Retinal model is an essential part in the retinal prosthesis. Based on the retinal physiology and the experimental data, the model is able to simulate the information processing in the retina, and can be used to investigate the relation between the input image and the neuron firing. We can categorize the models into circuit realization and algorithm realization. This article is a state-of-art review of different types of retinal models.
Algorithms ; Humans ; Models, Biological ; Models, Neurological ; Neural Networks (Computer) ; Prostheses and Implants ; Retina ; anatomy & histology ; physiology

OBJECTIVEUsing the algorithm on the layered structure of the retina and quantitative analysis of the automatic segmentation technique is the key to the early diagnosis of glaucoma and other retinopathy on optical coherence tomography. Existing methods require high quality image and have low reliability. This paper used the improved complex nonlinear diffuse filtering and other methods to solve this problem.

METHODSThis paper includes algorithm such as automatic threshold, improved complex nonlinear diffusion filtering, morphological operations and peak detection. Use the method for the segmentation of 20 retinal layers images which acquired on the self-builder OCT system, the boundary of inner limiting membrane(ILM), outer nuclear layer(ONL), the photoreceptor segments(IS/ OS) and the RPE_ChCap layer are detected accurately. At last, the photoreceptor layer thickness is measured.

RESULTSThe results of segmentation and measurement are good corresponded with expert manual segmentation and measurements, retinal foveal measurements data is consistent with Zeiss Stratus OCT central retinal thickness 212+/-20 micro m.

CONCLUSIONThe algorithm proposed is prospective applied to clinical diagnosis of retinal diseases.

Algorithms ; Humans ; Retina ; anatomy & histology ; Software ; Tomography, Optical Coherence ; instrumentation ; methods

The retinal image registration has important applications in the processes of auxiliary diagnosis and treatment for a variety of diseases. The retinal image registration can be used to measure the disease process and the therapeutic effect. A variety of retinal image registration techniques have been studied extensively in recent years. However, there are still many problems existing and there are numerous research possibilities. Based on extensive investigation of existing literatures, the present paper analyzes the feature of retinal image and current challenges of retinal image registration, and reviews the transformation models of the retinal image registration technology and the main research algorithms in current retinal image registration, and analyzes the advantages and disadvantages of various types of algorithms. Some research challenges and future developing trends are also discussed.
Algorithms ; Humans ; Image Enhancement ; methods ; Image Interpretation, Computer-Assisted ; methods ; Retina ; anatomy & histology ; pathology ; Retinoscopy ; methods

OBJECTIVEOptical coherence tomography images may be distorted by motion artifacts in dynamic imaging, so it may lead to misdiagnosis in clinical diagnosis. Motion artifacts correction has become an urgent issue in optical coherence tomography imaging.

METHODSFirstly, using the improved complex nonlinear diffusion preprocessing filtering reduced the noise of the sequence images, then using the image mass center aligned the distortion data in the Y direction, finally, using the method of deviation average corrected motion artifacts along the Y direction.

RESULTSAfter correction, the motion artifacts in the longitudinal 2D images and the 3D image disappeared, the surface of the 2D and the 3D image became more smooth, the structure between layers of the images got clear and distinct, retinal en-face single slice image was sharp, and the fundus tissue structure could be observed.

CONCLUSIONThe algorithm of correction makes the physical structure of the retinal display truly after motion artifacts correction.

Algorithms ; Artifacts ; Humans ; Imaging, Three-Dimensional ; Motion ; Retina ; anatomy & histology ; Tomography, Optical Coherence

PURPOSE: To determine the normal range of retinal nerve fiber layer (RNFL) thickness of normal children and adolescents by optical coherence tomography (OCT). METHODS: This study analyzed 144 eyes of 72 normal children and adolescents by OCTIII (Zeiss-Humphrey, San Leandro, CA., USA) and the results were compared with the RNFL thickness of Korean adults. RESULTS: The mean RNFL thickness of the 72 normal children and adolescents was 105.53+/-10.33 micrometer. The mean values for left and right eyes were 104.28+/-7.68 micrometer and 106.79+/-12.98 micrometer, respectively. There was no significant difference in mean RNFL thickness between the 4 quadrants of the left and right eyes (p=0.926). Additionally, the mean RNFL thickness showed a similar size pattern regardless of age (p=0.99). RNFL thickness was found to be greater in adults than in children or adolescents, although the difference was not statistically significant (p=0.295. Likewise, no significant difference was found with gender (p=0.822) or in the pattern of RNFL thickness of 12 sectors between children and adults (p=0.08). CONCLUSIONS: This study reports RNFL thickness, as determined by OCT, for normal children and adolescents. We found this measurement method to be suitable for the early diagnosis of glaucoma and to the examination of its progression in these subjects. The findings could be used as clinical parameters for adolescent glaucoma.
Tomography, Optical Coherence ; Retina/*anatomy & histology ; Reference Values ; Nerve Fibers/*ultrastructure ; Male ; Humans ; Female ; Child ; Adult ; Adolescent

OBJECTIVETo study the extent of retinal vascular development and influencing factors at birth and the relation between retinal vascularization and retinopathy of prematurity (ROP).

METHODSFrom October, 2006 to December 2006, retinal vascularization was screened and evaluated in 84 neonates at different weeks of gestation and birth weights (BWs), had dilated fundus evaluation for zone of retinal vascularization by the 130 degrees lens of a digital fundus camera. The infants' pupils were dilated with 2.5% phenylephrine and 0.5% cyclopentolate eye drops. The study cohort was divided into subgroups depending on the weeks of gestation and birth weights. The control group consisted of healthy term infants. Maternal and neonatal factors were ascertained and analysed.

RESULTSVascularization up to zone I and II was considered to be immature retina; vascularization up to zone III or beyond was considered to be mature retina. In this study, 11 of 12 infants who were born at < 30 weeks of gestation, 12 of 26 infants who were born at < 31 approximately 33 weeks of gestation, 1 of 26 babies who were born at < 34 approximately 36 weeks of gestation and none of 20 babies who were born at < 37-40 weeks of gestation had immature retina; 12 of 15 babies at < 1500 g BW, 8 of 14 infants at 1500 g < BW < 1700 g, 4 of 11 infants at 1700 g < BW < 2000 g and of 44 infants at > 2000 g BW had immature retina. Those infants who were born at > 34 weeks of gestational age and at > 2000 g BW had mature retina. Infants who were born between 31 to 34 weeks of gestation and at 1501 to 2000 g BW had variable extent of retinal vascularization at birth. Vascularization was associated with postconceptional age (F = 31.9193, P = 0.000), birth weight (F = 32.4532, P = 0.000), anemia (F = 36.9391, P = 0.000), surfactant (F = 24.000, P = 0.0000), poor nutrition (F = 4.184, P = 0.041), RDS (F = 17.6191, P = 0.000), cesarean delivery (F = 10.972, P = 0.0022) and oxygen > 48 h (F = 22.076, P = 0.0000). Vascularization was affected mainly by the postconceptional age (95% CI = 1.57-261.728, P = 0.021). At last, 15/24 infants with immature retina developed ROP while none of the infants with mature retina developed ROP (chi2 = 45.1087, P = 0.000).

CONCLUSIONThere is considerable variability in the extent of retinal vascularization in infants who we born between 31 to 34 weeks of gestation. Modifiable maternal and fetal factors could influence extent of vascularization at birth. Immature retina is the critical factor of ROP. Gestational age is the main factor of the immature retina in premature infants.

Birth Weight ; Female ; Humans ; Infant, Newborn ; Infant, Premature ; Male ; Neovascularization, Physiologic ; Retina ; anatomy & histology ; Retinal Vessels ; growth & development

Purpose: To determine the proportion of glaucoma suspects with abnormal nerve fiber layer measurement using GDx nerve fiber analyzer Methodology: The study population consisted of glaucoma suspects between ages 30-70 years, who underwent glaucoma workup including retinal nerve fiber layer measurement (GDx NFA) Results: 35 eyes of glaucoma suspects were analyzed. 28/35 were found to have normal NFL thickness; 5/35 have 1 abnormal GDx parameters; 1/35 with 3 abnormal GDx parameters; 1/35 with 3 GDx abnormal parameters. Linear regression analysis showed no correlation between C:D and GDx parameters Conclusion: This study confirms that superior maximum is useful to the other parameters but there is a need to collect more samples. (Author)
Human ; Male ; Female ; Aged ; Middle Aged ; Adult ; RETINA/ANATOMY & HISTOLOGY ; NERVE FIBERS ; GLAUCOMA ; HUMAN ; OPTIC DISK ; SCANNING LASER POLARIMETRY ; LASER/DIAGNOSTIC USE

In view of the evaluation of fundus image segmentation, a new evaluation method was proposed to make up insufficiency of the traditional evaluation method which only considers the overlap of pixels and neglects topology structure of the retinal vessel. Mathematical morphology and thinning algorithm were used to obtain the retinal vascular topology structure. Then three features of retinal vessel, including mutual information, correlation coefficient and ratio of nodes, were calculated. The features of the thinned images taken as topology structure of blood vessel were used to evaluate retinal image segmentation. The manually-labeled images and their eroded ones of STARE database were used in the experiment. The result showed that these features, including mutual information, correlation coefficient and ratio of nodes, could be used to evaluate the segmentation quality of retinal vessel on fundus image through topology structure, and the algorithm was simple. The method is of significance to the supplement of traditional segmentation evaluation of retinal vessel on fundus image.
Algorithms ; Databases, Factual ; Diagnostic Imaging ; methods ; Diagnostic Techniques, Ophthalmological ; Fundus Oculi ; Humans ; Image Processing, Computer-Assisted ; Retina ; Retinal Vessels ; anatomy & histology

PURPOSE: To evaluate a simplified method to measure peripapillary choroidal thickness using commercially available, three-dimensional optical coherence tomography (3D-OCT). METHODS: 3D-OCT images of normal eyes were consecutively obtained from the 3D-OCT database of Korea University Medical Center On the peripapillary images for retinal nerve fiber layer (RNFL) analysis, choroidal thickness was measured by adjusting the segmentation line for the retinal pigment epithelium to the chorioscleral junction using the modification tool built into the 3D-OCT image viewer program. Variations of choroidal thickness at 12 sectors of the peripapillary area were evaluated. RESULTS: We were able to measure the peripapillary choroidal thickness in 40 eyes of our 40 participants, who had a mean age of 41.2 years (range, 15 to 84 years). Choroidal thickness measurements had strong inter-observer correlation at each sector (r = 0.901 to 0.991, p < 0.001). The mean choroidal thickness was 191 +/- 62 microm. Choroidal thickness was greatest at the temporal quadrant (mean +/- SD, 210 +/- 78 microm), followed by the superior (202 +/- 66 microm), nasal (187 +/- 64 microm), and inferior quadrants (152 +/- 59 microm). CONCLUSIONS: The measurement of choroidal thickness on peripapillary circle scan images for RNFL analysis using the 3D-OCT viewing program was highly reliable and efficient.
Adolescent ; Adult ; Aged ; Aged, 80 and over ; Choroid/*anatomy & histology ; Databases, Factual ; Female ; Humans ; Imaging, Three-Dimensional/*methods/statistics & numerical data ; Male ; Middle Aged ; Observer Variation ; Retina/*anatomy & histology ; Tomography, Optical Coherence/*methods/statistics & numerical data ; Young Adult

OBJECTTo investigate the therapeutic effect of microencapsulated porcine retinal pigmented epithelial cells (RPE-M) transplantation on rat model of Parkinson's disease (PD).

METHODSPrimary porcine RPE cells were harvested by enzyme digestion and expanded in culture medium. Determine the levels of dopamine (DA) and homovanillic acid (HVA) by high performance liquid chromatography electrochemical (HPLC) assay, and the levels of brain-derived neurotrophic factor (BDNF) and glial-derived neurotrophic factor (GDNF) were detected by ELISA. Alginate-polylysine-alginate (APA) microencapsulated cells were produced by using a high voltage electrostatic system. PD rat model was established by unilateral injection of 6-hydroxydopamine (6-OHDA) into the medial forebrain bundle (MFB). After that, the RPE-M was transplanted into the corpus striatum of PD rat, and then the rotation test scores were recorded and biochemical changes of the corpus striatum were tested.

RESULTSThe levels of DA, HVA, BDNF and GDNF secreted by RPE were stable in the RPE culture supernatant and were not changed by the microencapsulation. Eighty-three percent rats developed PD by unilateral lesion of 6-OHDA in the MFB. The RPE-M transplantation had therapeutic effect on 33% PD rats.

CONCLUSIONPorcine RPE cells grow actively in vitro and could secrete DA, HVA, BDNF, and GDNF constantly, which does not be affected by the passage culture and the APA miroencapsulation. RPE-M transplantation of may be a curative therapy for PD.

Adrenergic Agents ; toxicity ; Animals ; Brain-Derived Neurotrophic Factor ; metabolism ; Cell Transplantation ; methods ; Cells, Cultured ; Disease Models, Animal ; Dopamine ; metabolism ; Enzyme-Linked Immunosorbent Assay ; Epithelial Cells ; metabolism ; transplantation ; Glial Cell Line-Derived Neurotrophic Factor ; metabolism ; Male ; Oxidopamine ; toxicity ; Parkinson Disease ; etiology ; surgery ; Rats ; Rats, Sprague-Dawley ; Retina ; cytology ; Swine ; anatomy & histology ; Time Factors ; Transplantation, Heterologous ; methods ; Tyrosine 3-Monooxygenase ; metabolism