Comparison of different spectral domain OCT scanning protocols for diagnosing preperimetric glaucoma

Minimum Rim Width and Peripapillary Retinal Nerve Fiber Layer Thickness for Diagnosing Early to Moderate Glaucoma

PRCIS

In a cross-sectional study from a Brazilian multiracial population, minimum rim width (MRW) and peripapillary retinal nerve fiber layer thickness measurements from OCT showed comparable diagnostic performance in discriminating early to moderate glaucoma from healthy eyes.

PURPOSE

The purpose of this study is to compare the ability of MRW and peripapillary retinal nerve fiber layer thickness (RNFLT) measurements in discriminating early to moderate glaucoma from healthy eyes in a Brazilian population.

METHODS

A total of 155 healthy controls and 118 patients with mild to moderate glaucoma (mean deviation >-12 dB) underwent MRW and RNFLT measurements with optical coherence tomography. Only 1 eye per patient was included in the analysis. A receiver operating characteristic (ROC) regression model was used to evaluate the diagnostic accuracy of MRW and RNFLT, whereas adjusting for age and Bruch membrane opening area. Sensitivities at fixed specificities of 95% were calculated for each parameter.

RESULTS

Global RNFLT and MRW showed comparable area under the ROC curves [0.93 (0.91-0.96) and 0.93 (0.89-0.96), respectively; P =0.973]. Both parameters had similar sensitivities (75% vs. 74%, respectively; P =0.852) at a fixed specificity of 95%. The best sector for diagnosing glaucoma for both parameters was the temporal inferior sector, which showed an area under the ROC curve of 0.93 (0.87-0.96) for RNFLT and 0.91 (0.86-0.95) for MRW ( P =0.320). The temporal inferior sector showed similar sensitivities for RNFLT and MRW measurements (83% vs. 77%, respectively) at a fixed specificity of 95% (P =0.230).

CONCLUSIONS

MRW and RNFLT measurements showed comparable diagnostic performance in discriminating early to moderate glaucoma from healthy eyes in a Brazilian multiracial population.

Ganglion Cell Complex Analysis: Correlations with Retinal Nerve Fiber Layer on Optical Coherence Tomography

The aim of this review is to analyze the correlations between the changes in the ganglion cell complex (GCC) and the retinal nerve fiber layer (RNFL) on optical coherence tomography in different possible situations, especially in eyes with glaucoma. For glaucoma evaluation, several studies have suggested that in the early stages, GCC analysis, especially the thickness of the infero and that of the inferotemporal GCC layers, is a more sensitive examination than circumpapillary RNFL (pRNFL). In the moderate stages of glaucoma, inferior pRNFL thinning is better correlated with the disease than in advanced cases. Another strategy for glaucoma detection is to find any asymmetry of the ganglion cell-inner plexiform layers (GCIPL) between the two macular hemifields, because this finding is a valuable indicator for preperimetric glaucoma, better than the RNFL thickness or the absolute thickness parameters of GCIPL. In preperimetric and suspected glaucoma, GCC and pRNFL have better specificity and are superior to the visual field. In advanced stages, pRNFL and later, GCC reach the floor effect. Therefore, in this stage, it is more useful to evaluate the visual field for monitoring the progression of glaucoma. In conclusion, GCC and pRNFL are parameters that can be used for glaucoma diagnosis and monitoring of the progression of the disease, with each having a higher accuracy depending on the stage of the disease.

On the protective role of the blood vessels in glaucomatous damage: A transversal study

PURPOSE

To corroborate whether vessels on the surface of the optic nerve head can provide protection against the loss of underlying axons in subjects with manifest glaucoma.

METHODS

In this pilot study, thirty-six glaucomatous eyes with a perimetric defect in the Bjerrum area were included. The retinal nerve fiber layer (RNFL) thickness was measured in each of the sectors of the clock-hour map obtained by Cirrus HD-OCT considering the presence or absence of blood vessels. These sectors were related with their corresponding areas of the retina examined in the visual field using a mathematical model of the retina introduced by Jansonius, in order to determine the values of threshold sensitivity in those areas in the presence or absence of vessels.

RESULTS

We corroborated the protective role of the blood vessel for peripapillary RNFL thickness of clock-hour 12 despite obtaining a p-value (p = 0.023; w = 228.5) close to the acceptance zone (p ≥ 0.05). The mean ± standard deviation with vessel and without vessel were 70.95 ± 24.35 and 88.46 ± 23.96, respectively. No differences were found between the mean values of threshold sensitivity to the presence or absence of blood vessels in each of the sectors considered.

CONCLUSIONS

Our findings do not allow us to affirm that there is an association between the presence of a vessel and protection against glaucomatous damage in subjects with an advanced manifestation of the disease. In the future, more extensive studies are needed to study this relationship in subjects with early glaucoma.

Clinical Applications of Artificial Intelligence in Glaucoma

Ophthalmology is one of the major imaging-intensive fields of medicine and thus has potential for extensive applications of artificial intelligence (AI) to advance diagnosis, drug efficacy, and other treatment-related aspects of ocular disease. AI has made impressive progress in ophthalmology within the past few years and two autonomous AI-enabled systems have received US regulatory approvals for autonomously screening for mid-level or advanced diabetic retinopathy and macular edema. While no autonomous AI-enabled system for glaucoma screening has yet received US regulatory approval, numerous assistive AI-enabled software tools are already employed in commercialized instruments for quantifying retinal images and visual fields to augment glaucoma research and clinical practice. In this literature review (non-systematic), we provide an overview of AI applications in glaucoma, and highlight some limitations and considerations for AI integration and adoption into clinical practice.

Quantifying biomarkers of axonal degeneration in early glaucoma to find the disc at risk

To evaluate regional axonal-related parameters as a function of disease stage in primary open angle glaucoma (POAG) and visual field (VF) sensitivity. Spectral domain optical coherence tomography was used to acquire 20° scans of POAG (n = 117) or healthy control (n = 52) human optic nerve heads (ONHs). Region specific and mean nerve fibre layer (NFL) thicknesses, border NFL and peripapillary NFL, minimum rim width (MRW)/ area (MRA) and prelamina thickness; and volume were compared across POAG disease stages and with visual field sensitivity. Differences identified between early glaucoma (EG), preperimetric glaucoma (PG) and control (C) ONHs included thinner PG prelamina regions than in controls (p < 0.05). Mean border NFL was thinner in EG (p < 0.001) and PG (p = 0.049) compared to control eyes; and EG mean, and inferior and ST, border NFL was thinner than in PG (p < 0.01). Mean, superior and inferior PG peripapillary NFL were thinner than in controls (p < 0.05), and EG ST peripapillary NFL was thinner than in PG (p = 0.023). MRW differences included: PG SN and inferior less than in controls (p < 0.05); thinner EG mean regional, inferior, nasal, and ST MRW versus PG MRW (p < 0.05). Regional border NFL, peripapillary NFL, MRW, MRA, prelamina thickness (except centre, p = 0.127) and prelamina volume (p < 0.05) were significantly associated with VF mean deviation (MD). Novel axon-derived indices hold potential as biomarkers to detect early glaucoma and identify ONHs at risk.

[Comparative study of retinal microcirculation in primary angle closure disease and early primary open-angle glaucoma]

PURPOSE

To compare microcirculatory changes in patients with early stages of primary angle closure disease (PACD) and primary open-angle glaucoma (POAG).

MATERIAL AND METHODS

The study retrospectively analyzed the clinical data of 60 eyes with PACD, 30 with initial POAG, and 30 eyes without any ophthalmic pathologies. Vessel density (VD) in the optic nerve head and peripapillary retina (wiVD Disc), as well as in the inner layers of fovea and parafovea (wiVD Macula) and their different sectors were determined in all patients by optical coherence tomography angiography (OCTA). The correlation of VD with axial length (AL), anterior chamber depth (ACD), lens thickness (TL), and corneal-compensated intraocular pressure (IOPcc) was assessed.

RESULTS

The wiVD Disc in PACD (42.47±4.23%) was lower than in POAG eyes (47.46±2.10%), p<0.001, but the difference for wiVD Macula was not significant: 41.71±4.55% and 39.29±2.46%, respectively (p=0.47). In both PACD and POAG, all OCTA parameters were lower than in normal eyes: p=0.000 for both wiVD Disc and wiVD Macula. WiVD Disc correlated with ACD both in PACD (r=0.724, p=0.012) and in POAG (r= 0.685, p=0.012), but a correlation with IOPcc was found only in PACD (r= -0.670, p=0.033). The largest number of inverse correlations was found between TL and VD both for wiVD Disc (r= -0.714, p=0.006) and the parameters of macular area (in para- and perifovea).

CONCLUSION

OCTA parameters differ significantly from the norm even in the early stages of both PACD and POAG. In PACD, there was a significant decrease in microcirculation in the peripapillary retina compared to POAG, which had an inverse correlation with IOPcc; there was also an inverse correlation of OCTA parameters in the optic nerve head and macula with lens thickness.

Macula and optic disk features in methamphetamine and crystal methamphetamine addicts using optical coherence tomography

PURPOSE

Methamphetamine and crystal methamphetamine abusers were compared with healthy subjects using optical coherence tomography to assess their retinal nerve fiber layer, macula, and optic disk characteristics.

METHODS

Forty-one methamphetamine and crystal methamphetamine abusers and 42 healthy subjects (mean ± SD of age: 35.82 ± 8.6 and 37.76 ± 9.1 years, respectively) were incorporated in this cross-sectional study. The drug abusers had a history of at least five years of substance use through smoking. Fourier-domain optical coherence tomography was used to image and assess the characteristics of retinal nerve fiber layer, macular thickness, and optic disk in the study groups.

RESULTS

The retinal nerve fiber layer thickness was significantly lower in the superior and temporal retinal quadrants of drug abusers than healthy subjects (P = 0.008 and P = 0.028, respectively). This study did not find a significant difference between drug abusers and healthy controls regarding optic to disk ratio, rim area, and disk area (P > 0.05). The comparison between the study groups showed that the reductions in perifovea and the superior quadrant of parafoveal thickness were statistically significant (P < 0.001 and P = 0.029, respectively).

CONCLUSION

Fourier-domain optical coherence tomography measurements showed that the retinal nerve fiber layer and macular thickness were different between methamphetamine and crystal methamphetamine abusers and healthy subjects, which should be considered in clinical practice. It seems that these drug abuses can cause alterations in retinal morphology.

Infrared- and white-light retinal sensitivity in glaucomatous neuropathy

Glaucoma causes irreversible neuropathy, which, untreated, may lead to blindness. In this case-control study, we measured two-photon infrared (IR) light sensitivity in glaucomatous eyes to propose a new method to quantify the visual loss. In total, 64 patients were recruited with an equal distribution between glaucoma and control groups. Retinal sensitivity to IR light was assessed using a two-photon excitation device. A fundus-driven microperimeter was used to measure retinal sensitivity to visible light. The retinal nerve fiber layer (RNFL) thickness was quantified automatically with optical coherence tomography. The IR sensitivity of glaucoma and control eyes differed significantly (P = .003): 9.8 (6.5 to 13.1) dB vs. 10.9 (8.2 to 13.0) dB. Although in the visible-light microperimetry, retinal sensitivity was decreased in glaucoma (17.0, range: 6.9 to 20.0 dB) compared to the controls (17.7, range: 11.6 to 20.0 dB), this difference did not reach the significance level. A significant thinning of the RNFL in the glaucoma group was observed (P < .001). IR sensitivity significantly correlated with the RNFL in three of the four assessed quadrants instead of only one in visible-light microperimetry. Although further research is needed, this proof-of-concept study suggests that IR-light sensitivity can be used to support the detection of glaucomatous neuropathy.

Microperimetry, Humphrey field analyzer, and optical coherence tomography in detecting glaucoma: a comparative performance study

PURPOSE

To evaluate and compare the diagnostic performance of microperimetry (MP), visual field (VF) 10-2 and 24-2 tests, and spectral-domain optical coherence tomography (SD-OCT) in primary open-angle glaucoma (POAG).

METHODS

The study consisted of 35 POAG and 42 control eyes were enrolled in this prospective study. Eligible participants were ≥ 50 years old. VF assessments were carried out using the Humphrey field analyzer (HFA) and Macular Integrity Assessment. Optic nerve head (ONH), retinal nerve fiber layer thickness (RNFLT), and ganglion cell inner-plexiform-layer thickness (GCIPLT) were measured by SD-OCT. Areas under the receiver operating characteristic curves (AUC) and sensitivities at 95% specificity were calculated for each parameter.

RESULTS

HFA 24-2 had the largest AUC value among the functional parameters to differentiate POAG from control eyes [AUC: 0.950 (0.906-0.994), sensitivity at 95%:60]. HFA 24-2 showed a significantly better performance than the 10-2 test (p = 0.036). Among the SD-OCT structural parameters, minimum GCIPLT had the largest AUC value to differentiate POAG from control eyes [AUC: 0.952 (0.905-0.999), sensitivity at 95%:80]. In comparison of the functional and structural parameters, HFA 24-2 showed a significantly better performance than the 10-2 test (p = 0.036). In macular parameters, minimum GCPLT performed significantly better than HFA 10-2 (p = 0.015) in detecting POAG. There was no statistically significant difference between the comparative diagnostic performance of the RNFL, ONH, HFA, and MP (p > 0.05 for all comparisons).

CONCLUSION

The structural and functional test results revealed that GCIPLT measurements had the highest diagnostic performance in detecting POAG. HFA 24-2 test performed better than 10-2 test in distinguishing glaucoma from healthy eyes. MP showed a similar performance with HFA 10-2 and may be considered a complementary diagnostic tool.

A Case for The Use of Artificial Intelligence in Glaucoma Assessment

We hypothesize that artificial intelligence applied to relevant clinical testing in glaucoma has the potential to enhance the ability to detect glaucoma. This premise was discussed at the recent Collaborative Community for Ophthalmic Imaging meeting, "The Future of Artificial Intelligence-Enabled Ophthalmic Image Interpretation: Accelerating Innovation and Implementation Pathways," held virtually September 3-4, 2020. The Collaborative Community in Ophthalmic Imaging (CCOI) is an independent self-governing consortium of stakeholders with broad international representation from academic institutions, government agencies, and the private sector whose mission is to act as a forum for the purpose of helping speed innovation in healthcare technology. It was one of the first two such organizations officially designated by the FDA in September 2019 in response to their announcement of the collaborative community program as a strategic priority for 2018-2020. Further information on the CCOI can be found online at their website (https://www.cc-oi.org/about). Artificial intelligence for glaucoma diagnosis would have high utility globally, as access to care is limited in many parts of the world and half of all people with glaucoma are unaware of their illness. The application of artificial intelligence technology to glaucoma diagnosis has the potential to broadly increase access to care worldwide, in essence flattening the Earth by providing expert level evaluation to individuals even in the most remote regions of the planet.

Structural abnormalities associated with glaucoma using swept-source optical coherence tomography in patients with systemic sclerosis

PURPOSE

Vasospasm represents an early event in systemic sclerosis (SSc). Ocular vasospasm may induce optic nerve head (ONH) damage and has been involved in the pathogenesis of glaucoma, especially normal-tension glaucoma (NTG). We aimed to investigate the presence of structural abnormalities associated with NTG using swept-source optical coherence tomography (SS-OCT) and to correlate the OCT parameters with clinical, capillaroscopy and digital blood flow measures in patients with SSc.

METHODS

In this cross-sectional study, 40 patients with SSc and 23 age-matched controls were included. The following parameters were measured using SS-OCT: mean and sectoral retinal nerve fibre layer (RNFL) thickness, macular ganglion cell layer complex (GCC) thickness and ONH morphology. Nailfold capillaroscopy (NFC) and digital blood flow measurements using laser Doppler imaging (LDI) were performed in all subjects.

RESULTS

Patients with SSc showed a thinner temporal RNFL than the controls (69.23 ± 11.74 versus 83.35 ± 20.19 µm, p = 0.001). The other parameters were similar between the two groups. In SSc patients, there was an inverse correlation between the disease duration and the average, superior and inferior RNFL thickness and the GCC thickness and between Raynaud's phenomenon duration and the average RNFL and GCC thickness (p < 0.05). NFC and LDI measurements did not show correlations with OCT parameters.

CONCLUSION

A thinner temporal RNFL and the correlation between Raynaud's phenomenon and disease duration and structural abnormalities on OCT suggest the presence of early ganglion cell damage in patients with SSc. Although mild, these findings indicate the need to monitor ocular abnormalities in SSc.

Correlation of optical coherence tomography and Doppler ultrasonography findings in pseudoexfoliation syndrome

PURPOSE

We aimed to investigate the correlation between the color Doppler imaging (CDI) results and parameters determined by spectral domain optical coherence tomography (SD-OCT) in cases with pseudoexfoliation syndrome (XFS).

METHODS

99 participants were included in this prospective study. Retinal nerve fiber layer (RNFL), ganglion cell complex (GCC), optic nerve head (ONH) measurements were recorded. Perfusions of the ophthalmic artery (OA) and central retinal artery (CRA) were determined and resistivity indices (RI) were calculated.

RESULTS

No statistically significant differences were determined between the groups regarding the RNFL and ONH parameters. Only the minimum GCC thickness value was determined to be reduced in XFS group (n = 49) when compared to the controls (n = 50) (p = 0.018). The OA-RI and CRA-RI values of XFS group were significantly higher than the control group (p < 0.001 and p = 0.001). In XFSs, negative correlations were present between OA-RI and the minimum, average, inferior and inferotemporal regions of GCC thickness (r = - 0.448 p = 0.001, r = - 0.275 p = 0.040, r = - 0.295 p = 0.027, r = - 0.304 p = 0.024, respectively), and also between CRA-RI and minimum GCC values (r = - 0.317, p = 0.017). While a significant relationship was present between age and OA-RI and CRA-RI values in controls, no such correlation was present in XFSs.

CONCLUSIONS

The vascular resistance increased with age in controls, whereas it was independent of age in XFS group. In XFSs, RIs correlated significantly with certain GCC values, but not with RNFL and ONH parameters. It would be beneficial to follow the XFS with CDI as it provides supportive parameters to GCC in order to recognize early changes in XFS.

Measurements of OCT Angiography Complement OCT for Diagnosing Early Primary Open-Angle Glaucoma

PURPOSE

To compare measurements of global and regional circumpapillary capillary density (cpCD) with retinal nerve fiber layer (RNFL) thickness and characterize their relationship with visual function in early primary open-angle glaucoma (POAG).

DESIGN

Cross-sectional study.

PARTICIPANTS

Eighty healthy eyes, 64 preperimetric eyes, and 184 mild POAG eyes from the Diagnostic Innovations in Glaucoma Study.

METHODS

Global and regional RNFL thickness and cpCD measurements were obtained using OCT and OCT angiography (OCTA). For direct comparison at the individual and diagnostic group level, RNFL thickness and capillary density values were converted to a normalized relative loss scale.

MAIN OUTCOME MEASURES

Retinal nerve fiber layer thickness and cpCD normalized loss at the individual level and diagnostic group. Global and regional areas under the receiver operating characteristic curve (AUROC) for RNFL thickness and cpCD to detect preperimetric glaucoma and glaucoma, R² for the strength of associations between RNFL thickness function and capillary density function in diagnostic groups.

RESULTS

Both global and regional RNFL thickness and cpCD decreased progressively with increasing glaucoma severity (P < 0.05, except for temporal RNFL thickness). Global and regional cpCD relative loss values were higher than those of RNFL thickness (P < 0.05) in preperimetric glaucoma (except for the superonasal region) and glaucoma (except for the inferonasal and superonasal regions) eyes. Race, intraocular pressure (IOP), and cpCD were associated with greater cpCD than RNFL thickness loss in early glaucoma at the individual level (P < 0.05). Global measurements of capillary density (whole image capillary density and cpCD) had higher diagnostic accuracies than RNFL thickness in detecting preperimetric glaucoma and glaucoma (P < 0.05; except for cpCD/RNFL thickness comparison in glaucoma [P = 0.059]). Visual function was significantly associated with RNFL thickness and cpCD globally and in all regions (P < 0.05, except for temporal RNFL thickness-function association [P = 0.070]).

CONCLUSIONS

Associations between capillary density and visual function were found in the regions known to be at highest risk for damage in preperimetric glaucoma eyes and all regions of mild glaucoma eyes. In early glaucoma, capillary density loss was more pronounced than RNFL thickness loss. Individual characteristics influence the relative magnitudes of capillary density loss compared with RNFL thickness loss. Retinal nerve fiber layer thickness and microvascular assessments are complementary and yield valuable information for the detection of early damages seen in POAG.

Slowed Saccadic Reaction Times in Seemingly Normal Parts of Glaucomatous Visual Fields

Purpose: In eye movement perimetry, peripheral stimuli are confirmed by goal-directed eye movements toward the stimulus. The saccadic reaction time (SRT) is regarded as an index of visual field responsiveness, whereas in standard automated perimetry (SAP), the visual field sensitivity is tested. We investigated the relation between visual field sensitivity and responsiveness in corresponding locations of the visual field in healthy controls and in patients with mild, moderate and advanced glaucoma.

Materials and Methods: Thirty-four healthy control subjects and 42 glaucoma patients underwent a 54-point protocol in eye movement perimetry (EMP) and a 24-2 SITA standard protocol in a Humphrey Field Analyzer. The visual field points were stratified by total deviation sensitivity loss in SAP into 6 strata. A generalized linear mixed model was applied to determine the influence of the various factors.

Results: The generalized linear mixed model showed that the mean SRT increased with increasing glaucoma severity, from 479 ms in the control eyes to 678 ms in the eyes of patients with advanced glaucoma (p < 0.001). Mean SRTs significantly increased with increasing SAP sensitivity loss. Even at the locations where no sensitivity loss was detected by SAP (total deviation values greater or equal than 0 dB), we found lengthened SRTs in mild, moderate and advanced glaucoma compared to healthy controls (p < 0.05) and in moderate and advanced glaucoma compared to mild glaucoma (p < 0.05). At locations with total deviation values between 0 and −3 dB, −3 and −6 dB and −6 and −12 dB, we found similar differences.

Conclusions: The lengthened SRT in areas with normal retinal sensitivities in glaucomatous eyes, i.e., planning and execution of saccades to specific locations, precede altered sensory perception as assessed with SAP. Better understanding of altered sensory processing in glaucoma might allow earlier diagnosis of emerging glaucoma.

Optical Coherence Tomography and Glaucoma

Early detection and monitoring are critical to the diagnosis and management of glaucoma, a progressive optic neuropathy that causes irreversible blindness. Optical coherence tomography (OCT) has become a commonly utilized imaging modality that aids in the detection and monitoring of structural glaucomatous damage. Since its inception in 1991, OCT has progressed through multiple iterations, from time-domain OCT, to spectral-domain OCT, to swept-source OCT, all of which have progressively improved the resolution and speed of scans. Even newer technological advancements and OCT applications, such as adaptive optics, visible-light OCT, and OCT-angiography, have enriched the use of OCT in the evaluation of glaucoma. This article reviews current commercial and state-of-the-art OCT technologies and analytic techniques in the context of their utility for glaucoma diagnosis and management, as well as promising future directions. Expected final online publication date for the Annual Review of Vision Science, Volume 7 is September 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Evaluation of ganglion cell-inner plexiform layer thickness in the diagnosis of preperimetric glaucoma and comparison to retinal nerve fiber layer

Purpose:

The aim of this study was to evaluate the diagnostic ability of optic nerve head (ONH), RNFL, and GC-IPL parameters in differentiating eyes with PPG from normals.

Methods:

This was a retrospective, cross-sectional, observational study. We studied 73 eyes of 41 patients and compared them to 65 eyes of 34 normal persons. Each patient underwent detailed ocular examination, standard automated perimetry, GC-IPL, ONH, and RNFL analysis. PPG was defined as eyes with normal visual field results and one or more localized RNFL defects that were associated with a glaucomatous disc appearance (e.g., notching or thinning of neuroretinal rim) and IOP more than 21 mm Hg. Diagnostic abilities of GC-IPL, ONH, and RNFL parameters were computed using area under receiver-operating curve (AUROC), sensitivity and specificity, and likelihood ratios (LRs).

Results:

All GC-IPL parameters differed significantly from normal. The ONH, RNFL, and GC-IPL parameters with best area under curves (AUCs) to differentiate PPG were vertical cup to disc ratio (0.76), inferior quadrant RNFL thickness (0.79), and inferotemporal quadrant GC-IPL thickness (0.73), respectively. Similarly, best LRs were found for clock hour 5, 6, and 12 thicknesses among RNFL; inferior sector and inferotemporal sector thicknesses among GC-IPL parameters.

Conclusion:

Diagnostic abilities of GC-IPL parameters were comparable to RNFL parameters in differentiating PPG patients from normals. The likelihood of ruling in a disease was greater with GC-IPL parameters.

Comparison of diagnostic ability of standard automated perimetry, short wavelength automated perimetry, retinal nerve fiber layer thickness analysis and ganglion cell layer thickness analysis in early detection of glaucoma

Purpose:

The aim of this study was to compare the diagnostic ability of macular ganglion cell layer (GCL) analysis using spectral domain optical coherence tomography against retinal nerve fiber layer analysis (RNFL), short-wavelength automated perimetry (SWAP), and standard automated perimetry (SAP) in early detection of glaucoma.

Methods:

Participants fulfilling the inclusion criteria were consecutively enrolled from the glaucoma clinic of tertiary care eye hospital in Western India from November 2015 to October 2016. The subjects underwent a detailed evaluation by trained glaucoma specialists. On suspicion of glaucoma, the patients underwent SAP, SWAP, and SD-OCT for GCL and RNFL analysis.

Results:

There were 91 patients in total of which experts classified 54 eyes into GON and 37 eyes into nonglaucomatous group. Sensitivity of SAP (42.59%) was significantly lower (P < 0.05) than that of average GCL thickness (79.63%) and average RNFL thickness (72.22%). Specificity and positive LR of SWAP (97.3% and 19.19, respectively) and SAP (94.6% and 7.88, respectively) were greater than those of GCL (81.08% and 4.21) and RNFL (67.57% and 2.23) parameters. Negative LR of average GCL thickness (0.25) was superior to that of average RNFL thickness (0.411), SWAP (0.495), and SAP (0.607).

Conclusion:

Macular GCL parameters perform better than RNFL parameters in patients with early glaucomatous damage. There is superior ability of SWAP over SAP in detecting glaucomatous changes in glaucoma suspect group. GCL thickness analysis has higher sensitivity and negative likelihood ratio, whereas SWAP had higher specificity and positive likelihood ratio. Thus, combining both tests can lead to better diagnostic ability for early glaucomatous damage.

Interpreting Deep Learning Studies in Glaucoma: Unresolved Challenges

ABSTRACT

Deep learning algorithms as tools for automated image classification have recently experienced rapid growth in imaging-dependent medical specialties, including ophthalmology. However, only a few algorithms tailored to specific health conditions have been able to achieve regulatory approval for autonomous diagnosis. There is now an international effort to establish optimized thresholds for algorithm performance benchmarking in a rapidly evolving artificial intelligence field. This review examines the largest deep learning studies in glaucoma, with special focus on identifying recurrent challenges and limitations within these studies which preclude widespread clinical deployment. We focus on the 3 most common input modalities when diagnosing glaucoma, namely, fundus photographs, spectral domain optical coherence tomography scans, and standard automated perimetry data. We then analyze 3 major challenges present in all studies: defining the algorithm output of glaucoma, determining reliable ground truth datasets, and compiling representative training datasets.

Artificial intelligence and complex statistical modeling in glaucoma diagnosis and management

PURPOSE OF REVIEW

The field of artificial intelligence has grown exponentially in recent years with new technology, methods, and applications emerging at a rapid rate. Many of these advancements have been used to improve the diagnosis and management of glaucoma. We aim to provide an overview of recent publications regarding the use of artificial intelligence to enhance the detection and treatment of glaucoma.

RECENT FINDINGS

Machine learning classifiers and deep learning algorithms have been developed to autonomously detect early structural and functional changes of glaucoma using different imaging and testing modalities such as fundus photography, optical coherence tomography, and standard automated perimetry. Artificial intelligence has also been used to further delineate structure-function correlation in glaucoma. Additional 'structure-structure' predictions have been successfully estimated. Other machine learning techniques utilizing complex statistical modeling have been used to detect glaucoma progression, as well as to predict future progression. Although not yet approved for clinical use, these artificial intelligence techniques have the potential to significantly improve glaucoma diagnosis and management.

SUMMARY

Rapidly emerging artificial intelligence algorithms have been used for the detection and management of glaucoma. These algorithms may aid the clinician in caring for patients with this complex disease. Further validation is required prior to employing these techniques widely in clinical practice.

Disc-fovea Angle Is Associated With Visual Field Defect Location in Patients With Glaucoma

PRECIS

The current study showed that glaucomatous eyes from patients with central visual field defects presented less negative disc-fovea angle compared with patients with peripheral defects.

PURPOSE

The purpose of this study was to investigate the relationship between disc-fovea angle and visual field defect location in patients with glaucoma.

MATERIALS AND METHODS

This was a cross-sectional study including glaucoma patients divided into isolated central and isolated peripheral scotoma groups. The main outcome measure was disc-fovea angle measurement between groups. Secondary outcomes included disc-fovea distance, vertical disc diameter, and fovea vertical deviation.

RESULTS

We included 50 glaucoma patients (50 eyes; 27 with central scotoma and 23 with peripheral scotoma). Mean deviation from visual fields was -3.05±1.67 and -2.95±1.49 dB (P=0.829) (central and peripheral scotoma groups, respectively). We found that eyes in the central group had lower values of disc-fovea angle (-5.85±2.67 vs. -7.97±2.26 degrees, P=0.004), shorter disc-fovea distance (4.38±0.70 vs. 4.98±0.78 mm, P=0.006), and shorter fovea vertical deviation (-0.43±0.19 vs. -0.68±0.22 mm, P<0.001) compared with eyes in the peripheral group.

CONCLUSIONS

This study showed an association between disc-fovea angle and central visual field defects in patients with glaucoma. Our findings suggest that eyes with a less negative disc-fovea angle should undergo a more careful investigation of the central visual field, even at early stages of the disease.

Overhead Mounted Optical Coherence Tomography in Childhood Glaucoma Evaluation

PRéCIS:: Overhead mounted spectral-domain optical coherence tomography (OCT) enables high-quality imaging of the optic nerve and macula in childhood glaucoma, and is particularly useful when standard tabletop OCT has failed or is not possible.

PURPOSE

Tabletop OCT, integral to adult glaucoma management, can be limited in childhood glaucoma patients because of young age, poor cooperation, and/or technical challenges. To address these imaging difficulties, we determined the feasibility and quality of an overhead mounted unit in childhood glaucoma. Secondary aims included evaluation of peripapillary retinal nerve fiber layer (pRNFL), parafoveal total retinal thickness, and parafoveal ganglion cell complex (GCC) thickness.

MATERIALS AND METHODS

Children and adults with a diagnosis of childhood glaucoma were imaged with an overhead mounted spectral-domain OCT as part of a prospective cross-sectional study. Participants had poor quality or unobtainable tabletop OCT and were scheduled for an examination under anesthesia and/or surgery as part of standard care.

RESULTS

A total of 88 affected eyes in 60 of 65 (92.3%) enrolled patients (mean age, 5.9±5.9 y; range, 0.2 to 24.5) were successfully imaged. The mean image quality for analyzed scans was 22.9±6.0 dB (n=236 images). Mean values for pRNFL (80.5±31.0 µm; n=86), parafoveal total retinal thickness (301.10±39.9 µm; n=79), and parafoveal GCC thickness (96.0±21.6 µm; n=74) were calculated.

CONCLUSIONS

Overhead mounted OCT allowed high-quality image acquisition and analysis in childhood glaucoma patients unable to be imaged with the tabletop counterpart, presenting an opportunity for improved clinical management and study of childhood glaucoma-related pathophysiology. pRNFL, parafoveal total retinal thickness, and parafoveal GCC thickness were decreased for affected eyes of children under 6 years of age compared with age-matched controls from a companion normative study.

Assessment of a Segmentation-Free Deep Learning Algorithm for Diagnosing Glaucoma From Optical Coherence Tomography Scans

Importance

Conventional segmentation of the retinal nerve fiber layer (RNFL) is prone to errors that may affect the accuracy of spectral-domain optical coherence tomography (SD-OCT) scans in detecting glaucomatous damage.

Objective

To develop a segmentation-free deep learning (DL) algorithm for assessment of glaucomatous damage using the entire circle B-scan image from SD-OCT.

Design, Setting, and Participants

This cross-sectional study at a single institution used data from SD-OCT images of eyes with glaucoma (perimetric and preperimetric) and normal eyes. The data set was randomly split at the patient level into a training (50%), validation (20%), and test data set (30%). Data were collected from March 2008 to April 2019, and analysis began April 2018.

Exposures

A convolutional neural network was trained to discriminate glaucomatous from normal eyes using the SD-OCT circle B-scan without segmentation lines.

Main Outcomes and Measures

The ability to discriminate glaucoma from healthy eyes was evaluated by comparing the area under the receiver operating characteristic curve and sensitivity at 80% or 95% specificity for the DL algorithm's predicted probability of glaucoma vs conventional RNFL thickness parameters given by SD-OCT software. The performance was also assessed in preperimetric glaucoma, as well as by visual field severity using Hodapp-Parrish-Anderson criteria.

Results

A total of 20 806 SD-OCT images from 1154 eyes of 635 individuals (612 [53%] with glaucoma and 542 normal eyes [47%]) were included. The mean (SD) age at SD-OCT scan was 70.8 (10.4) years in individuals with glaucoma and 55.8 (14.1) years in controls. There were 187 women (53.3%) in the glaucoma group and 165 (59.8%) in the control group. Of 612 eyes with glaucoma, 432 (70.4%) had perimetric and 180 (29.6%) had preperimetric glaucoma. The DL algorithm had a significantly higher area under the receiver operating characteristic curve than global RNFL thickness (0.96 vs 0.87; difference = 0.08 [95% CI, 0.04-0.12]) and each RNFL thickness sector for discriminating between glaucoma and controls (all P < .001). At 95% specificity, the DL algorithm (81%; 95% CI, 64%-97%) was more sensitive than global RNFL thickness (67%; 95% CI, 58%-76%). The areas under the receiver operating characteristic curve were also significantly greater for the DL algorithm compared with RNFL thickness at each stage of disease, especially preperimetric and mild perimetric glaucoma.

Conclusions and Relevance

A segmentation-free DL algorithm performed better than conventional RNFL thickness parameters for diagnosing glaucomatous damage on OCT scans, especially in early disease. Future studies should investigate how such an approach contributes to diagnostic decisions when combined with other relevant clinical information, such as risk factors and perimetry results.

Retinal neurovascular changes in chronic kidney disease

PURPOSE

To examine retinal neurovascular changes in patients with chronic kidney disease (CKD).

METHODS

Case-control study. A total of 171 CKD cases and 40 controls were recruited (mean age 62.9 ± 10.3 versus 60.8 ± 9.2, p = 0.257). Retinal neural parameters, including parafoveal retinal thickness (PfRT), macular ganglion cell complex thickness (GCCt), global loss volume (GLV), focal loss volume (FLV) and peripapillary retinal nerve fibre layer thickness (RNFLt), were measured using optical coherence tomography (OCT). Microvascular parameters, including foveal avascular zone size, vessel density over the parafoveal superficial vascular plexus (SVP-VD), parafoveal deep vascular plexus (DVP-VD) and radial peripapillary capillary (RPC-VD), were measured using OCT angiography.

RESULTS

Chronic kidney disease (CKD) patients showed reduced PfRT, GCCt and RNFLt and increased GLV and FLV compared with the controls (all p < 0.005). Among patients with CKD, estimated glomerular filtration rate was an independent factor associated with PfRT (coefficient 0.19, p = 0.015), GCCt (coefficient 0.10, p = 0.006), GLV (coefficient - 0.08, p = 0.001), FLV (coefficient - 0.02, p = 0.006) and RNFLt (coefficient 0.15, p = 0.002). Parafoveal retinal thickness (PfRT), GCCt, GLV, FLV and RNFLt were correlated with SVP-VD (all p < 0.001) but not with DVP-VD (all p > 0.1).

CONCLUSIONS

Chronic kidney disease (CKD) patients demonstrated a significant reduction in macular thickness and changes in retinal neural parameters. These changes were associated with the severity of CKD and correlated with the microvascular rarefaction in the parafoveal SVP.

Asymmetry analysis of optical coherence tomography angiography macular perfusion density measurements in preperimetric and perimetric glaucoma

Macular retinal layer thickness asymmetry indices, particularly for the ganglion cell layer, are promising early indicators of glaucomatous damage. We evaluated macular perfusion density asymmetry (MPDA) among normal, preperimetric glaucoma (PPG), and perimetric glaucoma (PG) eyes, and we tested the performance of MPDA in differentiating between control and glaucoma eyes with or without visual field (VF) defects. In this study, 116 eyes (39 normal, 27 PPG, and 50 PG eyes) with optical coherence tomography angiography images of the macula were analysed. No significant difference was found in outer and inner MPDA between the control and PPG groups. However, outer MPDA was significantly higher in the PG group than in the PPG group (p = 0.009). Asymmetry of perfusion density and structural parameters was compared; no significant difference was found between controls and glaucoma patients. Outer MPDA had significantly higher discrimination ability between PPG and PG than did macular ganglion cell layer–inner plexiform layer thickness asymmetry (p = 0.039). In conclusion, the discriminant capability of MPDA for discriminating between glaucoma patients with and without VF defects is significantly higher than that of structural asymmetry. MPDA may be helpful in monitoring glaucoma progression in clinical practice.

Pre-perimetric Open Angle Glaucoma with Young Age of Onset: Natural Clinical Course and Risk Factors for Progression

PURPOSE

To investigate the natural clinical course of more than 5 years and the risk factors of progression in patients with pre-perimetric open angle glaucoma (OAG) of "young age of onset (under age 40)" without treatment.

DESIGN

Retrospective observational case series.

METHODS

Optic disc photography, red-free retinal nerve fiber layer (RNFL) photography, optical coherence tomography, and visual field (VF) examinations were performed every 6 months. Glaucoma progression was defined as structural or functional deterioration. A linear mixed-effects model was used to estimate the rate of structural and functional changes. Kaplan-Meier survival analysis and log-rank testing were used to compare survival experiences, and Cox proportional hazards modeling was performed to identify risk factors for glaucoma progression.

RESULTS

Of the 98 eyes of 98 patients (mean age, 30.6 years old), glaucoma progression was detected in 42 eyes (42.9%). The rate of average RNFL thickness thinning was -0.46 ± 0.50 μm/y, and the mean deviation (MD) change was -0.03 ± 0.13 dB/y. The glaucoma progression probability at 5 years was 39% by structural criteria and 5% by functional criteria. Older age at diagnosis (P = .004), presence of temporal raphe sign (horizontal straight line on macular ganglion cell-inner plexiform layer thickness map) (P = .011), lamina pore visibility (P = .034), and greater pattern standard deviation (P = .005) were significant factors for glaucoma progression.

CONCLUSIONS

In untreated pre-perimetric OAG patients with a "young age of onset" condition, the estimated MD slope for the disease course of more than 5 years was -0.03 dB/y, and the average RNFL thinning rate was -0.46 μm/y. The predictors for progression were structural parameters of temporal raphe sign, lamina pore visibility, and functional parameter of pattern standard deviation.

Pattern Electroretinograms in Preperimetric and Perimetric Glaucoma

PURPOSE

To investigate whether visual function can be graded in detail using pattern electroretinogram (PERG) in preperimetric to perimetric glaucoma.

DESIGN

Cross-sectional observational study.

METHODS

Twenty-six normal subjects, 113 preperimetric glaucoma patients (which included glaucoma suspect patients), and 52 early perimetric glaucoma patients with a mean deviation (MD) >-10 dB were included. Structural and functional measurements were performed using spectral-domain optical coherence tomography and a commercial ERG stimulator, respectively.

RESULTS

The average retinal nerve fiber layer (RNFL) and ganglion cell-inner plexiform layer (GCIPL) thickness were thinnest in the perimetric group, followed by the preperimetric group and the control group (P < .001). PERG N95 amplitude was the largest in the control group, followed by the preperimetric group and the perimetric group (P < .001). Among the preperimetric glaucoma patients, presence of the RNFL defect was associated with lower PERG N95 amplitude (P = .013). The N95 amplitude showed a significant relationship with average RNFL thickness (r = 0.336, P < .001) and GCIPL thickness (r = 0.376, P < .001). In the preperimetric group with the RNFL defect, the N95 amplitude showed larger areas under the receiver operating characteristic curve (0.779) than the MD (0.533, P = .005).

CONCLUSIONS

PERG N95 amplitudes decreased from the control to preperimetric glaucoma group and were reduced more in perimetric glaucoma. The functional assessment for detecting early glaucomatous damage could be complemented by PERG N95 amplitude. Usefulness of PERG parameters except N95 amplitude seemed to be limited in a clinical setting because of relatively low diagnostic performance in preperimetric glaucoma.

Effect of Scan Size on Glaucoma Diagnostic Performance Using OCT Angiography En Face Images of the Radial Peripapillary Capillaries

PRECIS

When comparing 4.5×4.5 mm to 6.0×6.0 mm optical coherence tomography angiography scans of the radial peripapillary capillaries (RPCs) for glaucoma diagnostic capability, there was a trend of 4.5 scans outperforming 6.0 scans, especially for inferior, nasal, and superior quadrants.

OBJECTIVES

The main purpose of this study was to compare diagnostic ability of peripapillary vessel parameters from 4.5×4.5 mm (4.5) and 6.0×6.0 mm (6.0) spectral-domain optical coherence tomography angiography scans of the RPC in detecting primary open-angle glaucoma from nonglaucoma eyes.

METHODS

Consecutive patients from an academic glaucoma clinic underwent 4.5 and 6.0 scans (CIRRUS HD-OCT 5000 with AngioPlex OCT Angiography; ZEISS, Dublin, CA). Automatic segmentation created en face RPC images. Vessel area density, vessel skeleton density, and flux were calculated using custom quantification software, and perfusion density and flux index (FI) using automated quantification software. Area under the curve statistics included age and hypertension in the analysis.

RESULTS

Of 173 eyes from 123 patients who underwent both 4.5 and 6.0 imaging, 32 primary open-angle glaucoma eyes from 32 patients and 95 nonglaucoma eyes from 95 patients were studied. For the global region of 4.5 versus 6.0 scans, area under the curve was 0.940 and 0.916 for vessel area density (P=0.286); 0.941 and 0.921 for vessel skeleton density (P=0.385); 0.942 and 0.916 for flux (P=0.239); 0.912 and 0.884 for perfusion density (P=0.103); and 0.913 and 0.865 for FI (P=0.159), respectively. For the quadrant regions, 4.5 images significantly outperformed 6.0 images for the superior and inferior quadrants for flux and superior and nasal quadrants for FI (P-values=0.007, 0.047, 0.011, 0.007, respectively); other quadrant differences were not significant.

CONCLUSIONS

Parameters from 4.5 scans generally outperformed those from 6.0 scans in the global and quadrant regions, suggesting greater digital resolution in 4.5 scans of the immediate peripapillary RPC is important in detecting glaucomatous changes.

Using Enhanced Depth Imaging Optical Coherence Tomography-Derived Parameters to Discriminate between Eyes with and without Glaucoma: A Cross-Sectional Comparative Study

INTRODUCTION

New technologies have been developed in order to decrease interpersonal influence and subjectivity during the glaucoma diagnosis process. Enhanced depth imaging spectral-domain OCT (EDI OCT) has turned up as a favorable tool for deep optic nerve head (ONH) structures assessment.

OBJECTIVE

A prospective cross-sectional study was conducted to compare the diagnostic performance of different EDI OCT-derived parameters to discriminate between eyes with and without glaucoma.

MATERIAL AND METHODS

The following ONH parameters were measured: lamina cribrosa (LC) thickness and area; prelaminar neural tissue (PLNT) thickness and area; average Bruch's membrane opening - minimum rim width (BMO-MRW), superior BMO-MRW, and inferior BMO-MRW. Peripapillary retinal nerve fiber layer (pRNFL) thickness was also obtained.

RESULTS

Seventy-three participants were included. There were no significant differences between AUCs for average BMO-MRW (0.995), PLNT area (0.968), and average pRNFL thickness (0.975; p ≥ 0.089). However, AUCs for each of these 3 parameters were significantly larger than LC area AUC (0.701; p ≤ 0.001). Sensitivities at 80% specificity were: PLNT area = 92.3%, average BMO-MRW = 97.4%, and average pRNFL thickness = 94.9%.

CONCLUSIONS

Comparing the diagnostic performance of different EDI OCT ONH parameters to discriminate between eyes with and without glaucoma, we found better results for neural tissue-based indexes (BMO-MRW and PLNT area) compared to laminar parameters. In this specific population, these neural tissue-based parameters (including PLNT area, which was investigated by the first time in the present study) had a diagnostic performance comparable to that of the conventional pRNFL thickness protocol.

Study of correlation between stereopsis and retinal nerve fiber layer thickness in cases of glaucoma

Background

Glaucoma is an important and common optic neuropathy characterized by progressive loss of retinal ganglion cells and associated morphological changes to the optic nerve and retinal nerve fiber layer (RNFL). The most common assessment of visual function in glaucoma uses perimetric measurements of visual sensitivity. Only few studies have evaluated the binocular function in patients with glaucoma. This study was taken up to establish the correlation of RNFL thickness, in glaucoma, with near and distance stereopsis.

Methods

This pilot, cross-sectional observational study included 100 diagnosed cases of glaucoma and 100 normal participants as controls, studied over a period of one year. The records of all the participants were checked, and only established cases of glaucoma after fulfilling the inclusion and exclusion criteria were included. Analysis of the RNFL using spectral-domain optical coherence tomography was carried out. All the participants were thereafter evaluated for stereoacuity by near (at 40 inches) and distance (at 3 meter) Randot stereoacuity charts.

Results

There was a negative correlation between the RNFL thickness and the absolute value of streoacuity (-0.303 for distance versus -0.101 for near in cases and -0.308 for distance and -0.416 for near in control group), decreasing the actual functional stereoacuity, therefore the cases with lower RNFL thickness had lower stereoacuity both for distance and near, however it was statistically significant only for distance (p=0.002).

Conclusion

Functional aspects, such as stereoacuity, may also be affected in the glaucoma because of decrease in RNFL thickness. Therefore, binocular status should also be evaluated in cases of glaucoma.

Macular imaging with optical coherence tomography in glaucoma

With the advent of spectral-domain optical coherence tomography, imaging of the posterior segment of the eye can be carried out rapidly at multiple anatomical locations, including the optic nerve head, circumpapillary retinal nerve fiber layer, and macula. There is now ample evidence to support the role of spectral-domain optical coherence tomography imaging of the macula for detection of early glaucoma. Macular spectral-domain optical coherence tomography measurements demonstrate high reproducibility, and evidence on its utility for detection of glaucoma progression is accumulating. We present a comprehensive review of macular spectral-domain optical coherence tomography imaging emerging as an essential diagnostic tool in glaucoma.

Diagnostic utility of neuroretinal rim thickness, measured in clock-hour sectors with HD optical coherence tomography, in preperimetric glaucoma

BACKGROUND

We evaluated the usefulness of neuroretinal rim (NRR) thicknesses, measured in clock-hour sectors with Cirrus HD optical coherence tomography, for diagnosing preperimetric glaucoma (PPG).

METHODS

This prospective study included 39 eyes of 39 patients with PPG and 39 eyes of 39 controls that were matched to patients for age and refractive error. We measured the circumpapillary retinal nerve fiber layer (cpRNFL) thickness, macular ganglion cell-inner plexiform layer (GCIPL) thickness, and optic nerve head (ONH) parameters with optical coherence tomography. The clock-hour NRR thicknesses were derived from a 360° circumferential rim thickness curve. We analyzed the area under the receiver operating characteristics curve (AUROC), cutoff values, and sensitivities at specificities of 90% and 95%.

RESULTS

The largest area under the receiver operating characteristics curves were observed for the NRR thickness at 6 o'clock (0.823), the inferior RNFL thickness (0.821), the average RNFL thickness (0.819), and the NRR thickness at 7 o'clock (0.818). The performance of the NRR thickness at 6 o'clock was comparable to the best performances of the cpRNFL, GCIPL, and ONH parameters (all p > 0.05).

CONCLUSION

The ability of the clock-hour NRR thickness assessment to diagnose PPG was comparable to the diagnostic abilities of cpRNFL, GCIPL, and ONH parameters. The best indicator of PPG was the NRR thickness parameter that was at 6 o'clock. This finding could play a role in detecting early structural changes in PPG.

Ganglion Cell Complex Analysis in Glaucoma Patients: What Can It Tell Us?

Glaucoma is a group of optic neuropathies characterized by a progressive degeneration of retina ganglion cells (RGCs) and their axons that precedes functional changes detected on the visual field. The macular ganglion cell complex (GCC), available in commercial Fourier-domain optical coherence tomography, allows the quantification of the innermost retinal layers that are potentially involved in the glaucomatous damage, including the retinal nerve fiber (RNFL), ganglion cell and inner plexiform layers. The average GCC thickness and its related parameters represent a reliable biomarker in detecting preperimetric glaucomatous damage. The most accurate GCC parameters are represented by average and inferior GCC thicknesses, and they can be associated with progressive visual field loss. Although the diagnostic accuracy increases with more severe glaucomatous damage and higher signal strength values, it is not affected by increasing axial length, resulting in a more accurate discrimination of glaucomatous damage in myopic eyes with respect to the traditional RNFL thickness. The analysis of the structure-function relationship revealed a good agreement between the loss in retinal sensitivity and GCC thickness. The use of a 10-2° visual field grid, adjusted for the anatomical RGCs displacement, describes more accurately the relationship between RGCs thickness and visual field sensitivity loss.

Macular vessel density versus ganglion cell complex thickness for detection of early primary open-angle glaucoma

Background

To evaluate the macular vessel density (VD) and ganglion cell complex (GCC) thickness in pre-perimetric (PPG) and early perimetric primary open-angle glaucoma (PG) eyes, and to compare the diagnostic ability of the two measurements to discriminate PPG and early PG eyes from healthy eyes.

Methods

Seventy-nine eyes in 72 subjects (31 normal, 26 PPG, and 22 early PG eyes) were included in the consecutive case series. Macular VD and GCC thickness were acquired simultaneously using the 6 × 6 mm² high-density AngioRetina scanning mode. Diagnostic abilities were assessed using the area under the receiver operating characteristic curve (AUROC).

Results

Compared to healthy eyes, whole image VD (wiVD) and GCC thickness were significantly lower in PPG and early PG eyes (all P < 0.025). The percent reduction of wiVD was lower than that of GCC thickness in early PG eyes (P < 0.05), while they were similar in PPG eyes (P > 0.05). Regionally, greater VD attenuation and GCC thinning were identified in the perifovea than in the parafovea in both groups (all P < 0.05). Moreover, the percent reduction of VD was less than that of GCC thickness in the perifoveal region in PPG eyes (P < 0.05). The AUROCs for wiVD and GCC thickness were 0.824 and 0.881, respectively, in PPG eyes (P > 0.05), and 0.918 and 0.977, respectively, in early PG eyes (P > 0.05).

Conclusions

Macular VD and GCC thickness significantly decreased in PPG and early PG eyes. The perifoveal region appeared to be more vulnerable to macular VD attenuation and GCC thinning in early glaucoma. Our results showed that macular VD measurements may be helpful for detecting and understanding early glaucomatous damage.

[Modern view on ocular hypertension]

Increased intraocular pressure is the main, and the only modifiable risk factor in the development of glaucoma. This review analyzes studies on differential diagnostics of ocular hypertension and risk factors of its conversion to glaucoma, and gives recommendations based on literature data for the most correct algorithm for management of patients with ocular hypertension.

Macular and Multifocal PERG and FD-OCT in Preperimetric and Hemifield Loss Glaucoma

PURPOSE

To evaluate the ability of macular and multifocal (mf) pattern electroretinogram (PERG) to differentiate preperimetric glaucoma (PG) and glaucoma with hemifield loss (GHL) from controls, to compare the discrimination ability of PERG and fourier-domain optical coherence tomography (FD-OCT), and to assess the relationship between measurements.

PATIENTS AND METHODS

Standard automated perimetry, steady-state and transient PERG and mfPERG measurements were obtained from PG (n=14, 24 eyes), GHL (n=5, 7 eyes), and controls (n=19, 22 eyes). Circumpapillary retinal nerve fiber layer (cpRNFL), full-thickness macula, and segmented macular layer thicknesses on FD-OCT were investigated. Measurements were compared using mixed effects linear models. The relationships between measurements and the diagnostic performance of each technology were assessed.

RESULTS

Compared with controls, average P50 peak time transient PERG responses were reduced in PG and GHL, whereas average latency and amplitude steady-state and mfPERG responses were abnormal only in GHL. cpRNFL and macular thickness measurements in PG and GHL differed significantly from controls. A significant relationship was found between PERG and most FD-OCT or SAP parameters. Partial least squares discriminant analysis revealed that OCT parameters, along with mfPERG and transient PERG parameters had similar ability to discriminate PG and GHL from healthy controls.

CONCLUSIONS

PERG and OCT parameters may be abnormal, with significant correlations between measurements, in PG eyes. Both technologies may be useful for detection of early glaucoma.

Diagnostic Capability of Three-Dimensional Macular Parameters for Glaucoma Using Optical Coherence Tomography Volume Scans

Purpose

To compare the diagnostic capability of three-dimensional (3D) macular parameters against traditional two-dimensional (2D) retinal nerve fiber layer (RNFL) thickness using spectral domain optical coherence tomography. To determine if manual correction and interpolation of B-scans improve the ability of 3D macular parameters to diagnose glaucoma.

Methods

A total of 101 open angle glaucoma patients (29 with early glaucoma) and 57 healthy subjects had peripapillary 2D RNFL thickness and 3D macular volume scans. Four parameters were calculated for six different-sized annuli: total macular thickness (M-thickness), total macular volume (M-volume), ganglion cell complex (GCC) thickness, and GCC volume of the innermost 3 macular layers (retinal nerve fiber layer + ganglion cell layer + inner plexiform layer). All macular parameters were calculated with and without correction and interpolation of frames with artifacts. The areas under the receiver operating characteristic curves (AUROC) were calculated for all the parameters.

Results

The 3D macular parameter with the best diagnostic performance was GCC-volume-34, with an inner diameter of 3 mm and an outer of 4 mm. The AUROC for RNFL thickness and GCC-volume-34 were statistically similar for all regions (global: RNFL thickness 0.956, GCC-volume-34 0.939, P value = 0.3827), except for the temporal GCC-volume-34, which was significantly better than temporal RNFL thickness (P value = 0.0067). Correction of artifacts did not significantly change the AUROC of macular parameters (P values between 0.8452 and 1.0000).

Conclusions

The diagnostic performance of best macular parameters (GCC-volume-34 and GCC-thickness-34) were similar to or better than 2D RNFL thickness. Manual correction of artifacts with data interpolation is unnecessary in the clinical setting.

Color visual acuity in preperimetric glaucoma and open-angle glaucoma

Purpose

To investigate the clinical significance of color visual acuity (CVA) in preperimetric glaucoma (PPG) and open-angle glaucoma (OAG).

Methods

A total of 123 eyes of 73 subjects (22 normal eyes, 14 PPG eyes, and 87 OAG eyes; mean age: 44.9 ± 10.1 years, age range: 21–64 years) were enrolled. CVA was tested for red, green-yellow, blue-green and blue-purple with a newly developed test.

Results

There was no statistical difference in clinical background factors, including age, sex, intraocular pressure, or spherical equivalent between the three groups. Red VA and blue-green VA were significantly worse in the OAG eyes than in the normal eyes (P = 0.008 and P = 0.015, respectively), although green-yellow VA and blue-purple VA were not significantly worse. Furthermore, red VA and blue-green VA were significantly correlated with MD in a group of eyes with either PPG or OAG (r = -0.23, P = 0.023; r = -0.25, P = 0.012, respectively), but green-yellow VA and blue-purple VA were not.

Conclusion

Red VA and blue-green VA were detectably worse in eyes with OAG, in close association with the degree of functional loss. This suggests that measuring CVA with the new color test described here may be a promising supplement to existing methods of detecting glaucoma and evaluating its severity.

Macular ganglion cell-inner plexiform vs retinal nerve fiber layer measurement to detect early glaucoma with superior or inferior hemifield defects

BACKGROUND

To compare the diagnostic ability of Cirrus high-definition spectral-domain optical coherence tomography measurements of the macular ganglion cell-inner plexiform layer (GCIPL) vs the circumferential retinal nerve fiber layer (cpRNFL) to detect early glaucoma with hemifield visual field (VF) defects.

METHODS

This prospective study included 96 patients with primary open-angle glaucoma (48 with superior hemifield defects and 48 with inferior hemifield defects) and 48 normal control subjects. All glaucomatous eyes had a mean deviation of the VF defect ≥-6.0 dB confined to one hemifield. cpRNFL and GCIPL thicknesses were recorded. Area under the receiver operating characteristic curve (AUROC) was calculated for each parameter and compared.

RESULTS

All GCIPL parameters and most cpRNFL parameters (except at the nasal quadrant, and 2-, 3-, and 4-o'clock sectors) were significantly lower in glaucomatous eyes vs those in normal controls. In the superior hemifield defect group, the best discriminating parameters were 7-o'clock-sector cpRNFL thickness (AUROC value, 0.963), inferior cpRNFL thickness (0.926), and inferotemporal GCIPL thickness (0.923). Performance was comparable between the best measures of GCIPL analysis (inferotemporal GCIPL thickness) and those of cpRNFL (7-o'clock-sector thickness, p = 0.28). In the inferior hemifield defect group, the best discriminating parameters were 11- and 10-o'clock-sector cpRNFL thickness (0.940 and 0.904, respectively), and average cpRNFL thickness (0.909). Performance was comparable between the best measures from each method (superotemporal GCIPL thickness vs. 11-o'clock-sector cpRNFL thickness [0.857 vs 0.940, p = 0.07]).

CONCLUSION

Diagnostic abilities of GCIPL parameters and cpRNFL parameters for early glaucoma were comparable for eyes with either superior or inferior hemifield VF defects.

Glaucoma Diagnosis with Machine Learning Based on Optical Coherence Tomography and Color Fundus Images

This study aimed to develop a machine learning-based algorithm for glaucoma diagnosis in patients with open-angle glaucoma, based on three-dimensional optical coherence tomography (OCT) data and color fundus images. In this study, 208 glaucomatous and 149 healthy eyes were enrolled, and color fundus images and volumetric OCT data from the optic disc and macular area of these eyes were captured with a spectral-domain OCT (3D OCT-2000, Topcon). Thickness and deviation maps were created with a segmentation algorithm. Transfer learning of convolutional neural network (CNN) was used with the following types of input images: (1) fundus image of optic disc in grayscale format, (2) disc retinal nerve fiber layer (RNFL) thickness map, (3) macular ganglion cell complex (GCC) thickness map, (4) disc RNFL deviation map, and (5) macular GCC deviation map. Data augmentation and dropout were performed to train the CNN. For combining the results from each CNN model, a random forest (RF) was trained to classify the disc fundus images of healthy and glaucomatous eyes using feature vector representation of each input image, removing the second fully connected layer. The area under receiver operating characteristic curve (AUC) of a 10-fold cross validation (CV) was used to evaluate the models. The 10-fold CV AUCs of the CNNs were 0.940 for color fundus images, 0.942 for RNFL thickness maps, 0.944 for macular GCC thickness maps, 0.949 for disc RNFL deviation maps, and 0.952 for macular GCC deviation maps. The RF combining the five separate CNN models improved the 10-fold CV AUC to 0.963. Therefore, the machine learning system described here can accurately differentiate between healthy and glaucomatous subjects based on their extracted images from OCT data and color fundus images. This system should help to improve the diagnostic accuracy in glaucoma.

Using Deep Learning and Transfer Learning to Accurately Diagnose Early-Onset Glaucoma From Macular Optical Coherence Tomography Images

PURPOSE

We sought to construct and evaluate a deep learning (DL) model to diagnose early glaucoma from spectral-domain optical coherence tomography (OCT) images.

DESIGN

Artificial intelligence diagnostic tool development, evaluation, and comparison.

METHODS

This multi-institution study included pretraining data of 4316 OCT images (RS3000) from 1371 eyes with open angle glaucoma (OAG) regardless of the stage of glaucoma and 193 normal eyes. Training data included OCT-1000/2000 images from 94 eyes of 94 patients with early OAG (mean deviation > -5.0 dB) and 84 eyes of 84 normal subjects. Testing data included OCT-1000/2000 from 114 eyes of 114 patients with early OAG (mean deviation > -5.0 dB) and 82 eyes of 82 normal subjects. A DL (convolutional neural network) classifier was trained using a pretraining dataset, followed by a second round of training using an independent training dataset. The DL model input features were the 8 × 8 grid macular retinal nerve fiber layer thickness and ganglion cell complex layer thickness from spectral-domain OCT. Diagnostic accuracy was investigated in the testing dataset. For comparison, diagnostic accuracy was also evaluated using the random forests and support vector machine models. The primary outcome measure was the area under the receiver operating characteristic curve (AROC).

RESULTS

The AROC with the DL model was 93.7%. The AROC significantly decreased to between 76.6% and 78.8% without the pretraining process. Significantly smaller AROCs were obtained with random forests and support vector machine models (82.0% and 67.4%, respectively).

CONCLUSION

A DL model for glaucoma using spectral-domain OCT offers a substantive increase in diagnostic performance.

Diagnostic ability of macular ganglion cell asymmetry in Preperimetric Glaucoma

Background

To evaluate the diagnostic ability of macular ganglion cell asymmetry to diagnose preperimetric glaucoma (PPG), using Cirrus spectral domain optical coherence tomography (OCT).

Methods

This prospective study included 67 eyes of 67 patients with PPG and 67 eyes of 67 age- and refractive error-matched controls. We measured circumpapillary RNFL (cpRNFL) thickness, macular ganglion cell-inner plexiform layer (GCIPL) thickness and optic nerve head (ONH) parameters using OCT. Macular ganglion cell asymmetries were expressed as absolute difference and ratios between inferior hemisphere and superior hemisphere, inferotemporal (IT) and superotemporal (ST), IT and superonasal (SN), IT and inferonasal (IN), ST and IN as well as temporal and nasal. An asymmetry index was assigned by taking the absolute value of log₁₀ of the ratio. The area under the receiver operating characteristics curve (AUROC), partial AUROC (pAUROC) ≥ specificities 90 and 95%, cutoff values and sensitivities at specificities 90 and 95% was analyzed.

Results

Parameters with largest AUROCs were IT GCIPL thickness (0.784), average RNFL thickness (0.767), and average C/D (0.746). For macular asymmetry parameters, log IT/SN index had the largest AUROC (0.734), followed by log IT/IN index (0.725), and absolute difference of IT−SN GCIPL thickness (0.715). Performance was comparable between the best measures of asymmetry analysis (log IT/SN index) and those of cpRNFL, GCIPL, and ONH parameters (all P > 0.05). The IT/SN asymmetry index not only had the largest pAUROC based on the pAUROCs ≥90 and 95% specificity (0.044 and 0.019) but also had the highest diagnostic sensitivity at 90 and 95% specificities (52.2 and 46.3%).

Conclusions

GCIPL asymmetry measurements have diagnostic ability comparable to cpRNFL, GCIPL, and ONH analysis for PPG. The best macular ganglion cell asymmetry parameter was IT/SN asymmetry index, which could be a new parameter to detect early structural changes in PPG.

Electronic supplementary material

The online version of this article (10.1186/s12886-018-1019-4) contains supplementary material, which is available to authorized users.

From Machine to Machine: An OCT-Trained Deep Learning Algorithm for Objective Quantification of Glaucomatous Damage in Fundus Photographs

PURPOSE

Previous approaches using deep learning (DL) algorithms to classify glaucomatous damage on fundus photographs have been limited by the requirement for human labeling of a reference training set. We propose a new approach using quantitative spectral-domain (SD) OCT data to train a DL algorithm to quantify glaucomatous structural damage on optic disc photographs.

DESIGN

Cross-sectional study.

PARTICIPANTS

A total of 32 820 pairs of optic disc photographs and SD OCT retinal nerve fiber layer (RNFL) scans from 2312 eyes of 1198 participants.

METHODS

The sample was divided randomly into validation plus training (80%) and test (20%) sets, with randomization performed at the patient level. A DL convolutional neural network was trained to assess optic disc photographs and predict SD OCT average RNFL thickness.

MAIN OUTCOME MEASURES

The DL algorithm performance was evaluated in the test sample by evaluating correlation and agreement between the predictions and actual SD OCT measurements. We also assessed the ability to discriminate eyes with glaucomatous visual field loss from healthy eyes with area under the receiver operating characteristic (ROC) curves.

RESULTS

The mean prediction of average RNFL thickness from all 6292 optic disc photographs in the test set was 83.3±14.5 μm, whereas the mean average RNFL thickness from all corresponding SD OCT scans was 82.5±16.8 μm (P = 0.164). There was a very strong correlation between predicted and observed RNFL thickness values (Pearson r = 0.832; R² = 69.3%; P < 0.001), with mean absolute error of the predictions of 7.39 μm. The area under the ROC curves for discriminating glaucomatous from healthy eyes with the DL predictions and actual SD OCT average RNFL thickness measurements were 0.944 (95% confidence interval [CI], 0.912-0.966) and 0.940 (95% CI, 0.902-0.966), respectively (P = 0.724).

CONCLUSIONS

We introduced a novel DL approach to assess fundus photographs and provide quantitative information about the amount of neural damage that can be used to diagnose and stage glaucoma. In addition, training neural networks to predict SD OCT data objectively represents a new approach that overcomes limitations of human labeling and could be useful in other areas of ophthalmology.

An evidence-based approach to the routine use of optical coherence tomography

Optical coherence tomography is an imaging technology that has revolutionised the detection, assessment and management of ocular disease. It is now a mainstream technology in clinical practice and is performed by non-specialised personnel in some settings. This article provides a clinical perspective on the implications of that movement and describes best practice using multimodal imaging and an evidence-based approach. Practical, illustrative guides on the interpretation of optical coherence tomography are provided for three major diseases of the ocular fundus, in which optical coherence tomography is often crucial to management: age-related macular degeneration, diabetic retinopathy and glaucoma. Topics discussed include: cross-sectional and longitudinal signs in ocular disease, so-called 'red-green' disease whereby clinicians rely on machine/statistical comparisons for diagnosis in managing treatment-naïve patients, and the utility of optical coherence tomography angiography and machine learning.

Measurement of the hypotenuse of the vertical optic nerve head cup with spectral-domain optical coherence tomography for the structural diagnosis of glaucoma

Purpose

To evaluate the hypotenuse of the vertical optic nerve head cup (HVOC), measured using the length and depth of the cup obtained with enhanced depth imaging spectral-domain optic coherence tomography (SD-OCT), as a biomarker for glaucoma diagnosis.

Methods

This was a prospective cross-sectional study of patients with glaucoma and controls. SD-OCT was performed in all participants to assess average circumpapillary retinal nerve fiber layer (RNFL) thickness. A vertical B-scan of the optic nerve head (ONH) was obtained for HVOC measurement. The length and depth of the optic nerve cup formed the sides of a right triangle that were used to calculate the HVOC. Participants also underwent standard automated perimetry.

Results

One hundred and fifty-six eyes were divided into three groups: mean deviation (MD) <−7 dB (60 eyes); MD ≥−7 dB (74 eyes); and healthy subjects (22 eyes). The mean (SD) HVOC in these groups was 1,419.8 (347.2) µm, 1,234.6 (258.8) µm, and 685.79 (315.4) µm (P<0.01), respectively. In the secondary structure–function analysis, only discs with a vertical diameter of 1.51–2.00 mm were included (120 eyes). The HVOCs were divided into four percentile groups, with the following means: 940, 1,128, 1,390, and 1,662 µm. There was a significant difference in MD between percentile groups 1 and 3 (P<0.03), 1 and 4 (P<0.001), 2 and 3 (P<0.02), and 2 and 4 (P<0.001). RNFL thickness differed among all percentile groups (P<0.001).

Conclusion

HVOC may provide an additional morphometric biomarker for the structural evaluation of ONH remodeling in glaucoma.

Preperimetric Glaucoma Prospective Study (PPGPS): Predicting Visual Field Progression With Basal Optic Nerve Head Blood Flow in Normotensive PPG Eyes

Purpose

To investigate the site specificity of visual field changes in eyes with normotensive preperimetric glaucoma (PPG), and to determine factors influencing visual field progression.

Methods

This prospective study comprised 84 eyes of 84 normotensive PPG patients followed for at least 16 months. Optic nerve head (ONH) blood flow was assessed with tissue-area mean blur rate (MBR_T), derived from laser speckle flowgraphy. Total deviation (TD) was measured in each sector of the Garway-Heath map to evaluate the site specificity of visual field loss. Subjects with a TD slope in the first quartile were classified as progressive, and other subjects as nonprogressive. Linear and multiple regression analyses were performed to determine factors affecting visual field progression.

Results

TD in the superior sector significantly decreased in the subjects overall during the follow-up periods (−0.48 ± 1.92 dB/y, P = 0.025). Linear regression analysis showed that basal MBR_T-inferior was correlated significantly with TD-superior slope (r = 0.332, P = 0.002). Furthermore, basal MBR_T was significantly lower in this sector in the progressive than the nonprogressive group (P = 0.010). Multiple linear regression analysis revealed that basal MBR_T-inferior was the only predictive factor for TD-superior slope (β = 0.329, P = 0.005).

Conclusions

These findings suggest that superior-sector visual field progression is most common in normotensive PPG eyes, and that reduced basal ONH blood flow is associated with visual field progression.

Translational Relevance

These findings provide new insight into the involvement of ONH blood flow impairment in glaucoma pathogenesis, and demonstrate the importance of assessing ONH blood flow to determine visual field progression in normotensive PPG.

Evaluation of spectral domain optical coherence tomography parameters in ocular hypertension, preperimetric, and early glaucoma

Purpose:

The objective of this study is to evaluate the diagnostic ability of retinal nerve fiber layer (RNFL), macular, optic nerve head (ONH) parameters in healthy subjects, ocular hypertension (OHT), preperimetric glaucoma (PPG), and early glaucoma (EG) patients, to reveal factors affecting the diagnostic ability of spectral domain-optical coherence tomography (SD-OCT) parameters and risk factors for glaucoma.

Methods:

Three hundred and twenty-six eyes (89 healthy, 77 OHT, 94 PPG, and 66 EG eyes) were analyzed. RNFL, macular, and ONH parameters were measured with SD-OCT. The area under the receiver operating characteristic curve (AUC) and sensitivity at 95% specificity was calculated. Logistic regression analysis was used to determine the glaucoma risk factors. Receiver operating characteristic regression analysis was used to evaluate the influence of covariates on the diagnostic ability of parameters.

Results:

In PPG patients, parameters that had the largest AUC value were average RNFL thickness (0.83) and rim volume (0.83). In EG patients, parameter that had the largest AUC value was average RNFL thickness (0.98). The logistic regression analysis showed average RNFL thickness was a risk factor for both PPG and EG. Diagnostic ability of average RNFL and average ganglion cell complex thickness increased as disease severity increased. Signal strength index did not affect diagnostic abilities. Diagnostic ability of average RNFL and rim area increased as disc area increased.

Conclusion:

When evaluating patients with glaucoma, patients at risk for glaucoma, and healthy controls RNFL parameters deserve more attention in clinical practice. Further studies are needed to fully understand the influence of covariates on the diagnostic ability of OCT parameters.

Preperimetric Glaucoma Prospective Observational Study (PPGPS): Design, baseline characteristics, and therapeutic effect of tafluprost in preperimetric glaucoma eye

Purpose

There is no consensus on the diagnosis or treatment policy for Preperimetric Glaucoma (PPG) because the pathogenesis of PPG is not clear at this time. Preperimetric Glaucoma Prospective Observational Study (PPGPS) is a first multicenter, prospective, observational study to clarify the pathogenesis of PPG. This article indicates study design, patient baseline characteristics, and analysis focused on optic nerve head (ONH) blood flow in PPG, as well as the intraocular pressure (IOP) -lowering effect and ONH blood flow-improving effects of Tafluprost.

Method

In this study, 122 eyes from 122 subjects (mean age: 53.1 ± 14.3) newly diagnosed as PPG were enrolled. The circumpapillary retinal nerve fiber layer thickness (cpRNFLT) was evaluated with optical coherence tomography (OCT). The ONH blood flow was measured with laser speckle flowgraphy. The therapeutic effect of Tafluprost was evaluated at Month 0 (ONH blood flow-improving effect) and Month 4 (IOP-lowering effect).

Results

The untreated IOP, cpRNFLT, and baseline Mean deviation (MD) value was 16.4 ± 2.5 mmHg, 80.4 ± 8.2 μm, and -0.48 ± 1.29 dB, respectively. In the site-specific visual field evaluation using the sector map, there was no appreciable site-specific visual field defect in the eye with PPG. The inferior region of cpRNFLT in 4-quadrant OCT sector analysis and 6 o’clock region in 12-o’clock OCT sector analysis was the highest rate of abnormality in PPG eyes. Topical administration of Tafluprost significantly reduced IOP from 16.4 ± 2.5 mmHg at baseline to 14.5 ± 2.3 mmHg at Month 4 (P < 0.001, paired t-test). In the linear regression analysis, there was a significant relationship between the increase of ONH blood flow and baseline value.

Conclusion

PPGPS is a first prospective study focusing on the pathology of PPG. This study is expected to elucidate the pathology of PPG, with evidence useful for determining a treatment strategy for PPG.