Retinal Nerve Fiber Layer Thickness Measurement by Fourier-domain Optical Coherence Tomography: A Comparison Between Cirrus-HD OCT and RTVue in Healthy Eyes

Differentiating Multiple Sclerosis and Glaucoma With Sectoral Pattern Analysis of Peripapillary Nerve Fiber Layer

Purpose

To distinguish between multiple sclerosis (MS) and glaucoma by nerve fiber layer (NFL) thinning patterns.

Methods

MS patients were diagnosed by the 2017 McDonald Criteria; glaucoma patients had disc rim thinning or an NFL defect, with or without perimetric defect. The peripapillary NFL thickness was divided into eight sectors, and percentage reduction (% reduction) was calculated relative to normative reference values. The MS and glaucoma eyes were grouped based on the severity of NFL thinning in the worst sector: significant reduction (<1 percentile of normal reference), borderline reduction (1%∼5%), and no reduction (>5%). We devised four diagnostic indexes, and the area under the curve of receiver operating characteristics (AROC) and accuracy were used to evaluate the indexes.

Results

We enrolled 58 control subjects (58 eyes), 56 MS subjects (112 eyes), and 92 glaucoma subjects (92 eyes) at two centers. The most pronounced percent reduction in MS eyes occurred in the temporal-upper and temporal-lower sectors. In glaucoma eyes, this occurred in the inferior-temporal, inferior-nasal, and superior-temporal sectors. The temporal pattern index had the best AROC (0.96, 0.91-1.00) and accuracy (92.6%) in the significant reduction group. It had good AROC (0.88, 0.78-0.99) and accuracy (76.7%) in the borderline reduction group.

Conclusions

Normalizing NFL reduction as a percentage of normal reference accentuated patterns characteristic of MS and glaucoma. Quantitative pattern indexes were effective in differentiating the two diseases.

Translational Relevance

The utility of optical coherence tomography in the differential diagnosis of optic neuropathies is enhanced by analyzing the retinal nerve fiber layer percentage reduction pattern.

Retinal nerve fibre layer thickness in a normal black South African population

BACKGROUND

The measurement of retinal nerve fibre layer (RNFL) thickness on spectral domain OCT (SD-OCT) are compared with built-in age- and gender-matched European normative databases and this difference is used to assist with glaucoma diagnosis. However, there are differences in RNFL thickness between population groups. Therefore, using the built in European normative database as a comparison across all population groups could lead to erroneous results, due to the basic assumption that the normative values for non-European populations are the same as their European counterparts.

METHODS

Cross-sectional study of RNFL thickness in normal black South African patients.

RESULTS

One hundred and thirty-two eyes of 132 patients were enroled in this study. The mean (SD) age of patients in this study was 41.3 (12.5) years. Males comprised 40.9% (n = 54; p = 0.0367). All RNFL sectors except the temporal sector were significantly thicker than the reference database. The RNFL sectors measured as follows: global (108.7 µm, p < 0.001), superotemporal (152.4 µm, p < 0.001), superonasal (132.6 µm, p < 0.001), inferotemporal (150.1 µm, p < 0.001), inferonasal (129.2 µm, p < 0.001), nasal (77.7 µm, p < 0.001), temporal 74.8 µm, p = 0.9534).

CONCLUSION

The RNFL thickness of normal black South Africans is significantly thicker than that of the European database on the Spectralis SD-OCT. This needs to be taken into account when performing RNFL thickness measurements on black patients.

Retinal nerve fibre layer thickness values and their associations with ocular and systemic parameters in Black South Africans

PURPOSE

To measure the retinal nerve fibre layer (RNFL) thickness values and investigate their associations with other parameters in healthy eyes of Black South Africans.

METHODS

600 participants with healthy eyes, of whom 305 (50.83%) were males and 295 (49.17%) were females, with a mean age of 28.15 ± 13.09 years, underwent a detailed ophthalmic examination. RNFL thickness was measured by iVue SD-OCT.

RESULTS

The mean global RNFL thickness was 110.01 ± 7.39 µm. The RNFL was thickest inferiorly (135.06 ± 9.66 µm) and superiorly (131.72 ± 10.46 µm), thinner nasally (87.24 ± 13.22 µm), and thinnest temporally (73.63 ± 15.66 µm). Multivariate analysis showed that thicker mean global RNFL thickness was significantly associated with younger age, shorter axial length (AL) and hyperopia (p < 0.001). Mean RNFL thickness decreased by approximately 0.11 µm per year of aging life, and by 1.02 µm for each 1-mm of axial elongation. There was a 0.62 µm RNFL thickness increase for every dioptre change in spherical power towards more hyperopia.

CONCLUSION

Mean RNFL thickness values and their associations established in this population may be of clinical value when assessing factors that influence this parameter and diagnosing diseases affecting it.

Retinal nerve fibre layer thickness in a general population in Iran

BACKGROUND

To determine retinal nerve fibre layer (RNFL) thickness distribution and its related factors in a general population of 45 to 69 year olds in Iran.

DESIGN

Population-based cross-sectional study.

PARTICIPANTS

Of the 5190 participants of phase one of Shahroud Eye Cohort Study, 4737 participated in Phase two (participation rate = 91.3%).

METHODS

All study participants underwent visual acuity measurement, refraction tests, slit lamp examination and ophthalmoscopic fundus exam. Tests also included imaging with Cirrus HD-OCT 4000 and its RNFL thickness data were used in this study.

MAIN OUTCOME MEASURES

The overall RNFL thickness and the average RNFL thickness in different quadrants.

RESULTS

Mean RNFL thickness in the superior, inferior, nasal and temporal quadrants were 92.47 µm [95% confidence interval (CI): 92.14-92.80], 111.22 µm (95% CI: 110.7-111.73), 118.93 µm (95% CI: 118.31-119.55), 74.83 µm (95% CI: 74.07-75.59) and 65.48 µm (95% CI: 65.06-65.90). Multiple linear regression models indicated that RNFL thickness in all quadrants decreased with ageing, was lower in females (coefficient:-0.87 and P = 0.015), decreased by 1.42 µm (P < 0.001) for each millimetre increase in axial length and decreased by 0.41 µm (P = 0.041) for each diopter decrease in spherical equivalent refraction of myopia.

CONCLUSION

RNFL thickness in the 45 to 69-year-old Iranian population is lower compared to other studies. This difference should be noted in making disease diagnoses, particularly glaucoma. Also, there is a significant relationship between ageing and RNFL thinning in all quadrants. Longer axial length, myopia and male gender are associated with reduced RNFL thickness.

Reproducibility of Circumpapillary Retinal Nerve Fiber Layer Thickness Measurements Evaluated by Circle and Annulus Area With and Without Correction for Ocular Rotation

PURPOSE

To compare the reproducibility of annulus area measurements of the circumpapillary retinal nerve fiber layer thickness (cpRNFLTannulus) using spectral-domain optical coherence tomography (SD-OCT) with that of conventional cpRNFLT (cpRNFLTring) measurements and evaluate the effect of correction of ocular rotation on the reproducibility.

MATERIALS AND METHODS

Peripapillary SD-OCT raster scans were performed on 2 different days in 48 normal subjects and 59 patients with glaucoma using the Topcon OCT-1000. In the raster scan dataset, the cpRNFLTring and cpRNFLTannulus were averaged along a circle (3.4-mm diameter) and in an annulus area (diameters from 2.8 to 4.0 mm) centered on the barycenter of the disc. The measurement reproducibility, effects of ocular rotational correction, and factors affecting the reproducibility were studied.

RESULTS

The intervisit reproducibility values, expressed as the coefficients of variation, for the cpRNFLTannulus, were significantly smaller than those for the cpRNFLTring measurements in sectors 30 degrees wide in glaucomatous eyes (P=0.006) and in sectors 10 degrees wide in normal and glaucomatous eyes (P<0.001). The ocular rotational angles averaged 7.1 and 7.2 degrees with intervisit differences of 1.4 and 1.8 degrees, respectively, in normal and glaucomatous eyes. Correction for the ocular rotation had little effect on the reproducibility. The mean deviation and cpRNFLT were correlated negatively with the coefficient of variation (β=-0.93 to -0.83; P=0.027 to 0.028).

CONCLUSIONS

The cpRNFLTannulus measurement yielded better reproducibility than the cpRNFLTring measurement, and multiple linear regression analysis showed that the more advanced the glaucomatous damage, the worse the intervisit reproducibility.

Syndromic parkinsonism and dementia associated with OPA1 missense mutations

Objective

Mounting evidence links neurodegenerative disorders such as Parkinson disease and Alzheimer disease with mitochondrial dysfunction, and recent emphasis has focused on mitochondrial dynamics and quality control. Mitochondrial dynamics and mtDNA maintenance is another link recently emerged, implicating mutations in the mitochondrial fusion genes OPA1 and MFN2 in the pathogenesis of multisystem syndromes characterized by neurodegeneration and accumulation of mtDNA multiple deletions in postmitotic tissues. Here, we report 2 Italian families affected by dominant chronic progressive external ophthalmoplegia (CPEO) complicated by parkinsonism and dementia.

Methods

Patients were extensively studied by optical coherence tomography (OCT) to assess retinal nerve fibers, and underwent muscle and brain magnetic resonance spectroscopy (MRS), and muscle biopsy and fibroblasts were analyzed. Candidate genes were sequenced, and mtDNA was analyzed for rearrangements.

Results

Affected individuals displayed a slowly progressive syndrome characterized by CPEO, mitochondrial myopathy, sensorineural deafness, peripheral neuropathy, parkinsonism, and/or cognitive impairment, in most cases without visual complains, but with subclinical loss of retinal nerve fibers at OCT. Muscle biopsies showed cytochrome c oxidase‐negative fibers and mtDNA multiple deletions, and MRS displayed defective oxidative metabolism in muscle and brain. We found 2 heterozygous OPA1 missense mutations affecting highly conserved amino acid positions (p.G488R, p.A495V) in the guanosine triphosphatase domain, each segregating with affected individuals. Fibroblast studies showed a reduced amount of OPA1 protein with normal mRNA expression, fragmented mitochondria, impaired bioenergetics, increased autophagy and mitophagy.

Interpretation

The association of CPEO and parkinsonism/dementia with subclinical optic neuropathy widens the phenotypic spectrum of OPA1 mutations, highlighting the association of defective mitochondrial dynamics, mtDNA multiple deletions, and altered mitophagy with parkinsonism. Ann Neurol 2015;78:21–38

Analysis of peripapilary retinal nerve fiber layer thickness of healthy Chinese from northwestern Shanghai using Cirrus HD-OCT

AIM

To investigate peripapillary retinal nerve fiber layer (RNFL) thickness of healthy Chinese individuals from northwestern Shanghai using Cirrus HD-OCT (Carl Zeiss Meditec, Inc. Dublin, CA, USA).

METHODS

The peripapillary RNFL thickness of 720 eyes from 360 healthy Chinese participants were measured using the Optic Disc Cube 200×200 protocol. Each eye was scanned 3 times. Global and each quadrant's RNFL thickness around the optic nerve were compared between genders, and interocular differences were analyzed. The correlation between global RNFL thickness and age were also assessed in this study.

RESULTS

The mean global, superior, nasal, inferior and temporal RNFL thickness of all the eyes were 96.04±7.40 µm, 118.36±13.52 µm, 67.63±8.60 µm, 125.17±13.48 µm, 72.49±10.70 µm, respectively. When analyzing between genders, the mean nasal RNFL thickness of male and female were 68.29±8.44 µm and 66.97±8.70 µm, with statistically significant difference (P=0.038), while the data of global, superior, inferior and temporal quadrant showed no significant difference (all P>0.05). When analyzing interocular differences, the mean RNFL thickness of all the right eyes and all the left eyes were 116.46±13.17 µm and 120.27±13.61 µm in superior quadrant (P<0.001); 68.74±8.80 µm and 66.52±8.25 µm in nasal quadrant (P<0.001); 73.16±10.95 and 71.83±10.41 in temporal quadrant (P<0.001), all having statistically significant differences. There were no statistically significant interocular differences of global and inferior RNFL thickness (both P>0.05). There was a significantly negative correlation (r=-0.618, P<0.001) between the mean global RNFL thickness and the age.

CONCLUSION

In healthy Chinese from northwestern Shanghai, there were no significant differences detected interocular difference and between genders in the mean global RNFL thickness. Nevertheless, significant difference existed in the nasal quadrant between genders, and interocular differences existed in the superior, nasal and temporal quadrants. The RNFL thickness appeared to gradually decrease with age.

Analysis of normal retinal nerve fiber layer thickness by age, sex, and race using spectral domain optical coherence tomography

PURPOSE

To determine the effects of age, sex, and race on the retinal nerve fiber layer (RNFL) in the normal human eye as measured by the spectral domain optical coherence tomography (SD-OCT) Spectralis machine (Heidelberg Engineering).

METHODS

Peripapillary SD-OCT RNFL thickness measurements were determined in normal subjects seen at a university-based clinic. One randomly selected eye per subject was used for analysis in this cross-sectional study. Multiple regression analysis was applied to assess the effects of age, sex, ethnicity, and mean refractive error on peripapillary RNFL thickness. Results are expressed as means±SD wherever applicable.

RESULTS

The study population consisted of 190 healthy participants from 9 to 86 years of age. Of the 190 participants, 62 (33%) were men, 125 (66%) Caucasians, 26 (14%) African Americans, 14 (7%) Hispanics, 16 (8%) Asians, and 9 (5%) other races. The mean RNFL thickness for the normal population studied was 97.3 ± 9.6 µm. Normal RNFL thickness values follow the ISNT rule with decreasing RNFL thickness values starting from the thickest quadrant inferiorly to the thinnest quadrant temporally: inferior quadrant (126 ± 15.8), superior quadrant (117.2±16.13), nasal quadrant (75 ± 13.9), and temporal quadrant (70.6 ± 10.8 µm). Thinner RNFL measurements were associated with older age (P<0.001); being Caucasian, versus being either Hispanic or Asian (P=0.02 and 0.009, respectively); or being more myopic (P<0.001). For every decade of increased age, mean RNFL thickness measured thinner by approximately 1.5 µm (95% confidence interval, 0.24-0.07). Comparisons between ethnic groups revealed that Caucasians had mean RNFL values (96 ± 9.2 µm) slightly thinner than those of Hispanics (102.9 ± 11 µm; P=0.02) or Asians (100.7 ± 8.5 µm; P=0.009). African Americans RNFL values (99.2 ± 10.2 µm) were not significantly different when compared with Caucasians. There was no relationship between RNFL thickness and sex.

CONCLUSIONS

The thickest RNFL measurements were found in the inferior quadrant, followed by the superior, nasal, and temporal quadrants (ISNT rule applied to the RNFL). Thinner RNFL measurements were associated with older age and increasing myopia. Caucasians tend to have thinner RNFL values when compared with Hispanics and Asians. SD-OCT analysis of the normal RNFL showed results similar to time domain OCT studies.

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.

Peripapillary retinal nerve fibre layer thickness measurement with SD-OCT in normal and glaucomatous eyes: distribution and correlation with age

AIM

To determine peripapillary retinal fiber layer thickness (RNFL) measured with spectral domain optical coherence tomography (SD-OCT) in normal and glaucomatous eyes in a large sample of exclusively white population and compare results with other similarly constructed studies.

METHODS

Average, maximum, minimum and per quadrant RNFL thickness were measured in normal and glaucomatous Greek patients with a scanning laser ophthalmoscope (SLO)/SD-OCT device. The effect of age in normal RNFL thickness was also determined.

RESULTS

A total of 278 normal (278 patients) and 67 glaucomatous (67 patients) eyes were included in the study. Average RNFL thickness was 114.8±13.3µm in normal and 92.1±18.5µm in glaucomatous eyes (P<0.001). In normal discs, superior quadrant was the thickest, followed by the inferior, nasal and temporal. Decline of normal RNFL thickness with age was statistically significant for average RNFL thickness (1.92µm per decade of life) and for the superior and inferior quadrants of the disc.

CONCLUSION

SD-OCT peripapillary RNFL measurements can be used to distinguish between normal and glaucomatous eyes and establish normative databases, since normal disc measurements differ between different ethnic groups and between different SD-OCT devices.

Cirrus high-definition optical coherence tomography versus spectral optical coherence tomography/scanning laser ophthalmoscopy in the diagnosis of glaucoma

PURPOSE

This study was performed to compare the positive predictive value of peripapillary retinal nerve fiber layer (RNFL) thickness measurements obtained using Cirrus high-definition optical coherence tomography (Cirrus HD-OCT; Carl Zeiss Meditec, Dublin, CA) and spectral OCT/scanning laser ophthalmoscopy (SLO) (OPKO/OTI, Miami, FL) in the diagnosis of glaucoma.

METHODS

A total of 50 eyes of 50 healthy subjects and 60 eyes of 60 subjects with glaucoma were included. All participants underwent RNFL thickness measurement using Cirrus HD-OCT and spectral OCT/SLO on the same day. Average, quadrant, clock-hour RNFL thicknesses, area under the receiver operating characteristic curve (AUC), and sensitivities at fixed specificities (80% and 95%) were calculated for comparison.

RESULTS

RNFL thickness as measured by spectral OCT/SLO was greater than that measured using Cirrus HD-OCT (p < 0.001). For both the Cirrus HD-OCT and spectral OCT/SLO, the parameter with the largest AUC was average RNFL thickness (0.954 and 0.944, respectively). The AUCs of RNFL thickness for the discrimination of glaucoma did not differ significantly between the devices (p > 0.05), with the exception of RNFL thickness in the nasal area (nasal quadrant, clock-hour sectors 3 and 4); in these areas, spectral OCL/SLO yielded greater AUCs than Cirrus HD-OCT (p < 0.05). Sensitivities varied similarly to AUCs.

CONCLUSIONS

RNFL thicknesses measures using Cirrus HD-OCT and spectral OCT/SLO were not interchangeable. The utility of RNFL thickness measurements in the diagnosis of glaucoma was similar for both the devices.

Influence of axial length on peripapillary retinal nerve fiber layer thickness in children: a study by RTVue spectral-domain optical coherence tomography

PURPOSE

To evaluate the influence of axial length on peripapillary retinal nerve fiber layer (RNFL) thickness in myopic, hyperopic and emmetropic children eyes by RTVue optical coherence tomography (OCT).

METHODS

One hundred twenty eyes of 120 children including 40 myopic, 40 emmetropic and 40 hyperopic eyes were enrolled in the study. Peripapillary RNFL thickness measurements were performed using spectral-domain RTVue OCT (Optovue, Fremont, CA). RNFL thickness parameters were obtained from all octametric sections: upper temporal (TU), superotemporal (ST), superonasal (SN), upper nasal (NU), lower nasal (NL), inferonasal (IN), inferotemporal (IT) and lower temporal (TL). Spherical equivalent refractive error was determined via cycloplegic auto-refraction (Topcon, Tokyo, Japan). The axial length was measured using IOLMaster (Carl Zeiss MEDITEC). Littmann formula was used for correction of axial length-related ocular magnification effect.

RESULTS

Peripapillary RNFL thicknesses were significantly different among the three groups in all sectors except for NU and IT sectors. RNFL thicknesses in all sectors except for TU and TL sectors had significant negative correlations with axial length. However, these differences (excluding TU and TL sectors) and correlations disappeared after correction of magnification effect.

CONCLUSION

In conclusion, axial length influences peripapillary RNFL thickness as measured by RTVue OCT. However, this appears to be due to the ocular magnification effects associated with axial length and can be corrected for with the application of the Littman formula.

Comparison of retinal nerve fiber layer thickness measurements by spectral-domain optical coherence tomography systems using a phantom eye model

To quantify differences in nerve fiber layer thickness measurements by various spectral-domain optical coherence tomography (SD-OCT) systems, we developed a phantom eye model. We tested twelve SD-OCT systems of four manufacturers. All systems combined overestimated the 49 µm thick phantom RNFL thickness on average by 18 µm. Within brands, thickness measurements differed statistically significant for one Topcon, one RTVue and one Cirrus. Between brands, thickness determined with RTVue and Topcon differed statistically significant from Cirrus and Spectralis. The maximum difference between mean thicknesses is 3.6 µm within brands and 7.7 µm between brands.

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.

Reproducibility of optical coherence tomography measurements in children

PURPOSE

To determine the interobserver and intraobserver reproducibility of a Fourier-domain optical coherence tomography device (Cirrus HD OCT; Carl Zeiss Meditec, Dublin, California, USA) in normal pediatric eyes.

DESIGN

Prospective cross-sectional study.

METHODS

One hundred healthy children were recruited prospectively and consecutively. Only 1 randomly chosen eye per subject was included in the study. The eye underwent 3 scans centered on the optic disc and another 3 scans centered on the macula that were acquired by a single operator. A fourth examination was performed by a second operator. Interobserver and intraobserver reproducibility were described by intraclass correlation coefficients (ICCs) and coefficients of variation (COVs).

RESULTS

The mean age was 9.15 years (range, 6.22 to 11.31 years; standard deviation, 1.05 years). Mean retinal nerve fiber layer thickness was 99.53 μm (standard deviation, 10.10 μm), and mean macular thickness was 282.91 μm (standard deviation, 11.83 μm). All the parameters evaluated were highly reproducible. Intraobserver COVs of the retinal nerve fiber layer measurements ranged from 2.24% to 5.52%, and the COV of macular thickness was 0.97%. The intraclass correlation coefficient was greater than 0.8 for all the parameters. The interobserver COV ranged from 2.23% to 5.18%, and the COV of macular thickness was 0.82%. In all the evaluated parameters, the intraclass correlation coefficient was more than 0.75. Repeatability was slightly better in children older than 10 years than in children younger than 9 years.

CONCLUSIONS

Retinal nerve fiber layer and macular measurements obtained by Fourier-domain optical coherence tomography showed good repeatability for healthy eyes in the pediatric population. Cirrus HD OCT examinations of the retina are reliable in children.

Peripapillary retinal nerve fiber layer thickness measurement by 2 different spectral domain optical coherence tomography machines

PURPOSE

To determine agreement between peripapillary retinal nerve fiber layer (RNFL) thickness measurements by 2 spectral domain optical coherence tomography (SD-OCT) instruments.


METHODS

. This was an observational, cross-sectional study. Both eyes of 89 subjects, 44 healthy subjects (mean age, 47±15 years) and 45 patients with glaucoma (mean age, 55±14 years), were imaged using Cirrus OCT (Carl Zeiss Meditec, Inc. Dublin, CA, USA) and Topcon OCT (3D-OCT 1000, Topcon Corporation, Tokyo, Japan). One eye was randomly selected in each subject and peripapillary RNFL thickness measurements were compared. Bland-Altman plots were used to assess the level of agreement.


RESULTS

. Average peripapillary RNFL thickness measurements were significantly larger with Topcon OCT compared to Cirrus OCT in normal (101±12 vs 91±8 µm, p<0.001) and glaucomatous eyes (89±18 vs 76±16 µm, p<0.001). The limits of agreement for average peripapillary RNFL thickness measurements were poor, (-11 to 32 µm) in normal and (-4 to 30 µm) in glaucomatous eyes.


CONCLUSIONS

. Peripapillary RNFL thickness values obtained by Topcon OCT are significantly higher than those measured by Cirrus OCT in both normal and glaucomatous eyes. Clinicians should be aware of this discrepancy especially when monitoring patients imaged by different OCT instruments; measured values cannot be used interchangeably.

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.

Effects of changing operators and instruments on time-domain and spectral-domain OCT measurements of retinal nerve fiber layer thickness

BACKGROUND AND OBJECTIVE

To determine the amount of interoperator and interinstrument variability introduced into retinal nerve fiber layer (RNFL) thickness measured with Stratus OCT and Cirrus HD-OCT (Carl Zeiss Meditec, Dublin, CA) in normal and glaucomatous eyes.

PATIENTS AND METHODS

Thirty-seven eyes from 37 subjects (20 normal and 17 with glaucoma) were included in the study. Each eye was scanned with one Stratus OCT and one Cirrus OCT by two operators. The eyes were then scanned with a different Stratus OCT and Cirrus OCT by one of the operators. Average, quadrant, and clock-hour RNFL measurements were compared between operators and between instruments after determining the proportion of variance due to subjects, operators, and instruments by means of variance component analysis.

RESULTS

Significant differences were observed between Stratus OCT instruments, but not between Cirrus OCT instruments, in average (P = .01), inferior (P = .006), and nasal (P < .001) quadrant RNFL thickness in glaucomatous eyes. Interoperator differences in RNFL thickness measured with both types of instruments were non-significant. The interoperator variability ranged from 0% to 1% on Stratus OCT and was 0% on Cirrus OCT, whereas the interinstrument variability ranged from 0% to 3% for Stratus OCT and from 0% to 1% for Cirrus OCT.

CONCLUSION

The interoperator variability of RNFL thickness measured with Stratus OCT and Cirrus OCT, as well as the interinstrument variability of measurements obtained with Cirrus OCT, are non-significant. However, there is significant variability between RNFL measurements performed on two different Stratus OCT instruments.

Spectral-domain optical coherence tomography for the diagnosis and follow-up of glaucoma

PURPOSE OF REVIEW

As spectral-domain optical coherence tomography (SD-OCT) progressively replaces time-domain OCT (TD-OCT) in the clinical and research setting, several commercially available instruments and new software upgrades for glaucoma diagnosis and progression analysis have been developed. Over the last year, several studies have been performed to assess the diagnostic performance of most of these instruments necessitating a review of their findings.

RECENT FINDINGS

When compared with the measurements provided by TD-OCT, the conventional peripapillary circular scans by SD-OCT, which aim to measure the retinal nerve fiber layer (RNFL) thickness, show higher repeatability and similar diagnostic sensitivity. New software capabilities, such as the RNFL deviation map of Cirrus HD-OCT (Carl Zeiss Meditec, Dublin, CA) or the macular Ganglion Cell Complex scan of RTVue (Optovue, Fremont, CA), provide complementary information that enhances our ability to discriminate between healthy and glaucomatous eyes.

SUMMARY

SD-OCT-based instruments represent a technological advancement in the diagnosis of glaucoma. Improved repeatability will facilitate more reliable follow-up and progression analysis.

Retinal nerve fiber layer assessment: area versus thickness measurements from elliptical scans centered on the optic nerve

PURPOSE

An evaluation of the retinal nerve fiber layer (RNFL) provides important information on the health of the optic nerve. Standard measurements of the RNFL consider only thickness, but an accurate assessment should also consider axial length, size of the optic nerve head (ONH), blood vessel contribution, and distance of the scan from the ONH margin. In addition, although most primate ONHs are elliptical, the circular scan centered on the ONH is the mainstay in both clinical and research analyses. The purpose of this study was to evaluate thickness and area measures of RNFL cross sections when axial length and ONH shape are included.

METHODS

Circular, raster, and radial scans of left eye optic nerves were acquired from 40 normal rhesus monkeys (Macaca mulatta) using spectral domain optical coherence tomography. The disc margin was identified by manually selecting the RPE/Bruch's membrane opening and ONH border tissue. With a pixel-to-micrometer conversion computed from a three-surface schematic eye, RNFL scans were interpolated at 300 to 600 μm (50-μm increments) from the edge of the ONH. The thickness and area of the RNFL at each distance were obtained by custom programs. Blood vessels in the RNFL were selected and removed from the overall RNFL measures.

RESULTS

The average RNFL thickness decreased systematically from 149 ± 12.0 μm for scans 300 μm from the disc margin to 113 ± 7.2 μm at an eccentricity of 600 μm (P < 0.05). In contrast, the cross-sectional areas of the RNFL did not vary with scan location from the disc margin (0.85 ± 0.07 mm(2) at 300 μm compared with 0.86 ± 0.06 mm(2) at 600 μm). Blood vessels accounted for 9.3% of total RNFL thickness or area, but varied with retinal location. On average, 17.6% of the superior and 14.2% of the inferior RNFL was vascular, whereas blood vessels accounted for only 2.3% of areas of the temporal and nasal RNFL regions.

CONCLUSIONS

In nonhuman primates, with appropriate transverse scaling and ONH shape analysis, the cross-sectional area of the RNFL is independent of scan distance, up to 600 μm from the rim margin, indicating that the axonal composition changes little over this range. The results suggest that, with incorporation of transverse scaling, the RNFL cross-sectional area, rather than RNFL thickness, provides an accurate assessment of the retinal ganglion cell axonal content within the eye.