Outer Plexiform Layer Thickness Research Articles

Visual Acuity-Related Outer Retinal Structural Parameters on Swept Source Optical Coherence Tomography and Angiography in XLRS Patients and Carriers.

To assess the quantitative differences in vessel density and retinal thickness of X-linked retinoschisis (XLRS) patients and RS1 mutation carriers, and the correlation with best-corrected visual acuity (BCVA) with swept source optical coherence tomography (SS-OCT) and OCT angiography (OCTA). We analyzed the correlation between the BCVA of XLRS patients and the SS-OCT and OCTA findings including the detailed structural characteristics of XLRS patients. Besides the schitic changes in various retinal layers, the structural disturbance of outer retina was universally found. In 29 eyes included in the quantitative analysis, XLRS patients showed lower vessel density of the superficial capillary plexus, deep capillary plexus and lower thickness of the outer nuclear layer. BCVA was correlated with the thickness of the outer plexiform layer and outer nuclear layer and the thickness from the outer limiting membrane to the retinal pigment epithelium. Carriers showed higher thickness of outer plexiform layer and smaller foveal avascular zone area. SS-OCT and OCTA could identify the pathological alterations of the individual retinal layers and capillaries, which could pinpoint the exact location of the damages related to visual impairment. In the carriers, the subtle alterations that can be detected with SS-OCT, despite their normal visual acuity, may be caused by the lyonization. Swept source optical coherence tomography can be used as an efficient technique to expose the retinal damage related to visual impairment for prognosis and follow-up.

Leber hereditary optic neuropathy (LHON): Retinal structure and function correlations

AbstractPurpose: LHON mainly affects small‐calibre ganglion cells in the papillomacular bundle which is electroretinographically reflected mainly as abnormal wave N95 of the pattern ERG (PERG) and photopic negative response (PhNR). In this study we investigated whether there is a reflection of the disease in oscillatory potentials (OPs), which are thought to reflect activity of the inner retinal generators, and whether there is a correlation with retinal structure as assessed by OCT segmentation to explore potential structural/functional biomarkers in LHON.Methods: Seven patients (mean age = 28.4 ± 5.6) with genetically confirmed LHON were compared to 12 healthy volunteers (mean age = 35.0 ± 12.1). PhNR, dark and light adapted OPs were derived from full‐field ERG signals. Segmentation analysis of retinal layers in ETDRS rings performed using the Heidelberg Engineering Spectralis SD‐OCT was correlated with oscillatory potentials derived from dark‐adapted and light‐adapted ERG signals filtered at 75 Hz cut‐off frequency that were shown to be affected in LHON in a previous study shown at this EVER meeting (Barboni et al.).Results: Dark‐adapted OP2 component filtered at 75 Hz cutoff frequency displayed a significant negative correlation with outer plexiform layer (OPL) thickness (Spearman correlation = 0.94; p = 0.005) for outer ETDRS ring. The OP3 and OP4 showed marginal correlation with the outer ETDRS ring (Spearman correlation = 0.812; p = 0.050 and Spearman correlation = 0.840; p = 0.036). Marginally significant positive correlation was found with the OP3 (Spearman correlation = 0.812; p = 0.050). We found no significant correlation between OPs and any other retinal layers, nor were light‐adapted PhNRs associated with OCT layer thickness.Conclusions: In chronic stage of the LHON, oscillatory potentials may be associated with OCT parameters, most notably dark adapted OP2 with OPL thickness. These data emphasize possible involvement of fast retinal generators as an additional biomarker in LHON patients.

Comparison of Each Retinal Layer Thicknesses between Eyes with Central Retinal Vein Occlusion and Normal Contralateral Eyes.

PurposeTo evaluate the difference in each retinal layer thickness in central retinal vein occlusion (CRVO) with resolved macular edema after intravitreal antivascular endothelial growth factor injection and normal contralateral eyes..MethodsPatients with ischemic and nonischemic CRVO whose macular edema resolved after intravitreal antivascular endothelial growth factor injections and did not recur for at least 6 months, and a normal contralateral eye were enrolled. Each retinal layer thickness between CRVO and normal contralateral eyes was compared according to Early Treatment Diabetic Retinopathy Study subfields using spectral domain optical coherence tomography.ResultsThe thicknesses of outer nuclear layer, photoreceptor layer, and retinal pigment epithelium in central ring, ganglion cell layer, inner plexiform layer, outer nuclear layer, and photoreceptor layer in the inner ring, and ganglion cell layer in the outer ring of CRVO eyes were significantly thinner than those of normal contralateral eyes (all p < 0.05). Whereas, inner nuclear layer and outer plexiform layer thicknesses in central ring of CRVO eyes were 23.86 ± 8.8 and 25.76 ± 7.6 μm, respectively, which was significantly thicker than those of normal contralateral eyes (19.52 ± 7.7 and 22.76 ± 6.5 μm; p = 0.019 and p = 0.043, respectively). Additionally, the mean best-corrected visual acuity of CRVO eyes were significantly correlated with photoreceptor layer thickness in central ring (p = 0.005).ConclusionsIn CRVO eyes with resolved macular edema, the outer retinal layers were thinner as well as inner retinal layers, whereas inner plexiform layer and outer nuclear layer were thicker than normal fellow eyes. Additionally, photoreceptor layer thickness in foveal area had a significant impact on visual acuity in CRVO.

Histological Studies on Ageing Changes in the Retina of Buffaloes (Bubalus bubalis)

Background: Affections of eye are commonly encountered in all the species of animals. The age-related changes of the retina primarily cause loss of visual acuity as well as reduction of the visual field. Hence, the current study was carried out to establish basic data related to ageing changes in the retina of buffaloes. Methods: The study was conducted on 63 eye balls of locally available buffaloes of different breeds. These buffaloes were categorized into 3 groups i.e., group I (1-5 yrs), group II (6-10 yrs) and group III (11 yrs and above). The eyeballs were isolated and fixed with Davidson’s fluid. The paraffin sections were subjected for routine histological study. Result: The thickness of retinal pigment epithelium was increased from group I to III buffaloes from 6.06±0.18 to 8.44±0.32 and the quantity of melanin pigment was decreased with advancement of age. Rod and cone cells of the photoreceptor layer were tightly packed in young age, loosely arranged in old animals. The mean thickness (µm) of photoreceptors and outer nuclear layers together was decreased from 64.22±1.84 to 58.72±2.1 with age advancement. The displacement of nuclei from outer nuclear layer into outer plexiform layer was significantly decreased in old animals. The outer limiting membrane was continuous and uninterrupted throughout the life. The thickness of outer plexiform layer was increased with advancement of age from 8.78±0.58 to 10±0.51 due to enhancement of synaptic fibers density. As age advances the number and density of horizontal, bipolar and amacrine cells were decreased and also the mean thickness (µm) of this layer was decreased from 30.83±1.48 to 22.56±0.62 in the inner nuclear layer. The thickness of inner plexiform layer was increased from 42.44±2.23 to 45.39±0.81 with advancement of age due to increased cystoids spaces and thickening of retinal blood vessels. In ganglionic cell layer, the number of α-ganglion cells were more than the β-ganglion cells, their common number were decreased approximately from 16-20 cells/sq.mm to 7-10 cells/sq.mm, whereas the average size was increased from 4.72±0.49 to 15.83±0.83 with advancement of age. In aged buffaloes nerve fiber layer showed corpora amylacea and thickened blood vessels. The inner limiting membrane became thick and uninterrupted in old buffaloes. The total thickness (µm) of retina in group I, II and III buffaloes were 235.5±7.25, 184.33±3.64 and 201.05±5.15 respectively.

Posterior ocular structural and vascular alterations in severe COVID-19 patients.

PurposeThis study aimed to evaluate posterior ocular structural and vascular changes in severe coronavirus disease 2019 (COVID-19) patients.MethodsThis was an observational, prospective, and controlled study including 106 eyes of 53 severe COVID-19 patients, compared to after recovery and 106 eyes of 53 age- and gender-matched healthy controls. All subjects were previously healthy adults and were assessed using spectral domain optical coherence tomography (SD-OCT) and ImageJ software. Subfoveal over a 1500-μm span and macular over a 6000-μm span cross-sectional areas of the vascular, stromal, and total choroid were measured.ResultsOf the 53 included patients, 28 (52.8%) were male, and 25 (47.2%) were female, with a mean age of 50.2 ± 7.4 years. In the active period of the disease, compared to after recovery and healthy controls, the outer plexiform layer thickness showed a significant increase (p = 0.004), and mean choroidal thickness was significantly higher (p < 0.0001); however, choroidal vascularity was significantly lower (p < 0.0001). The stromal area to vascular area (S/V) ratio of the choroid was significantly increased (p < 0.0001). All quadrants of the peripapillary retinal nerve fiber layer (RNFL) thicknesses were significantly increased (for all, p < 0.05). The reflectivity of OCT echo of the choroid and peripapillary RNFL was significantly higher (p = 0.023, p < 0.0001, respectively).ConclusionThis study detected significant posterior ocular structural and vascular alterations in patients with severe COVID-19 infections. These findings may be associated with direct host-virus interaction or linked to an autoimmune process, vasculopathy, or viral-mediated inflammation.

Association of Cognitive Function and Retinal Neural and Vascular Structure in Type 1 Diabetes.

Cognitive dysfunction is a growing and understudied public health issue in the aging type 1 diabetic population and is difficult and time-consuming to diagnose. Studies in long duration type 1 diabetes have reported the presence of proliferative diabetic retinopathy was associated with cognitive dysfunction. This study assessed whether structural and vascular abnormalities of the retina, representing an extension of the central nervous system, are associated with cognitive impairment and other complications of type 1 diabetes. An observational cross-sectional study of individuals with 50 or more years of type 1 diabetes (Joslin Medalist Study) was conducted at a university hospital in the United States. The study included 129 participants with complete cognitive testing. Validated cognitive testing measures included psychomotor speed, and immediate, and delayed memory. Optical coherence tomography (OCT) and OCT angiography (OCTA) were performed to obtain neural retinal layer thicknesses and vascular density for superficial (SCP) and deep retinal capillary plexus (DCP). Multivariable modeling was adjusted for potential confounders associated with outcomes in unadjusted analyses. Decreased vessel density of the SCP and DCP was associated with worse delayed memory (DCP: P = .002) and dominant hand psychomotor speed (SCP: P = .01). Thinning of the retinal outer nuclear layer was associated with worse psychomotor speed both in nondominant and dominant hands (P = .01 and P = .05, respectively). Outer plexiform layer thickness was associated with delayed memory (P = .04). These findings suggest that noninvasive retinal imaging using OCT and OCTA may assist in estimating the risks for cognitive dysfunction in people with type 1 diabetes.

Detection of Reduced Retinal Vessel Density in Eyes with Geographic Atrophy Secondary to Age-Related Macular Degeneration Using Projection-Resolved Optical Coherence Tomography Angiography

To compare retinal vessel density in eyes with geographic atrophy (GA) secondary to age-related macular degeneration (AMD) to age-matched healthy eyes by using projection-resolved optical coherence tomography angiography (PR-OCTA). Prospective cross-sectional study. Study participants underwent macular 3-× 3-mm OCTA scans with spectral domain OCTA. Reflectance-compensated retinal vessel densities were calculated on projection-resolved superficial vascular complex (SVC), intermediate capillary plexus (ICP), and deep capillary plexus (DCP). Quantitative analysis using normalized deviation compared the retinal vessel density in GA regions, 500-μm GA rim regions, and non-GA regions to similar macular locations in control eyes. Ten eyes with GA and 10 control eyes were studied. Eyes with GA had significantly lower vessel density in the SVC (54.8 ± 2.4% vs. 60.8 ± 3.1%; P<0.001), ICP (34.0 ± 1.5% vs. 37.3 ± 1.7%; P=0.003) and DCP (24.4 ± 2.3% vs. 28.0 ± 2.3%; P < 0.001) than control eyes. Retinal vessel density within the GA region decreased significantly in SVC, ICP, and DCP. Retinal vessel density in the GA rim region decreased in SVC and ICP but not in DCP. The non-GA region did not significantly deviate from normal controls. Eyes with GA had significantly reduced photoreceptor layer thickness; but similar nerve fiber layer, ganglion cell complex, inner nuclear layer, and outer plexiform layer thickness. Eyes with GA have reduced retinal vessel density in SVC, ICP, and DCP compared to those in controls. Loss is greatest within regions of GA. Vessel density may be more sensitive than retinal layer thickness measurement in the detection of inner retinal change in eyes with GA.

Association between Visual Acuity and Retinal Layer Metrics in Diabetics with and without Macular Edema

Purpose Diabetes is known to cause alterations in retinal microvasculature and tissue that progressively lead to visual impairment. Optical coherence tomography (OCT) is useful for assessment of total retinal thickening due to diabetic macular edema (DME). In the current study, we determined associations between visual acuity (VA) and retinal layer thickness, reflectance, and interface disruption derived from enface OCT images in subjects with and without DME. Materials and Methods Best corrected VA was measured and high-density OCT volume scans were acquired in 149 diabetic subjects. A previously established image segmentation method identified retinal layer interfaces and locations of visually indiscernible (disrupted) interfaces. Enface thickness maps and reflectance images of the nerve fiber layer (NFL), combined ganglion cell and inner plexiform layer (GCLIPL), inner nuclear layer (INL), outer plexiform layer (OPL), outer nuclear layer (ONL), photoreceptor outer segment layer (OSL), and retinal pigment epithelium (RPE) were generated in the central macular subfield. The associations among VA and retinal layer metrics were determined by multivariate linear regressions after adjusting for covariates (age, sex, race, HbA1c, diabetes type, and duration) and correcting for multiple comparisons. Results In DME subjects, increased GCLIPL and OPL thickness and decreased OSL thickness were associated with reduced VA. Furthermore, increased NFL reflectance and decreased OSL reflectance were associated with reduced VA. Additionally, increased areas of INL and ONL interface disruptions were associated with reduced VA. In subjects without DME, increased INL thickness was associated with reduced VA, whereas in subjects without DME but with previous antivascular endothelium growth factor treatment, thickening of OPL was associated with reduced VA. Conclusions Alterations in retinal layer thickness and reflectance metrics derived from enface OCT images were associated with reduced VA with and without presence of DME, suggestive of their potential for monitoring development, progression, and treatment of DME.

Characterization of photoreceptor degeneration in the rhodopsin P23H transgenic rat line 2 using optical coherence tomography.

PurposeTo characterize the optical coherence tomography (OCT) appearances of photoreceptor degeneration in the rhodopsin P23H transgenic rat (line 2) in relation to the histological, ultrastructural, and electroretinography (ERG) findings.Materials and methodsHomozygous rhodopsin P23H transgenic albino rats (line 2, very-slow degeneration model) were employed. Using OCT (Micron IV®; Phoenix Research Labs, Pleasanton, CA, USA), the natural course of photoreceptor degeneration was recorded from postnatal day (P) 15 to P 287. The OCT images were qualitatively observed by comparing them to histological and ultrastructural findings at P 62 and P 169. In addition, each retinal layer was quantitatively analyzed longitudinally during degeneration, compared it to that observed in wild type Sprague-Dawley (SD) rats. The relationships between the ERG (full-field combined rod-cone response, 3.0 cds/m2 stimulation) findings and OCT images were also analyzed.ResultsIn the qualitative study, the two layers presumably corresponding to the photoreceptor inner segment ellipsoid zone (EZ) and interdigitation zone (IZ) were identified in the P23H rat until PN day 32. However, the photoreceptor inner and outer segment (IS/OS) layer became diffusely hyperreflective on OCT after P 46, and the EZ and IZ zones could no longer be identified on OCT. In contrast, in the SD rats, the EZ and IZ were clearly distinguished until at least P 247. The ultrastructural study showed partial disarrangements of the photoreceptor outer segment discs in the P23H rats at P 62, although a light-microscopic histological study detected almost no abnormality in the outer segment. In the quantitative study, the outer retinal layer including the outer plexiform layer (OPL) and the outer nuclear layer (ONL) became significantly thinner in the P23H rats than in the SD rats after P 71. The thickness of the IS/OS layer was maintained in the P23H rats until P 130, and it became statistically thinner than in the SD rats at P 237. The longitudinal attenuation in the amplitude of the a- and b-waves of ERG was significantly correlated with the thickness of the combined OPL and ONL but not with that of the IS/OS layer.ConclusionOCT showed the degenerated photoreceptor IS/OS layer in rhodopsin P23H transgenic rats (line 2) as a diffuse hyperreflective zone, even in the early stage, with the partially disarranged and destabilized OS discs recognizable by ultrastructural assessment but not by a histological study. The amplitude of the a- and b-waves mainly depends on the thickness of the OPL and ONL layer rather than the thickness of the photoreceptor IS/OS layer in P23H rats.

Retinal single-layer analysis with optical coherence tomography shows inner retinal layer thinning in Huntington's disease as a potential biomarker.

There have been ongoing clinical trials of therapeutic agents in Huntington's disease (HD) which requires development of reliable biomarkers of disease progression. There have been studies in the literature with conflicting results on the involvement of retina in HD, and up to date there is not a study evaluating the single retinal layers in HD. We aimed to evaluate the specific retinal changes in HD and their usability as potential disease progression markers. This cross-sectional study used spectral-domain optical coherence tomography with automatic segmentation to measure peripapillary retinal nerve fiber layer (pRNFL) thickness and the thickness and volume of retinal layers in foveal scans of 15 patients with HD and 15 age- and sex-matched controls. Genetic testing results, disease duration, HD disease burden scores and Unified HD Rating Scales motor scores were acquired for the patients. Temporal pRNFL, macular RNFL (mRNFL), ganglion cell layer (GCL), inner plexiform layer (IPL), inner nuclear layer and outer plexiform layer thicknesses and IPL, retinal pigment epithelium and outer macular volume were found lower in HD compared to controls, while outer nuclear layer and outer retinal layer thickness were increased (p<0.05). We found significant correlations between inner retinal layer thicknesses, most significantly with mRNFL and GCL and disease progression markers. The outcomes of this study points out that retinal layers, most significantly mRNFL and GCL, are strongly correlated with the disease progression in HD and could serve as useful biomarkers for disease progression.

Normative Data for Retinal-Layer Thickness Maps Generated by Spectral-Domain OCT in a White Population

(1) To collect a dataset of normative Early Treatment Diabetic Retinopathy Study (ETDRS) thickness map values for single retinal layers automatically segmented by Spectralis (Heidelberg Engineering, Heidelberg, Germany) spectral-domain OCT (SD-OCT) in a healthy white population. (2) To test the effect of age, sex, and axial length (AXL) on such values. Cross-sectional study. Healthy adult emmetropic white subjects with no history of ongoing or past conditions known to affect retinal anatomy. SD-OCT scans (30× 25-degree volume) centered on the fovea were collected. Retinal-layer automatic segmentation was performed. Mean thickness values of 9 ETDRS sectors were calculated for each layer in 1 eye from each subject. The effect of age, sex, and AXL on the thickness of the central subfield, inner ring (IR), and outer ring (OR) of the ETDRS grid was tested. Scans were performed twice on a subset of patients to assess the repeatability of measurements. Retinal-layer thickness. Two hundred eyes from 200 subjects (110 females, mean age 39.9±13.9 years [range 20-74 years]) were used for this study. The mean AXL was 24.30±1.07 mm (range 22.23-27.14 mm). Full retinal thickness was higher in males regardless of the subfield (all P < 0.05). Ganglion cell layer thickness correlated positively with AXL in the C (P= 0.02) but negatively in the OR (P= 0.0001). The inner plexiform layer was thicker in males in the IR (P= 0.01) and thinner in longer eyes in the OR (P= 0.002). The inner nuclear layer was thicker in males in the C and the IR (P= 0.002 and P= 0.0009, respectively). The outer plexiform layer thickness did not change with age and gender but correlated positively with AXL in the C (P= 0.009). Males had thicker outer nuclear layers in all subfields (all P < 0.05). The thickness of the nerve fiber layer and retinal pigment epithelium was not affected by the studied variables in any subfield. The intraclass correlation coefficient ranged from 0.872 for the outer plexiform layer to 0.990 for the retinal nerve fiber layer and the ganglion cell layer. The thickness values of each retinal layer in a large white population are provided. The thickness of retinal layers is influenced by gender, sex, and AXL, with a variable extent depending on the analyzed ETDRS map ring.

Retinal Morphology and Sensitivity Are Primarily Impaired in Eyes with Neuromyelitis Optica Spectrum Disorder (NMOSD).

BackgroundPrevious studies of neuromyelitis optica spectrum disorder (NMOSD) using spectral domain optical coherence tomography (SD-OCT) showed that the outer nuclear layer (ONL) in eyes without a history of optic neuritis (ON) was thinner than that of healthy controls. It remains unclear whether the ONL thinning is caused by a direct attack on the retina by an autoantibody or a retrograde degeneration.ObjectiveTo determine the mechanisms involved in the retinal damage in eyes with NMOSD without ON.MethodsSD-OCT was used to determine the thicknesses of the different retinal layers of 21 eyes of 12 NMOSD patients without prior ON and 19 eyes of 10 healthy controls. Eyes with peripapillary retinal nerve fiber layer (RNFL) thinning were excluded to eliminate the confounding effects of retrograde degeneration. Microperimetry was used to determine the central retinal sensitivity. The data of the two groups were compared using generalized estimated equation models to account for inter-eye dependencies.ResultsThe ganglion cell plus inner plexiform layer and the inner nuclear layer plus outer plexiform layer thicknesses of the NMOSD eyes were not significantly different from that of the control eyes (P = 0.28, P = 0.78). However, the ONL and average macular thickness (AMT) in the NMOSD eyes were significantly thinner than that of the control eyes (P = 0.022, P = 0.036). The retinal sensitivity in the central 10°, 10° to 2°, and 2° sectors were significantly lower in the NMOSD eyes than in the control eyes (P = 0.013, P = 0.022, P = 0.002).ConclusionsThe ONL thinning, AMT thinning, and reduced retinal sensitivity in eyes with NMOSD without significant peripapillary RNFL thinning are most likely due to direct retinal pathology.

SD‐OCT for study of retinal layers segmentation in patients under Hydroxychloroquine treatment

PurposeHydroxychloroquine has been used for decades in treatment of rheumatic disorders. Macular toxicity is an adverse effect dependent to duration of treatment and daily dosage. Although, the exactly retinal structure under this toxic effect is not yet totally understandable.To study the sectorial effect of Hydroxychloroquine in all retinal layers in 1st, 2nd, 3th and 6th mm centered on fovea by automatic segmentation using Spectral‐Domain Optical Coherence Tomography.MethodsRetrospective, non‐randomized study involving 44 eyes of 44 patients under treatment with Hydroxychloroquine. The authors have created two age‐matched groups. A group 1 of patients in treatment duration under 10 years (n = 30) and a group 2 above 10 years of treatment (n = 14).ResultsThe inner retinal layers thickness of 1st and 2nd mm is impaired in group 2 but the results did not showed significant difference between groups. The automatically segmentation of layer by layer did not prove a sectorial defect in inner retina. The thickness of Outer Nuclear Layer (ONL) was impaired in group 2, in opposition to Outer Plexiform Layer (OPL). This analysis has demonstrated a tendency for inversion of ONL and OPL thickness values in both groups.ConclusionsThe toxicity of Hydroxychloroquine apparently was not responsible for significant alterations in inner retinal thickness. That is a tendency for reduction in ONL thickness. The higher thickness of OPL in group 2 is a surprising aspect that needs additional analysis. The outcomes were very dependent to the limited number of patients in our sample. Further longitudinal studies about this topic will be necessary.

Alterations in Retinal Layer Thickness and Reflectance at Different Stages of Diabetic Retinopathy by En Face Optical Coherence Tomography.

PurposeThis article reports a method for en face optical coherence tomography (OCT) imaging and quantitative assessment of alterations in both thickness and reflectance of individual retinal layers at different stages of diabetic retinopathy (DR).MethodsHigh-density OCT raster volume scans were acquired in 29 diabetic subjects divided into no DR (NDR) or non-proliferative DR (NPDR) groups and 22 control subjects (CNTL). A customized image segmentation method identified eight retinal layer interfaces and generated en face thickness maps and reflectance images for nerve fiber layer (NFL), ganglion cell and inner plexiform layers (GCLIPL), inner nuclear layer (INL), outer plexiform layer (OPL), outer nuclear layer (ONL), photoreceptor outer segment layer (OSL), and retinal pigment epithelium (RPE). Mean thickness and intensity values were calculated in nine macular subfields for each retinal layer.ResultsEn face thickness maps and reflectance images of retinal layers in CNTL subjects corresponded to normal retinal anatomy. Total retinal thickness correlated negatively with age in nasal subfields (R ≤−0.31; P ≤ 0.03, N = 51). In NDR subjects, NFL and OPL thickness were decreased (P = 0.05), and ONL thickness was increased (P = 0.04) compared to CNTL. In NPDR subjects, GCLIPL thickness was increased in perifoveal subfields (P < 0.05) and INL intensity was higher in all macular subfields (P = 0.04) compared to CNTL.ConclusionsDepth and spatially resolved retinal thickness and reflectance measurements are potential biomarkers for assessment and monitoring of DR.

Reliability of Intra-Retinal Layer Thickness Estimates.

PurposeMeasurement of intra-retinal layer thickness using optical coherence tomography (OCT) has become increasingly prominent in multiple sclerosis (MS) research. Nevertheless, the approaches used for determining the mean layer thicknesses vary greatly. Insufficient data exist on the reliability of different thickness estimates, which is crucial for their application in clinical studies. This study addresses this lack by evaluating the repeatability of different thickness estimates.MethodsStudies that used intra-retinal layer segmentation of macular OCT scans in patients with MS were retrieved from PubMed. To investigate the repeatability of previously applied layer estimation approaches, we generated datasets of repeating measurements of 15 healthy subjects and 13 multiple sclerosis patients using two OCT devices (Cirrus HD-OCT and Spectralis SD-OCT). We calculated each thickness estimate in each repeated session and analyzed repeatability using intra-class correlation coefficients and coefficients of repeatability.ResultsWe identified 27 articles, eleven of them used the Spectralis SD-OCT, nine Cirrus HD-OCT, two studies used both devices and two studies applied RTVue-100. Topcon OCT-1000, Stratus OCT and a research device were used in one study each. In the studies that used the Spectralis, ten different thickness estimates were identified, while thickness estimates of the Cirrus OCT were based on two different scan settings. In the simulation dataset, thickness estimates averaging larger areas showed an excellent repeatability for all retinal layers except the outer plexiform layer (OPL).ConclusionsGiven the good reliability, the thickness estimate of the 6mm-diameter area around the fovea should be favored when OCT is used in clinical research. Assessment of the OPL was weak in general and needs further investigation before OPL thickness can be used as a reliable parameter.

Effect of voltage-dependent calcium channel α1F subunit deficiency on the structure and function of the murine retina

To investigate the distribution and biological roles of voltage-dependent calcium channel (VDCC) α1F subunit in murine retina. Experimental study.α1F(-/-) (homozygous mutant) mice (n = 35) and α1F(+/+) (wild type) mice (n = 35) were used in this study. Immunohistochemistry was performed to determine the expression of VDCC α1F subunit in the mouse retina. Retinae in α1F(-/-) mice and age-matched control mice at 3, 6, 9, 14-day and 3-month after birth were paraffin embedded, sectioned and HE stained, and full-field electroretinogram (ERG) were also recorded at these time points.Statistics were based on independent samples t-test. (1) α1F subunit was absent in α1F(-/-) mice retina. But in α1F(+/+) mice retina, α1F subunit was expressed most strongly in the outer plexiform layer (OPL), less in the inner plexiform layer (IPL) and ganglion cell layer (GCL). (2) OPL thickness in the subunit deficient mice gradually reduced after birth and lost at adult age. (3) In dark-adapted ERGs,standard response showed that the b-wave amplitude of α1F(-/-) mice [(163.8 ± 26.7) µV] significantly decreased compared with that of α1F(+/+) mice [(408.4 ± 54.5) µV] (t = -9.017, P = 0.000), whereas the a-wave amplitude of α1F(-/-) group [(208.2 ± 27.3) µV] was similar to that of control group [(196.0 ± 24.2) µV] (t = 0.748, P = 0.476). This study demonstrates that the lack of VDCC α1F subunit affect the structure and function in the OPL of the murine retina.

Gene therapy rescues photoreceptor blindness in dogs and paves the way for treating human X-linked retinitis pigmentosa

Hereditary retinal blindness is caused by mutations in genes expressed in photoreceptors or retinal pigment epithelium. Gene therapy in mouse and dog models of a primary retinal pigment epithelium disease has already been translated to human clinical trials with encouraging results. Treatment for common primary photoreceptor blindness, however, has not yet moved from proof of concept to the clinic. We evaluated gene augmentation therapy in two blinding canine photoreceptor diseases that model the common X-linked form of retinitis pigmentosa caused by mutations in the retinitis pigmentosa GTPase regulator (RPGR) gene, which encodes a photoreceptor ciliary protein, and provide evidence that the therapy is effective. After subretinal injections of adeno-associated virus-2/5-vectored human RPGR with human IRBP or GRK1 promoters, in vivo imaging showed preserved photoreceptor nuclei and inner/outer segments that were limited to treated areas. Both rod and cone photoreceptor function were greater in treated (three of four) than in control eyes. Histopathology indicated normal photoreceptor structure and reversal of opsin mislocalization in treated areas expressing human RPGR protein in rods and cones. Postreceptoral remodeling was also corrected: there was reversal of bipolar cell dendrite retraction evident with bipolar cell markers and preservation of outer plexiform layer thickness. Efficacy of gene therapy in these large animal models of X-linked retinitis pigmentosa provides a path for translation to human treatment.

Unusual retinal layer organization in HPC-1/syntaxin 1A knockout mice

HPC-1/syntaxin 1A (STX1A) is abundantly expressed in neurons. STX1A is believed to regulate exocytosis in synaptic vesicles. In our recent studies, STX1A knockout (KO) mice showed normal development, and basal synaptic transmission in cultured hippocampal neurons appeared to be normal. However, behavioral abnormalities were observed in STX1A KO mice. In the normal rodent retina, the STX1A protein is expressed in two synaptic layers (plexiform layers). Here, to evaluate the effects of the loss of STX1A on retinal structure, we examined the retinal layer structure in STX1A KO mice using hematoxylin staining and immunostaining. We found that the general layer structures in the retina were preserved in all genotypes. However, the outer plexiform layer (OPL) was significantly thicker in KO and heterozygous mutant (HT) mice compared with that in wild-type (WT) mice. No significant differences were observed in the thicknesses of the other layers. Immunostaining for protein kinase C α showed that the alignment of rod bipolar cell bodies in the inner nuclear layer (INL) was slightly disrupted in HT and KO retinas. Furthermore, the dendrites of these cells in the OPL of KO mice were sparse, compared to those in WT mice. Our results show that STX1A KO mice have increased thickness of the OPL and changes in the morphology of the INL that may contribute to the change in OPL thickness. We suggest that STX1A may play a role in the structural formation of the INL and OPL in the retina.

Thickness Mapping of Retinal Layers by Spectral-Domain Optical Coherence Tomography

To report normal baseline thickness maps for 6 retinal layers generated by segmentation of spectral-domain optical coherence tomography (SD-OCT) images in normal subjects. Intersubject thickness variability and thickness variations in 9 macular sectors were established. Prospective cross-sectional study. SD-OCT imaging was performed in 15 normal subjects. Nineteen SD-OCT images were acquired, encompassing a 6 × 5-mm retinal area, centered on the fovea. Each image was analyzed using an automated segmentation algorithm to derive thickness profiles of 6 retinal layers. Thickness data obtained from all scans were combined to generate thickness maps of 6 retinal layers: nerve fiber layer, ganglion cell layer + inner plexiform layer, inner nuclear layer, outer plexiform layer, outer nuclear layer + photoreceptor inner segments, and photoreceptor outer segments. Mean and standard deviation of thickness measurements were calculated in 9 macular sectors and 6 retinal layers. Intersubject and intrasector thickness variations were established based on standard deviation of measurements. Minimum and maximum thickness of the nerve fiber layer were observed in the foveal and nasal perifoveal areas, respectively. The largest thickness variation among subjects and intrasector variability were observed in perifoveal areas. Thickness of the ganglion cell layer + inner plexiform layer and intersubject thickness variability were largest in parafoveal areas. The inner nuclear layer thickness was relatively constant in parafoveal and perifoveal areas and intrasector thickness variations were largest in the foveal area. The outer plexiform layer thickness was relatively constant in foveal and parafoveal areas and higher than in perifoveal areas. Intersubject thickness variability in inner nuclear layer and outer plexiform layer was relatively uniform in all macular sectors. The outer nuclear layer + photoreceptor inner segments thickness map displayed maximum thickness in the foveal area and intersubject thickness variability was largest superior to the fovea. Thickness of the photoreceptor outer segments layer, thickness variations among subjects, and intrasector thickness variability were relatively constant. There was a significant correlation between total retinal thickness derived by thickness mapping and SD-OCT commercial software. Normal thickness maps for 6 retinal layers were generated and thickness variations among subjects and macular areas were assessed. This technique is promising for investigating thickness changes attributable to disease in specific retinal layers and macular areas.

Macular Segmentation with Optical Coherence Tomography

To develop a software algorithm to perform automated segmentation of retinal layer structures on linear macular optical coherence tomography (StratusOCT; Carl Zeiss Meditec, Inc., Dublin, CA) scan images and to test its performance in discriminating normal from glaucomatous eyes in comparison with conventional circumpapillary nerve fiber layer (cpNFL) thickness measurement. Four layer structures within the retina were defined: the macular nerve fiber layer (mNFL), the inner retinal complex (IRC; retinal ganglion cell [RGC] layer + inner plexiform and nuclear layers), outer plexiform layer (OPL), and outer retinal complex (ORC; outer nuclear layer + photoreceptor layer). Normal and glaucomatous eyes underwent fast macular map and fast NFL OCT scans. Linear macular images were analyzed using the developed algorithm, and the results were compared with the cpNFL thickness measurement. Forty-seven subjects (23 normal and 24 with glaucoma) were analyzed. mNFL, cpNFL, IRC, and the total retinal thicknesses were significantly greater in normal than in glaucomatous eyes (P < or = 0.0002; Wilcoxon), whereas OPL thickness did not show a significant difference (P = 0.46). ORC thickness was significantly greater in glaucomatous than normal eyes (P = 0.035). Areas under the receiver operator characteristic curve (AROCs) for discriminating normal from glaucomatous eyes were highest with mNFL + IRC (0.97) and lowest with OPL (0.56). AROCs for OPL and ORC were significantly smaller than those for mNFL, IRC, mNFL+IRC, and cpNFL (P < or = 0.01). AROCs for IRC, mNFL + IRC, and cpNFL were significantly larger than for retinal thickness (P < or = 0.049). Among the best-performing parameters (mNFL, IRC, mNFL + IRC, and cpNFL) there was no significant difference in AROCs (P > or = 0.15). The newly developed macular segmentation algorithm described herein demonstrated its ability to quantify objectively the glaucomatous damage to RGCs and NFL and to discriminate between glaucomatous and normal eyes. Further algorithm refinement and improvements in resolution and image quality may yield a more powerful methodology for clinical glaucoma evaluation.