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The influence of corneal astigmatism on retinal nerve fiber layer thickness and optic nerve head parameter measurements by spectral-domain optical coherence tomography

The influence of corneal astigmatism on retinal nerve fiber layer thickness and optic nerve head parameter measurements by spectral-domain optical coherence tomography

Figure 1 An example of a measurement of the retinal nerve fiber layer characteristics in an right eye with a-6.625D of spherical equivalent, a -1.6 of CA and a 26.42mm of axial length: (a) Fundus photograph of the optic disc. Dotted line represents imaginary horizontal meridian; (b) the peak locations at the superior and inferior area were 40 and 212, respectively; (c) the peak locations were translated to units of degrees by multiplying 360/256. Angles between the horizontal meridian and the superotemporal / inferotemporal peak locations were defined as the α (superotemporal) and β (inferotemporal) angles, so RNFL peak locations of this eye were α = 40 × 360/256 = 56.25(degree), β = 360-212 × 360/256 = 61.88(degree).
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ARA 290 Improves Symptoms in Patients with Sarcoidosis-Associated Small Nerve Fiber Loss and Increases Corneal Nerve Fiber Density

ARA 290 Improves Symptoms in Patients with Sarcoidosis-Associated Small Nerve Fiber Loss and Increases Corneal Nerve Fiber Density

Corneal Confocal Microscopy Corneal nerve fiber density was deter- mined by corneal confocal microscopy carried out by using the Rostock Cornea Module with the Heidelberg Retina Tomograph III using established meth- odology (28). Briefly, after the applica- tion of a topical anesthetic, the sterile objective of the confocal microscope was placed on the apex of the cornea, as determined by the characteristic orientation of the nerve fibers in a superior–inferior direction. By using the automatic scan feature of the device, confocal images of graduated depth in the plane of the cornea were acquired. The field of view of each image was 0.4 × 0.4 mm. Images containing sensory nerve fibers within the subbasal layer between the Bowman layer and the basal epithelium were further analyzed. Collected images were subjected to auto- mated analysis using a custom macro written for Fiji, a public-domain image analysis program, version 1.47e (29). This macro maps all neurites in the image on the basis of their brightness and tubeness. The area covered by the mapping is then expressed as a percent- age of total image area. For each patient, the 10 images with the highest nerve fiber density were averaged to generate a representative sample for that patient for that eye. Because the variation be- tween eyes of different patients was sim- ilar to the variation between eyes of in- dividual patients (standard deviation of the mean neurite area between patients = 562; standard deviation of the difference between eyes of individual patients = 501), each eye was treated as an inde- pendent sample. The automated analysis was validated by comparison of 78 ran- domly selected images in which total neurite length in each image was deter- mined by manually outlining individual neurites. Linear regression analysis showed an excellent goodness of fit (95% confidence interval of the slope: 0.99–1.19; R 2 = 0.76; p < 0.0001) between
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Perimetric and retinal nerve fiber layer findings in patients with Parkinson’s disease

Perimetric and retinal nerve fiber layer findings in patients with Parkinson’s disease

A number of previous studies [10-12], although not all [14-16], provided evidence of reduced RNFL thickness in PD patients. Inzelberg et al. [11] reported a reduction in the infero temporal RNFL thickness, which was topo- graphically matched to the VF defects, in a subset of five patients with reliable VFs. A reduction in average RNFL thickness, macular thickness and volume was also reported in another study in PD patients [11]. Decreased RNFL thickness has also been suggested in PD patients examined with scanning laser ophthalmoscopy [21]. Moschos et al. [12] reported reduced temporal and infer- ior RNFL thickness in PD patients compared to controls. However, in agreement with our results, mean RNFL thickness did not differ between the groups. In addition, OCT findings with spectral domain OCT (SD-OCT) suggest a decreased thickness of the paramacular inner retina, including the nerve fiber layer, the ganglion cell layer and the inner plexiform layer in PD patients, while outer retinal layer thickness was not found to differ from controls [22]. Increased inner nuclear layer thickness has been identified in a more recent study [16].
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An atypical case of optic disk drusen with nerve fiber layer thickening

An atypical case of optic disk drusen with nerve fiber layer thickening

a scanning laser ophthalmoscope showed hyperreflectance lesions on the disk and shadowing areas beneath the optic nerve head consistent with ODD. Orbital ultrasound and tomography revealed protuberances with hyperechogenicity and calcification in both eyes. It was considered that these findings were consistent with ODD. Repeated visual field tests (by Octopus 101 perimeter; Haag Streit Interziag Inc., Switzerland) showed peripheral concentric narrowing in both eyes (Figures 2 and 3). Using OCT software, peripapillary nerve fiber layer thickening corresponded to visual field defects in the superior and inferior quadrants in which the drusen was detected in both eyes (Figures 4, 5A, and 5B). Based on the clinical appearance of the optic disks and the ancillary tests, a diagnosis of buried ODD was made. It was recommended that the patient be re-examined in a further six indirect light reflexes were intact, with no relative afferent
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Retinal Nerve Fiber Layer Thickness in a Subset of Karachi (Pakistan) Population

Retinal Nerve Fiber Layer Thickness in a Subset of Karachi (Pakistan) Population

Optical coherence tomography (OCT) is a technique that allows in vivo imaging of ocular tissue to a very high magnification. It is a non- invasive imaging technique providing high resolution dimensions of retinal nerve fiber layer (RNFL) thickness, macular thickness and optic nerve head measurements [1-4]. Many studies suggest that the RNFL and macular thickness show discrepancy among different ethnic groups [5-7]. A study by Grover et al in Florida suggested the mean RNFL thickness of 166.9±20.9 µm [5]. Whereas, Appukuttan et al from India found mean RNFL thickness of 101.43±8.63 µm in their population [6]. O’ Rese et al did their study in Miami among different ethnic groups and found significant difference in their mean RNFL thickness (p=<0.001). They found 93.9±1.2 µm for Africans, 96.4±1.1 µm for Chinese, 90.1±0.8 µm for Europeans and 95.6±1.4 µm for Hispanics [7]. Therefore, racial difference has to be given importance while diagnosing and following patients from different ethnic groups. Clinicians have to take into account the likelihood of RNFL thickness variation in different races in order to avoid any confusion in the diagnosis.
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Assessment of the retinal nerve fiber layer in individuals with obstructive sleep apnea

Assessment of the retinal nerve fiber layer in individuals with obstructive sleep apnea

Images that were obtained during eye movement, unfocused and/or poorly centered images, and those with a quality scan score of less than seven were excluded. Good-quality images from SLP were defined by residual anterior segment retardation of 15 nm or less and an atypical scan score not greater than 25. SLP parameters used as outcome measures for this investigation included nerve fiber indicator (NFI), temporal-superior- nasal-inferior-temporal (TSNIT) average, superior average, inferior average, and TSNIT standard deviation (SD). The NFI is a global measure based on the entire RNFL thickness map, and it is calculated using a support vector machine algorithm based on several RNFL parameters. NFI ranges from 1 to 100, with lower values (around <25) indicating normal RNFL. Although some studies indicate that the NFI is the most sensitive parameter of SLP for glaucoma diagnosis [39, 40], its calculation method is based on various parameters and therefore it does not directly indicate RNFL thickness.
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Ability of a neuro-ophthalmologist to estimate retinal nerve fiber layer thickness

Ability of a neuro-ophthalmologist to estimate retinal nerve fiber layer thickness

Figure 1 (A) Correlation graphs of retinal nerve fiber layer (RNFL) thickness estimations for physicians A, B, and C compared with optical coherence tomography (OCT). An exact reproducibility between physician and OCT results in a point plotted on the 45° graph line. A physician overestimation compared with OCT plots above the line, and an underestimation plots under the line. The further away a point is from the 45° line, the greater the difference between the RNFL estimation of the physician from the OCT. Below, percent of eyes (x-axis) that had RNFL thickness estimation agreement for each range in the y-axis between (B) two physicians and (C) physician and OCT.
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Correlation between central corneal thickness (CCT) and retinal nerve fiber layer (RNFL) analysis obtained by scanning laser polarimetry (GDX VCC) in primary open angle glaucoma patients (POAG) and POAG suspects

Correlation between central corneal thickness (CCT) and retinal nerve fiber layer (RNFL) analysis obtained by scanning laser polarimetry (GDX VCC) in primary open angle glaucoma patients (POAG) and POAG suspects

seated straight and made to focus on the target away from fixation during measurements.Repeated sets of three readings were taken until the values differed by less than 10 µ and the mean value taken for the study. Color stereoscopic optic disc photographs and red-free nerve fiber layer photographs were captured on the Zeiss fundus camera. Baseline standard achromatic perimetry on the Humphrey field analyzer using the 24-2 testing protocol by Swedish interactive threshold algorithm standard strategy was performed .

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Age-related changes in the peripheral retinal nerve fiber layer thickness

Age-related changes in the peripheral retinal nerve fiber layer thickness

to 6 mm distance from the optic disc were evaluated, because the data collected beyond this distance were almost null in groups 2 and 3. Figure 3 shows three representa- tive composite images obtained from different age groups containing the RNFL thickness data. Table 1 presents the peripheral RNFL thickness (mean ± SD) at 6 mm from the optic disc (nasally and temporally) in three age groups. Our group comparison detected an age-related decline in the peripheral RNFL thickness (the Kruskal–Wallis one way analysis of variance on ranks, P = 0.002 and P = 0.001 for nasal and temporal sides, respectively). As also illus- trated in Figure 4, the age-related decline detected in the peripheral RNFL thickness was 5.7-fold and 1.3-fold for nasal and temporal sides, respectively. Note that perhaps due to lower thickness of the nerve fiber layer in the retinal periphery, a prominent inter-individual variability was detectable, particularly for the nasal side with higher rate of age-related thinning.
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Form of Nerve Impulse and its Features of
Propagation along the Nerve Fiber cells in Living Systems

Form of Nerve Impulse and its Features of Propagation along the Nerve Fiber cells in Living Systems

It is known that the nerve system is very important organization in animal and humanity. The animal and humanity cannot live and move without the work of nerve system. Their a basic and important function is to transport the nerve information into all organizations to indicate their works and motions by virtue of the nerve information. This means that the features of nerve impulse and its t propagation play very important rules in life activities. However, a lot of problems for the nerve impulse, for example, its mechanism of form and generation, the features of its propagation and the effects and functions of nerve impulse, and so on, have not been researched systematically and deeply up to now. However, these problems are very important in nerve sciences and biology, thus we cannot understand and know clearly the theorem of work of each organization and their mechanism of cooperation and synergistic effects. Therefore, to research them are quite necessary. In order to explain these problems, we research and elucidate first the molecular structure of nerve cell in this paper. After this we study again and systematically the form of nerve impulse and its features of propagation along the nerve fiber cells.
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Diagnostic Methods for Optic Nerve Head and Retinal Nerve Fiber Evaluation in Glaucoma

Diagnostic Methods for Optic Nerve Head and Retinal Nerve Fiber Evaluation in Glaucoma

Glaucoma diagnosis primarily relies on Tonometry, Perimetry and Optic nerve head (ONH) evaluation. Tonometry involves measurement of IOP. IOP is one of the factors required for primary investigation. Perimetry relies on detection of the functional change that is loss of vision. This test measures side (peripheral) vision. Peripheral vision loss is the result of Glaucoma. ONH evaluation is used for detection of structural changes in ONH. IOP alone is not indicative of Glaucoma unless it is grossly abnormal. Visual Field loss is the late manifestation of the disease. In Glaucoma, structural changes in the ONH precede functional changes in the visual field. Comprehensive examination of the patient’s ONH helps in early Glaucoma diagnosis [4, 7]. Optic disc and Retinal nerve fiber layer (RNFL) assessment can be performed according to five rules that include the evaluation of optic disc size, rim shape and area, presence of RNFL loss, presence of parapapillary atrophy and presence of retinal or optic disc haemorrhages. By following these five rules, a thorough and systematic review of the optic disc and RNFL occurs. This improves the ability to diagnose and manage glaucoma [7]. Early treatment reduces rate of progression of the disease thus preventing visual field loss and blindness. Normal eyes show a characteristic configuration of rim thickness. This is called as ISNT rule. The neuroretinal rim is broadest in the inferior rim, followed by superior and nasal rims and is thinnest in the temporal region. The ISNT rule is useful in differentiating normal and glaucomatous optic nerves [8].
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Cone dysfunctions in retinitis pigmentosa with retinal nerve fiber layer thickening

Cone dysfunctions in retinitis pigmentosa with retinal nerve fiber layer thickening

Retinitis pigmentosa (RP) is one of the most common forms of hereditary retinal degeneration. It is characterized by the progressive loss of outer retinal function and may eventually lead to blindness, which is incurable. Integrity of the inner retinal layer has been suggested as a prerequisite for successful replacement/restoration therapy in the outer retinal layer (ORL). Optical coherence tomography (OCT) providing high- resolution, cross-sectional images which correspond to histological sections can be used in evaluation of the retinal nerve fiber layer (RNFL). 1 Recently, variability in
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NERVE FIBER DIAMETER MEASUREMENTS USING HEMATOXYLIN AND EOSIN STAINING AND BRIGHTFIELD MICROSCOPY TO ASSESS THE NOVEL METHOD OF CHARACTERIZING PERIPHERAL NERVE FIBER DISTRIBUTIONS BY GROUP DELAY

NERVE FIBER DIAMETER MEASUREMENTS USING HEMATOXYLIN AND EOSIN STAINING AND BRIGHTFIELD MICROSCOPY TO ASSESS THE NOVEL METHOD OF CHARACTERIZING PERIPHERAL NERVE FIBER DISTRIBUTIONS BY GROUP DELAY

Peripheral neuropathies are a set of common diseases that affect the peripheral nervous system, causing damage to vital connections between various parts of the body and the brain and spinal cord. Different clinical conditions are known to selectively impact various size nerve fibers, which often makes it difficult to diagnose which peripheral neuropathy a patient might have. The nerve conduction velocity diagnostic test provides clinically useful information in the diagnosis of some peripheral neuropathies. This method is advantageous because it tends to be minimally invasive yet it provides valuable diagnostic information. However, this test does not determine characteristics of peripheral nerve fiber size distributions, and therefore does not show any detailed information regarding the nerve fibers within the nerve trunk. Being able to determine which nerve fibers are contributing to the evoked potential within a nerve trunk could provide additional information to clinicians for the diagnosis of specific pathologies of the peripheral nervous system, such as chronic inflammatory demyelinating polyneuropathy or early diabetic peripheral neuropathy. In this study, three rat sciatic nerves are sectioned and stained with hematoxylin and eosin in order to measure the nerve fiber diameters within the nerve trunk. Stained samples are viewed using brightfield microscopy and images are analyzed using ImageJ. Histograms were created to show the frequency of various nerve fiber diameters. The nerve fiber diameters measured during this research are consistent with the range of previously published diameter values and will be used to support continuing research for a novel method to characterize peripheral nerve fiber size distributions using group delay.
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Peripapillary Retinal Nerve Fiber Layer Thickness in Patients with Chronic Migraine

Peripapillary Retinal Nerve Fiber Layer Thickness in Patients with Chronic Migraine

Episodic migraine is defined as 0-14 attacks of headache days per month and chronic migraine is defined as 15 or more attack of headache days per month. 1 Although the etiology of migraine is unknown, several studies have shown diminished cerebral blood flow during migraine attacks in the occipital hemisphere and also hypoperfusion of retina and optic nerve resulting in ganglion cell loss. 8.9 The retinal nerve fiber layer (RNFL) contains the axon of the retinal ganglion cells. The chronic attacks of migraine which is characterized by recurrent vasospasms and focal ischemia could explain structural optic nerve and retina damage with subsequent reduction in peripapillary RNFL. 10,11
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Peripapillary retinal nerve fiber layer and foveal thickness in hypermetropic anisometropic amblyopia

Peripapillary retinal nerve fiber layer and foveal thickness in hypermetropic anisometropic amblyopia

observed in this condition is still under investigation. The loss of vision is thought to be secondary to abnormal relationships of the neuronal network within the primary visual cortex. Nevertheless, it has been hypothesized that amblyopia may affect the postnatal maturation of the retina, including the postnatal reduction of retinal ganglion cells, which could lead to a measurable increase in retinal nerve fiber layer (RNFL) thickness. Interestingly enough, where some studies have found increased RNFL thickness in amblyopic eyes, others have not. 13–15 Red-free ophthalmoscopy, scanning
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Normal myelination of anatomic nerve fiber bundles: MR analysis

Normal myelination of anatomic nerve fiber bundles: MR analysis

It is difficult to distinguish fiber bundles from sur- rounding tissue by MR imaging in adults. This is because the white matter surrounding each fiber bun- dle has the same signal intensity as the fiber bundle. However, some fiber bundles are distinguishable by MR imaging after growth. Curnes et al (19) used the term compact to describe those fiber bundles in adults that have low signal intensity on T2-weighted images (the posterior and anterior limbs of the inter- nal capsule, the anterior commissure, the mamillotha- lamic tract, the fornix, the splenium and genu of the corpus callosum, the optic radiation, the optic tract, the superior frontooccipital fascicles, the cingulum, the uncinate fascicles, and the superior longitudinal fascicles). These authors considered the high density of the fiber bundles and the thick myelin sheaths to be the reasons that fiber bundles have lower signal in- tensity than surrounding white matter.
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Changes in retinal nerve fiber layer and optic disc algorithms by optical coherence tomography in glaucomatous Arab subjects

Changes in retinal nerve fiber layer and optic disc algorithms by optical coherence tomography in glaucomatous Arab subjects

Despite the recent introduction of spectral domain OCT, Stratus OCT 3000 (Carl Zeiss Meditec, Inc, Dublin, CA, USA) is one of the new generation of instruments with improved capabilities. The number of measurements per scan was increased up to 768 A-scans per image, and the axial resolution improved from 100 µ to 10 µ , in order to enhance the ease of use of the instrument. In addition, the Stratus OCT also incorporates 18 different protocols that are used for image acquisition, and an algorithm to assess the optic nerve head (ONH). It is also equipped with multiple RNFL and ONH asymmetry parameters that are used for detection of glaucoma.
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Managing elevated intraocular pressure in a patient with optic nerve hypoplasia

Managing elevated intraocular pressure in a patient with optic nerve hypoplasia

ONH visual field defects may mimic that caused by processes that cause progressive degeneration, such as glaucoma. In that the patient presented here demonstrated bilateral superior arcuate scotomas, retinal nerve fiber layer loss, and elevated intraocular pressure, there existed a clinical conundrum: determining whether the findings were secondary to progressive nerve fiber layer damage from glaucoma, or longstanding and due to ONH, or a combina- tion of both. In this situation, the only way to determine etiology would be to allow for progression by leaving the
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Intermediate filaments of zebrafish retinal and optic nerve astrocytes and Müller glia: differential distribution of cytokeratin and GFAP

Intermediate filaments of zebrafish retinal and optic nerve astrocytes and Müller glia: differential distribution of cytokeratin and GFAP

membrane and contributing to the bundled nerve fiber and inner plexiform layers. According to Watanabe and Raff [15], a similar situation exists in mammalian retina with respect to non-Müller astrocytes entering the retina from the optic nerve along retinal vasculature, and in the mature retina, locating near the retinal vasculature and nerve fiber layer (although mammalian astrocytes do express GFAP and not cytokeratin). Because of the apparent absence of GFAP expression by any cell type in the zebrafish optic nerve - either injured or uninjured - studies of the role astrocytes may play during ONR in
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Analysis of Optic Disc and Vertical Cup Disc Ratio among Glaucoma Suspects in a Black Population

Analysis of Optic Disc and Vertical Cup Disc Ratio among Glaucoma Suspects in a Black Population

The subjects included in the study were glaucoma suspects aged 18 years and above with open angles on gonioscopy (grade 3 and 4 Shaffers’ system) consenting to the study as well as those with normal central visual field and signal strength above 5 on optical coherence tomography testing. The participant’s pupils were dilated using tropicamide 1% and phenylephrin 2.5%. A slit lamp binocular indirect ophthalmoscopy using +78D (Volks) lens was used to examine the optic nerve head and retinal nerve fiber layer. Participants without superficial splinter hemorrhages, focal loss of neuroretinal rim (notching), generalized loss of neuroretinal rim (VCDR ≥0.5), cup-disc ratio asymmetry (≥ 0.2) or loss of retinal nerve fibers proceeded with the study. Also included were participants whose optic nerve head and nerve fibers appeared normal but had IOP greater than 21 mmHg. Red- free illumination of the posterior pole was also done to evaluate the retinal nerve fiber layer. Automated visual-field examination was done using 24-2 Swedish interactive thresholding algorithm standard visual-field examination ( Humphery visual-field analyzer, model 750). Participants with normal fields were then dilated for the OCT testing using tropicamide 1% and phenylephrine 2.5%. The same procedures for obtaining OCT measurements was followed for both eyes. Signal strength of 6 or higher is considered adequate for analysis of the results.
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