Changes In Retinal Morphology Research Articles

High-Resolution Multimodal Imaging of Multiple Evanescent White Dot Syndrome

The integrity of macular morphology was examined in a patient with multiple evanescent white dot syndrome (MEWDS) diagnosed through clinical and investigational adaptive optics (AO) retinal imaging techniques. Imaging was performed during the acute and recovery phases to examine changes in retinal morphology, revealing characteristic small multifocal white dots in the perifoveal region and a granular appearance in the fovea. Fluorescein angiography revealed early and intermediate hyperfluorescence, and regions of decreased fundus autofluorescence were observed. Photoreceptor disruption was apparent during the acute phase and recurrence. Conventional multimodal imaging combined with AO imaging offers more insight into the pathology of MEWDS by providing complementary views of the retina throughout the acute phase, recovery, and recurrence.

Vitreal, retinal, and choroidal findings in active and scarred toxoplasmosis lesions: a prospective study by spectral-domain optical coherence tomography

The aim of our study was to investigate vitreal, retinal, and choroidal morphologic changes in active and scarred toxoplasmosis lesions using spectral-domain optical coherence tomography (SD-OCT). In this prospective study, 19 eyes of 15 consecutive patients with ocular toxoplasmosis were included. Complete ophthalmologic examination and SD-OCT were done at the initial visit and during follow-up. Retina and choroid SD-OCT protocols directed to macular area and lesions observed on clinical examination were used. Seventeen active lesions and 56 retinochoroidal scars were studied. In the acute phase, disruption, thickening, and hyper-reflectivity of the neurosensory retina with photoreceptor (PR) interruption and retinal pigment epithelial (RPE) elevation were found. The choroid became thickened and hyporeflective. During follow-up, neurosensory retinal layers thinning and disorganization, PR interruption, and RPE elevation and/or atrophy were demonstrated. The choroid returned to normal thickness and became more hyperreflective. Five active lesions presented with hyperreflective oval deposits within the vitreoretinal interface, adjacent to or far away from the lesions. During follow-up, the deposits became smaller, entered into the inner retina layers and faded with time until complete resolution. Multiple hyperreflective dots in the vitreous cavity, compatible with vitritis, and posterior hyaloid thickening were demonstrated in the acute phase, with complete resolution and detachment of the posterior hyaloid during follow-up. Four types of scars were specified according to outer retina-choroid interface changes; atrophic, elevated, deep, and combined (atrophic & elevated). Epiretinal membrane segments were found over active and scarred lesions. SD-OCT imaging showed toxoplasmic retinochoroidal lesions and scars to be complex and characterized acutely by thickening and disorganization of both the retina and underlying choroid, and following scar formation by varying degrees of thinning, often in conjunction with irregularity of the outer retinal layers.

Retinal morphological and functional changes in an animal model of retinitis pigmentosa

The P23H-1 transgenic rat carries a mutated mouse opsin gene, in addition to endogenous opsin genes, and undergoes progressive photoreceptor loss that is generally characteristic of human autosomal dominant retinitis pigmentosa (RP). Here, we examined morphological changes correlated with visual function that is comparable to clinical application in the pigmented P23H-1 rat retina as photoreceptor degeneration progressed. We found that rod function was compromised as early as postnatal day 28 and was a good indicator for tracking retinal degeneration. Cone function was normal and did not change until the thickness of the photoreceptor layer was reduced by 75%. Similar to the threshold versus intensity curves used to evaluate vision of RP patients, light-adaptation curves showed that cone thresholds depended on the number of remaining functioning cones, but not on its length of outer segments (OS). By 1 year of age, both rod and cone functions were significantly compromised. Correlating with early abnormal rod function, rods and related secondary neurons also underwent progressive degeneration, including shortening of inner and OS of photoreceptors, loss of rod bipolar and horizontal cell dendrites, thickening of the outer Müller cell processes, and reduced density of pre- and postsynaptic markers. Similar early morphological modifications were also observed in cones and their related secondary neurons. However, cone function was maintained at nearly normal level for a long period. The dramatic loss of rods at late stage of degeneration may contribute to the dysfunction of cones. Attention has to be focused on preserving cone function and identifying factors that damage cones when therapeutic regimes are applied to treat retinal degeneration. As such, these findings provide a foundation for future studies involving treatments to counter photoreceptor loss.

RETINAL NEOVASCULARIZATION SECONDARY TO PROLIFERATIVE DIABETIC RETINOPATHY CHARACTERIZED BY SPECTRAL DOMAIN OPTICAL COHERENCE TOMOGRAPHY

The purpose of this study was to characterize diabetic retinal neovascularization (NV) and accompanying retinal and vitreal morphologic changes using high-resolution spectral domain optical coherence tomography. A cross-sectional retrospective analysis was performed on 16 eyes of 14 nonconsecutive subjects with proliferative diabetic retinopathy that were seen between August 2011 and December 2011 at the New England Eye Center, Boston, MA. Patients who had NV of the disk, NV elsewhere, and intraretinal microvascular abnormalities were scanned using optical coherence tomography directly over the region of the abnormal vessels. Characteristic changes of the retinal vasculature, retina, and vitreous were seen in the 16 eyes with NV. This study describes optical coherence tomography characteristics of 1) NV of the disk, 2) NV elsewhere, 3) intraretinal microvascular abnormality, 4) NV causing traction without retinal detachment; and 5) NV causing traction with retinal detachment. The morphologic appearance of vitreous traction was found to be consistent with the previous histologic reports. It is possible to image diabetic NV using spectral domain optical coherence tomography and to visualize the spectrum of retinal, retinal vascular, and vitreal changes seen through these areas of abnormal retinal vasculature.

Treatment with 670 nm Light Up Regulates Cytochrome C Oxidase Expression and Reduces Inflammation in an Age-Related Macular Degeneration Model

Inflammation is an umbrella feature of ageing. It is present in the aged retina and many retinal diseases including age-related macular degeneration (AMD). In ageing and in AMD mitochondrial function declines. In normal ageing this can be manipulated by brief exposure to 670 nm light on the retina, which increases mitochondrial membrane potential and reduces inflammation. Here we ask if 670 nm exposure has the same ability in an aged mouse model of AMD, the complement factor H knockout (CFH−/−) where inflammation is a key feature. Further, we ask whether this occurs when 670 nm is delivered briefly in environmental lighting rather than directly focussed on the retina. Mice were exposed to 670 nm for 6 minutes twice a day for 14 days in the form of supplemented environmental light. Exposed animals had significant increase in cytochrome c oxidase (COX), which is a mitochondrial enzyme regulating oxidative phosphorylation.There was a significant reduction in complement component C3, an inflammatory marker in the outer retina. Vimetin and glial fibrillary acidic protein (GFAP) expression, which reflect retinal stress in Muller glia, were also significantly down regulated. There were also significant changes in outer retinal macrophage morphology. However, amyloid beta (Aβ) load, which also increases with age in the outer retina and is pro-inflammatory, did not change. Hence, 670 nm is effective in reducing inflammation probably via COX activation in mice with a genotype similar to that in 50% of AMD patients even when brief exposures are delivered via environmental lighting. Further, inflammation can be reduced independent of Aβ. The efficacy revealed here supports current early stage clinical trials of 670 nm in AMD patients.

Relationship between macular morphology and visual function in diabetic macular edema

To investigate the changes and relation between macular morphology and macular visual function in different degrees of diabetic macular edema. Seventy-eight eyes of 41 diabetic retinopathy patients were included and graded for diabetic macular edema as follows:31 were graded as no macular edema (NE), 26 as non-clinically significant macular edema (NCSME), and 21 as clinically significant macular edema (CSME). Best corrected visual acuity, macular sensitivity, and macular thickness of all included eyes were examed and quantified. Macular sensitivity and retinal fixation were investigated with MP-1 microperimetry. Optical coherence tomography (OCT) was used to quantify macular thickness. Macular thickness significantly increased and macular sensitivity markedly decreased from the NE to the CSME group (P < 0.01), Visual acuity obviously decreased in the CSME group (P < 0.01) compared to the NE and NCSME group, but there was no statistical difference between the NE group and NCSME group. Retinal fixation type was not significantly different among three groups. Visual acuity and macular sensitivity correlated significantly in these three groups (r = -0.751, P < 0.01; r = -0.583, P < 0.01; r = -0.679, P < 0.01). The correlations were noted between retinal sensitivity and macular thickness as well as between visual acuity and macular thickness in the CSME group (r = -0.465, P < 0.05; r = 0.599, P < 0.01), but not in the NE group or in the NCSME group. Patients will have retinal morphologic and functional changes in early stage of DME, both of which are significantly related as the disease develops. MP-1 microperimetry proved to be consistent with VA in the evaluation of visual function, and may be more sensitive to investigate the changes of macular visual function in the early stage of macular edema.

The observation of frequency domain optical coherence tomography in traumatic macular disease without fundus abnormalities

Objective To observe the macular image characteristics of frequency domain optical co- herent tomography （FD-OCT） in a series of patients with ocular trauma who complained of visual decline but with normal funds photography and funds fluorescein angiography （FFA）. Methods Retrospective case se- ties. 25 cases of out-patients who complained of visual decline with ocular trauma but which fundus and FFA examinations could not be found abnormal were enrolled in the study from December 2009 to December 2011 in our hospital. FD-OCT images of traumatic eyes （25 eyes） and the contralateral eyes without ocular trauma （25 eyes） were retrospectively analyzed. Retinal thickness and morphological changes at the macular fovea of FD - OCT images were compared between the traumatic eyes （ trauma group） and the contl＇alateral eyes without ocular trauma （ normal group）. The correlation between the LogMar best-corrected visual acuity and retinal thickness of the trauma group was evaluated. Results Retinal thickness in the macular fovea of the normal group and the trauma group were （ 192.81 ± 14.74）μm and （ 128±41.63） μm. Retinal thickness of the trauma group was significantly decreased comparing with normal group （ t = 5. 836, P 〈 0. 001 ）, and there was a negative correlation between the thickness of macular fovea and LogMar best-corrected visual acuity in the trauma group（r = -0. 689, P = 0. 001 ）. FD-OCT images showed both groups had normal macular curve. In the trauma group, the status of the inner and outer segments （IS/OS） photoreceptor junction and outer segments photoreceptor were all appeared damages ： the IS/OS junction line and outer segments photoreceptor were discontinuous in 6 cases （6 eyes） ; outer segments photoreceptor disappeared and IS/OS junc- tion line discontinuous accompanied by thinning of the retina in 11 cases （ 11 eyes） ; outer segments photore- ceptor and IS/OS junction line disappeared accompanied by retinal thickness significantly thinner in 8 cases （8 eyes）. Conclusion FD-OCT can display the photoreceptor microstructure changes of macular fovea, which can not be detected by routine examinations. The images may be useful for evaluation and clinical di- agnosis of traumatic macular disease. Key words: Ocular trauma; Macular disease ; Frequency domain ; Optical coherence tomography

Decrease of ATP by Mitochondrial m-calpain Inhibitory Peptide in the Rat Retinas

Activations of mitochondrial calpains cause apoptosis-inducing factor-dependent apoptosis of retinal photoreceptor cells in the Royal College of Surgeons (RCS) rat, an animal model of retinitis pigmentosa. In the present study, we attempted to develop specific inhibitors of mitochondrial calpains that would prevent the retinal degeneration. We examined the inhibitory potency of 20-mer peptides of the m-calpain for mitochondrial calpains activity, determined the inhibitory regions, and conjugated the cell-penetrating peptides (CPP). The cytotoxicity and delivery of the peptide was evaluated using mouse photoreceptor-derived 661W cells. After intravitreal injection of the peptide in RCS rats, we examined the peptide delivery to the retina, photoreceptor cell death numbers, responses of the electroretinogram (ERG), concentrations of intracellular ATP, and changes of retinal morphology. Results showed that one of the peptides inhibited the activity of the mitochondrial m-calpain. The HIV-1 tat-conjugated m-calpain peptide, HIV-Nm, could preserve the inhibitory potency of the mitochondrial m-calpain, and penetrate into the 661W cells. While intravitreal injection of HIV-Nm made it possible to deliver to the retina, it did not prevent photoreceptor cell death. Furthermore, it caused the ERG attenuation and the decrease in the intracellular ATP only a day after the injection. Although HIV-Nm did not cause histological change of the retina after 1 or 2 days of the administration, the morphological abnormality of the retina was observed after 3-14 days. Our results demonstrated that HIV-Nm failed to prevent the photoreceptor cell death, but rather caused the attenuation of ERG response and the decrease of ATP.

Functional Retinal Impairment in Type 1 Diabetic Patients without any Signs of Retinopathy

Purpose: To investigate functional and morphological retinal changes in the long-term follow-up in subjects with type 1 diabetes mellitus (DM1) without any signs of retinal vasculopathy. Methods: Functional testing included Humphrey Matrix perimetry (30-2 threshold program) and white-on-white Humphrey perimetry (HFA, 30-2 SITA standard), while retinal nerve fibre layer (RNFL) thickness was measured by scanning laser polarimetry with variable corneal birefringence compensator. Results: Data from 20 eyes of 20 subjects with DM1 were analysed. No changes of HFA mean deviation (MD: -2.20 ± 3.44 vs. -1.63 ± 2.47; p = 0.14) and pattern standard deviation (PSD: 2.50 ± 1.71 vs. 2.28 ± 1.36; p = 0.31), and Matrix MD (-1.06 ± 3.62 vs. -1.24 ± 2.99; p = 0.65) were found after 5 years. A significant change was found for Matrix PSD between baseline and the end of follow-up (2.76 ± 0.59 vs. 3.1 ± 0.68; p = 0.0078). RNFL parameters were not changed. A significant relationship was found between HbA1c levels and changes from baseline of Matrix PSD (R² 0.29, p = 0.02). Conclusions: Progressive retinal functional impairment could be detected in DM1 subjects by frequency doubling perimetry before the onset of any overt retinal vasculopathy and functional impairment seems to be significantly related to glycaemic control.

Quadrantal macular retinal thickness changes in strabismus subjects with abnormal binocular vision development

To investigate retinal morphological changes in strabismus patients with abnormal binocular vision development by comparing differences in quadrantal macular retinal thickness. Six strabismus patients (6 dominant and 5 non-dominant eyes) with abnormal binocular vision (mean age 22years), and 11 control subjects (11 dominant and 11 non-dominant eyes) (mean age 21years) were enrolled. Macular retinal thickness measurements were performed by optical coherence tomography, with total macular retinal (TMR) and ganglion cell complex (GCC) thicknesses measured in 3- and 6-mm regions in each quadrant. Measurement values were then used to determine quadrant ratios. Compared to the dominant eyes of the controls, the superior/inferior (S/I) ratio of the TMR thickness and GCC thickness in the 3-mm region was significantly lower in the dominant eyes of the strabismus group (P<0.05, each). The superior temporal/inferior temporal (ST/IT) ratio of the GCC thickness in the dominant eyes of the strabismus group was also significantly lower (P<0.01). Dominant eyes of the strabismus group with abnormal binocular vision development exhibited thinner superior temporal GCC thicknesses in the 3-mm region. Retinal ganglion cells in this region might be affected by efferent neural degeneration that originates in the visual pathway responsible for adaptations to the visual experience.

Defective FGF signaling causes coloboma formation and disrupts retinal neurogenesis

The optic fissure (OF) is a transient opening on the ventral side of the developing vertebrate eye that closes before nearly all retinal progenitor cell differentiation has occurred. Failure to close the OF results in coloboma, a congenital disease that is a major cause of childhood blindness. Although human genetic studies and animal models have linked a number of genes to coloboma, the cellular and molecular mechanisms driving the closure of the OF are still largely unclear. In this study, we used Cre-LoxP-mediated conditional removal of fibroblast growth factor (FGF) receptors, Fgfr1 and Fgfr2, from the developing optic cup (OC) to show that FGF signaling regulates the closing of the OF. Our molecular, cellular and transcriptome analyses of Fgfr1 and Fgfr2 double conditional knockout OCs suggest that FGF signaling controls the OF closure through modulation of retinal progenitor cell proliferation, fate specification and morphological changes. Furthermore, Fgfr1 and Fgfr2 double conditional mutant retinal progenitor cells fail to initiate retinal ganglion cell (RGC) genesis. Taken together, our mouse genetic studies reveal that FGF signaling is essential for OF morphogenesis and RGC development.

Optomotor and immunohistochemical changes in the juvenile S334ter rat

The aim of this study was to examine the temporal relationship between behaviorally measured visual thresholds, photoreceptor degeneration and dysfunction, synaptic and neuronal morphology changes in the retina in the S334ter line 4 rat. Specifically, we examined the optokinetic tracking (OKT) behavior in S334ter rats daily and found that OKT thresholds reflected normal values at eye opening but quickly reduced to a non-response level by postnatal day (P) 22. By contrast, the scotopic electroretinogram (ERG) showed a much slower degeneration, with substantial scotopic function remaining after P90 as previously demonstrated for this line of rats. Photopic b-wave amplitudes revealed functional levels between 70 and 100% of normal between P30 and P90. Histological evidence demonstrated that photoreceptor degeneration occurred over many months, with an outer nuclear layer (ONL) roughly half the thickness of a normal age-matched control at P90. Immunohistochemical analysis revealed a number of changes in retinal morphology in the Tg S334ter line 4 rat that occur at or before P40 including: elevated levels of rod opsin expression in the ONL, cone photoreceptor morphology changes, glial cell activation, inner retinal neuron sprouting, and microglial cell activation. Many of these changes were evident at P30 and in some cases as early as eye opening (P15). Thus, the morphological changes occurred in concert with or before the very rapid loss of the behavioral (OKT) responses, and significantly before the loss of photoreceptors and photoreceptor function.

SPECTRAL-DOMAIN OPTICAL COHERENCE TOMOGRAPHY IMAGING OF RETINAL CHANGES AFTER CONVENTIONAL MULTICOLOR LASER, SUBTHRESHOLD MICROPULSE DIODE LASER, OR PATTERN SCANNING LASER THERAPY IN JAPANESE WITH MACULAR EDEMA

To perform optical coherence tomography imaging of retinal healing after conventional multicolor laser, pattern scanning laser, or micropulse laser treatment and compare the characteristics of each method. This was a single-center interventional case series study. Twenty-nine patients with macular edema underwent laser photocoagulation. Changes of retinal morphology because of laser-tissue interaction were assessed within 3 months by using a spectral-domain optical coherence tomography. Immediately after conventional multicolor laser or pattern scanning laser treatment, a hyperreflective band appeared at the laser sites. The photoreceptor inner segment-outer segment line disappeared in all the patients treated with a conventional multicolor laser, but was intact in 22.2% (2/9 eyes) after pattern scanning laser. From 1 week to 1 month, the bands resolved. At 3 months, recovery of the inner segment-outer segment line surrounding the laser site was seen in all patients after conventional grid photocoagulation and pattern scanning laser. Retinal morphology did not change at any time during the observation period after subthreshold micropulse diode laser photocoagulation. The characteristic in vivo effects of retinal photocoagulation were monitored over time by spectral-domain optical coherence tomography. Changes of retinal morphology appeared less intense after pattern scanning laser than conventional grid laser treatment.

Changes in retinal ganglion cell morphology after optic nerve crush and experimental glaucoma

AbstractPurpose To study sequential changes in retinal ganglion cell (RGC) morphology in mice after induction of experimental glaucoma.Methods Experimental glaucoma was induced in mice that selectively express yellow fluorescent protein (YFP) in RGCs. Mice were sacrificed 1, 3 and 6 weeks after induction of glaucoma by bead injection. All YFP‐RGCs were identified in retinal whole‐mounts. Confocal images of randomly selected RGCs were quantified for somal fluorescence brightness, soma size, neurite outgrowth, and dendritic complexity (Sholl analysis).Results After 6 weeks of glaucoma, 31% of axons died, but there was no loss of YFP‐RGC bodies. In combined data from all timepoints, the RGC soma area was larger than control (P = 0.04, generalized estimating equation model). At 3 weeks, glaucoma RGCs had significantly larger values for dendritic structure and complexity than controls (P = 0.044), but no statistical difference was found at 6 weeks.Conclusion Despite the moderate loss of axons, significant changes in YFP‐RGC morphology were not observed after 6 weeks of follow‐up.

Rodent model of nonarteritic ischemic optic neuropathy and its electrophysiological evaluation

Our aim was to establish a rodent model of nonarteritic ischemic optic neuropathy (rNAION). To induce rNAION, after administration of Rose Bengal (RB) (2.5 mM), the small vessels of the left optic nerve were photoactivated using a 514-nm argon green laser with about 500-μm spot size for 12 s (RB-laser induction). To evaluate the induction, funduscopic examination, fluorescein angiography (FA), visualization of capillaries within the optic disc, histologic evaluation, and electrophysiological testing were performed. In the RB-laser-induction eyes, the optic disc became swollen on day 3 followed by atrophy on week 8. FA showed filling defects in the choroid and optic disc at an early stage, followed by hyperfluorescence at a late stage. The capillaries within the optic disc were reduced markedly. Histopathologic examination showed acellular nerve fiber layer (NFL) swelling anterior to the optic disc. The morphologic retinal changes were apparent only in the retinal ganglion cell (RGC) layer, with a reduction in the number of cells. Visually evoked potential (VEP) amplitude decreased significantly, but electroretinography (ERG) showed no significant difference. The positive scotopic threshold response (pSTR) was not reduced on the 1st day but was significantly reduced 3 days after induction. The findings are similar to human NAION. Therefore, RB-laser induction is well suited to establish the presence of rNAION.

Early signs of longitudinal progressive cone photoreceptor degeneration in achromatopsia

AimsTo characterise longitudinal progressive retinal changes in achromatopsia.MethodsUltrahigh-resolution spectral optical coherence tomography (Copernicus, 3 μm axial resolution) was used to obtain tomograms of the fovea from five children and three...

Comparison of Features on SD-OCT Between Acute Central Serous Chorioretinopathy and Exudative Age-Related Macular Degeneration

To compare the spectral-domain optical coherence tomography (SD-OCT) features of acute central serous chorioretinopathy (CSC) versus exudative age-related macular degeneration (AMD) and explore disease-specific features of each disease. SD-OCT images obtained at the time of diagnosis in 39 eyes with acute CSC (symptom onset < 2 months) and 52 eyes with exudative AMD were compared. Multiple regression analysis was performed to identify disease-specific features. The relationship between anatomical findings and visual function was also assessed. There were significant morphologic differences on SD-OCT between the two diseases, including the presence and height of retinal fluid and morphologic changes of retinal pigment epithelium (RPE). Multiple regression analysis revealed that a reflective band with posterior shadowing was a disease-specific finding indicating exudative AMD; however, other SD-OCT findings were attributed to differences in age of onset between the two diseases. Visual acuity was correlated with subretinal fluid in CSC, whereas pigment epithelial detachment, intraretinal fluid, and diverse RPE morphologic abnormalities were associated with visual decline in exudative AMD. A reflective band with posterior shadowing is a disease-specific feature of exudative AMD that may be useful for the differential diagnosis. High-resolution SD-OCT images of the retinal layers identified distinguishing pathologic features of the outer retina between the two diseases. The OCT features associated with visual function were different between the two diseases.

SPECTRAL DOMAIN OPTICAL COHERENCE TOMOGRAPHY CLASSIFICATION OF ACUTE POSTERIOR MULTIFOCAL PLACOID PIGMENT EPITHELIOPATHY

To study the retinal morphologic changes occurring in acute posterior multifocal placoid pigment epitheliopathy using spectral domain optical coherence tomography. Prospective observational case series of 12 eyes (6 consecutive patients) diagnosed with acute posterior multifocal placoid pigment epitheliopathy. All patients underwent complete ophthalmologic examination, fundus photography, fluorescein angiography, and spectral domain optical coherence tomography at the initial visit. During follow-up, ophthalmologic examination and spectral domain optical coherence tomography scans were performed. The scans were directed to the lesions observed on the clinical examination and fluorescein angiography. Spectral domain optical coherence tomography classification containing four distinct stages for acute posterior multifocal placoid pigment epitheliopathy is proposed. Stage 1 demonstrates a dome-shaped elevation with disruption of the photoreceptor junction that flattens shortly after. Stage 2, occurring 2 weeks later, demonstrates distinct separation between the photoreceptor junction and the retinal pigment epithelium (RPE). Stage 3, visible 6 weeks post disease initiation, demonstrates accentuated RPE hyperreflectivity and union of the RPE and photoreceptor junction. Stage 4, the resolution phase, starts at 3 months demonstrating reformation of 2 distinct visible layers of photoreceptors and RPE. The morphologic retinal findings in acute posterior multifocal placoid pigment epitheliopathy visible by the spectral domain optical coherence tomography occur in the outer retina, mainly the photoreceptors and RPE. Most findings reached nearly complete resolution and were correlated with improvement in visual acuity.

Monitoring Morphological Changes in the Retina of Rhodopsin−/−Mice with Spectral Domain Optical Coherence Tomography

The rhodopsin(-/-) C57Bl/6 (rho(-/-)) mouse is a very important model for understanding retinal degenerative diseases. In this study, spectral domain optical coherence tomography (SD-OCT) was used to monitor the dynamic morphological changes in retina of rho(-/-) mice. Rho(-/-) mice and wild type C57Bl/6 (B6) mice at the age of 3, 6, 9, and 12 weeks were investigated using SD-OCT to obtain cross-sectional images of the retina. The outer nuclear layer (ONL) thickness was measured. Histological sections were used to compare to the OCT data. Electroretinograms (ERG) were performed to evaluate the physiological change for establishing the relationship between retinal morphology and its functional changes. There was no apparent morphological or functional change in B6 mice at any time point. The SD-OCT measurement showed that the ONL thickness in rho(-/-) mice was significantly decreased from 40.6 μm to 6.0 μm from week 3 to week 12 postnatal. Histological examinations identified a similar trend, although the average thickness of ONL from histological sections at these time points was slightly larger (ranging from 55.4 μm to 14.9 μm). The ERG in rho(-/-) mice indicated functional changes that were in concordant with morphological changes; a significant linear positive association was identified between the amplitude of b-wave and the ONL thickness. Our findings confirmed that the functional changes in retina were concordant with morphological changes measured by SD-OCT in vivo, which indicates that SD-OCT can be used as a reliable noninvasive method to monitor the degenerative progression in retinal disease models.

An automated computational framework for retinal vascular network labeling and branching order analysis

Changes in retinal vascular morphology are well known as predictive clinical signs of many diseases such as hypertension, diabetes and so on. Computer-aid image processing and analysis for retinal vessels in fundus images are effective and efficient in clinical diagnosis instead of tedious manual labeling and measurement. An automated computational framework for retinal vascular network labeling and analysis is presented in this work. The framework includes 1) detecting and locating the optic disc; 2) tracking the vessel centerline from detected seed points and linking the breaks after tracing; 3) extracting all the retinal vascular trees and identifying all the significant points; and 4) classifying terminal points into starting points and ending points based on the information of optic disc location, and finally assigning branch order for each extracted vascular tree in the image. All the modules in the framework are fully automated. Based on the results, morphological analysis is then applied to achieve geometrical and topological features based on branching order for one individual vascular tree or for the vascular network through the retinal vascular network in the images. Validation and experiments on the public DRIVE database have demonstrated that the proposed framework is a novel approach to analyze and study the vascular network pattern, and may offer new insights to the diagnosis of retinopathy.