Comparison of retinal nerve fiber layer and central macular thickness measurements among five different optical coherence tomography instruments in patients with multiple sclerosis and optic neuritis

Normative Data and Conversion Equation for Spectral-Domain Optical Coherence Tomography in an International Healthy Control Cohort

BACKGROUND

Spectral-domain (SD-) optical coherence tomography (OCT) can reliably measure axonal (peripapillary retinal nerve fiber layer [pRNFL]) and neuronal (macular ganglion cell + inner plexiform layer [GCIPL]) thinning in the retina. Measurements from 2 commonly used SD-OCT devices are often pooled together in multiple sclerosis (MS) studies and clinical trials despite software and segmentation algorithm differences; however, individual pRNFL and GCIPL thickness measurements are not interchangeable between devices. In some circumstances, such as in the absence of a consistent OCT segmentation algorithm across platforms, a conversion equation to transform measurements between devices may be useful to facilitate pooling of data. The availability of normative data for SD-OCT measurements is limited by the lack of a large representative world-wide sample across various ages and ethnicities. Larger international studies that evaluate the effects of age, sex, and race/ethnicity on SD-OCT measurements in healthy control participants are needed to provide normative values that reflect these demographic subgroups to provide comparisons to MS retinal degeneration.

METHODS

Participants were part of an 11-site collaboration within the International Multiple Sclerosis Visual System (IMSVISUAL) consortium. SD-OCT was performed by a trained technician for healthy control subjects using Spectralis or Cirrus SD-OCT devices. Peripapillary pRNFL and GCIPL thicknesses were measured on one or both devices. Automated segmentation protocols, in conjunction with manual inspection and correction of lines delineating retinal layers, were used. A conversion equation was developed using structural equation modeling, accounting for clustering, with healthy control data from one site where participants were scanned on both devices on the same day. Normative values were evaluated, with the entire cohort, for pRNFL and GCIPL thicknesses for each decade of age, by sex, and across racial groups using generalized estimating equation (GEE) models, accounting for clustering and adjusting for within-patient, intereye correlations. Change-point analyses were performed to determine at what age pRNFL and GCIPL thicknesses exhibit accelerated rates of decline.

RESULTS

The healthy control cohort (n = 546) was 54% male and had a wide distribution of ages, ranging from 18 to 87 years, with a mean (SD) age of 39.3 (14.6) years. Based on 346 control participants at a single site, the conversion equation for pRNFL was Cirrus = -5.0 + (1.0 × Spectralis global value). Based on 228 controls, the equation for GCIPL was Cirrus = -4.5 + (0.9 × Spectralis global value). Standard error was 0.02 for both equations. After the age of 40 years, there was a decline of -2.4 μm per decade in pRNFL thickness ( P < 0.001, GEE models adjusting for sex, race, and country) and -1.4 μm per decade in GCIPL thickness ( P < 0.001). There was a small difference in pRNFL thickness based on sex, with female participants having slightly higher thickness (2.6 μm, P = 0.003). There was no association between GCIPL thickness and sex. Likewise, there was no association between race/ethnicity and pRNFL or GCIPL thicknesses.

CONCLUSIONS

A conversion factor may be required when using data that are derived between different SD-OCT platforms in clinical trials and observational studies; this is particularly true for smaller cross-sectional studies or when a consistent segmentation algorithm is not available. The above conversion equations can be used when pooling data from Spectralis and Cirrus SD-OCT devices for pRNFL and GCIPL thicknesses. A faster decline in retinal thickness may occur after the age of 40 years, even in the absence of significant differences across racial groups.

The use of OCT to detect signs of intracranial hypertension in patients with sagittal suture synostosis: Reference values and correlations

PURPOSE

To obtain pediatric normative reference values and determine whether optical coherence tomography (OCT) corresponds better with clinical signs of intracranial hypertension (ICH) compared to the traditional screening method fundoscopy in a large cohort of one type of single suture craniosynostosis.

METHODS

Control subjects without optic nerve diseases and isolated sagittal synostosis patients aged 3-10 years who underwent fundoscopy and OCT were included in this prospective cohort study. Normative reference values were obtained through bootstrap analysis. Main outcome was the association between peripapillary total retinal thickness (TRT) and total retinal volume (TRV) and appearance on fundoscopy. Signs and symptoms suggestive of ICH, including skull growth arrest, fingerprinting, and headache, were scored.

RESULTS

Sixty-four healthy controls and 93 isolated sagittal synostosis patients were included. Normative cut-off values for mean TRT are < 256 μm and > 504 μm and for mean TRV < 0.21 mm³ and > 0.39 mm³. TRT was increased in 16 (17%) and TRV in 15 (16%) of 93 patients, compared to only 4 patients with papilledema on fundoscopy (4%). Both parameters were associated with papilledema on fundoscopy (OR = 16.7, p = 0.02, and OR = 18.2, p = 0.01). Skull growth arrest was significantly associated with abnormal OCT parameters (OR = 13.65, p < 0.01).

CONCLUSIONS

The established cut-off points can be applied to screen for ICH in pediatrics. The present study detected abnormalities with OCT more frequent than with fundoscopy, which were associated with skull growth arrest. Therefore, a combination of OCT, fundoscopy, and skull growth arrest can improve clinical decision-making in craniosynostosis.

OCT Variability Prevents Their Use as Robust Biomarkers in Multiple Sclerosis

Objective

To evaluate the agreement between the peripapillary retinal nerve fiber layer (pRNFL) and foveal thickness (FT) measurements among three different spectral domain-optical coherence tomography (SD-OCT) instruments in a sample of multiple sclerosis (MS) patients and a healthy age-matched control group.

Methods

An observational cross-sectional study with three groups: healthy subjects and MS patients w/w a previous clinical diagnosis of optic neuritis (ON) was conducted. The pRNFL and FT were measured using three different SD-OCT instruments (OCT PRIMUS 200 and OCT CIRRUS 500 SD-OCT [Carl Zeiss Meditec] and OCT 3D 2000 [Topcon]).

Results

Twenty eyes from 10 healthy subjects matched in age with MS patients without a previous history of eye disease and 62 MS eyes from 31 MS patients (29 eyes without history of ON and 33 eyes with history of ON) were enrolled. Healthy subjects and MS patients without ON did not show differences between the pRNFL and FT thickness (P>0.99) with any of the instruments. However, MS eyes with a previous episode of ON showed thinner pRNFL and FT (P<0.01). PRIMUS and CIRRUS OCT showed better agreement of the pRNLF and FT in both healthy and MS eyes. However, 3D OCT showed less agreement in the pRNFL measurement with CIRRUS in both healthy and MS eyes.

Interpretation

Although OCT is a valuable technology to improve MS patient assessment, differences between devices must be taken into account. It is necessary to create an international group that standardizes the measurement conditions and above all that provides reference bases for normal subjects.

Exploring the role of macular thickness as a potential early biomarker of neurodegeneration in acute schizophrenia

OBJECTIVE

The retina has been investigated as a gateway to assess the neurodegenerative changes in the brain. Schizophrenia is also conceptualized as a neurodegenerative disorder like Alzheimer's and Parkinson's disease. The current literature suggests reduced retinal nerve fibre layer (RNFL) thickness and macular thickness (MT), as a marker of neurodegeneration, in patient suffering from chronic schizophrenia. This study aims to compare RNFL thickness and MT in acute schizophrenic patients with age and sex matched healthy controls.

METHODS

Twenty acutely ill schizophrenic patients and 20 normal controls were included in the study after proper informed consent. RNFL thickness and MT was measured using spectral domain Optical Coherence Tomography after clinical psychological assessment and ocular examination.

RESULTS

The two groups were comparable in terms of socio-demographic variables. The average RNFL thickness of patients and healthy controls was 102.11 ± 29.18 µm and 105.14 ± 27.35 µm, respectively. Central macular thickness was 181.12 ± 13.63 µm in patients and 234.58 ± 10.71 µm in controls. There was a statistically significant reduction in thickness of macula (p < 0.05) but not for RNFL (p = 0.339).

CONCLUSION

The study concludes that macular thinning rather than reduced RNFL is an early manifestation in acute schizophrenia patients and can be considered as a potential early biomarker of neurodegeneration in schizophrenia.

Comparison of the Iowa Reference Algorithm to the Heidelberg Spectralis optical coherence tomography segmentation algorithm

For spectral-domain optical coherence tomography (SD-OCT) studies of neurodegeneration, it is important to understand how segmentation algorithms differ in retinal layer thickness measurements, segmentation error locations and the impact of manual correction. Using macular SD-OCT images of frontotemporal degeneration patients and controls, we compare the individual and aggregate retinal layer thickness measurements provided by two commonly used algorithms, the Iowa Reference Algorithm and Heidelberg Spectralis, with manual correction of significant segmentation errors. We demonstrate small differences of most retinal layer thickness measurements between these algorithms. Outer sectors of the Early Treatment Diabetic Retinopathy Study grid require a greater percent of eyes to be corrected than inner sectors of the retinal nerve fiber layer (RNFL). Manual corrections affect thickness measurements mildly, resulting in at most a 5% change in RNFL thickness. Our findings can inform researchers how to best use different segmentation algorithms when comparing retinal layer thicknesses.

The Topographical Relationship between Visual Field Loss and Peripapillary Retinal Nerve Fibre Layer Thinning Arising from Long-Term Exposure to Vigabatrin

BACKGROUND

The antiepileptic drug vigabatrin is associated with characteristic visual field loss (VAVFL) and thinning of the peripapillary retinal nerve fibre layer (PPRNFL); however, the relationship is equivocal.

OBJECTIVE

The aim of this study was to determine the function-structure relationship associated with long-term exposure to vigabatrin, thereby improving the risk/benefit analysis of the drug.

METHODS

A cross-sectional observational design identified 40 adults who had received long-term vigabatrin for refractory seizures, who had no evidence of co-existing retino-geniculo-cortical visual pathway abnormality, and who had undergone a standardized protocol of perimetry and of optical coherence tomography (OCT) of the PPRNFL. Vigabatrin toxicity was defined as the presence of VAVFL. The function-structure relationship for the superior and inferior retinal quadrants was evaluated by two established models applicable to other optic neuropathies.

RESULTS

The function-structure relationship for each model was consistent with an optic neuropathy. PPRNFL thinning, expressed in micrometres, asymptoted at an equivalent visual field loss of worse than approximately - 10.0 dB, thereby preventing assessment of more substantial thinning. Transformation of the outcomes to retinal ganglion cell soma and axon estimates, respectively, resulted in a linear relationship.

CONCLUSIONS

Functional and structural abnormality is strongly related in individuals with vigabatrin toxicity and no evidence of visual pathway comorbidity, thereby implicating retinal ganglion cell dysfunction. OCT affords a limited measurement range compared with perimetry: severity cannot be directly assessed when the PPRNFL quadrant thickness is less than approximately 65 µm, depending on the tomographer. This limitation can be overcome by transformation of thickness to remaining axons, an outcome requiring input from perimetry.

A cross-sectional and longitudinal study evaluating brain volumes, RNFL, and cognitive functions in MS patients and healthy controls

BACKGROUND

The principal biomarker of neurodegeneration in multiple sclerosis (MS) is believed to be brain volume, which is associated with cognitive functions and retinal nerve fibre layer (RNFL). A cross-sectional and longitudinal assessment of the relationship between RNFL, cognitive functions and brain volume.

METHODS

At baseline, relapsing patients and healthy controls underwent 1.5 T MRI to estimate the normalized volume of brain (NBV), grey (NGV), white (NWV) and peripheral grey (pNGV) matter. Cognitive functions were evaluated by BICAMS, RNFL by Spectral-Domain OCT. Patients were re-evaluated after 12 months.

RESULTS

Cognitive functions, brain volume, and RNFL differed between the group of 66 patients and that of 16 healthy controls. In the MS group, at baseline, an association was found between: p-NGV and symbol-digit (SDMT) (p = 0.022); temporal-RNFL and NBV (p = 0.007), NWV (p = 0.012), NGV (p = 0.048), and p-NGV (p = 0.021); papillo-macular bundle-RNFL and NBV (p = 0.013), NWV (p = 0.02), NGV (p = 0.049), and p-NGV (p = 0.032). Over the observational period, we found a reduction of brain volume (p < 0.001), average-RNFL (p = 0.001), temporal-RNFL (p = 0.006), and papillo-macular bundle-RNFL (p = 0.009). No association was found between OCT, MRI, and cognitive changes.

CONCLUSIONS

Brain volume, cognitive functions, and RNFL are continuous measures of different neurodegenerative aspects. BICAMS and OCT have low costs and can be easily used in clinical practice to monitor neurodegeneration.

Subfoveal choroidal thickness and volume in severe internal carotid artery stenosis patients

AIM

To demonstrate the differences of retinal and choroidal structure changes in internal carotid artery (ICA) patients of China by enhanced-depth imaging optical coherence tomography (EDI-OCT).

METHODS

A retrospective review was conducted of 46 patients with a diagnosis of ICA stenosis greater than 65% on only one side (the opposite ICA Stenosis had less than 40% stenosis) from June 2015 through June 2016. All of the patients were combined with amaurosis fugax, but without any abnormality with other ocular examination. Thickness and volume of choroid and retina were manually measured by EDI-OCT. Differences were compared between ICA stenosis eyes and fellow eyes.

RESULTS

There were no significant differences in the retinal thickness, macular retinal nerve fiber layer (mRNFL) thickness, inner thickness, or outer retinal thickness between the ICA Stenosis group and the control group (P=0.834, 0.187, 0.552, and 0.903, respectively). The mean central choroidal thickness of the ICA Stenosis group was significantly lower than that of the control group (239.70±23.76 µm vs 257.46±22.13 µm, P<0.001). The percentage of ICA stenosis was significantly associated with the central choroidal thickness, central retinal thickness, foveal center choroidal volume, and foveal center retinal volume (r=0.854, 0.678, 0.729, and 0.785, respectively; P<0.001). There were no significant differences in the retinal and choroidal volume values in the 4 inner and 4 outer sectors between the two groups.

CONCLUSION

The choroidal thickness in severe ICA stenosis eyes is lower than in fellow eyes. The choroidal thinning may occur before the retinal changes in patients with ocular ischemic syndrome. Evaluations of choroidal thickness may be useful to choose the optimal therapeutic schedule for ICA patients.

Retinal nerve fiber layer thickness by Stratus and Cirrus OCT in retrobulbar optic neuritis and nonarteritic ischemic optic neuropathy

PURPOSE

To compare retinal nerve fiber layer thickness (RNFLT) measurements by Stratus and Cirrus optical coherence tomography (OCT) and to evaluate agreement between the 2 instruments in retrobulbar optic neuritis (RON), nonarteritic ischemic optic neuropathy (NAION), and healthy controls.

METHODS

A total of 89 eyes with RON, 92 with NAION (6 to 12 months after diagnosis of acute disease), and 159 control eyes were studied. Average RNFLT was measured by Stratus and Cirrus OCTs. Comparisons among groups were performed by analysis of variance. Agreement between the 2 instruments was assessed using intraclass correlation coefficient (ICC) with 95% confidence interval (CI) and Bland-Altman analysis. Statistical significance was set at p≤0.05.

RESULTS

Average RNFLT was lower in NAION eyes than in RON and control ones using both OCT devices (60.0 ± 1.2, 69.9 ± 1.2, and 97.4 ± 0.9 μm, p&lt;0.001 by Cirrus; 49.7 ± 1.5, 65.9 ± 1.9, and 99.2 ± 1.3 μm, p&lt;0.001 by Stratus). The RNFLT values were higher with Cirrus than with Stratus in NAION (+10.30 μm, confidence interval [CI] 7.82-12.79 μm) and RON (+4.01 μm, CI 1.32-6.70 μm) eyes, and slightly lower in control ones (-1.75 μm, CI -3.51 to 0.01 μm). A stronger agreement between the 2 instruments was found in control and RON eyes than in NAION ones (ICC 0.682, CI 0.566-0.771; 0.635, CI 0.467-0.758; 0.321, CI 0.132-0.472, respectively).

CONCLUSIONS

Both Stratus and Cirrus OCT can identify RNFLT reduction in previous RON and NAION. Absolute RNFLT values differ between the 2 instruments; hence they are not to be considered interchangeable.

Anatomical and functional retinal changes in multiple sclerosis

AIMS

The aims of this study was to report anatomical changes of the ganglion cell complex (GCC), retinal nerve fiber layer (RNFL) thickness, and macular volume in patients with multiple sclerosis (MS). We also investigated the correlation between anatomical and functional changes in terms of visual acuity and macular sensitivity investigated and visual fields.

METHODS

Prospective comparative study included 105 eyes of 53 consecutive patients. The patients were divided into two groups: group A included 56 eyes of 28 patients with diagnosis of MS; group B involved 49 eyes of 25 healthy patients. The examination included Goldmann tonometry, biomicroscopic and fundus oculi examination, retinography, GCC examination, circumpapillary RNFL (cpRNFL), and macular volume. The functional test included measurement of best-corrected visual acuity (BCVA), visual field, and MP.

RESULTS

MS group showed a significant reduced GCC, cpRNFL, macular volume, BCVA, visual field, and macular sensitivity compared with the control group (P<0.001). This reduction was more representative (P<0.001) in patients with MS complicated by optic neuritis (ON). We found in the MS group a strong correlation between GCC thickness and macular volume (r(2)=0.59, P<0.001) and also between GCC and RNFL thickness (r(2)=0.48, P<0.001). There was also a correlation between macular sensitivity and macular volume reduction (r(2)=0.25, P<0.001) and also between RNFL and macular volume (r(2)=0.43, P<0.001).

CONCLUSIONS

The significant statistical evidence and the strong correlation between anatomical and functional parameters support the use of OCT and MP in the evaluation, treatment, and follow-up of patients diagnosed with MS.

Acute optic neuritis: Unmet clinical needs and model for new therapies

Idiopathic demyelinating optic neuritis (ON) most commonly presents as acute unilateral vision loss and eye pain and is frequently associated with multiple sclerosis. Although emphasis is often placed on the good recovery of high-contrast visual acuity, persistent deficits are frequently observed in other aspects of vision, including contrast sensitivity, visual field testing, color vision, motion perception, and vision-related quality of life. Persistent and profound structural and functional changes are often revealed by imaging and electrophysiologic techniques, including optical coherence tomography, visual-evoked potentials, and nonconventional MRI. These abnormalities can impair patients' abilities to perform daily activities (e.g., driving, working) so they have important implications for patients' quality of life. In this article, we review the sequelae from ON, including clinical, structural, and functional changes and their interrelationships. The unmet needs in each of these areas are considered and the progress made toward meeting those needs is examined. Finally, we provide an overview of past and present investigational approaches for disease modification in ON.

Applying an Open-Source Segmentation Algorithm to Different OCT Devices in Multiple Sclerosis Patients and Healthy Controls: Implications for Clinical Trials

Background. The lack of segmentation algorithms operative across optical coherence tomography (OCT) platforms hinders utility of retinal layer measures in MS trials. Objective. To determine cross-sectional and longitudinal agreement of retinal layer thicknesses derived from an open-source, fully-automated, segmentation algorithm, applied to two spectral-domain OCT devices. Methods. Cirrus HD-OCT and Spectralis OCT macular scans from 68 MS patients and 22 healthy controls were segmented. A longitudinal cohort comprising 51 subjects (mean follow-up: 1.4 ± 0.9 years) was also examined. Bland-Altman analyses and interscanner agreement indices were utilized to assess agreement between scanners. Results. Low mean differences (-2.16 to 0.26 μm) and narrow limits of agreement (LOA) were noted for ganglion cell and inner and outer nuclear layer thicknesses cross-sectionally. Longitudinally we found low mean differences (-0.195 to 0.21 μm) for changes in all layers, with wider LOA. Comparisons of rate of change in layer thicknesses over time revealed consistent results between the platforms. Conclusions. Retinal thickness measures for the majority of the retinal layers agree well cross-sectionally and longitudinally between the two scanners at the cohort level, with greater variability at the individual level. This open-source segmentation algorithm enables combining data from different OCT platforms, broadening utilization of OCT as an outcome measure in MS trials.

Baseline retinal nerve fiber layer thickness and macular volume quantified by OCT in the North American phase 3 fingolimod trial for relapsing-remitting multiple sclerosis

BACKGROUND

Patients with multiple sclerosis (MS) demonstrate thinning of peripapillary retinal nerve fiber layer (RNFL) and decreased macular volume as measured by optical coherence tomography (OCT). To our knowledge, there are no previous reports from a large MS OCT database with strict quality control measures that quantitate RNFL and macula in patients with relapsing-remitting multiple sclerosis.

METHODS

The University of California Davis OCT Reading Center gathered OCT data at baseline as part of the North American phase 3 trial of fingolimod (Gilenya). Average RNFL thickness (RNFLT) and macular volume (TMV) were measured using time domain OCT (TD-OCT). RNFL quadrants, clock hours, and macular subfields were included. With strict quality control and accounting for signal strength differences, scans were categorized as "reduced" or "not reduced" for each field, based on being less than 5th percentile for age-matched controls derived from the normative database in the scanner software. Patients were deemed "abnormal" if at least 1 eye had reduced values for a given parameter. Patients with abnormalities in corresponding RNFL and macular subfields were compared by cross-tabulation.

RESULTS

The TD-OCT data were prospectively collected from 939 of the 1,083 trial patients, 712 of whom met all final quality and data inclusion criteria. Of the final cohort, 242 (34.0%) demonstrated reduced (less than 5th percentile) average RNFLT in at least 1 eye. One hundred seventy-eight (25.0%) patients had reduced TMV. One hundred twenty-eight (18.0%) demonstrated both reduced TMV and RNFLT in the same eye, whereas 42 (5.8%) had reduced TMV and RNFLT in both eyes. Of the 242 patients with reduced average RNFL thickness, 128 (52.9%) also had reduced TMV. Fifty patients had reduced TMV in the absence of reduced RNFLT in at least 1 eye, a cohort prevalence of 7.0%. Quadrant and subfield analysis showed a predominance of temporal and inferior RNFL thinning, with inferior macular thinning corresponding best to RNFL thinning.

CONCLUSION

RNFL and macular thinning/volume loss is common at baseline in relapsing-remitting multiple sclerosis, as measured by TD-OCT. When the RNFL is thin, the macular volume is reduced in more than half of the patients. There is a population of reduced TMV without any reduction in RNFLT. Documenting the prevalence and distribution of these structural abnormalities supports recent reports and suggests new retinal areas to probe for functional vision changes in MS.

The retinal nerve fiber layer of patients with neuromyelitis optica and chronic relapsing optic neuritis is more severely damaged than patients with multiple sclerosis

BACKGROUND

To compare the retinal nerve fiber layer (RNFL) in eyes of patients with relapsing remitting multiple sclerosis (RRMS), neuromyelitis optica (NMO) and chronic relapsing inflammatory optic neuritis (CRION).

METHODS

Evaluation of 62 patients with RRMS, NMO, and CRION in a cross-sectional study with spectral domain optical coherence tomography.

RESULTS

A total of 124 eyes were evaluated (96 RRMS, 18 NMO, and 10 CRION). Frequency of optic neuritis for each disease was: 34% for RRMS, 84% for NMO, and 100% for CRION. Visual acuity and RNFL thickness were significantly worse in NMO and CRION eyes than in RRMS, but there were no differences between NMO and CRION eyes. A RNFL of 41 μm was 100% specific for optic neuritis associated with NMO and CRION when compared to RRMS.

CONCLUSION

This study established RNFL values to differentiate optic neuritis of RRMS from NMO and CRION. Although similarities observed between NMO and CRION eyes might suggest that they are within the same disease spectrum, it is still recommended that these 2 conditions be differentiated on clinical grounds. Optical coherence tomography serves as an additional diagnostic tool and can be used to monitor disease progression.

Prospective study on retinal nerve fibre layer thickness changes in isolated unilateral retrobulbar optic neuritis

Purpose. To investigate the retinal nerve fibre layer (RNFL) thickness after unilateral acute optic neuritis using optical coherence tomography (OCT). Patients and Methods. This prospective cohort study recruited consecutive patients with a first episode of isolated, unilateral acute optic neuritis. RNFL thickness and visual acuity (VA) of the attack and normal fellow eye were measured at presentation and 3 months in both the treatment and nontreatment groups. Results. 11 subjects received systemic steroids and 9 were treated conservatively. The baseline RNFL thickness was similar in the attack and fellow eye (P ≥ 0.4). At 3 months, the attack eye had a thinner temporal (P = 0.02) and average (P = 0.05) RNFL compared to the fellow eye. At 3 months, the attack eye had significant RNFL thinning in the 4 quadrants and average thickness (P ≤ 0.0002) compared to baseline. The RNFL thickness between the treatment and nontreatment groups was similar at baseline and 3 months (P ≥ 0.1). Treatment offered better VA at 3 months (0.1 ± 0.2 versus 0.3 ± 0.2 LogMAR, P = 0.04). Conclusion. Generalized RNFL thinning occurred at 3 months after a first episode of acute optic neuritis most significantly in the temporal quadrant and average thickness. Visual improvement with treatment was independent of RNFL thickness.

Retinal hyperaemia-related blood vessel artifacts are relevant to automated OCT layer segmentation

A frequently observed local measurement artifact with spectral domain OCT is caused by the void signal of the retinal vasculature. This study investigated the effect of suppression of blood vessel artifacts with and without retinal hyperaemia. Spectral domain OCT scans, centred on the optic nerve head, were performed in 46 healthy subjects (92 eyes). Baseline scans were made during rest, while for the follow-up scan, 23 subjects (50 %) performed strenuous physical exercise. Systemic and retinal hyperaemia were quantified. Quantification of retinal nerve fibre layer (RNFL) thickness was performed with and without suppression of retinal blood vessel artifacts. The potential systematic effect on RNFL thickness measurements was analysed using Bland-Altman plots. At baseline (no retinal hyperaemia), there was a systematic difference in RNFL thickness (3.4 μm, limits of agreement -0.9 to 7.7) with higher values if blood vessel artifacts were not suppressed. There was significant retinal hyperaemia in the exercise group (p < 0.0001). Baseline thickness increased from 93.18 to 93.83 μm (p < 0.05) in the exercise group using the algorithm with blood vessel artifact suppression, but no significant changes were observed using the algorithm without blood vessel artifact suppression. Retinal hyperaemia leads to blood vessel artifacts which are relevant to the precision of OCT layer segmentation algorithms. The two algorithms investigated in this study can not be used interchangeably. The algorithm with blood vessel artifact suppression was more sensitive in detecting small changes in RNFL thickness. This may be relevant for the use of OCT in a range of neurodegenerative diseases were only a small degree of retinal layer atrophy have been found so far.

Color-code agreement among stratus, cirrus, and spectralis optical coherence tomography in relapsing-remitting multiple sclerosis with and without prior optic neuritis

PURPOSE

To evaluate the agreement of retinal nerve fiber layer (RNFL) color codes among Stratus, Cirrus, and Spectralis optical coherence tomography (OCT) in patients with relapsing-remitting multiple sclerosis.

DESIGN

Prospective cohort study.

METHODS

In 140 eyes from 70 patients having relapsing-remitting multiple sclerosis from January 2011 to September 2011, peripapillary RNFL thickness was measured using the fast RNFL program by Stratus, the optic disc cube protocol by Cirrus, and the N-site axonal analysis by Spectralis.

RESULTS

Overall, a moderate to good RNFL color code agreement was found (0.435-0.884), except for the nasal quadrant. The temporal quadrant was the most abnormal color coding by both Cirrus (64.7%) and Spectralis (61.7%) in both the optic neuritis (ON) and non-ON group and by Stratus (58.8%) in the ON group. Abnormal temporal RNFL color-code rate was significantly higher in ON eyes than non-ON eyes by Cirrus (P < .001), Stratus (P < .001), and Spectralis (P = .030). Overall, Cirrus significantly displayed abnormal findings while both Stratus and Spectralis displayed normal results for the inferior quadrant (P < .05). On the other hand, Spectralis OCT showed a significantly higher rate of abnormal findings while Cirrus displayed normal results for the temporal quadrant in non-ON eyes (P < .001).

CONCLUSIONS

We found a substantial color-code disagreement among devices in patients with relapsing-remitting multiple sclerosis regarding the ON antecedent. In non-ON eyes, Spectralis yielded a significantly higher thinning for temporal quadrant than Cirrus, suggesting that N-site axonal analysis could define axonal damage in relapsing-remitting multiple sclerosis patients earlier than conventional RNFL analysis.

The use of fourth-generation optical coherence tomography in multiple sclerosis: a review

Optical coherence tomography (OCT) has been routinely used to obtain high spatial resolution images of the retina and choroid non-invasively. Within the past decade, a fourth-generation OCT device using Fourier domain (FD) analysis has been developed that provides higher velocity and higher axial resolution images with better reproducibility than the previous generation time domain (TD) OCT technology. This review addresses the use of fourth-generation, FD ocular OCT in patients with multiple sclerosis.

Interocular asymmetry of foveal thickness in Parkinson disease

Purpose. To quantify interocular asymmetry (IA) of foveal thickness in Parkinson disease (PD) versus that of controls. Design. Prospective case-control series. Methods. In vivo assessment of foveal thickness of 46 eyes of 23 PD patients and 36 eyes of 18 control subjects was studied using spectral domain optical coherence tomography (SD-OCT). Inner versus outer layer retinal segmentation and macular volumes were quantified using the manufacturer's software, while foveal thickness was measured using the raw data from each eye in a grid covering a 6 by 6 mm area centered on the foveola in 0.25 mm steps. Thickness data were entered into MATLAB software. Results. Macular volumes differed significantly at the largest (Zone 3) diameter centered on the foveola (ETDRS protocol). By segmenting inner from outer layers, we found that the IA in PD is mostly due to changes on the slope of the foveal pit at the radial distances of 0.5 and 0.75 mm (1.5 mm and 1 mm diameter). Conclusions. About half of the PD patients had IA of the slope of the foveal pit. IA is a potentially useful marker of PD and is expected to be comparable across different SD-OCT equipment. Data of larger groups may be developed in future multicenter studies.

Better performance of RTVue than Cirrus spectral-domain optical coherence tomography in detecting band atrophy of the optic nerve

BACKGROUND

To assess the agreement and diagnostic performance between retinal nerve fiber layer (RNFL) thickness measurements obtained using the Cirrus (Carl Zeiss Meditec) and RTVue (Optovue Inc.) devices for detection of band atrophy (BA) in patients with permanent temporal hemianopia.

METHODS

In this retrospective study, 26 eyes with BA and 64 control eyes were enrolled. The Cirrus optic disc cube protocol and the RTVue optic nerve head map protocol were used. The Cirrus measurements were extracted and regrouped to be topographically matched with the RTVue measurements. Concordance correlation and 95 % limits of agreement were assessed. Areas under the receiver operating characteristic curves (AUC) and the Spearman's correlation coefficient between average Humphrey total deviation in the temporal hemifield and average RNFL thickness were calculated.

RESULTS

RTVue measured consistently thicker values than Cirrus in controls, whereas in eyes with BA, nasal segment measurements from the RTVue were thinner than those obtained using the Cirrus. Each quadrant showed moderate to close agreement in controls, whereas in eyes with BA, the nasal and temporal quadrants exhibited poor agreement. The RTVue measurements demonstrated significantly higher AUCs for nasal segments just above (0.95) and below (0.96) the horizontal meridian than Cirrus measurements (0.80 and 0.66, respectively) and a significant correlation with visual field loss (r(s) = 0.46, P = 0.02 for RTVue vs. r(s) = 0.26, P = 0.22 for Cirrus).

CONCLUSIONS

The RTVue RNFL thickness measurements in nasal sectors showed better diagnostic performance in detecting BA and higher correlations with temporal hemianopia than the Cirrus measurements.

Time-Domain and Spectral-Domain Optical Coherence Tomography of Retinal Nerve Fiber Layer in MS Patients and Healthy Controls

Objective. The aim of this study was to compare retinal nerve fiber layer thickness (RNFLT) between spectral-domain (SD-) and time-domain optical coherence tomography (TD-OCT) in MS patients and healthy controls (HC). Furthermore, RNFLT between MS eyes with and without optic neuritis (ON) and HC should be explored. Finally, the relationship between RNFLT, disease duration, EDSS, and disease modifying therapy (DMT) should be established. Design. Prospective, cross-sectional study. Participants. 28 MS patients and 35 HC. Methods. Both groups underwent TD- and SD-OCT measurements. RFNLT was correlated between the two machines and between MS eyes with and without ON and HC. Furthermore, RNFLT was correlated to disease duration, EDSS and DMT. Results. A strong correlation (Pearson's r = 0.921, P < 0.001), but a statistically significant difference of 2 μm (P < 0.001), was found between the two devices. RNFLT was significantly different between MS eyes with history of ON (mean RFNLT (SD) 72.21 μm (15.83 μm)), MS eyes without history of ON 93.03 μm (14.25 μm), and HC 99.07 μm (7.23 μm) (P < 0.001). Conclusions. The measurements between different generation of OCT machines are not interchangeable, which should be taken into account if comparing results between different machines and switching OCT machine in longitudinal studies.

Vision in multiple sclerosis: the story, structure-function correlations, and models for neuroprotection

Visual dysfunction is one of the most common clinical manifestations of multiple sclerosis (MS). Just over a decade ago, MS clinical trials did not include visual outcomes, but experts recognized the need for more sensitive measures of visual function. Low-contrast letter acuity emerged as the leading candidate to measure visual disability in MS, and subsequent studies found low-contrast acuity testing to correlate well with brain MRI lesion burden, visual-evoked potentials, quality of life (QOL), and retinal nerve fiber layer (RNFL) loss, as measured by optical coherence tomography (OCT). OCT in MS has allowed for assessment of structure-function correlations that make the anterior visual pathway and acute optic neuritis (ON) ideal models for testing novel agents for neuroprotection and repair. New therapies that reduce axonal loss by neuroprotective or myelin repair mechanisms can now be assessed noninvasively by OCT and coupled with visual function data. Based on OCT studies in MS, RNFL thickness is reduced significantly among patients (92 μm) vs controls (105 μm) and is particularly reduced in MS eyes with a history of ON (85 μm). Worsening of visual function by a clinically significant ≥ 7 letters or approximately 1.5 lines for low-contrast acuity is associated with approximately 4.5 μm reductions in RNFL thickness in MS eyes. Longitudinal studies of OCT have also shown RNFL axonal loss over time that occurs even in the absence of acute ON and that correlates with clinically meaningful worsening of vision and QOL, even in patients with benign MS. The latest OCT investigations involve high-resolution spectral-domain (SD) OCT with segmentation and measurement of specific retinal layers using computerized algorithms. These methods allow quantitation of ganglion cell (neuronal) layer loss and axonal degeneration in MS in vivo. In this review, we examine the data from these studies and ongoing trials that highlight the entity of ON as a model to investigate neuroprotection and neurorepair. In doing so, we also present representative group data from studies that have examined visual function, OCT measures, and QOL scales in patients with MS and ON and disease-free controls. These data, and those from recent meta-analyses, may be used to provide reference values for the development of clinical trial protocols.

Ganglion cell loss in relation to visual disability in multiple sclerosis

PURPOSE

We used high-resolution spectral-domain optical coherence tomography (SD-OCT) with retinal segmentation to determine how ganglion cell loss relates to history of acute optic neuritis (ON), retinal nerve fiber layer (RNFL) thinning, visual function, and vision-related quality of life (QOL) in multiple sclerosis (MS).

DESIGN

Cross-sectional study.

PARTICIPANTS

A convenience sample of patients with MS (n = 122; 239 eyes) and disease-free controls (n = 31; 61 eyes). Among MS eyes, 87 had a history of ON before enrollment.

METHODS

The SD-OCT images were captured using Macular Cube (200×200 or 512×128) and ONH Cube 200×200 protocols. Retinal layer segmentation was performed using algorithms established for glaucoma studies. Thicknesses of the ganglion cell layer/inner plexiform layer (GCL+IPL), RNFL, outer plexiform/inner nuclear layers (OPL+INL), and outer nuclear/photoreceptor layers (ONL+PRL) were measured and compared in MS versus control eyes and MS ON versus non-ON eyes. The relation between changes in macular thickness and visual disability was also examined.

MAIN OUTCOME MEASURES

The OCT measurements of GCL+IPL and RNFL thickness; high contrast visual acuity (VA); low-contrast letter acuity (LCLA) at 2.5% and 1.25% contrast; on the 25-item National Eye Institute Visual Function Questionnaire (NEI-VFQ-25) and 10-Item Neuro-Ophthalmic Supplement composite score.

RESULTS

Macular RNFL and GCL+IPL were significantly decreased in MS versus control eyes (P<0.001 and P = 0.001) and in MS ON versus non-ON eyes (P<0.001 for both measures). Peripapillary RNFL, macular RNFL, GCL+IPL, and the combination of macular RNFL+GCL+IPL were significantly correlated with VA (P≤0.001), 2.5% LCLA (P<0.001), and 1.25% LCLA (P≤0.001). Among OCT measurements, reductions in GCL+IPL (P<0.001), macular RNFL (P = 0.006), and the combination (macular RNFL+GCL+IPL; P<0.001) were most strongly associated with lower (worse) NEI-VFQ-25 and 10-Item Supplement QOL scores; GCL+IPL thinning was significant even accounting for macular RNFL thickness (P = 0.03 for GCL+IPL, P = 0.39 for macular RNFL).

CONCLUSIONS

We demonstrated that GCL+IPL thinning is most significantly correlated with both visual function and vision-specific QOL in MS, and may serve as a useful structural marker of disease. Our findings parallel those of magnetic resonance imaging studies that show gray matter disease is a marker of neurologic disability in MS.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found after the references.