Macular ganglion cell-inner plexiform layer: automated detection and thickness reproducibility with spectral domain-optical coherence tomography in glaucoma

Macular ganglion cell/inner plexiform layer measurements by spectral domain optical coherence tomography for detection of early glaucoma and comparison to retinal nerve fiber layer measurements

PURPOSE

To evaluate the performance of ganglion cell layer/inner plexiform layer (GCL/IPL) measurements with spectral-domain optical coherence tomography (Cirrus HD-OCT) for detection of early glaucoma and to compare results to retinal nerve fiber layer (RNFL) measurements.

DESIGN

Cross-sectional prospective diagnostic study.

METHODS

We enrolled 99 subjects, including 59 eyes with glaucoma (47 subjects) (mean deviation >-6.0 dB) and 91 normal eyes (52 subjects). Patients underwent biometry and peripapillary and macular OCT imaging. Performance of the GCL/IPL and RNFL algorithms was evaluated with area under receiver operating characteristic curves (AUC), likelihood ratios, and sensitivities/specificities adjusting for covariates. Combination of best parameters was explored.

RESULTS

Average (SD) mean deviation in the glaucoma group was -2.5 (1.9) dB. On multivariate analyses, age (P < 0.001) and axial length (P = 0.03) predicted GC/IPL measurements in normal subjects. No significant correlation was found between average or regional GC/IPL thickness and respective outer retina (OR) thickness measurements (P > 0.05). Average RNFL thickness performed better than average GCL/IPL measurements for detection of glaucoma (AUC = 0.964 vs 0.937; P = 0.04). The best regional measures from each algorithm (inferior quadrant RNFL vs minimum GCL/IPL) had comparable performances (P = 0.78). Entering the GC/IPL to OR ratio into prediction models did not enhance the performance of the GCL/IPL measures. Combining the best parameters from each algorithm improved detection of glaucoma (P = 0.04).

CONCLUSIONS

Regional GCL/IPL measures derived from Cirrus HD-OCT performed as well as regional RNFL outcomes for detection of early glaucoma. Using the GC/IPL to OR ratio did not enhance the performance of GCL/IPL parameters. Combining the best measures from the 2 algorithms improved detection of glaucoma.

Macular structure parameters as an automated indicator of paracentral scotoma in early glaucoma

PURPOSE

To evaluate the predictive ability of macular parameters defined in the significance map created using spectral-domain optical coherence tomography (SD-OCT) for paracentral visual field defects in early glaucoma.

DESIGN

Prospective comparative study.

METHODS

We studied 78 early-glaucomatous eyes of 78 patients, who underwent SD-OCT and standard automated perimetry 10-2. Macular layer parameters included the retinal nerve fiber layer (RNFL), ganglion cell layer (GCL) + inner plexiform layer (IPL), and RNFL + GCL + IPL. The minimal distance between the area with abnormal (P < 1%) thickness and foveal center was defined as the shortest distance. A wider area of an abnormally thinned (<1%) region, within either an inferior or a superior hemicircle with a diameter of 6 mm centered at the fovea, was defined as the macular abnormal area. A circumpapillary RNFL parameter was defined in its 36 sectors. Areas under the receiver operating characteristic curves (ROCs) were calculated to discriminate between eyes with (n = 39) and without (n = 39) paracentral visual field defects in the central 5 degrees.

RESULTS

Measurement reproducibility was almost perfect in the macular parameters at P < 1% (intraclass correlation, 0.907-0.942). Areas under the ROC were significantly higher (P ≤ 0.01) in the macular parameters (0.870-0.930), including the shortest distance of GCL + IPL/RNFL + GCL + IPL, and the macular abnormal area of RNFL/GCL + IPL/RNFL + GCL + IPL than in the circumpapillary RNFL parameter (0.676). When specificity was fixed at ≥90%, the shortest distance of GCL + IPL (area under the ROC = 0.874) and the macular abnormal area of RNFL (area under the ROC = 0.894) showed sensitivities greater than 50%.

CONCLUSIONS

Macular structural parameters defined on an SD-OCT significance map may be potentially useful predictors of the presence of paracentral scotoma.

Correlation of magnetic resonance imaging optic nerve parameters to optical coherence tomography and the visual field in glaucoma

BACKGROUND

To determine the viability of using magnetic resonance imaging measurement of optic nerve morphology as an objective analysis of glaucomatous damage.

DESIGN

Retrospective study conducted at Tohoku University Hospital.

PARTICIPANTS

Thirty-eight eyes of 19 patients with open-angle glaucoma.

METHODS

Patients were scanned with T2-weighted and 3-T diffusion tensor magnetic resonance imaging, and parameters of the optic nerve, including fractional anisotropy, apparent diffusion coefficient and cross-sectional area, were determined. Conventional parameters of glaucomatous damage, including circumpapillary and macular retinal nerve fibre layer thickness, and mean deviation and average total deviation of the central 16 test points from the Humphrey Field Analyzer, were then compared with the magnetic resonance imaging-derived parameters. Spearman's coefficient of correlation was calculated to determine the significance of the correlation.

MAIN OUTCOME MEASURE

Correlation coefficient between the magnetic resonance imaging parameters and the parameters of glaucomatous damage.

RESULTS

Mean deviation was significantly correlated with all magnetic resonance imaging parameters (fractional anisotropy: r = 0.53, apparent diffusion coefficient: r = -0.44, cross-sectional area: r = 0.70). Circumpapillary retinal nerve fibre layer thickness was significantly correlated with fractional anisotropy (r = 0.60) and cross-sectional area (r = 0.47), but not apparent diffusion coefficient (r = -0.29). Central macular function and macular retinal nerve fibre layer thickness were also significantly correlated with magnetic resonance imaging parameters.

CONCLUSIONS

Optic nerve magnetic resonance imaging parameters were significantly correlated to glaucomatous damage. Magnetic resonance imaging analysis of the optic nerve may, thus, have value as an objective instrument to assess glaucomatous degeneration, including the function of the macula.

Reproducibility of SD-OCT-based ganglion cell-layer thickness in glaucoma using two different segmentation algorithms

PURPOSE

To compare the reproducibility of spectral-domain optical coherence tomography (SD-OCT)-based ganglion cell-layer-plus-inner plexiform-layer (GCL+IPL) thickness measurements for glaucoma patients obtained using both a publicly available and a commercially available algorithm.

METHODS

Macula SD-OCT volumes (200 × 200 × 1024 voxels, 6 × 6 × 2 mm(3)) were obtained prospectively from both eyes of patients with open-angle glaucoma or with suspected glaucoma on two separate visits within 4 months. The combined GCL+IPL thickness was computed for each SD-OCT volume within an elliptical annulus centered at the fovea, based on two algorithms: (1) a previously published graph-theoretical layer segmentation approach developed at the University of Iowa, and (2) a ganglion cell analysis module of version 6 of Cirrus software. The mean overall thickness of the elliptical annulus was computed as was the thickness within six sectors. For statistical analyses, eyes with an SD-OCT volume with low signal strength (<6), image acquisition errors, or errors in performing the commercial GCL+IPL analysis in at least one of the repeated acquisitions were excluded.

RESULTS

Using 104 eyes (from 56 patients) with repeated measurements, we found the intraclass correlation coefficient for the overall elliptical annular GCL+IPL thickness to be 0.98 (95% confidence interval [CI]: 0.97-0.99) with the Iowa algorithm and 0.95 (95% CI: 0.93-0.97) with the Cirrus algorithm; the intervisit SDs were 1.55 μm (Iowa) and 2.45 μm (Cirrus); and the coefficients of variation were 2.2% (Iowa) and 3.5% (Cirrus), P < 0.0001.

CONCLUSIONS

SD-OCT-based GCL+IPL thickness measurements in patients with early glaucoma are highly reproducible.

Relationship between ganglion cell-inner plexiform layer and optic disc/retinal nerve fibre layer parameters in non-glaucomatous eyes

AIMS

To determine the relationship between macular ganglion cell-inner plexiform layer (GC-IPL) thickness and optic disc/retinal nerve fibre layer (RNFL) parameters in non-glaucomatous eyes measured by spectral-domain optical coherence tomography (SD-OCT).

METHODS

491 non-glaucomatous Chinese aged 40-80 years were recruited from a population-based study and underwent standardised ophthalmic examination. SD-OCT was used to measure GC-IPL thickness, optic disc parameters and RNFL thickness. Univariate and multiple linear regression analyses were performed to assess the association between GC-IPL and optic disc/RNFL parameters.

RESULTS

In univariate analyses, all RNFL parameters and rim area were significantly correlated with all macular GC-IPL parameters (p<0.001, r=0.12-0.56). In multiple regression analyses, after adjusting for age, gender, disc area, signal strength and axial length, average RNFL thickness (per µm decrease) was most strongly correlated with average GC-IPL thickness (β=-0.30, standardised β=-0.499, p<0.001) compared with other optic disc/RNFL parameters.

CONCLUSIONS

Our study demonstrated only fair correlations between macular GC-IPL and optic disc/RNFL parameters measured by SD-OCT. This information is important for further evaluation of macular GC-IPL thickness as an additional marker in detecting glaucomatous damage and progression.

[Diagnostic use of macular layer analysis by SD-OCT in primary open angle glaucoma]

PURPOSE

The purpose of this study is to evaluate the diagnostic ability of segmentation of the various internal macular layers by spectral domain optical coherence tomography (Cirrus HD-OCT, Carl Zeiss Meditec (CZM), Dublin, CA, USA) and to compare it to that of the peripapillary retinal nerve fiber layer (cpRNFL) in primary open angle glaucoma (POAG).

MATERIALS AND METHODS

This study included 252 eyes diagnosed with primary open angle glaucoma (POAG) (164 early POAG, 44 moderate POAG and 44 advanced POAG) and 223 eyes of control subjects. All patients underwent visual field testing (Humphrey Field Analyser, SITA-Standard 24-2, CZM), and SD-OCT imaging (Cirrus HD-OCT) of the macular and optic nerve head regions (ganglion cell analysis (GCA), macular cube 200×200; optic disc cube 200×200). OCT macular scans were segmented into macular nerve fiber layer (mNFL), ganglion cell layer with inner plexiform layer (GCIPL), outer retinal layers, and ganglion cell complex (GCC) (mNFL+GCIPL). Glaucoma discriminating ability was assessed using the area under the receiver operator characteristic curve (AUC) for all macular parameters and mean circumpapillary retinal nerve fibre layer (cpRNFL).

RESULTS

For the entire POAG population of this study, the minimum GCIPL index provided greater diagnostic ability than the other parameters studied, with a statistically significant difference in their AUC (minimum GCIPL [0.887], mean GCIPL [0.865], GCC [0.863], cpRNFL [0.823], mean mNFL [0.786] and minimum mNFL [0.742]). The results were similar in the early POAG group but without any statistically significant difference with the cpRNFL parameter. In the moderate POAG group, the diagnostic ability was similar for all indices, whereas in the advanced POAG group, minimum GCIPL and GCC gave the largest AUC indices.

DISCUSSION AND CONCLUSION

The minimum macular GCIPL is a new index obtained with the GCA algorithm of the Cirrus HD-OCT. It appears to have an excellent ability to detect glaucoma at every stage and demonstrates performance comparable to that of the cpRNFL parameter, in combination with which it may provide important complementary information for clinical practice.

Association between ganglion cell complex and axial length

PURPOSE

We evaluated the association between each layer of macular ganglion cell complex (mGCC) and axial length measured with spectral-domain optical coherence tomography (OCT).

METHODS

One hundred and one eyes of 101 healthy younger women were assessed in this prospective study. In one eye, mGCC was measured two times with 3D-OCT 2000 (Topcon). The associations between mGCC and axial length were analyzed using single regression analysis. To support the data of this study, repeatability also was assessed by intraclass correlation coefficient (ICC), coefficient of variance (CoV), and test-retest standard deviation (TRTSD).

RESULTS

In each layer of the mGCC, ICC ranged from 0.980 to 0.997; CoV ranged from 0.8 to 2.4 %; TRTSD ranged from 0.8 to 3.0 μm. For every 1 mm of greater axial length, total macular retinal nerve fiber layer (mRNFL) thickness increased by 1.1 μm (p < 0.01), and total macular ganglion cell layer and inner plexiform layer (mGCL+) and mGCC thickness decreased by 2.5 μm (p < 0.001) and 1.4 μm (p = 0.018), respectively.

CONCLUSIONS

In healthy younger participants, mGCC measurement using 3D OCT-2000 showed good repeatability. As axial length increased, total mGCC decreased, whereas total mRNFL and mGCL+ showed an inverse correlation.

Advances in the Structural Evaluation of Glaucoma with Optical Coherence Tomography

Optical coherence tomography (OCT) is capable of providing quantitative and objective assessments of the optic disc, macula and retinal nerve fiber layer in glaucoma. The recent advent of spectral domain OCT (SD-OCT) has enhanced the resolution, decreased scan acquisition time, and improved the reproducibility of measurements compared to older versions of this technology. However, although OCT has been successfully used for detection of disease and evaluation of progression, the limited agreement between structural and functional tests indicates the strong need for a combined approach for detecting and monitoring the disease. A recently described approach for estimation of rates of retinal ganglion cell loss from a combination of SD-OCT and functional data is a promising method for diagnosing, staging, detecting progression, and estimating rates of glaucomatous deterioration.

Diagnosis of glaucoma and detection of glaucoma progression using spectral domain optical coherence tomography

PURPOSE OF REVIEW

With the rapid adoption of spectral domain optical coherence tomography (SDOCT) in clinical practice and the recent advances in software technology, there is a need for a review of the literature on glaucoma detection and progression analysis algorithms designed for the commercially available instruments.

RECENT FINDINGS

Peripapillary retinal nerve fiber layer (RNFL) thickness and macular thickness, including segmental macular thickness calculation algorithms, have been demonstrated to be repeatable and reproducible, and have a high degree of diagnostic sensitivity and specificity in discriminating between healthy and glaucomatous eyes across the glaucoma continuum. Newer software capabilities such as glaucoma progression detection algorithms provide an objective analysis of longitudinally obtained structural data that enhances our ability to detect glaucomatous progression. RNFL measurements obtained with SDOCT appear more sensitive than time domain OCT (TDOCT) for glaucoma progression detection; however, agreement with the assessments of visual field progression is poor.

SUMMARY

Over the last few years, several studies have been performed to assess the diagnostic performance of SDOCT structural imaging and its validity in assessing glaucoma progression. Most evidence suggests that SDOCT performs similarly to TDOCT for glaucoma diagnosis; however, SDOCT may be superior for the detection of early stage disease. With respect to progression detection, SDOCT represents an important technological advance because of its improved resolution and repeatability. Advancements in RNFL thickness quantification, segmental macular thickness calculation and progression detection algorithms, when used correctly, may help to improve our ability to diagnose and manage glaucoma.

Measurement of macular ganglion cell layer and circumpapillary retinal nerve fiber layer to detect paracentral scotoma in early glaucoma

BACKGROUND

Glaucoma patients with paracentral scotoma are at higher risk of losing central vision than those without glaucoma. The purpose of this study was to determine whether macular inner retinal layer (MIRL) measurements with spectral-domain optical coherence tomography (SD-OCT) outperform circumpapillary retinal nerve fiber layer (cpRNFL) measurements in discriminating between eyes with and without paracentral scotoma.

METHODS

This retrospective study included 63 early glaucomatous eyes of 63 patients with (PSI group) or without (PSF group) paracentral visual field (VF) defects. MIRL thicknesses, including macular ganglion cell complex (mGCC), macular ganglion cell layer + inner plexiform layer (mGCL+), macular RNFL (mRNFL), and cpRNFL thickness were measured using a SD-OCT instrument (3D OCT-2000). The MIRL and cpRNFL were divided into 50 grid cells and 36 sectors, respectively, which were numbered from center/temporal to periphery/nasal. Discriminating ability of the methods for number of cells/sectors with abnormal thickness (<5% of normal) and average thickness in the hemisphere corresponding to the VF defects (termed hemi-thickness) was compared by area under the receiver operating characteristics curves (AROCs).

RESULTS

The number of abnormal nearest sectors of cpRNFL and all MIRL parameters were significantly smaller in the PSI group than in the PSF group (P ≤ 0.001-0.047), whereas no significant differences were found for average or hemi-cpRNFL thickness. The AROCs of the number of abnormal nearest cells for mGCC and mGCL+ and average hemi-thickness for mGCC, mGCL+, and mRNFL were comparable and significantly higher than those of the number of abnormal nearest sectors/cells for cpRNFL (P = 0.0002-0.0063) and mRNFL (P = 0.0003-0.0267) parameters.

CONCLUSIONS

Regional assessment of MIRL thickness as measured by SD-OCT may potentially be an effective method for predicting central involvement of VF defects in early glaucoma.

Glaucoma Diagnosis and Monitoring Using Advanced Imaging Technologies

Advanced ocular imaging technologies facilitate objective and reproducible quantification of change in glaucoma but at the same time, impose new challenges on scientists and clinicians for separating true structural change from imaging noise. This review examines time-domain and spectral-domain optical coherence tomography, confocal scanning laser ophthalmoscopy and scanning laser polarimetry technologies and discusses the diagnostic accuracy and the ability of each technique for evaluation of glaucomatous progression. A broad review of the current literature reveals that objective assessment of retinal nerve fiber layer, ganglion cell complex and optic nerve head topography may improve glaucoma monitoring when used as a complementary tool in conjunction with the clinical judgment of an expert.

One Year of Glaucoma Research in Review: 2011 to 2012

PURPOSE

To provide the practicing clinical ophthalmologist with an update of pertinent glaucoma literature published over the past 12 months.

METHODS

The authors conducted a one year (July 1, 2011 to June 30, 2012) English language glaucoma literature search on Pubmed using the following terms: automated perimetry, optic nerve imaging, optical coherence tomography, glaucoma structure and function, intraocular pressure, central corneal thickness, medical therapy and compliance in glaucoma, glaucoma laser treatment, cataract extraction and intraocular pressure, secondary glaucoma, glaucoma surgery, pediatric glaucoma, molecular biology in glaucoma, and miscellaneous topics in glaucoma.

DESIGN

Literature review.

RESULTS

This review includes original and review articles that reflect novel aspects and updates in the field of glaucoma, while excluding letters to the editor, unpublished works, and abstracts.

CONCLUSIONS

This review is not meant to be all-inclusive-rather, it highlights literature that is most applicable to ophthalmologists in practice.

The shape of the ganglion cell plus inner plexiform layers of the normal human macula

PURPOSE

To use surfaces generated by two-dimensional penalized splines (2D P-splines) to characterize the shape of the macular ganglion cell plus inner plexiform layers (GCL+IPL) in a group of normal humans.

METHODS

Macular images of the right eyes of 23 normal subjects ranging in age from 18 to 75 years were obtained with spectral-domain optical coherence tomography (SD-OCT). The thickness of GCL+IPL was determined by manual segmentation, areas with blood vessels were removed, and the resulting maps were fit by smooth surfaces in polar coordinates centered on the fovea.

RESULTS

Smooth surfaces based on 2D P-splines could precisely represent GCL+IPL thickness data, with errors comparable to the axial resolution of the SD-OCT instrument. Metrics were developed for the size, shape, and slope of the edge of the foveal depression and size and shape of the surrounding macular ridge. The slope of the foveal edge was negatively correlated with foveal size (r = -0.60). The size of the macular ridge was positively correlated with foveal size (r = 0.75), with a slope near unity (0.90 ± 0.18). The centroids of the foveal edge and macular ridge clustered near the foveal center. The foveal edge and macular ridge were well fit by ellipses. The mean GCL+IPL thickness formed an elliptical annulus elongated by approximately 30% in the horizontal direction.

CONCLUSIONS

The methods developed here provide precise characterization of retinal layers for the study of glaucoma, foveal development, and other applications.

Clinical application of ocular imaging

The broadening frontier of technology used in ocular imaging is continuously affecting the landscape of clinical eye care. With each wave of enhanced imaging modalities, the field faces the difficulties of optimally incorporating these devices into the clinic. Ocular imaging devices have been widely incorporated into clinical management after their diagnostic capabilities have been documented in a wide range of ocular disease. In this review, we are presenting the main commercially available devices for imaging of the posterior segment of the eye.

Macular assessment using optical coherence tomography for glaucoma diagnosis

Optical coherence tomography (OCT) is an interferometry-based imaging modality that generates high-resolution cross-sectional images of the retina. Circumpapillary retinal nerve fibre layer (cpRNFL) and optic disc assessments are the mainstay of glaucomatous structural measurements. However, because these measurements are not always available or precise, it would be useful to have another reliable indicator. The macula has been suggested as an alternative scanning location for glaucoma diagnosis. Using time-domain (TD) OCT, macular measurements have been shown to provide good glaucoma diagnostic capabilities. Performance of cpRNFL measurement was generally superior to macular assessment. However, macular measurement showed better glaucoma diagnostic performance and progression detection capability in some specific cases, which suggests that these two measurements may be combined to produce a better diagnostic strategy. With the adoption of spectral-domain OCT, which allows a higher image resolution than TD-OCT, segmentation of inner macular layers becomes possible. The role of macular measurements for detection of glaucoma progression is still under investigation. Improvement of image quality would allow better visualisation, development of various scanning modes would optimise macular measurements, and further refining of the analytical algorithm would provide more accurate segmentation. With these achievements, macular measurement can be an important surrogate for glaucomatous structural assessment.

Assessment of Structural Glaucoma Progression

Purpose

To provide an update on the role of optic nerve head and peripapillary retinal nerve fiber layer imaging in monitoring glaucoma progression.

Methods

Review of literature.

Results

Imaging technologies, such as optical coherence tomography, scanning laser polarimetry, and confocal scanning laser ophthalmoscopy, objectively and quantitatively measure the structural change associated with glaucoma. Rates of retinal nerve fiber layer (RNFL) and rim area loss are significantly faster in progressing compared with nonprogressing subjects. A number of strategies to detect progression have been proposed. The precision of these methods is generally high. However, there is no agreement as to which instrument or parameter is most appropriate for the evaluation of structural progression associated with glaucoma at this moment. The agreement between structural and functional glaucoma progression is generally poor regardless of the strategies used. Structural progression analyses appear to complement visual field progression analyses, detecting a different subset of progressing subjects.

Summary

Imaging devices are promising tools for monitoring patients with glaucoma. Combining structural and functional analyses is useful for accurate monitoring of glaucoma progression.

How to cite this article

Miki A. Assessment of Structural Glaucoma Progression. J Current Glau Prac 2012;6(2):62-67.

Glaucoma diagnostic accuracy of ganglion cell-inner plexiform layer thickness: comparison with nerve fiber layer and optic nerve head

PURPOSE

To determine the diagnostic performance of macular ganglion cell-inner plexiform layer (GCIPL) thickness measured with the Cirrus high-definition optical coherence tomography (HD-OCT) ganglion cell analysis (GCA) algorithm (Carl Zeiss Meditec, Dublin, CA) to discriminate normal eyes and eyes with early glaucoma and to compare it with that of peripapillary retinal nerve fiber layer (RNFL) thickness and optic nerve head (ONH) measurements.

DESIGN

Evaluation of diagnostic test or technology.

PARTICIPANTS

Fifty-eight patients with early glaucoma and 99 age-matched normal subjects.

METHODS

Macular GCIPL and peripapillary RNFL thicknesses and ONH parameters were measured in each participant, and their diagnostic abilities were compared.

MAIN OUTCOME MEASURES

Area under the curve (AUC) of the receiver operating characteristic.

RESULTS

The GCIPL parameters with the best AUCs were the minimum (0.959), inferotemporal (0.956), average (0.935), superotemporal (0.919), and inferior sector (0.918). There were no significant differences between these AUCs and those of inferior quadrant (0.939), average (0.936), and superior quadrant RNFL (0.933); vertical cup-to-disc diameter ratio (0.962); cup-to-disc area ratio (0.933); and rim area (0.910), all P>0.05.

CONCLUSIONS

The ability of macular GCIPL parameters to discriminate normal eyes and eyes with early glaucoma is high and comparable to that of the best peripapillary RNFL and ONH parameters.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found after the references.