN is introduced. It is convenient to use and allows the refractive error correction for the visual acuity
measurement.
To evoke the OKN, moving strips with various spatial frequencies are generated on the monitor in front of the patients’ view.
The OKN is observed by the wearable EOG eyeglasses. Both the EOG signal acquisition circuit and chrome electrodes were integrated
with the eyeglasses. The EOG signal is processed through an acquisition circuit to personal computer for the further analysis
and the real-time display of the EOG signal according to the visual stimuli.
The proposed system can monitor OKN well, while making patients more comfortable by removing bulky and burdensome devices.
Also it can adopt the lenses for the refractive error correction. Those advantages make visual acuity test more objective
and accurate.
KeywordsVisual acuity test-objective-EOG-wearable-OKN
03/2010: pages 271-274;
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ABSTRACT: To establish a Korean normative database of retinal nerve fiber layer (RNFL) thickness.
Data was collected from 103 healthy volunteers. Total ophthalmologic examinations, including fast RNFL thickness analysis by time domain optical coherence tomography (STRATUS OCT) were performed. The RNFL thickness of 64 glaucoma patients with localized RNFL defects and 48 independent healthy subjects were collected. The RNFL thickness of both the glaucoma patients and the healthy subjects was evaluated using both normative databases.
The average RNFL thickness of Koreans was 108.3 +/- 10.3 microm. The sensitivity rates recorded in the Korean normative database with 5% and 1% significance were 0.984 and 0.984, with specificity values of 0.938 and 1.000. By comparison, the sensitivity rates in the conventional normative database with 5% and 1% significance are 0.984 and 0.953, and the specificity values are 1.000 and 1.000.
In detecting localized RNFL defects, the Korean database showed higher sensitivity than the conventional database.
Japanese Journal of Ophthalmology 03/2010; 54(2):144-50. · 0.92 Impact Factor
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ABSTRACT: Recent studies of retina discovered that myopic refraction has a correlation with smaller retinal vessel diameters and variation
in retinal arteriolar caliber is an important sign of systemic hypertension. Also, lower retinal arteriole to venule ratio
(AVR) can predict the risk of hypertension.
To utilize these valuable information in prognosing related diseases more precisely and quickly, this paper suggests an automated
measurement algorithm of retinal vessel diameters. In this method, there is no requirement for human intervention such as
classification of vessels by hand or initial information of each vessel’s position. This method is focused on a region around
the optic disc for accurate measurements of retinal vessel’s diameters. Region of donut shape, which is centered at optic
disc, has clearer contrast than other region and make it possible to classify vessels into two types, arteriole and venule
reliably.
From the green channel image data, vessel’s diameters can be automatically measured by using intensity profile graphs and
significant features of retina, and it will help to obtain more accurate AVR, variance and mean values of width in the region
of interest.
Keywordsretinal vessel diameter-fundus photograph-optic disc-arteriole to venule ratio
01/2010: pages 277-280;
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ABSTRACT: This paper introduces a real-time eye tracking system mounted on an eyeglasses frame, utilizing color camera as the video
input device instead of infrared (IR) camera.
IR camera system is preferred in many studies because pupil is very easily discernable with clear margin under proper IR illumination.
However, IR illumination increases not only the total weight but also the size of the system, resulting in bulky and heavy
head-mount system or table-mount system with chin rest. In addition, IR camera cannot detect the pupil of the examinee wearing
eyeglasses because of the reflection of the IR illumination on the eyeglasses.
Color camera doesn’t need additional light source except daylight or room light, which allows less intrusive system with light
weight and small size. However, captured images are worse than IR camera, showing blurred boundary and shimmering noise. Thus
it needs compensation algorithms which will be described through this paper.
Keywordseye tracker-wearable-visual spectrum-webcam
01/2010: pages 267-270;
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ABSTRACT: To investigate the efficacy of a computerized optokinetic nystagmus (OKN) test in evaluating the objective distance visual acuity and to determine the correlation between subjective and objective visual acuities.
This prospective, noninterventional study included 83 eyes of 83 volunteers. Objective visual acuity was defined as the smallest size stripe that evoked the OKN response (induction method) or as the smallest dot size that suppressed the OKN response (suppression method). Distance visual acuity was measured by computerized OKN and infrared oculography at distance. The reproducibility of the test was evaluated by intraclass correlation coefficient (ICC). The correlation between measured objective and subjective visual acuity was then evaluated with linear regression analysis. Subjects were grouped according to their objective visual acuity, and the mean subjective visual acuities were compared with those of the objective visual acuity groups.
There was a significant correlation between distance objective and subjective visual acuity (correlation coefficient R(2), induction method:suppression method = 0.566:0.832, P < 0.05). The mean subjective visual acuity was significantly different in the objective visual acuity groups (Welch's ANOVA, P = 0.000 for induction and suppression methods). The objective visual acuity test showed good reproducibility (ICC; induction method:suppression method = 0.945:0.988, P < 0.05).
The computerized OKN test could serve as an objective and reliable tool for assessing distance visual acuity.
Investigative ophthalmology & visual science 10/2009; 51(2):752-7. · 3.43 Impact Factor
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ABSTRACT: To develop a liquid crystal polymer (LCP)-based, long-term implantable, retinal stimulation microelectrode array using a novel fabrication method.
The fabrication process used laser micromachining and customized thermal-press bonding to produce LCP-based microelectrode arrays. To evaluate the fabrication process and the resultant electrode arrays, in vitro reliability tests and in vivo animal experiments were performed. The in vitro tests consisted of electrode site impedance recording and electrode interlayer adhesion monitoring during accelerated soak tests. For in vivo testing, the fabricated electrode arrays were implanted in the suprachoroidal space of rabbit eyes. Optical coherence tomography (OCT) and electrically evoked cortical potentials (EECPs) were used to determine long-term biocompatibility and functionality of the implant.
The fabricated structure had a smooth, rounded edge profile and exhibited moderate flexibility, which are advantageous features for safe implantation without guide tools. After accelerated soak tests at 75 degrees C in phosphate-buffered saline, the electrode sites showed no degradation, and the interlayer adhesion of the structure showed acceptable stability for more than 2 months. The electrode arrays were safely implanted in the suprachoroidal space of rabbit eyes, and EECP waveforms were recorded. Over a 3-month postoperative period, no chorioretinal inflammation or structural deformities were observed by OCT and histologic examination.
LCP-based flexible microelectrode arrays can be successfully applied as retinal prostheses. The results demonstrate that such electrode arrays are safe, biocompatible, and mechanically stable and that they can be effective as part of a chronic retinal implant system.
Investigative ophthalmology & visual science 07/2009; 50(12):5859-66. · 3.43 Impact Factor
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ABSTRACT: To adopt micropatterning technology in manufacturing silicone elastomer-based microelectrode arrays for retinal stimulation, a silicone-polyimide hybrid microelectrode array was proposed and tested in vivo.
Gold microelectrodes were created by semiconductor manufacturing technology based on polyimide and were hybridized with silicone elastomer by spin coating. The stability of the hybrid between the two materials was flex and blister tested. The feasibility of the hybrid electrode was evaluated in the rabbit eye by reviewing optical coherence tomography (OCT) findings after suprachoroidal implantation.
The flex test showed no dehiscence between the two materials for 24 hours of alternative flexion and extension from -45.0 degrees to +45.0 degrees . During the blister test, delamination was observed at 8.33 +/- 1.36 psi of pressure stress; however, this property was improved to 11.50 +/- 1.04 psi by oxygen plasma treatment before hybridization. OCT examination revealed that the implanted electrodes were safely located in the suprachoroidal space during the 4-week follow-up period.
The silicone-polyimide hybrid microelectrode array showed moderate physical properties, which are suitable for in vivo application. Appropriate pretreatment before hybridization improved electrode stability. In vivo testing indicated that this electrode is suitable as a stimulation electrode in artificial retina.
Investigative ophthalmology & visual science 04/2009; 50(9):4337-41. · 3.43 Impact Factor
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ABSTRACT: To investigate the protective effect of clusterin on oxidative stress-induced cell death of human corneal endothelial cells.
Human corneal endothelial cells (HCECs) were cultured according to previously published methods. With treatment of various concentrations (0-50 mM) of tert-butyl hydroperoxide (tBHP) or clusterin, reactive oxygen species (ROS) producrion was measured using an oxidationsensitive fluorescent probe and 2'7'-dichlorofluorescin diacetate (DCFH-DA). Cell viability was assayed with a Cell Counting Kit-8.
In HCECs, DCF-DA staining revealed that cells treated with a higher concentration of tBHP had higher fluorescent intensity than cells treated with clusterin, compared to control cells. Clusterin significantly inhibited tBHP-induced ROS production. Cell viability decreased with higher tBHP concentration. Cells treated with clusterin had higher viability than control cells at 5 mM tBHP. Clusterin effectively protected HCECs from ROS-induced cell death.
Our data suggest that clusterin may protect HCECs from oxidative injury-mediated cell death via inhibition of ROS production.
Molecular vision 01/2009; 15:2789-95. · 2.20 Impact Factor
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ABSTRACT: To identify characteristics measured by optical coherence tomography (OCT) that are correlated with visual outcome after epiretinal membrane (ERM) removal by pars plana vitrectomy (PPV).
Interventional, prospective, randomized case series.
One hundred and one eyes of 101 patients with idiopathic ERM underwent PPV for ERM removal. Ophthalmic evaluations included best-corrected visual acuity (BCVA) and Stratus OCT preoperatively at 3 and 6 months postoperatively. Relations between three OCT features including integrity of junction between inner and outer segments of photoreceptors (IS/OS junction), macular thickness, foveal contour and the three visual acuity parameters such as preoperative BCVAs, postoperative BCVAs, and the differences between preoperative and postoperative BCVAs (BCVA differences) were evaluated with respect to time.
Eyes with disruption of IS/OS junction had significantly lower postoperative BCVA and BCVA differences than those without disruption (P < .0001, respectively). "Same" (increment or decrement of BCVA up to 1 Snellen line) and "Better" (visual increment of at least 2 Snellen lines) BCVA outcome groups were significantly different with respect to the status of IS/OS junction (P < .005). An increase in the proportion of eyes with photoreceptor disruption was observed at 3 months postoperatively, and this proportion was maintained afterward. Preoperative macular thicknesses showed a positive correlation with BCVA differences, and postoperative macular thicknesses negatively correlated with postoperative BCVA (r > 0.25; P < .05, respectively). Thickness difference and foveal contour were not correlated with the three parameters of visual outcome (P > .05, respectively).
Photoreceptor disruption detected by OCT was found to be a predictor of poor visual outcome in eyes with idiopathic ERM, and it was found that this disruption may be irreversible. Thus, early membrane removals may beneficially prevent further progression of photoreceptor damage in ERM patients with photoreceptor disruption.
American journal of ophthalmology 01/2009; 147(3):473-480.e3. · 3.83 Impact Factor
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ABSTRACT: Glaucoma is the second leading cause of blindness, and the retinal nerve fiber layer (RNFL) defect is the early sign of the glaucomatous optic nerve damage. To evaluate the RNFL, segmentation of the optic nerve head on the RNFL photograph should be the first step. This paper presents segmentation of optic nerve head using warping and random sample consensus (RANSAC). Sensitivity and positive predictability of the proposed method were 91% and 78% respectively.
Engineering in Medicine and Biology Society, 2007. EMBS 2007. 29th Annual International Conference of the IEEE; 09/2007
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ABSTRACT: To improve the usability of conventional indirect ophthalmoscope, we propose the newly designed binocular indirect ophthalmoscope which is inexpensive, comfortable, light-weighted, long-lasting, and provides stereopsis not only to examiner but also to observers. Our new system shows good performance compared to conventional indirect ophthalmoscope and also presents the stereoscopic assistant view through special visualization system.
Engineering in Medicine and Biology Society, 2007. EMBS 2007. 29th Annual International Conference of the IEEE; 09/2007
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ABSTRACT: Glaucoma is the second leading cause of blindness, and the retinal nerve fiber layer (RNFL) defect is the early sign of the glaucomatous optic nerve damage. To evaluate the RNFL, segmentation of the optic nerve head on the RNFL photograph should be the first step. This paper presents segmentation of optic nerve head using warping and random sample consensus (RANSAC). Sensitivity and positive predictability of the proposed method were 91% and 78% respectively.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 02/2007; 2007:900-3.
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ABSTRACT: To improve the usability of conventional indirect ophthalmoscope, we propose the newly designed binocular indirect ophthalmoscope which is inexpensive, comfortable, light-weighted, long-lasting, and provides stereopsis not only to examiner but also to observers. Our new system shows good performance compared to conventional indirect ophthalmoscope and also presents the stereoscopic assistant view through special visualization system.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 02/2007; 2007:2219-22.
