Nerve Fiber Bundles Research Articles

Reflectance Speckle of Retinal Nerve Fiber Layer Reveals Axonal Activity

This study investigated the retinal nerve fiber layer (RNFL) reflectance speckle and tested the hypothesis that temporal change of RNFL speckle reveals axonal dynamic activity. RNFL reflectance speckle of isolated rat retinas was studied with monochromatic illumination. A series of reflectance images was collected every 5 seconds for approximately 15 minutes. Correlation coefficients (CC) of selected areas between a reference and subsequent images were calculated and plotted as a function of the time intervals between images. An exponential function fit to the time course was used to evaluate temporal change of speckle pattern. To relate temporal change of speckle to axonal activity, in vitro living retina perfused at a normal (34°C) and a lower (24°C) temperature, paraformaldehyde-fixed retina, and retina treated with microtubule depolymerization were used. RNFL reflectance was not uniform; rather nerve fiber bundles had a speckled texture that changed with time. In normally perfused retina, the time constant of the CC change was 0.56 ± 0.26 minutes. In retinas treated with lower temperature and microtubule depolymerization, the time constants increased by two to four times, indicating that the speckle pattern changed more slowly. The speckled texture in fixed retina was stationary. Fixation stops axonal activity; treatments with either lower temperature or microtubule depolymerization are known to decrease axonal transport. The results obtained in this study suggest that temporal change of RNFL speckle reveals structural change due to axonal activity. Assessment of RNFL reflectance speckle may offer a new means of evaluating axonal function.

The Effects of Macular Ischemia on Visual Acuity in Diabetic Retinopathy

To investigate the impact of diabetic macular ischemia (DMI) on visual acuity (VA), through the analysis of novel fluorescein angiography (FA) parameters. Data were retrospectively collected over a 6-month period. DMI severity was graded using Early Treatment Diabetic Retinopathy Study (ETDRS) protocols. Custom software was used to quantify areas of the foveal avascular zone (FAZ), and of capillary nonperfusion over the papillo-macular nerve fiber layer bundle, and temporal macula, and associations tested with VA. A total of 488 patients with type 2 diabetes mellitus and FAs of sufficient quality to allow detailed quantitative analyses were included. ETDRS-DMI SEVerity was graded as: none, 39.7%; questionable, 18.4%; mild, 25.2%; moderate, 11.0%; and severe, 5.6%. Median FAZ areas were 0.19 mm(2) (interquartile range [IQR], 0.13-0.25); 0.25 mm(2) (IQR, 0.18-0.32); 0.27 mm(2) (IQR, 0.19-0.38); 0.32 mm(2) (IQR, 0.25-0.54); and 0.78 mm(2) (IQR, 0.60-1.32), respectively, and were significantly different between all grades (P < 0.002), apart from "questionable" versus "mild" grades. Significant association of VA to FAZ area was observed only in the moderate (β = 0.406, SE = 0.101, P = 0.001) and severe (β = 0.299, SE = 0.108, P = 0.006) subgroups, but not in milder ETDRS-DMI grades. A strong association with VA was observed in cases with papillomacular ischemia (β = 1.123, SE = 0.355, P = 0.005), independent of FAZ size or the presence of macular edema. Diabetic macular ischemia is associated with reduced VA in eyes with moderate to severe ETDRS-DMI grades of ischemia but preserved in milder grades. In addition, we describe the independent association of papillomacular nerve fiber bundle ischemia with reduced VA.

Fiber density estimation from single q-shell diffusion imaging by tensor divergence

Diffusion-weighted magnetic resonance imaging provides information about the nerve fiber bundle geometry of the human brain. While the inference of the underlying fiber bundle orientation only requires single q-shell measurements, the absolute determination of their volume fractions is much more challenging with respect to measurement techniques and analysis. Unfortunately, the usually employed multi-compartment models cannot be applied to single q-shell measurements, because the compartment's diffusivities cannot be resolved. This work proposes an equation for fiber orientation densities that can infer the absolute fraction up to a global factor. This equation, which is inspired by the classical mass preservation law in fluid dynamics, expresses the fiber conservation associated with the assumption that fibers do not terminate in white matter. Simulations on synthetic phantoms show that the approach is able to derive the densities correctly for various configurations. Experiments with a pseudo ground truth phantom show that even for complex, brain-like geometries the method is able to infer the densities correctly. In-vivo results with 81 healthy volunteers are plausible and consistent. A group analysis with respect to age and gender show significant differences, such that the proposed maps can be used as a quantitative measure for group and longitudinal analysis.

Small fibre pathology in patients with fibromyalgia syndrome

Fibromyalgia syndrome is a clinically well-characterized chronic pain condition of high socio-economic impact. Although the pathophysiology is still unclear, there is increasing evidence for nervous system dysfunction in patients with fibromyalgia syndrome. In this case-control study we investigated function and morphology of small nerve fibres in 25 patients with fibromyalgia syndrome. Patients underwent comprehensive neurological and neurophysiological assessment. We examined small fibre function by quantitative sensory testing and pain-related evoked potentials, and quantified intraepidermal nerve fibre density and regenerating intraepidermal nerve fibres in skin punch biopsies of the lower leg and upper thigh. The results were compared with data from 10 patients with monopolar depression without pain and with healthy control subjects matched for age and gender. Neurological and standard neurophysiological examination was normal in all patients, excluding large fibre polyneuropathy. Patients with fibromyalgia syndrome had increased scores in neuropathic pain questionnaires compared with patients with depression and with control subjects (P < 0.001 each). Compared with control subjects, patients with fibromyalgia syndrome but not patients with depression had impaired small fibre function with increased cold and warm detection thresholds in quantitative sensory testing (P < 0.001). Investigation of pain-related evoked potentials revealed increased N1 latencies upon stimulation at the feet (P < 0.001) and reduced amplitudes of pain-related evoked potentials upon stimulation of face, hands and feet (P < 0.001) in patients with fibromyalgia syndrome compared to patients with depression and to control subjects, indicating abnormalities of small fibres or their central afferents. In skin biopsies total (P < 0.001) and regenerating intraepidermal nerve fibres (P < 0.01) at the lower leg and upper thigh were reduced in patients with fibromyalgia syndrome compared with control subjects. Accordingly, a reduction in dermal unmyelinated nerve fibre bundles was found in skin samples of patients with fibromyalgia syndrome compared with patients with depression and with healthy control subjects, whereas myelinated nerve fibres were spared. All three methods used support the concept of impaired small fibre function in patients with fibromyalgia syndrome, pointing towards a neuropathic nature of pain in fibromyalgia syndrome.

High-Resolution Imaging of Retinal Nerve Fiber Bundles in Glaucoma Using Adaptive Optics Scanning Laser Ophthalmoscopy

To detect pathologic changes in retinal nerve fiber bundles in glaucomatous eyes seen on images obtained by adaptive optics (AO) scanning laser ophthalmoscopy (AO SLO). Prospective cross-sectional study. Twenty-eight eyes of 28 patients with open-angle glaucoma and 21 normal eyes of 21 volunteer subjects underwent a full ophthalmologic examination, visual field testing using a Humphrey Field Analyzer, fundus photography, red-free SLO imaging, spectral-domain optical coherence tomography, and imaging with an original prototype AO SLO system. The AO SLO images showed many hyperreflective bundles suggesting nerve fiber bundles. In glaucomatous eyes, the nerve fiber bundles were narrower than in normal eyes, and the nerve fiber layer thickness was correlated with the nerve fiber bundle widths on AO SLO (P < .001). In the nerve fiber layer defect area on fundus photography, the nerve fiber bundles on AO SLO were narrower compared with those in normal eyes (P < .001). At 60 degrees on the inferior temporal side of the optic disc, the nerve fiber bundle width was significantly lower, even in areas without nerve fiber layer defect, in eyes with glaucomatous eyes compared with normal eyes (P = .026). The mean deviations of each cluster in visual field testing were correlated with the corresponding nerve fiber bundle widths (P = .017). AO SLO images showed reduced nerve fiber bundle widths both in clinically normal and abnormal areas of glaucomatous eyes, and these abnormalities were associated with visual field defects, suggesting that AO SLO may be useful for detecting early nerve fiber bundle abnormalities associated with loss of visual function.

Akzidentelle Methylenblau-Färbung kornealer Nerven

A 10-year-old child presented after accidental exposure of the left eye to a blue hair dye containing methylene blue. Mild ocular surface changes and a selective blue staining of the usually invisible corneal nerve fibre bundles were present. Corneal sensitivity was reduced. Despite copious lubrication a transient neurotrophic keratitis developed which did not resolve until corneal sensitivity became normal 2 weeks later. Association of mild chemical burns with neurotrophic keratitis is unusual but is of high clinical relevance as keratitis is a vision-threatening complication.

Histopathological Changes in the Periphery of the Sciatic Nerve of Rats after Knee Joint Immobilization

[Purpose] This study was performed to investigate the histological changes that occur in the periphery of the sciatic nerve in rats undergoing knee immobilization. [Subjects and Methods] 29 male 9-week-old Wistar rats were divided randomly into a control group (C group, n = 7) and an immobilized group (I group, n = 22). The animals in the I group had the left knee joint immobilized in maximal flexion with plaster casts for two weeks. After the experimental period, we obtained cross-sections of tissues from the center of the left thigh, and the periphery of the sciatic nerve was observed under an optical microscope after hematoxylin-eosin staining. [Results] In contrast to the rats of C group, the rats in I group showed adherence between the bundle of nerve fibers and perineurium, as well as thickening of the perineurium. These histological changes were statistically significant. [Conclusions] Immobilization of the knee joints of rats resulted in characteristic histological changes in the connective tissue around the sciatic nerve.

Innervation and Immunohistochemical Characteristics of Epididymis in Alpaca Camelid (Vicugna Pacos)

Alpacas (Vicugna pacos) are domesticated camelids indigenous to south America and recently also bred in Europe and Italy for their high quality wool. There is little data available regarding the innervation of the male reproductive tract of this species. In the present study, the distribution of protein gene product 9.5 (PGP 9.5), neuropeptide Y (NPY), tyrosine hydroxilase (TH), calcitonin gene related peptide (CGRP) and substance P (SP) was analyzed in the epididymis by using immunohistochemical methods. Specimens of the caput, corpus and cauda epididymis were fixed in Bouin’s fluid and processed for immunohistochemistry analysis with primary antibodies against PGP 9.5, NPY, TH, CGRP and SP. Immunopositivity to PGP 9.5 and TH and NPY was observed in nerve fibre bundles and in single nerve fibres contained into the peritubular connective tissue. Many TH and NPY immunopositive cells were found to innervate blood vessels. Rare CGRP and SP immunopositive nerves were observed. Several PGP 9,5 and NPY immunopositive epithelial cells were observed in the caput epididymis. The results of the present study suggest a role for the innervations in modulate reproductive functions in the alpaca epididymis.

Structural-functional dissociation in glaucoma: An attempt to end controversy

Dear Editor, We read with interest the article titled “Evidence-based approach to glaucoma management” by Garudadri et al.[1] Standard automated perimetry (SAP) is the current standard in glaucoma diagnosis, but 20-40% retinal ganglion cells could be lost before a visual field defect could be picked up by SAP. The reported sensitivity and specificity of image technologies and their agreement with each other are far from ideal. Brain and eye have adaptive strategies to compensate scotoma. Safran and Landis[2] in a review article described the effects of plasticity in the adult visual cortex. Plasticity plays a crucial role in recovery from damage to the visual system. Cortical remapping generates a filling-in of visual field defects. Cortical rearrangement following lesions in the visual pathways helps to compensate for gaps in perception. Filling-in is a major cause of failure of patients with simple chronic glaucoma to recognize their visual defects at an early stage. Qing et al.,[3] have documented that more affected the visual field (SAP), the less affected the functional magnetic resonance image response. This phenomenon may imply a replasticity or a compensatory mechanism of the visual pathway. Peripheral scotoma may have a potentiating effect on the central reserved visual field. Decreased retina input may result in replasticity of the cortical neurons and enhance the information processing and integrity ability of the visual cortex. Measurement of blue chromatic thresholds in the macular region might make it possible to detect functional damage due to glaucoma prior to morphological changes of the optic nerve head of glaucoma patients. Probably a combination of decreased peripheral sensitivity with increased central retinal sensitivity may be suggestive of early glaucoma. Alzheimer's disease and Parkinson's disease cause retinal nerve fiber loss (RNFL). Evidence shows that microtubules in nerve fiber bundles are the major contributors for retinal nerve fiber layer birefringence, and microtubules are expected to disappear after the ganglion cells die. It remains to be clarified whether the time lag between cell death and microtubules disappearance or other subcellular changes differ between primary open angle glaucoma (POAG) and primary angle closure glaucoma. Preferred retinal locus (PRL) and oculomotor re-referencing are adaptive strategies of eye to compensate scotoma.[4] A PRL can be defined as a discrete retinal area that contains the center of target image for greater than 20% of a fixation interval. Oculomotor re-referencing is a phenomenon seen in patients who describe themselves as looking straight ahead when they are fixating with PRL (i.e., when the eye is not in the primary position). Fixation instability is a feature documented in early and moderate POAG.[5] This may be considered as an evidence for ocular adaptive strategy to compensate scotoma because eccentric fixation induces instability. Probably a combination of RNFL and recent onset fixation instability may improve sensitivity and specificity of image technologies. In conclusion, we agree with the authors advice that good history taking, proper clinical examination, documentation of details, supplemented with appropriate investigations, counseling, and proper follow-up enhance the care of the patient and family.

Intraosseous Schwannoma Originating in Inferior Alveolar Nerve: A Case Report

Schwannomas (neurilemmomas) are benign neoplasms derived from Schwann cells of the neurilemma and appear most frequently on the auditory nerve or peripheral nerves of the skin. They arise in the oral and maxillofacial region infrequently, and very rarely in the center of the jaw. We herein present a case of a rare mandibular intraosseous schwannoma derived from the main trunk of the inferior alveolar nerve in a 33-year-old man. Fusiform expansion in the mandibular canal was observed and a mass showing the target sign in the mandibular canal was confirmed on T2-weighted and Gd contrastenhanced T1-weighted MRI. Based on these findings, an inferior alveolar nerve-derived schwannoma or other benign nervous system neoplasm was diagnosed. A buccal side cortical bone flap in the mandibular molar region was removed to expose the mass, which was then peeled away from the nerve fibers and completely removed. Some inferior alveolar nerve fibers that were connected to the mass were removed at the same time, but the remaining nerve fiber bundle was preserved. Histopathology confirmed the diagnosis of a schwannoma with Antoni type A and Antoni type B regions. Although the patient experienced extremely mild paresthesia in the skin over the mental region and mental foramen at immediately after surgery, this had almost entirely disappeared at 7 years and 4 months later, and there has been no tumor recurrence.

Retina imaging by using compact line scanning quasi-confocal ophthalmoscope

A compact line scanning quasi-confocal ophthalmoscope (LSO) is presented in this letter. Compared with a conventional scanning laser ophthalmoscope (SLO), the bench-top LSO significantly reduces the size, complexity, and cost of SLO utility with routine use. The LSO uses one moving part to produce high-contrast and high-resolution quasi-confocal images with nearly the same performance as a SLO. The LSO has a moderate field of view (~10o), which enables images of the macula, the optic nerve head, and other targets to be obtained more quickly and efficiently. An image of the optic nerve head is taken in a preliminary investigation on human subjects. Individual nerve fiber bundles and vessels are resolved at a shallow depth, with a lateral resolution of nearly 10 \mu m.

Adaptive optics technology for high-resolution retinal imaging.

Adaptive optics (AO) is a technology used to improve the performance of optical systems by reducing the effects of optical aberrations. The direct visualization of the photoreceptor cells, capillaries and nerve fiber bundles represents the major benefit of adding AO to retinal imaging. Adaptive optics is opening a new frontier for clinical research in ophthalmology, providing new information on the early pathological changes of the retinal microstructures in various retinal diseases. We have reviewed AO technology for retinal imaging, providing information on the core components of an AO retinal camera. The most commonly used wavefront sensing and correcting elements are discussed. Furthermore, we discuss current applications of AO imaging to a population of healthy adults and to the most frequent causes of blindness, including diabetic retinopathy, age-related macular degeneration and glaucoma. We conclude our work with a discussion on future clinical prospects for AO retinal imaging.

Neurobiology of developmental dyslexia Part 2: A review of magnetic resonance imaging (MRI) studies of the corpus callosum

This paper forms part two of a review of the neurobiology of developmental dyslexia (DD) and here the focus is on magnetic resonance imaging (MRI) of the corpus callosum (CC) of dyslexic and non-dyslexic subjects. The CC is a bundle of nerve fibres connecting the left and the right hemisphere of the brain. Due to the role of this structure in inter-hemispheric transfer and integration between thehemispheres, the CC is significant in the search for the neurobiological basis of DD. (S Afr Optom 2012 71(1) 39-45)

Neurobiology of developmental dyslexia Part 2: A review of magnetic resonance imaging (MRI) studies of the corpus callosum

This paper forms part two of a review of the neurobiology of developmental dyslexia (DD) and here the focus is on magnetic resonance imaging (MRI)of the corpus callosum (CC) of dyslexic and non-dyslexic subjects. The CC is a bundle of nerve fibres connecting the left and the right hemisphere of the brain. Due to the role of this structure in inter-hemispheric transfer and integration between the hemispheres, the CC is significant in the search for the neurobiological basis of DD. (S Afr Optom 2012 71(1) 39-45)

Effect of axonal micro-tubules on the morphology of retinal nerve fibers studied by second-harmonic generation

Many studies suggest that the degradation of microtubules in the retinal ganglion cells may be an early event in the progression of glaucoma. Because reflectance and birefringence of the retinal nerve fibers arise primarily from microtubules, the optical properties have been intensively studied for early detection of the disease. We previously reported a novel nonlinear optical signal from axonal microtubules for visualizing the retinal nerve fibers, namely second-harmonic generation (SHG). We demonstrate the use of axonal SHG to investigate the effect of microtubules on the morphology of the retinal nerve fiber bundles. Time-lapse SHG imaging of ex vivo rat retinal flat mounts was performed during pharmacological treatment of nocodazole, and the intensity of axonal SHG and the changes in nerve fiber bundle morphology were monitored. We found that the microtubule disruption does not lead to immediate modification in the morphology of the nerve fibers. Our results indicate that microtubular SHG may provide a useful means for sensitive detection of axonal injuries. Since the intrinsic radiation depends on the regular architecture of the cytoskeleton element as maintained by active cellular regulations, the intensity of signal reflects the health of the retinal ganglion cell axons.

A mathematical model for describing the retinal nerve fiber bundle trajectories in the human eye: Average course, variability, and influence of refraction, optic disc size and optic disc position

Previously we developed a mathematical model for describing the retinal nerve fiber bundle trajectories in the superior-temporal and inferior-temporal regions of the human retina, based on traced trajectories extracted from fundus photographs. Aims of the current study were to (i) validate the existing model, (ii) expand the model to the entire retina and (iii) determine the influence of refraction, optic disc size and optic disc position on the trajectories. A new set of fundus photographs was collected comprising 28 eyes of 28 subjects. From these 28 photographs, 625 trajectories were extracted. Trajectories in the temporal region of the retina were compared to the existing model. In this region, 347 of 399 trajectories (87%) were within the 95% central range of the existing model. The model was extended to the nasal region. With this extension, the model can now be applied to the entire retina that corresponds to the visual field as tested with standard automated perimetry (up to approximately 30° eccentricity). There was an asymmetry between the superior and inferior hemifields and a considerable location-specific inter-subject variability. In the nasal region, we found two “singularities”, located roughly at the one and five o'clock positions for the right optic disc. Here, trajectories from relatively widespread areas of the retina converge. Associations between individual deviations from the model and refraction, optic disc size and optic disc position were studied with multiple linear regression. Refraction (P = 0.021) and possibly optic disc inclination (P = 0.09) influenced the trajectories in the superior-temporal region.

Distribution of Damage to the Entire Retinal Ganglion Cell Pathway

OBJECTIVES To test the hypothesis that the amount and distribution of glaucomatous damage along the entire retinal ganglion cell-axonal complex (RGC-AC) can be quantified and to map the RGC-AC connectivity in early glaucoma using automated image analysis of standard spectral-domain optical coherence tomography. METHODS Spectral-domain optical coherence tomography volumes were obtained from 116 eyes in 58 consecutive patients with glaucoma or suspected glaucoma. Layer and optic nerve head (ONH) analysis was performed; the mean regional retinal ganglion cell layer thickness (68 regions), nerve fiber layer (NFL) thickness (120 regions), and ONH rim area (12 wedge-shaped regions) were determined. Maps of RGC-AC connectivity were created using maximum correlation between regions' ganglion cell layer thickness, NFL thickness, and ONH rim area; for retinal nerve fiber bundle regions, the maximum "thickness correlation paths" were determined. RESULTS The mean (SD) NFL thickness and ganglion cell layer thickness across all macular regions were 22.5 (7.5) μm and 33.9 (8.4) μm, respectively. The mean (SD) rim area across all ONH wedge regions was 0.038 (0.004) mm2. Connectivity maps were obtained successfully and showed typical nerve fiber bundle connectivity of the RGC-AC cell body segment to the initial NFL axonal segment, of the initial to the final RGC-AC NFL axonal segments, of the final RGC-AC NFL axonal to the ONH axonal segment, and of the RGC-AC cell body segment to the ONH axonal segment. CONCLUSIONS In early glaucoma, the amount and distribution of glaucomatous damage along the entire RGC-AC can be quantified and mapped using automated image analysis of standard spectral-domain optical coherence tomography. Our findings should contribute to better detection and improved management of glaucoma.

Wavelength-Dependent Change of Retinal Nerve Fiber Layer Reflectance in Glaucomatous Retinas

Retinal nerve fiber layer (RNFL) reflectance is often used in optical methods for RNFL assessment in clinical diagnosis of glaucoma, yet little is known about the reflectance property of the RNFL under the development of glaucoma. This study measured the changes in RNFL reflectance spectra that occurred in retinal nerve fiber bundles with different degrees of glaucomatous damage. A rat model of glaucoma with laser photocoagulation of trabecular meshwork was used. Reflectance of the RNFL in an isolated retina was measured at wavelengths of 400-830 nm. Cytostructural distribution of the bundles measured optically was evaluated by confocal imaging of immunohistochemistry staining of cytoskeletal components, F-actin, microtubules, and neurofilaments. RNFL reflectance spectra were studied in bundles with normal-looking appearance, early F-actin distortion, and apparent damage of all cytoskeletal components. Changes of RNFL reflectance spectra were studied at different radii (0.22, 0.33, and 0.44 mm) from the optic nerve head (ONH). Bundles in 30 control retinas and 41 glaucomatous retinas were examined. In normal retinas, reflectance spectra were similar along the same bundles. In glaucomatous retinas, reflectance spectra changed along bundles with the spectra becoming flatter as bundle areas approached the ONH. Elevation of intraocular pressure (IOP) causes nonuniform changes in RNFL reflectance across wavelengths. Changes of reflectance spectra occur early in bundles near the ONH and prior to apparent cytoskeletal distortion. Using the ratio of RNFL reflectance measured at different wavelengths can provide early and sensitive detection of glaucomatous damage.

Average nerve width measurement obtained by optical coherence tomography and glaucoma

AbstractPurpose This study will investigate the optic nerve head (ONH) using optical coherence tomography (OCT) and analyze the correlations between neuroretinal rim and optic disc‐cup structure in order to apply the finding in glaucoma.Methods This cross‐sectional study enrolled 157 healthy subjects firstly and analyzed one randomly selected eye in each subject. The measurements for ONH parameters, including neuroretinal rim and optic disc‐cup structure (disc or cup areas and cup‐to‐disc ratios), were taken by a single experienced operator. The associations among neuroretinal rim and optic disc‐cup structure were determined. Independent parameter was further tested in 25 glaucomatous patients.Results In healthy subjects, average cup‐to‐disc area ratio estimated was 0.2827 ± 0.1134 (95% CI; range, 0.263 to 0.302); rim area (vertical cross section), vertical integrated rim area, horizontal integrated rim width, and rim area positively correlated with disc area (p&lt;0.05); rim area (vertical cross section), average nerve width, and vertical integrated rim area negatively correlated with cup area (p&lt;0.05); and rim area (vertical cross section), average nerve width, vertical integrated rim area, horizontal integrated rim width, and rim area negatively correlated with cup‐to‐disc ratios (p&lt;0.05). In further stepwise regression analysis, average nerve width was not associated with optic disc‐cup structure measurements (p&gt;0.05, F&lt;4.000) in healthy subjects. In glaucomatous patients, average nerve width was positively correlated with the mean deviation (dB) in standard automated perimetry (p&lt;0.001, r=0.709).Conclusion Average nerve width (the height of the nerve fiber bundle) is an independent rim parameter, and is helpful for the evaluation in glaucoma.

Effects of age and disc area on optical coherence tomography measurements and analysis of correlations between optic nerve head and retinal nerve fibre layer

BackgroundThe aim here was to investigate whether optic nerve head (ONH) parameters or retinal nerve fibre layer (RNFL) thickness correlate with age or disc area and whether the neuroretinal rim correlates with RNFL thickness.MethodsThis cross‐sectional study enrolled 133 healthy subjects and analysed one randomly selected eye of each subject. All measurements of ONH parameters (including neuroretinal rim, disc and cup areas and cup‐to‐disc ratios) and RNFL thickness (global and quadrants) were taken by a single experienced operator using optical coherence tomography (OCT).ResultsOf the rim parameters analysed, average nerve width (the height of the nerve fibre bundle) was independent of age or disc area (p > 0.05). Disc area correlated positively with cup area (p < 0.05) but not with cup‐to‐disc ratios (p > 0.05). Of the RNFL thickness measurements analysed, temporal RNFL was independent of both age and disc area (p > 0.05). According to the analysis of the correlation between RNFL thickness and neuroretinal rim, global or non‐temporal RNFL correlated positively with horizontal integrated rim width (p < 0.05, F > 4.000) and temporal RNFL was independent of all rim parameters (p > 0.05, F < 4.000).ConclusionAging effect on neuroretinal rim loss or RNFL thickness change is non‐uniform, and age is not a constant confounder when using OCT. The temporal RNFL is independent of age, disc area and neuroretinal rim.