Structural Change Can Be Detected in Advanced-Glaucoma Eyes

Discriminating performance of macular ganglion cell-inner plexiform layer thicknesses at different stages of glaucoma

AIM

To determine the discriminating performance of the macular ganglion cell-inner plexiform layer (GC-IPL) parameters between all the consecutive stages of glaucoma (from healthy to moderate-to-severe glaucoma), and to compare it with the discriminating performances of the peripapillary retinal nerve fiber layer (RNFL) parameters and optic nerve head (ONH) parameters.

METHODS

Totally 147 eyes (40 healthy, 40 glaucoma suspects, 40 early glaucoma, and 27 moderate-to-severe glaucoma) of 133 subjects were included. Optical coherence tomography (OCT) was obtained using Cirrus HD-OCT 5000. The diagnostic performances of GC-IPL, RNFL, and ONH parameters were evaluated by determining the area under the curve (AUC) of the receiver operating characteristics.

RESULTS

All GC-IPL parameters discriminated glaucoma suspect patients from subjects with healthy eyes and moderate-to-severe glaucoma from early glaucoma patients (P<0.017, for all). Also, minimum, inferotemporal and inferonasal GC-IPL parameters discriminated early glaucoma patients from glaucoma suspects, whereas no RNFL or ONH parameter could discriminate between the two. The best parameters to discriminate glaucoma suspects from subjects with healthy eyes were superonasal GC-IPL, superior RNFL and average c/d ratio (AUC=0.746, 0.810 and 0.746, respectively). Discriminating performances of all the parameters for early glaucoma vs glaucoma suspect comparison were lower than that of the other consecutive group comparisons, with the best GC-IPL parameters being minimum and inferotemporal (AUC=0.669 and 0.662, respectively). Moreover, minimum GC-IPL, average RNFL, and rim area (AUC=0.900, 0.858, 0.768, respectively) were the best parameters for discriminating moderate-to-severe glaucoma patients from early glaucoma patients.

CONCLUSION

GC-IPL parameters can discriminate glaucoma suspect patients from subjects with healthy eyes, and also all the consecutive stages of glaucoma from each other (from glaucoma suspect to moderate-to-severe glaucoma). Further, the discriminating performance of GC-IPL thicknesses is comparable to that.

Measurement Floors and Dynamic Ranges of OCT and OCT Angiography in Glaucoma

PURPOSE

To determine if OCT angiography (OCTA)-derived vessel density measurements can extend the available dynamic range for detecting glaucoma compared with spectral-domain (SD) OCT-derived thickness measurements.

DESIGN

Observational, cross-sectional study.

PARTICIPANTS

A total of 509 eyes from 38 healthy participants, 63 glaucoma suspects, and 193 glaucoma patients enrolled in the Diagnostic Innovations in Glaucoma Study.

METHODS

Relative vessel density and tissue thickness measurement floors of perifoveal vessel density (pfVD), circumpapillary capillary density (cpCD), circumpapillary retinal nerve fiber (cpRNFL) thickness, ganglion cell complex (GCC) thickness, and visual field (VF) mean deviation (MD) were investigated and compared with a previously reported linear change point model (CPM) and locally weighted scatterplot smoothing curves.

MAIN OUTCOME MEASURES

Estimated vessel density and tissue thickness measurement floors and corresponding dynamic ranges.

RESULTS

Visual field MD ranged from -30.1 to 2.8 decibels (dB). No measurement floor was found for pfVD, which continued to decrease constantly until very advanced disease. A true floor (i.e., slope of approximately 0 after observed CPM change point) was detected for cpRNFL thickness only. The post-CPM estimated floors were 49.5±2.6 μm for cpRNFL thickness, 70.7±1.0 μm for GCC thickness, and 31.2±1.1% for cpCD. Perifoveal vessel density reached the post-CPM estimated floor later in the disease (VF MD, -25.8±3.8 dB) than cpCD (VF MD, -19.3±2.4 dB), cpRNFL thickness (VF MD, -17.5±3.3 dB), and GCC thickness (VF MD, -13.9±1.8 dB; P < 0.001). The number of available measurement steps from normal values to the CPM estimated floor was greatest for cpRNFL thickness (8.9), followed by GCC thickness (7.4), cpCD (4.5), and pfVD (3.8).

CONCLUSIONS

In late-stage glaucoma, particularly when VF MD is worse than -14 dB, OCTA-measured pfVD is a promising tool for monitoring progression because it does not have a detectable measurement floor. However, the number of steps within the dynamic range of a parameter also needs to be considered. Although thickness parameters reached the floor earlier than OCTA-measured pfVD, there are more such steps with thickness than OCTA parameters.

Retinal Nerve Fiber Layer Features Identified by Unsupervised Machine Learning on Optical Coherence Tomography Scans Predict Glaucoma Progression

Purpose

To apply computational techniques to wide-angle swept-source optical coherence tomography (SS-OCT) images to identify novel, glaucoma-related structural features and improve detection of glaucoma and prediction of future glaucomatous progression.

Methods

Wide-angle SS-OCT, OCT circumpapillary retinal nerve fiber layer (cpRNFL) circle scans spectral-domain (SD)-OCT, standard automated perimetry (SAP), and frequency doubling technology (FDT) visual field tests were completed every 3 months for 2 years from a cohort of 28 healthy participants (56 eyes) and 93 glaucoma participants (179 eyes). RNFL thickness maps were extracted from segmented SS-OCT images and an unsupervised machine learning approach based on principal component analysis (PCA) was used to identify novel structural features. Area under the receiver operating characteristic curve (AUC) was used to assess diagnostic accuracy of RNFL PCA for detecting glaucoma and progression compared to SAP, FDT, and cpRNFL measures.

Results

The RNFL PCA features were significantly associated with mean deviation (MD) in both SAP (R² = 0.49, P < 0.0001) and FDT visual field testing (R² = 0.48, P < 0.0001), and with mean circumpapillary RNFL thickness (cpRNFLt) from SD-OCT (R² = 0.58, P < 0.0001). The identified features outperformed each of these measures in detecting glaucoma with an AUC of 0.95 for RNFL PCA compared to an 0.90 for mean cpRNFLt (P = 0.09), 0.86 for SAP MD (P = 0.034), and 0.83 for FDT MD (P = 0.021). Accuracy in predicting progression was also significantly higher for RNFL PCA compared to SAP MD, FDT MD, and mean cpRNFLt (P = 0.046, P = 0.007, and P = 0.044, respectively).

Conclusions

A computational approach can identify structural features that improve glaucoma detection and progression prediction.

OCT Circle Scans Can Be Used to Study Many Eyes with Advanced Glaucoma

Purpose

To examine the utility of optical coherence tomography (OCT) for studying eyes with advanced glaucoma [i.e., eyes with a 24-2 visual field (VF) mean deviation (MD) worse than -15 dB], we tested the hypothesis that if these eyes had a 10-2 total deviation (TD) map with points better than -8 dB, then the topographically corresponding regions on the circumpapillary retinal nerve fiber layer (cpRNFL) should show a preserved region.

Design

Evaluation of technology study.

Participants

39 eyes from 33 patients (mean: 68.8 ± 9.2 years) with a diagnosis of glaucoma had a 24-2 VF with a MD ≤ -15 dB (mean: -18.94 ± 2.95 dB). All eyes additionally had a 10-2 VF and an averaged OCT circle scan.

Methods

Each scan was inspected, and preserved cpRNFL regions of the disc associated with the macula (central ±8° were delin eated.

Main Outcome Measures

The number of eyes with preserved cpRNFL regions and their association with preserved VF locations (i.e. better than -8 dB) shown in the 10-2 VF TD map.

Results

38 of the 39 eyes had one or more points on the 10-2 VF with TD values that were better than -8 dB (mean: 25.7 ± 12.6 points). For all 39 eyes, there was a preserved portion of the cpRNFL on the circle scan within the disc region associated with the macula. However, for 3 of these eyes, this region was hypodense and could be a challenge for the clinician to identify.

Conclusion

OCT scans can be used to assess and potentially follow the preserved regions of cpRNFL associated with the macula in eyes with advanced glaucoma if there is a preserved region on the 10-2 VF better than -8 dB.

Peripapillary capillary vessel density progression in advanced glaucoma: a case report

Background

We report a case of advanced juvenile open-angle glaucoma (JOAG) in which peripapillary capillary vessel density (PcVD) in the inferior retina showed significant progression while the spatially corresponding retinal nerve fiber layer thickness (RNFLT) and visual field cluster defect values had reached their minimal detectable values, and showed no change during the follow-up (floor effect).

Case presentation

A 45-year old white female patient with very advanced under treatment JOAG in the left eye was prospectively investigated with the AngioVue OCT (Optovue Inc., Fremont, USA) for RNFLT and PcVD, and Octopus Normal G2 visual field testing, at 6-month intervals for 2.5 years (6 visits). Images quality was high (8/10 in 5 visits and 7/10 in one visit), and the optical media were clear. For the superior and inferior retina the baseline RNFLT and PcVD values were 48 and 43 μm, and 28.9 and 36.5%, respectively. Using the instrument’s linear regression analysis significant progression (P < 0.05) was seen only for the hemifield with greater baseline RNFLT (superior RNFLT: − 0.5 μm/year) and the hemifield with greater baseline PcVD (inferior PcVD: − 2.4%/year). All inferior visual field cluster defect values progressed significantly (2.0 to 5.1 dB/year) while in the superior clusters no progression was measurable due to software indicated floor effect.

Conclusion

Our case shows that PcVD progression can be measured in advanced glaucoma, that PcVD can show floor effect, and that it may indicate glaucomatous progression when the spatially corresponding RNFLT and visual field cluster defect do not show progression due to floor effect.

Racial Differences in Rate of Change of Spectral-Domain Optical Coherence Tomography-Measured Minimum Rim Width and Retinal Nerve Fiber Layer Thickness

PURPOSE

To compare race-related differences in estimated rate of change of Bruch's membrane opening-minimum rim width (BMO-MRW) and circumpapillary retinal nerve fiber layer thickness (RNFLT) in healthy, glaucoma suspect, and glaucoma eyes of individuals of European (ED) and African descent (AD).

DESIGN

Prospective cohort study.

METHODS

This study investigated rate of change of BMO-MRW and RNFLT in 124 healthy, 227 glaucoma suspect, and 177 glaucoma eyes followed for approximately 3 years and tested with optical coherence tomography every 6 months. Suspect eyes had a history of untreated intraocular pressure (IOP) ≥ 22 mm Hg or suspicion of glaucoma by optic disc photograph assessment without repeatable abnormal standard automated perimetry (SAP) results. Glaucoma eyes had repeatable abnormal SAP results (GHT ONL or PSD ≤ 5%). Mixed-effects models were used to estimate the rate of change after controlling for age, mean follow-up IOP, central corneal thickness, axial length, and BMO area.

RESULTS

A race-related difference in rate of change of global BMO-MRW but not average RNFLT in suspect eyes was observed. Rate of change of BMO-MRW was -1.82 μm/year and -2.20 μm/year in ED and AD suspect eyes, respectively (P = .03). Rate of change of RNFLT was -0.64 μm/year and -0.75 μm/year in ED and AD suspect eyes, respectively (P = .75). No race-related differences in change rate were found in healthy or glaucoma eyes.

CONCLUSION

Race is an important consideration when assessing structural change, particularly minimum rim width, in glaucoma suspect eyes. Differences in rate of structural change may help explain racial disparities in glaucoma susceptibility.

Detecting Glaucoma Progression Using Guided Progression Analysis with OCT and Visual Field Assessment in Eyes Classified by International Classification of Disease Severity Codes

PURPOSE

To compare the detection and rates of progressive retinal nerve fiber layer (RNFL) and ganglion cell-inner plexiform layer (GCIPL) loss with spectral-domain (SD) OCT and visual field (VF) loss using Guided Progression Analysis (GPA; Carl Zeiss Meditec, Dublin, CA) in glaucomatous eyes classified using International Classification of Diseases (ICD) diagnosis codes.

DESIGN

Retrospective cohort study.

PARTICIPANTS

Glaucoma patients with at least 3 years of follow-up and a minimum of 4 SD OCT and 5 reliable VF examinations.

METHODS

Glaucoma severity was classified using ICD, 10th Edition, Clinical Modification, diagnosis codes. Rates of RNFL, macular GCIPL, and VF loss were calculated, and progression estimates were compared using generalized estimating equations and McNemar's tests.

MAIN OUTCOME MEASURES

Progressive RNFL, GCIPL, and VF loss assessed by GPA criteria.

RESULTS

A total of 147 eyes of 116 patients (mean age, 69.9±8.5 years) were included with mean follow-up of 69.67±18.64 months. Overall, 38 of 147 eyes (25.9%) showed RNFL progression, 35 eyes (23.8%) showed GCIPL progression, and 20 eyes (13.6%) showed VF progression. Progression by all 3 methods was noted in 10 eyes (7.0%). Eyes with mild (n = 62) and severe (n = 46) glaucoma showed significantly more progression on SD OCT compared with VF (P < 0.001 and P = 0.004). Retinal nerve fiber layer, GCIPL, and VF progressors showed faster rates of loss in average RNFL, GCIPL, and VF mean deviation compared with nonprogressors (mean ± standard error: -1.47±0.30 μm/year vs. -0.03±0.12 μm/year [P = 0.0001], -1.68±0.34 μm/year vs. -0.29±0.07 μm/year [P = 0.0001], and -1.07±0.20 dB/year vs. -0.19±0.04 dB/year [P = 0.0001], respectively).

CONCLUSIONS

Spectral-domain OCT progression was significantly more common than VF progression in glaucomatous eyes classified with mild and severe disease. Structure and function should be monitored closely across the entire spectrum of glaucoma severity.

The Relationship Between Bruch's Membrane Opening-Minimum Rim Width and Retinal Nerve Fiber Layer Thickness and a New Index Using a Neural Network

PURPOSE

We evaluate the relationship between Bruch's membrane opening minimum rim width (BMO-MRW) and peripapillary retinal nerve fiber layer thickness (pRNFLT) and develop a new parameter combining BMO-MRW and pRNFLT using a neural network to maximize their compensatory values.

METHODS

A total of 402 subjects were divided into two groups: 273 (validation group) and 129 (neural net training) subjects. Linear quadratic and broken-stick regression models were used to explore the relationship between BMO-MRW and pRNFLT. A multilayer neural network was used to create a combined parameter, and diagnostic performances were compared using area under the receiver operating characteristic curves (AUROCs).

RESULTS

Regression analyses between BMO-MRW and pRNFLT revealed that the broken-stick model afforded the best fit. Globally, the tipping point was a BMO-MRW of 226.5 μm. BMO-MRW and pRNFLT were correlated significantly with visual field. When differentiating normal from glaucoma subjects, the neural network exhibited the largest AUROC. When differentiating normal from early glaucoma subjects, the overall diagnostic performance decreased, but the neural network still exhibited the largest AUROC.

CONCLUSIONS

The optimal relationship between BMO-MRW and pRNFLT was revealed using the broken-stick model. Considerable BMO-MRW thinning preceded pRNFLT thinning. The neural network significantly improved diagnostic power by combining BMO-MRW and pRNFLT.

TRANSLATIONAL RELEVANCE

A combined index featuring BMO-MRW and pRNFLT data can aid clinical decision-making, particularly when individual parameters yield confusing results. Our neural network effectively combines information from separate parameters.

Can Macula and Optic Nerve Head Parameters Detect Glaucoma Progression in Eyes with Advanced Circumpapillary Retinal Nerve Fiber Layer Damage?

PURPOSE

To evaluate the ability of OCT optic nerve head (ONH) and macular parameters to detect disease progression in eyes with advanced structural glaucomatous damage of the circumpapillary retinal nerve fiber layer (cRNFL).

DESIGN

Longitudinal study.

PARTICIPANTS

Forty-four eyes from 37 patients with advanced average cRNFL damage (≤60 μm) followed up for an average of 4.0 years.

METHODS

All patients were examined with spectral-domain OCT and visual field (VF) assessment during at least 4 visits.

MAIN OUTCOME MEASUREMENTS

Visual field mean deviation (MD) and VF index. OCT cRNFL (average, superior, and inferior quadrants), ganglion cell-inner plexiform layer (GCIPL) (average, superior, and inferior), rim area, cup volume, average cup-to-disc (C:D) ratio, and vertical C:D ratio.

RESULTS

At baseline, patients had a median VF MD of -10.18 dB and mean cRNFL of 54.55±3.42 μm. The rate of change for MD and VF index were significant. No significant rate of change was noted for cRNFL, whereas significant (P < 0.001) rates were detected for GCIPL (-0.57±0.05 μm/year) and ONH parameters such as rim area (-0.010±0.001 mm²/year).

CONCLUSIONS

Macula GCIPL and ONH parameters may be useful in tracking progression in patients with advanced glaucoma.

Utility of combining spectral domain optical coherence tomography structural parameters for the diagnosis of early Glaucoma: a mini-review

Optical coherence tomography (OCT) has moved to the forefront of imaging modalities in the management of glaucoma and retinal diseases. It is modifying how glaucoma and glaucoma progression are diagnosed clinically and augmenting our understanding of the disease. OCT provides multiple parameters from various anatomic areas for glaucoma diagnosis, evaluation of treatment efficacy, and progression monitoring. While the use of multiple parameters has increased the likelihood of detecting early structural changes, diagnosing glaucoma in early stages is often challenging when the damages are subtle and not apparent on OCT scans, in addition to the fact that assessment of OCT parameters often yields conflicting findings. One promising approach is to combine multiple individual parameters into a composite parameter from the same test to improve diagnostic accuracy, sensitivity, and specificity. This review presents current evidence regarding the value of spectral domain OCT composite parameters in diagnosing early glaucoma.

Interindividual Variations in Foveal Anatomy and Artifacts Seen on Inner Retinal Probability Maps from Spectral Domain OCT Scans of the Macula

Purpose

We tested the hypothesis that variations in foveal morphology can account for artifacts seen on optical coherence tomography (OCT) retinal ganglion cell (RGC) layer probability maps.

Methods

A total of 126 healthy subjects were tested with spectral domain (sd) OCT. Thickness and probability maps of the macular RGC plus inner plexiform layer (RGC+) were obtained with customized software. Macular b-scans were analyzed to derive three foveal anatomic parameters: width, depth, and slope. The distribution of these parameters was compared between eyes with and without circumfoveal artifacts seen in the central 4° of macular RGC+ probability maps.

Results

Of 126 healthy subjects, 12 (9.5%) had an abnormal circumfoveal region (artifact) on RGC+ probability maps. Based upon the normal distribution of the three anatomic parameters, only three of the 12 eyes (25%) fell outside the 95% confidence interval of one or more of the three foveal morphologic parameters. Multivariable logistic regression revealed that the parameter slope was significantly associated with the presence of these artifacts (odds ratio = 0.26; P = 0.019). However, the combination of these parameters and age explained only 11% of the total variance of these artifacts.

Conclusions

Fovea morphology, as measured based upon width, depth, and slope, has a minor role in explaining artifacts seen on macular scans. Variations in the distribution of RGC+ thickness that are not reflected in our measures warrant further investigation as potential sources of artifacts.

Translational Relevance

A small proportion of circumfoveal artifacts seen on RGC+ probability maps can be explained by variations in foveal anatomy.

Comparison of Changes in Macular Ganglion Cell-Inner Plexiform Layer Thickness Between Medically and Surgically Treated Eyes With Advanced Glaucoma

PURPOSE

To compare changes in the macular ganglion cell layer and inner plexiform layer (mGCIPL) thickness over 5 years between surgically treated eyes (STE) and medically treated eyes (MTE) with advanced glaucoma.

DESIGN

Retrospective, comparative case series.

METHODS

Eighty-six patients comprising 43 with open-angle glaucoma (OAG) with trabeculectomy and 43 with medically treated OAG. The mGCIPL thickness was measured more than 5 times during follow-up by optical coherence tomography. Main outcome measure was differences in mGCIPL thickness thinning rate between the groups.

RESULTS

The mean age at study initiation was 62.5 ± 9.2 years in STE and 62.7 ± 9.5 years in MTE. The mean deviations (MD), according to the Humphrey Field Analyzer central program 30-2, and the mGCIPL thickness in each sector showed no significant differences at initial measurement. The averaged intraocular pressure (IOP) throughout follow-up was 10.5 ± 2.0 mm Hg in STE and 10.8 ± 0.8 mm Hg in MTE (P = .429; Mann-Whitney U test). There was no significant difference in the MD changes over 5 years between the 2 groups (P = .405; Mann-Whitney U test). Changes in the mGCIPL thickness over 5 years in MTE were significantly greater than that in STE in all sectors (all 6 sectors P < .0001, Mann-Whitney U test). The IOP fluctuation over 5 years in STE was significantly less than that in MTE (P < .0001, Mann-Whitney U test).

CONCLUSIONS

The structure of the mGCIPL was better preserved in STE than in MTE, even when the IOPs during follow-up were similar.

Integrating Macular Ganglion Cell Inner Plexiform Layer and Parapapillary Retinal Nerve Fiber Layer Measurements to Detect Glaucoma Progression

PURPOSE

To investigate the temporal relationship among progressive macular ganglion cell inner plexiform layer (GCIPL) thinning, progressive parapapillary retinal nerve fiber layer (RNFL) thinning, and visual field (VF) progression in patients with primary open-angle glaucoma (POAG).

DESIGN

Prospective study.

PARTICIPANTS

One hundred thirty-six POAG patients (231 eyes) followed up for ≥5 years.

METHODS

OCT imaging of the macular GCIPL and parapapillary RNFL and perimetry were performed at ∼ 4-month intervals. Progressive GCIPL and RNFL thinning were determined by Guided Progression Analysis (GPA) of serial GCIPL and RNFL thickness maps. The specificities of GPA were calculated from the proportions of eyes with progressive GCIPL or RNFL thinning in 67 eyes of 36 healthy individuals followed up for ≥5 years. Visual field progression (likely or possible) was determined by the Early Manifest Glaucoma Trial criteria.

MAIN OUTCOME MEASURES

Hazard ratios for VF progression, progressive RNFL thinning, and progressive GCIPL thinning, as determined by time-varying Cox models.

RESULTS

GPA detected 57 eyes (24.7%) with progressive GCIPL thinning and 66 eyes (28.6%) with progressive RNFL thinning at a specificity of 95.5% and 91.0%, respectively. Thirty-five eyes (15.2%) demonstrated progressive RNFL and GCIPL thinning, whereas 53 eyes (22.9%) demonstrated progressive RNFL or GCIPL thinning. Eyes with progressive GCIPL thinning had a higher risk for progressive RNFL thinning (HR, 5.27; 95% confidence interval [CI], 2.89-9.62), whereas eyes with progressive RNFL thinning were also at a higher risk for progressive GCIPL thinning (HR, 2.99; 95% CI, 1.48-6.02), after adjusting for baseline covariates. The HRs for likely and possible VF progression were 3.48 (95% CI, 1.51-8.01) and 2.74 (95% CI, 1.26-5.98), respectively, on detection of progressive GCIPL thinning and 3.66 (95% CI, 1.68-7.97) and 2.54 (95% CI, 1.23-5.21), respectively, on detection of progressive RNFL thinning after adjusting for baseline covariates. Eyes with VF progression were not at risk of progressive RNFL or GCIPL thinning (P ≥ 0.493).

CONCLUSIONS

Progressive macular GCIPL thinning and progressive parapapillary RNFL thinning are mutually predictive. Because progressive RNFL thinning and progressive GCIPL thinning are both indicative of VF progression, integrating macular GCIPL and parapapillary RNFL measurements is relevant to facilitate early detection of disease deterioration in glaucoma patients.

Comparison of Glaucoma Progression Detection by Optical Coherence Tomography and Visual Field

PURPOSE

To compare longitudinal glaucoma progression detection using optical coherence tomography (OCT) and visual field (VF).

DESIGN

Validity assessment.

METHODS

We analyzed subjects with more than 4 semi-annual follow-up visits (every 6 months) in the multicenter Advanced Imaging for Glaucoma Study. Fourier-domain optical coherence tomography (OCT) was used to map the thickness of the peripapillary retinal nerve fiber layer (NFL) and ganglion cell complex (GCC). OCT-based progression detection was defined as a significant negative trend for either NFL or GCC. VF progression was reached if either the event or trend analysis reached significance.

RESULTS

The analysis included 356 glaucoma suspect/preperimetric glaucoma (GS/PPG) eyes and 153 perimetric glaucoma (PG) eyes. Follow-up length was 54.1 ± 16.2 months for GS/PPG eyes and 56.7 ± 16.0 for PG eyes. Progression was detected in 62.1% of PG eyes and 59.8% of GS/PPG eyes by OCT, significantly (P < .001) more than the detection rate of 41.8% and 27.3% by VF. In severity-stratified analysis of PG eyes, OCT had significantly higher detection rate than VF in mild PG (63.1% vs. 38.7%, P < .001), but not in moderate and advanced PG. The rate of NFL thinning slowed dramatically in advanced PG, but GCC thinning rate remained relatively steady and allowed good progression detection even in advanced disease. The Kaplan-Meier time-to-event analyses showed that OCT detected progression earlier than VF in both PG and GS/PPG groups.

CONCLUSIONS

OCT is more sensitive than VF for the detection of progression in early glaucoma. While the utility of NFL declines in advanced glaucoma, GCC remains a sensitive progression detector from early to advanced stages.

The Future of Imaging in Detecting Glaucoma Progression

Ocular imaging has been heavily incorporated into glaucoma management and provides important information that aids in the detection of disease progression. Longitudinal studies have shown that the circumpapillary retinal nerve fiber layer is an important parameter for glaucoma progression detection, whereas other studies have demonstrated that macular parameters, such as the ganglion cell inner plexiform layer and optic nerve head parameters, also are useful for progression detection. The introduction of novel technologies with faster scan speeds, wider scanning fields, higher resolution, and improved tissue penetration has enabled the precise quantification of additional key ocular structures, such as the individual retinal layers, optic nerve head, choroid, and lamina cribrosa. Furthermore, extracting functional information from scans such as blood flow rate and oxygen consumption provides new perspectives on the disease and its progression. These novel methods promise improved detection of glaucoma progression and better insight into the mechanisms of progression that will lead to better targeted treatment options to prevent visual damage and blindness.

Glaucoma

Glaucoma is a heterogeneous group of diseases characterised by cupping of the optic nerve head and visual-field damage. It is the most frequent cause of irreversible blindness worldwide. Progression usually stops if the intraocular pressure is lowered by 30-50% from baseline. Its worldwide age-standardised prevalence in the population aged 40 years or older is about 3·5%. Chronic forms of glaucoma are painless and symptomatic visual-field defects occur late. Early detection by ophthalmological examination is mandatory. Risk factors for primary open-angle glaucoma-the most common form of glaucoma-include older age, elevated intraocular pressure, sub-Saharan African ethnic origin, positive family history, and high myopia. Older age, hyperopia, and east Asian ethnic origin are the main risk factors for primary angle-closure glaucoma. Glaucoma is diagnosed using ophthalmoscopy, tonometry, and perimetry. Treatment to lower intraocular pressure is based on topical drugs, laser therapy, and surgical intervention if other therapeutic modalities fail to prevent progression.

Macular imaging by optical coherence tomography in the diagnosis and management of glaucoma

The macular area is important to the detection of glaucomatous retinal ganglion cell (RGC) damage. Macular thickness complementary to peripapillary retinal nerve fibre layer (RNFL) thickness can well reflect glaucomatous damage, given that the macula contains more than 50% of the RGCs in a multilayered pattern and larger RGC bodies compared with their axons. Thus, macular ganglion cell thickness parameters recently have been considered to be an effective glaucoma-diagnostic tool comparable to RNFL thickness parameters. Furthermore, spectral-domain optical coherence tomography ganglion cell-inner plexiform layer thickness and deviation maps can provide additional information essential for distinguishing glaucomatous changes from other, myopia-associated or macular disease-associated changes. Therefore, our aim with this study was to review the clinical application of macular imaging by optical coherence tomography and to provide essential clinical tips for its use in the diagnosis and management of glaucoma.

Will Perimetry Be Performed to Monitor Glaucoma in 2025?

Visual field testing has played an essential role in the diagnosis and management of glaucoma for more than a century. Methods to examine the visual field have been refined from early kinetic perimetry to current standard automated perimetry (SAP). Clinicians now use SAP for the diagnosis and management of glaucoma throughout the world. Various testing paradigms and analytic methods have been developed to simplify the diagnosis of glaucoma and the interpretation of progression. Moreover, strategies have been implemented to improve patient experience with visual field testing and to increase reliability. Objective functional tests, such as electroretinography, provide an alternative to subjective visual field testing but are not yet ready for widespread adoption. Standard automated perimetry is being adapted and improved constantly. New devices may allow patients to complete visual field tests at home, which could relieve patients and clinicians from in-office testing and allow for more frequent examinations. Glaucoma detection and progression analysis also are incorporating progressively more information and will be improved as deep learning strategies are applied. Finally, perimetric and structural testing likely will become more closely intertwined as testing platforms and progression analysis incorporate both of these measures. Visual field testing will continue to have an important role in the diagnosis and management of glaucoma.

Comparing the Rates of Retinal Nerve Fiber Layer and Ganglion Cell-Inner Plexiform Layer Loss in Healthy Eyes and in Glaucoma Eyes

PURPOSE

To compare the rates of circumpapillary retinal nerve fiber layer (RNFL) and macular retinal ganglion cell-inner plexiform layer (GCIPL) change over time in healthy and glaucoma eyes.

DESIGN

Cohort study.

METHODS

The rates of circumpapillary RNFL and macular GCIPL loss in 28 healthy subjects and 97 glaucoma subjects from the Diagnostic Innovations in Glaucoma Study (DIGS) were compared using mixed-effects models.

RESULTS

The median follow-up time and number of visits were 1.7 years and 6 visits and 3.2 years and 7 visits for healthy and glaucoma eyes, respectively. Significant rates of loss of both global circumpapillary RNFL and average macular GCIPL thickness were detectable in early and moderate glaucoma eyes; in severe glaucoma eyes, rates of average macular GCIPL loss were significant, but rates of global circumpapillary RNFL loss were not. In glaucoma eyes, mean rates of global circumpapillary RNFL thickness change (-0.98 μm/year [95% confidence interval (CI), -1.20 to -0.76]) and normalized global circumpapillary RNFL change (-1.7%/year [95% CI, -2.1 to -1.3]) were significantly faster than average macular GCIPL change (-0.57 μm/year [(95% CI, -0.73 to -0.41]) and normalized macular GCIPL change (-1.3%/year [95% CI, -1.7 to -0.9]). The rates of global and inferior RNFL change were weakly correlated with global and inferior macular GCIPL change (r ranges from 0.16 to 0.23, all P < .05).

CONCLUSIONS

In this cohort, the rate of circumpapillary RNFL thickness change was faster than macular GCIPL change for glaucoma eyes. Global circumpapillary RNFL thickness loss was detectable in early and moderate glaucoma, and average macular GCIPL thickness loss was detectable in early, moderate, and severe glaucoma, suggesting that structural changes can be detected in severe glaucoma.

Ganglion Cell-Inner Plexiform Layer Change Detected by Optical Coherence Tomography Indicates Progression in Advanced Glaucoma

PURPOSE

To examine the performance of Guided Progression Analysis (GPA; Carl Zeiss Meditec, Dublin, CA) in spectral-domain optical coherence tomography (OCT) in detecting progressive thinning of ganglion cell-inner plexiform layer (GCIPL) and retinal nerve fiber layer (RNFL) in glaucoma.

DESIGN

Longitudinal, observational study.

PARTICIPANTS

A total of 196 eyes of 123 primary open-angle glaucoma patients (mean follow-up, 5.0 years).

METHODS

Macular GCIPL and peripapillary RNFL thicknesses were measured by Cirrus HD-OCT (Zeiss, Dublin, CA), and progressive GCIPL and RNFL thinning were assessed by GPA. The reference standard of glaucoma progression was determined by visual field (VF) progression. Glaucomatous eyes were classified into mild (117 eyes) or moderate to advanced (79 eyes) groups based on VF defects. Ganglion cell-inner plexiform layer and RNFL thinning rates were compared between progressors and nonprogressors. Visual field survival estimates in eyes with and without progressive GCIPL and RNFL thinning were evaluated by Kaplan-Meier survival analysis and compared with the log-rank test.

MAIN OUTCOME MEASURES

Progressive GCIPL and RNFL thinning assessed by OCT GPA.

RESULTS

Seventy-six eyes (38.8%) and 43 eyes (21.9%) demonstrated progressive GCIPL and RNFL thinning, respectively, and 48 eyes (24.5%) were classified as progressors by reference standard. The rate of change in the average GCIPL thickness was significantly higher in progressors (-1.05±0.98 μm/year for mild glaucoma and -0.66±0.30 μm/year for moderate to advanced glaucoma) than in nonprogressors (-0.47±0.54 μm/year for mild glaucoma and -0.31±0.50 μm/year for moderate to advanced glaucoma), regardless of glaucoma severity (P < 0.05). Eyes with progressive GCIPL thinning had lower VF survival estimates than eyes without, regardless of glaucoma severity. However, the rate of change in the average RNFL thickness did not differ significantly in moderate to advanced glaucoma (P = 0.765; -0.26±0.55 μm/year for progressors and -0.33±0.92 μm/year for nonprogressors), and VF survival estimates did not differ significantly between eyes with and without progressive RNFL thinning in moderate to advanced glaucoma (P = 0.781).

CONCLUSIONS

Ganglion cell-inner plexiform layer GPA provides a new approach for evaluating glaucoma progression. It may be more useful for detecting progression in the advanced stages of glaucoma than RNFL GPA.

Estimating Optical Coherence Tomography Structural Measurement Floors to Improve Detection of Progression in Advanced Glaucoma

PURPOSE

"Floor effects" in retinal imaging are defined as the points at which no further structural loss can be detected. We estimated the measurement floors for spectral-domain optical coherence tomography (SDOCT) measurements and compared global change over time in advanced glaucoma eyes.

DESIGN

Validity study to investigate measurement floors.

METHODS

A longitudinal "Variability group" of 41 eyes with moderate to advanced glaucoma (standard automated perimetry mean deviation ≤-8 dB) was used to estimate measurement floors. Minimum rim width (MRW), ganglion cell-inner plexiform layer thickness (GC-IPLT), and circumpapillary retinal nerve fiber layer thickness (cpRNFLT) were determined. Floors were defined as the average image area with a loss less than first-percentile confidence interval of the variability in this group. Global rate of change and percentage of the region of interest that did not reach the measurement floor at baseline were calculated in 87 eyes with advanced glaucoma (SAP MD ≤-12 dB).

RESULTS

Global change over time in longitudinal eyes was -1.51 μm/year for MRW, -0.21 μm/year for GC-IPL, and -0.36 μm/year cpRNFL (all P ≤ .03). The percentage of region of interest that did not reach the floor at baseline was 19% for MRW, 36% for GC-IPLT, and 14% for cpRNFLT. Average (± standard deviation) floors were 105 μm (± 15.9 μm) for MRW, 38 μm (± 3.4 μm) for GC-IPLT, and 38 μm (± 4.2 μm) for cpRNFLT.

CONCLUSIONS

In advanced glaucoma, more GC-IPL tissue remains above the measurement floor compared with other measurements, suggesting GC-IPL thickness is the better candidate for detecting progression. Progression in SDOCT measurements is observable in advanced disease.