Comparison of ganglion cell and retinal nerve fiber layer thickness in primary open-angle glaucoma and normal tension glaucoma with spectral-domain OCT

Evaluation of effect of covıd-19 pandemic on anatomical and functional changes and vision-related quality of life in patients with glaucoma

BACKGROUND

To evaluate anatomical and functional changes and vision-related quality of life in patients whose glaucoma follow-up was disrupted by the COVID-19 restrictions.

METHODS

This retrospective observational study included 100 patients who were followed up at the glaucoma unit. For the patients whose follow-up evaluations were postponed due to COVID-19 restrictions, visual acuity (VA), intraocular pressure (IOP), retinal nerve fiber layer (RNFL) thickness, visual field parameters [mean deviation (MD), pattern standard deviation (PSD), and visual field index (VFI)], and the National Institute of Ophthalmology Visual Function Scale-25 (NEI-VFQ-25) score were evaluated based on the measurements performed at the last visit before COVID-19 (V1) and at the first visit after the removal of COVID-19 restrictions (V2).

RESULTS

The mean age of the patients was 61.1 ± 13.4 years, the mean follow-up time was 11.4 ± 4.2 months, and the mean interval between the last two visits was 7.2 ± 2.7 months. In the evaluation of the last two visits, VA was lower and IOP was higher at V2, and there was progression in the MD, PSD, and VFI values (p<0.05, for all). RNFL thickness progression was seen in 13-23% of the patients. According to the NEI-VFQ-25 evaluation, except for peripheral vision and near vision, all the remaining subscale scores and the total score were lower at V2 (p<0.05, for all).

CONCLUSIONS

This study demonstrates the devastating impact of the COVID-19 pandemic on the anatomical and functional changes and vision-related quality of life together in patients with glaucoma.

Visualising structural and functional characteristics distinguishing between newly diagnosed high-tension and low-tension glaucoma patients

PURPOSE

To determine whether there are quantifiable structural or functional differences that can distinguish between high-tension glaucoma (HTG; intraocular pressure [IOP] > 21 mm Hg) and low-tension glaucoma (LTG; IOP ≤ 21 mm Hg) at diagnosis.

METHOD

This was a retrospective, cross-sectional study. Clinical results of one eye from 90 newly diagnosed HTG and 319 newly diagnosed LTG patients (117 with very-low-tension glaucoma [vLTG; ≤15 mm Hg] and 202 with middling LTG [mLTG; >15 mm Hg, ≤21 mm Hg]) were extracted, which included relevant demographic covariates of glaucoma, quantitative optical coherence tomography (including the optic nerve head, retinal nerve fibre layer and ganglion cell-inner plexiform layer) measurements and standard automated perimetry global metrics. We used binary logistic regression analysis to identify statistically significant clinical parameters distinguishing between phenotypic groups for inclusion in principal component (PC) (factor) analysis (PCA). The separability between each centroid for each cohort was calculated using the Euclidean distance (d(x,y)).

RESULTS

The binary logistic regression comparing HTG and all LTG identified eight statistically significant clinical parameters. Subsequent PCA results included three PCs with an eigenvalue >1. PCs 1 and 2 accounted for 21.2% and 20.2% of the model, respectively, with a d(x,y) = 0.468, indicating low separability between HTG and LTG. The analysis comparing vLTG, mLTG and HTG identified 15 significant clinical parameters, which were subsequently grouped into five PCs. PCs 1 and 2 accounted for 24.1% and 17.8%, respectively. The largest separation was observed between vLTG and HTG (d(x,y) = 0.581), followed by vLTG and mLTG (d(x,y) = 0.435) and lastly mLTG and HTG (d(x,y) = 0.210).

CONCLUSION

Conventional quantitative structural or functional parameters could not distinguish between pressure-defined glaucoma phenotypes at the point of diagnosis and are therefore not contributory to separating cohorts. The overlap in findings highlights the heterogeneity of the primary open-angle glaucoma clinical presentations among pressure-defined groups at the cohort level.

Comparison of Diagnostic Ability Between Wide-Field Swept-Source Optical Coherence Tomography Imaging Maps and Heidelberg Retina Tomograph 3 Optic Nerve Head Assessment to Discriminate Glaucomatous and Non-glaucomatous Eyes

Background

In this study, we aimed to determine the diagnostic performance of optic nerve head (ONH), macular, and circumpapillary retinal nerve fiber layer (cpRNFL) thickness measurements of wide-field maps (12 × 9 mm) using swept-source optical coherence tomography (SS-OCT) compared to measurements of the ONH and RNFL parameters measured by Heidelberg Retina Tomograph (HRT3).

Methodology

This case-control study included 39 eyes of 39 glaucoma patients and 36 eyes of 36 normal subjects (control group). All participants underwent standard automated perimetry (SAP) as well as structural measurements by SS-OCT (DRI-OCT, Triton; Topcon Inc., Tokyo, Japan) and HRT3 (Heidelberg Engineering, Heidelberg, Germany). The abilities of the continuous parameters to discriminate between glaucoma and control groups were assessed using areas under the receiver operating characteristic curves (AUCs). To assess the glaucoma diagnostic abilities of each of the categorical variables, sensitivity, specificity, positive predictive value, and negative predictive value were tested.

Results

The highest sensitivities were achieved by the DRI-OCT categorical parameters of Superpixel-200 map and cpRNFL (12 sectors) thickness analysis. The best performing HRT3 continuous parameter was rim volume (AUC = 0.829, 95% confidence interval (CI) = 0.735-0.922), and the best continuous parameter for DRI-OCT wide-field was vertical cdr (AUC = 0.883, 95% CI = 0.805-0.951), followed by total cpRNFL thickness (AUC = 0.862, 95% CI = 0.774-0.951). AUCs for disc area, rim area, linear cdr, and RNFL thickness were not significantly different between the two technologies. Using either the most or the least specific criteria, SuperPixel-200 map always showed the highest sensitivity among the categorical parameters of both technologies (82.1% and 89.7%, respectively). The highest sensitivity among HRT3 classification parameters was shown by MRA and GPS classification algorithms.

Conclusions

Both wide-field DRI-OCT maps and HRT3 showed good diagnostic performance in discriminating glaucoma. Although DRI-OCT thickness values and normative diagnostic classification showed the best performance, more studies are required to determine the clinical role of wide-field DRI-OCT scan in glaucoma diagnosis.

Depicting Developing Trend and Core Knowledge of Primary Open-Angle Glaucoma: A Bibliometric and Visualized Analysis

Objective

The prevalence of glaucoma is rising due to an increasing aging population. Because of its insidious and irreversible nature, glaucoma has gradually become the focus of attention. We assessed primary open angle glaucoma, the most common type of glaucoma, to study its present status, global trend, and state of clinical research.

Methods

Publications from 2000 to 2021 in Web of Science database were retrieved and analyzed by bibliometrics. VOSviewer and Citespace were used for analysis.

Results

A total of 6,401 publications were included in this review, and we found that the number of publications increased from 139 in 2000 to 563 in 2021. American researchers have published the most papers and had the highest h-index and the most citations, while the Journal of Glaucoma has published the most papers on this topic. Some key researchers, contributing institutions, their partnerships, and scientific masterpieces were identified. The publications we reviewed fall into seven categories: publications on intraocular pressure, normal tension glaucoma, risk factors, the trabecular meshwork, optical coherence tomography, surgery, and mutation. Clear study hotspots were described, which began with epidemiology and transitioned to pathogenesis and diagnosis and then to treatment.

Conclusion

Studies on primary open angle glaucoma extend well beyond ophthalmology to biochemistry molecular biology, general internal medicine, pharmacology, pharmacy, science technology, and other areas. Interest, research and publications on primary open angle glaucoma are on the rise.

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.

Ganglion cell complex and macular thickness layers in primary open-angle glaucoma, pseudoexfoliation glaucoma and healthy eyes: A comparative study

PURPOSE

To investigate the differences in the ganglion cell complex (GCC) and macular thickness measurements between primary open-angle glaucoma (POAG), pseudoexfoliation glaucoma (PXG), and healthy eyes with optical coherence tomography (OCT)optovue.

METHODS

In this non-randomized comparative cross-sectional study, 43 healthy eyes, 68 POAG eyes, and 57 PXG eyes were included. Patients were matched for age and disease severity. OCT angiography images were obtained for automated measurement of the GCC and macular thickness layers (inner and outer).

RESULTS

All GCC parameters were significantly difference between healthy and glaucomatous eyes (mild, and moderate to severe disease).There were no significant differences in GCC parameters between POAG and PXG patients except focal loss volume (FLV) after adjustment. Moderate to severe PXG eyes exhibited significantly lower GCC, larger global loss volume (GLV) values, and FLV values when compared with mild PXG eyes (p<= 0.05). We found significant thinning patterns in inner retinal thickness (fovea, parafovea, and perifovea), and total retinal thickness (parafovea, and perifovea) in moderate to severe PXG eyes when comparing with POAG eyes. Patients with moderate to severe PXG also showed significantly thinning patterns in inner retinal layers (fovea, parafovea and perifovea) and total retinal thickness (nasal parafovea) in compared to mild PXG.

CONCLUSION

It appears that GCC thickness is not significantly different between POAG and PXG except FLV. Despite similar retinal thickness in mild disease, a significant reduction in total and inner retinal thickness was demonstrated in moderate to severe PXG compared to moderate to severe POAG, in fovea, parafovea and perifovea region.

The Evaluation of Retinal Nerve Fiber Layer and Ganglion Cell Complex Thickness in Adult Offspring of Primary Open-angle Glaucoma Patients

PRECIS

In the adult offspring of glaucoma patients, retinal nerve fiber layer (RNFL) and ganglion cell complex (GCC) thickness, especially in the inferior quadrant, were significantly decreased. This finding in the adult offspring of glaucoma patients may be important in evaluating the course of glaucoma disease.

PURPOSE

The aim of this study was to investigate RNFL and GCC thickness in adult offspring of primary open-angle glaucoma (POAG) patients and to compare the results with individuals without a family history for glaucoma disease.

MATERIALS AND METHODS

This was a cross-sectional observational study. Forty eyes of 40 individuals with self-reported family history for proven POAG and 40 eyes of 40 healthy individuals without a family history for glaucoma disease were included in the study. RNFL and macular GCC thickness were measured by spectral-domain optical coherence tomography, and the results were compared between the 2 groups.

RESULTS

In adult offspring of patients with POAG, RNFL and GCC thickness were thinner in all quadrants. Average RNFL and GCC decreased significantly in adult offspring of patients with POAG (P=0.039 and 0.015, respectively). Thinning in RNFL and GCC thickness was especially significant in the inferior quadrant (P=0.024 and 0.039, respectively). There was no significant difference between the groups in terms of mean deviation and pattern standard deviation values (P=0.064 and 0.091, respectively).

CONCLUSIONS

In adult offspring of POAG patients, especially in the inferior quadrant, the RNFL and GCC thickness are significantly lower than in subjects without a family history. Prospective, controlled clinical trials with longer follow-up are needed to better understand whether these changes are an early indicator of glaucoma, and the progression of glaucoma disease.

Can We Corroborate Peripapillary RNFL Analysis with Macular GCIPL Analysis? Our 2-Year Experience at a Single-Centre Tertiary Healthcare Hospital Using Two OCT Machines and a Review of Literature

Purpose

To determine whether macular volume and macular GCA measurements in patients are comparable to their RNFL thickness parameters.

Materials and Methods

The cross-sectional, observational study was conducted on 1380 eyes with 460 each, into three groups. Group I: patients with healthy eyes. Group II: patients diagnosed as pre-perimetric glaucoma. Group III: patients with diagnosed perimetric glaucoma. After patients were selected on the basis of inclusion and exclusion criteria, baseline standard ophthalmic examination was done by the same operator under the same settings, including SD-OCT using both the Spectralis SD-OCT and the Cirrus SD-OCT as elaborated below.

Statistical Analysis

Data were checked for normality before statistical analysis using Shapiro-Wilk test. Normally distributed continuous variables were compared using ANOVA. For all statistical tests, a p < 0.05 was taken to indicate a significant difference. Receiver operating characteristic (ROC) curves were used to define the ability RNFL and GCC parameters to distinguish perimetric and preperimetric glaucomatous eyes from control eyes.

Results

There was a statistically significant difference in the average, superior, inferior RNFL thickness and average, superior, inferior GCIPL thickness between Group I and Group II (p<0.001), between Group I and Group III (p<0.001) and also between Group II and Group III (p<0.001). The statistical significance was also reflected in their AUROCs.

Conclusion

Mean, superior, inferior GCIPL thickness along with macular volume analysis can substantiate RNFL analysis for diagnosis, serial monitoring and follow-up of glaucoma patients and suspects.

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.

Comparisons of ganglion cell-inner plexiform layer loss patterns and its diagnostic performance between normal tension glaucoma and primary open angle glaucoma: a detailed, severity-based study

AIM

To evaluate the patterns of macular ganglion cell-inner plexiform layer (GCIPL) loss in normal tension glaucoma (NTG) and primary open angle glaucoma (POAG) in a detailed, disease severity-matched way; and to assess the diagnostic capabilities of GCIPL thickness parameters in discriminating NTG or POAG from normal subjects.

METHODS

A total of 157 eyes of 157 subjects, including 57 normal eyes, 51 eyes with POAG and 49 eyes with NTG were enrolled and strictly matched in age, refraction, and disease severity between POAG and NTG groups. The average, minimum, superotemporal, superior, superonasal, inferonasal, inferior, and inferotemporal GCIPL thickness, and the average, superior, temporal, inferior, and nasal retinal nerve fiber layer (RNFL) thickness were obtained by Cirrus optical coherence tomography (OCT). The diagnostic capabilities of OCT parameters were assessed by area under receiver operating characteristic (AUROC) curves.

RESULTS

Among all the OCT thickness parameters, no statistical significant difference between NTG group and POAG group was found (all P>0.05). In discriminating NTG or POAG from normal subjects, the average and inferior RNFL thickness, and the minimum GCIPL thickness had better diagnostic capabilities. There was no significant difference in AUROC curve between the best GCIPL thickness parameter (minimum GCIPL) and the best RNFL thickness parameter in discriminating NTG (inferior RNFL; P=0.076) and indiscriminating POAG (average RNFL; P=0.913) from normal eyes.

CONCLUSION

Localized GCIPL loss, especially in the inferior and inferotemporal sectors, is more common in NTG than in POAG. Among all the GCIPL thickness parameters, the minimum GCIPL thickness has the best diagnostic performance in differentiating NTG or POAG from normal subjects, which is comparable to that of the average and inferior RNFL thickness.

Segmental inner macular layer analysis with spectral-domain optical coherence tomography for early detection of normal tension glaucoma

PURPOSE

To segment the inner macular layers (IML) and compare the discriminating abilities of the macular and peripapillary retinal nerve fiber layer (mRNFL and pRNFL, respectively) thicknesses in patients with early-stage normal tension glaucoma (NTG).

DESIGN

Cross-sectional study.

METHODS

Forty-nine normal subjects and 69 preperimetric glaucoma (PPG) and 60 NTG patients were enrolled. Spectral-domain optical coherence tomography (SD-OCT) was used to obtain pRNFL and macular thickness parameters and segment the IML in all subjects. Area under the receiver operating characteristic (AUROC) curves were used to compare the diagnostic capabilities of different parameters.

RESULTS

The pRNFL, total macular layer (TML), mRNFL, and macular ganglion cell layer (mGCL) were significantly thinner in the NTG group than in the PPG and normal groups. The global and superotemporal pRNFL and the mGCL in the superior outer area were the three best parameters for detecting early NTG. The discriminating capabilities of the superior and inferior mGCL were comparable to those of the corresponding pRNFL (p = 0.573, 0.841). Concerning location, the mGCL had higher AUROCs in the outer sectors (0.863, 0.837) than in the inner sectors (0.747, 0.747). Pearson's correlation coefficients also revealed significant correlations between the mGCL and pRNFL (superior: r = 0.499, inferior: r = 0.624). The strongest correlation was between the mGCL and mean deviation (MD) (superior: r = 0.434 and inferior: r = 0.402).

CONCLUSIONS

The diagnostic value of mGCL thickness is comparable to that of pRNFL thickness. IMLs in the outer sectors had better diagnostic capabilities than those in the inner sector for detecting early NTG.

Three-dimensional surface presentation of optic nerve head from SPECTRALIS OCT images: observing glaucoma patients

PURPOSE

To propose an innovative three-dimensional surface presentation of the optic nerve head (ONH) from the SPECTRALIS optical coherence tomography (OCT) device.

METHOD

A dataset of OCT ONH files from eight glaucoma follow-up patients was obtained. The set consisted of OCT ONH images for 20 right eyes (OD) and 17 left eyes (OS). Preprocessing steps followed with OCT reconstruction procedures were designed. The three-dimensional (3D) surface rendering was generated for all OCT ONH images. A set of eight International Organization for Standardization (ISO) roughness parameters were calculated to assess the disparities in the 3D ONH surface morphology during follow-up visit.

RESULTS

The 3D ONH surface presents a new OCT display to ophthalmology; so, the physician can examine the surface morphology of the OCT ONH region. The 3D ONH surface's shape varied noticeably during follow-up visits in glaucoma patients. The percentage disparity of ONH surface roughness's can be as small as 3% or almost zero, but it can be as large as 56% or 100%.

CONCLUSIONS

The approximation of OCT ONH 3D surface is feasible; it may possibly be beneficial to ophthalmology. It allows ophthalmologist to perceive the entire changes in the ONH surface morphology during the follow-up attendances; so, it can be used to observe patient health. The ISO roughness measurements are suggestive complementary factors to observe the alterations in the OCT ONH region.

Analysis of peripapillary retinal nerve fiber layer and inner macular layers by spectral-domain optical coherence tomography for detection of early glaucoma

AIM

To analyze the diagnostic capabilities of peripapillary retinal nerve fiber layer (pRNFL) thickness and segmented inner macular layer (IML) thickness measured by spectral-domain optical coherence tomography for detection of early glaucoma.

METHODS

Fifty-three patients with primary open angle glaucoma (POAG), 60 patients with normal tension glaucoma (NTG) and 32 normal control subjects were enrolled. Thicknesses of pRNFL, total macular layers (TML), and the IML, including macular RNFL (mRNFL) and macular ganglion cell layer (mGCL) were assessed. The areas under the receiver operating characteristic curves (AROC) were calculated to compare the diagnostic power of different parameters.

RESULTS

There were no differences in the parameters of pRNFL, TML, and IML between POAG and NTG groups. The thicknesses of superior and inferior mGCL showed significant correlation with mean deviation of visual field (R²=0.071, P=0.004; R²=0.08, P=0.002). The mGCL thickness significantly correlated with the pRNFL thickness in the superior and inferior quadrants (R²=0.156, P<0.001; R²=0.407, P<0.001). The thickness of the inferior-outer sector of macula had greater AROCs than those in the inferior-inner sector of macula. The AROCs for superior (0.894) and inferior (0.879) pRNFL thicknesses were similar with the AROCs for superior (0.839) and inferior mGCL (0.864) thicknesses. Sensitivities at 80% specificity for global pRNFL, inferior-outer mGCL and inferior-outer mRNFL thicknesses were 0.938, 0.867, and 0.725, respectively.

CONCLUSION

The diagnostic capability of the mGCL thickness is comparable to that of the pRNFL thickness in patients with early glaucoma. The inferior-outer sector of IML has a better diagnostic capability than the inferior-inner sector of IML for detection of early glaucoma.

Diagnostic ability of ganglion cell complex thickness to detect glaucoma in high myopia eyes by Fourier domain optical coherence tomography

AIM

To evaluate the ability of macular ganglion cell complex (GCC) thickness using Fourier domain optical coherence tomography (FD-OCT) to detect glaucoma in highly myopic eyes.

METHODS

Cross-sectional study. A total of 114 participants, consecutively were enrolled. Macular GCC thickness and peripapillary retinal nerve fiber layer (RNFL) thickness were obtained with RTVue FD-OCT. Receiver operating characteristics curves were constructed for each measurement parameter, and areas under the curves (AUCs) were compared.

RESULTS

Both the average GCC and average RNFL thickness showed negative correlations with axial length (rGCC=-0.404, P=0.001; rRNFL=-0.561, P<0.001). The largest AUCs from GCC, and RNFL parameters were 0.968 [global loss volume (GLV)], and 0.855 (average RNFL), respectively. GLV was significantly better for detecting high myopic glaucoma than average RNFL (P<0.001).

CONCLUSION

Macular GCC thickness has higher diagnostic power than peripapillary RNFL thickness to discriminate glaucoma patients from non-glaucoma subjects in high myopia.

In Vivo Imaging of the Retina, Choroid, and Optic Nerve Head in Guinea Pigs

PURPOSE

Guinea pigs are increasingly being used as a model of myopia, and may also represent a novel model of glaucoma. Here, optical coherence tomography (OCT) imaging was performed in guinea pigs. In vivo measurements of retinal, choroidal, and optic nerve head parameters were compared with histology, and repeatability and interocular variations were assessed.

METHODS

OCT imaging and histology were performed on adult guinea pigs (n = 9). Using a custom program in MATLAB, total retina, ganglion cell/nerve fiber layer (GC/NFL), outer retina, and choroid thicknesses were determined. Additionally, Bruch's membrane opening (BMO) area and diameter, and minimum rim width were calculated. Intraobserver, interocular, and intersession coefficients of variation (CV) and intraclass correlation coefficients (ICC) were assessed.

RESULTS

Retina, GC/NFL, outer retina and choroid thicknesses from in vivo OCT imaging were 147.7 ± 5.8 μm, 59.2 ± 4.5 μm, 72.4 ± 2.4 μm, and 64.8 ± 11.6 μm, respectively. Interocular CV ranged from 1.8% to 11% (paired t-test, p = 0.16 to 0.81), and intersession CV ranged from 1.1% to 5.6% (p = 0.12 to 0.82), with the choroid showing the greatest variability. BMO area was 0.192 ± 0.023 mm², and diameter was 493.79 ± 31.89 μm, with intersession CV of 3.3% and 1.7%, respectively. Hyper reflective retinal layers in OCT correlated with plexiform and RPE layers in histology.

CONCLUSION

In vivo OCT imaging and quantification of guinea pig retina and optic nerve head parameters were repeatable and similar between eyes of the same animal. In vivo visibility of retinal cell layers correlated well with histological images.

ABBREVIATIONS

optic nerve head (ONH), retinal ganglion cell (RGC), spectral domain optical coherence tomography (SD-OCT), enhanced depth imaging (EDI), minimum rim width (MRW), hematoxylin and eosin (H & E).

Microstructural visual pathway abnormalities in patients with primary glaucoma: 3 T diffusion kurtosis imaging study

AIM

To evaluate microstructural visual pathway damage in patients with primary glaucoma (PG) by using 3 T diffusion kurtosis imaging (DKI).

MATERIALS AND METHODS

The study was approved by the ethics committee, and all participants provided written informed consent. Ten patients with PG were examined. Twenty healthy individuals served as control subjects. DKI was performed with a GE Silent 3 T magnetic resonance imaging (MRI) unit. Mean diffusivity (MD), fractional anisotropy (FA), and mean kurtosis (MK) maps were automatically created. Mean MK, MD, and FA values were calculated for each part of the visual pathway.

RESULTS

No abnormalities in the shape and signal intensity were observed along the entire visual pathway in patients and the control group on the conventional MRI. Higher MD, and lower MK and FA were observed in the optic nerves (ON), lateral geniculate nucleus (LGN), optic radiations (OR), and visual cortex (VCx) of PG patients, as compared with control subjects. A significantly higher MD was observed in the ON (p<0.01), and significantly lower FA was observed in OR (p<0.05). Additionally, significantly lower MK was observed in the ON, LGN, and VCx, except for OR (p<0.01). Changes of DKI parameters in the ON were the most distinct.

CONCLUSION

Glaucoma is a complex neurological disease that affects the entire visual pathway. MK derived from DKI would be a better biomarkers than FA and MD in detecting microstructural damage.

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.

Patterns of Retinal Nerve Fiber Layer Loss in Different Subtypes of Open Angle Glaucoma Using Spectral Domain Optical Coherence Tomography

PURPOSE OF THE STUDY

The purpose of the study was to determine whether there are different patterns of retinal nerve fiber layer (RNFL) thinning as measured by spectral domain optical coherence tomography (SD-OCT) for 4 subtypes of open angle glaucoma (OAG): primary OAG (POAG), normal tension glaucoma (NTG), pseudoexfoliation glaucoma (PXG), and pigmentary glaucoma (PDG) and to compare them with normal controls.

MATERIALS AND METHODS

SD-OCT RNFL thickness values were measured for 4 quadrants and for 4 sectors (ie, superior-nasal, superior-temporal, inferior-nasal, and inferior-temporal). Differences in RNFL thickness values between groups were analyzed using analysis of variance. Paired t tests were used for quadrant comparisons.

RESULTS

Two hundred eighty-five participants (102 POAG patients, 33 with NTG, 48 with PXG, 13 with PDG, and 89 normal patients) were included in this study. All 4 subtypes of OAG showed significant RNFL thinning in the superior, inferior, and nasal quadrants as well as the superior-temporal and inferior-temporal sectors (all P-values <0.0001) compared with normals. POAG and NTG patients had greater RNFL thinning inferiorly and inferior-temporally than superiorly (P-values: 0.002 to 0.018 and 0.006, respectively) compared with PXG patients. In contrast, PDG patients had greater RNFL thinning superiorly and superior-nasally than inferiorly compared with other OAG subtypes (ie, POAG, NTG, PXG groups, with P-values: 0.009, 0.003, 0.009, respectively). Of the 4 OAG subtypes, PXG patients exhibited the greatest degree of inter-eye RNFL asymmetry.

CONCLUSIONS

This study suggests that SD-OCT may be able to detect significant differences in patterns of RNFL thinning for different subtypes of OAG.

Variations in optic nerve head morphology by intraocular pressure in open-angle glaucoma

PURPOSE

To compare optic disc topography in eyes in three intraocular pressure (IOP) groups of <15 mmHg, 15-20 mmHg, and ≥21 mmHg using spectral domain optical coherence tomography (SD-OCT) and confocal scanning laser ophthalmoscopy, adjusting for the degree of damage, as measured by retinal nerve fiber layer (RNFL) thickness and average visual field loss.

METHODS

A total of 184 eyes of 112 patients with primary open-angle glaucoma were recruited into groups based on baseline untreated intraocular pressure (IOP) of <15 mmHg (normal-tension glaucoma [NTG], very low), 15-20 mmHg (NTG, medium), or ≥21 mmHg (high-tension glaucoma [HTG]). Patients underwent scanning laser ophthalmoscopy, SD-OCT, and Humphrey visual field testing. Univariate and multivariate models were created, accounting for degree of retinal ganglion cell (RGC) loss by either OCT RNFL thickness or visual field mean deviation (MD).

RESULTS

Univariate and multivariate analyses demonstrated no morphological differences in HRT or OCT parameters among IOP groups that met Bonferroni-corrected statistical significance when using either MD or OCT RNFL as the damage criterion (p < 0.0063). The mean cup depth was shallower for the IOP <15 mmHg group than the IOP ≥21 mmHg group (p < 0.05) for both MD (p < 0.011) and OCT RNFL (p < 0.014).

CONCLUSION

Normal-tension and high-tension glaucoma are not distinguishable by optic nerve head topography with HRT and OCT when the degree of damage by Humphrey visual field testing is taken into account.

Parameters of ocular fundus on spectral-domain optical coherence tomography for glaucoma diagnosis

In this review, we summarize the progression of several parameters assessed by spectral-domain optical coherence tomography (SD-OCT) in recent years for the detection of glaucoma. Monitoring the progression of defects in the retinal nerve fiber layer (RNFL) thickness is essential. Imaging and analysis of retinal ganglion cells (RGCs) and inner plexiform layer (IPL), respectively, have been of great importance. Optic nerve head (ONH) topography obtained from 3D SD-OCT images is another crucial step. Other important assessments involve locating the Bruch's membrane opening (BMO), estimating the optic disc size and rim area, and measuring the lamina cribrosa displacement. Still other parameters found in the past three years for glaucoma diagnosis comprise central retinal artery resistive index, optic disc perfusion in optical coherence tomography angiography (OCTA) study, peripapillary choroidal thickness, and choroidal area in SD-OCT. Recently, several more ocular fundus parameters have been found, and compared with the earlier parameters to judge the accuracy of diagnosis. While a few of these parameters have been widely used in clinical practice, a fair number are still in the experimental stage.

A comparison of the diagnostic ability of vessel density and structural measurements of optical coherence tomography in primary open angle glaucoma

Purpose

To compare the diagnostic abilities of vessel density measurements of the optic nerve head (ONH), peripapillary and macular regions on optical coherence tomography (OCT) angiography in eyes with primary open angle glaucoma (POAG) with that of the ONH rim area, peripapillary retinal nerve fiber layer (RNFL) thickness and the macular ganglion cell complex (GCC) thickness measurements.

Methods

In a cross sectional study, 78 eyes of 50 control subjects and 117 eyes of 67 POAG patients underwent vessel density and structural measurements with spectral domain OCT. POAG was diagnosed based on the masked evaluation of optic disc stereo photographs. Area under receiver operating characteristic curves (AUC) and sensitivities at fixed specificities of vessel densities in ONH, peripapillary and macular regions were compared with rim area, RNFL and GCC thickness.

Results

The AUC (sensitivity at 95% specificity) of average vessel densities within the ONH, peripapillary and macular region were 0.77 (31%), 0.85 (56%) and 0.70 (18%) respectively. The same of ONH rim area, average RNFL and GCC thickness were 0.94 (83%), 0.95 (72%) and 0.93 (62%) respectively. AUCs of vessel densities were significantly lower (p<0.05) than that of the corresponding structural measurements. Pre-treatment IOP (coefficient: 0.08) affected (p<0.05) the AUC of ONH vessel density but not of any other vessel density or structural measurements.

Conclusions

Diagnostic abilities of ONH, peripapillary and the macular vessel densities in POAG were significantly lower than ONH rim area, peripapillary RNFL and macular GCC measurements respectively. At fixed levels of glaucoma severity, the diagnostic ability of the ONH vessel density was significantly greater in eyes with higher pre-treatment IOP.

Optic nerve head slope-based quantitative parameters for identifying open-angle glaucoma on SPECTRALIS OCT images

PURPOSE

To investigate monitoring slope-based features of the optic nerve head (ONH) cup as open-angle glaucoma (OAG) occurs.

METHOD

A dataset of 46 retrospective OCT cases was acquired from the SPECTRALIS Heidelberg Engineering OCT device. A set of five parameters, which are based on the ONH cup-incline, are measured on the OAG and normal subjects in the dataset. Then, three new ONH cup-shape indices were deduced. The ONH cup-incline parameters and ONH cup-shape indices are analyzed to estimate their clinical value.

RESULTS

The statistical difference between measurements on normal and glaucoma eyes was remarkably significant for all of the analyzed parameters and indices (p value < 0.001).

CONCLUSIONS

The geometric shape of the ONH cup can be transferred to numerical parameters and indices. The proposed ONH cup-incline parameters and ONH cup-shape indices have shown suggestive clinical value to identify the development of OAG. As OAG appears, the top ONH cup-incline parameters decrease while the bottom ONH cup-incline parameters increase. The ONH cup-shape indices suggest capability to discriminate OAG from normal eyes.

Retinal Ganglion Cell Layer Analysis by Optical Coherence Tomography in Toxic and Nutritional Optic Neuropathy

OBJECTIVE

To analyze the retinal ganglion cell layer (RGL) by optical coherence tomography (OCT) in toxic and nutritional optic neuropathy and to correlate its thickness and volume with functional damage.

METHODS

We conducted an observational cross-sectional study in healthy subjects and in patients with toxic optic neuropathy observed in the Neuro-Ophthalmology Department of Central Lisbon Hospital Center. Complete ophthalmologic examination, OCT (Heidelberg Spectralis), and automated static perimetry were performed. Thickness and macular volume of RGL layer and inner plexiform layer were measured after manual segmentation.

RESULTS

The study included 16 eyes of 12 healthy subjects and 16 eyes of 8 patients with toxic and nutritional optic neuropathy. Age and gender did not differ between the 2 groups. Ethambutol was the cause of toxic optic neuropathy in 4 patients and nutritional factors (tobacco-alcohol) in 4 patients. A statistically significant decrease in thickness and volume of RGL, in all quadrants at 2 and 3 mm, was detected in individuals with optic neuropathy compared with controls (P < 0.01). A positive correlation between RGL thickness and mean deviation (MD) and between RGL volume and MD was detected (P < 0.05). There was a negative correlation between MD and time of disease (r = 0.846 P = 0.001) and a positive correlation between MD and visual acuity in logMAR (r = 0.739 P = 0.006). A majority of the structural parameters also correlated negatively with time of disease (P < 0.05).

CONCLUSIONS

Decreased RGL thickness and volume detected in this study support a mechanism of RGL toxicity. RGL analysis may contribute to the diagnosis and management of toxic and nutritional optic neuropathies.

Macular Ganglion Cell-Inner Plexiform Layer and Retinal Nerve Fiber Layer Thickness in Eyes With Primary Open-Angle Glaucoma Compared With Healthy Saudi Eyes: A Cross-Sectional Study

PURPOSE

We compared the thickness of the ganglion cell-inner plexiform layer at the macula (mGCIPL) and the thickness of the retinal nerve fiber layer (RNFL) in different regions of the retina in eyes with primary open-angle glaucoma (POAG group) and normal eyes (control group).

DESIGN

This was a cross-sectional study performed in 2014.

METHODS

Spectral domain optical coherence tomography (SD-OCT) was used to measure mGCIPL and RNFL thickness. Age-adjusted means and standard deviation were calculated. Age, sex, refractive status, corneal thickness, and stage/severity of glaucoma (defined by vertical cup-to-disc ratio and visual field changes) were associated to outcomes. Statistical significance was indicated by P < 0.05.

RESULTS

There were 50 eyes in the POAG group and 52 eyes in the control group. The difference in age between patients in both groups was statistically significant (P < 0.001). The age-adjusted measurements were thinner for POAG with a mean difference (DF) of 11.1 μm for mGCIPL and 8 μm for mRNFL. The mGCIPL to mRFNL ratio was 2.1 in the POAG group and 1.9 in the control group (degrees of freedom = 0.2, P = 0.001). The mGCIPL and RNFL thickness decreased as the severity of glaucoma increased. The mGCIPL to mRNFL ratio was a predictor of the severity of field defects in POAG (AUROC = 0.66, P = 0.0002). Age and myopia were confounders to the association of OCT findings and the visual field changes in POAG (P = 0.07).

CONCLUSIONS

There was generalized thinning of retinal layers in eyes of nondiabetic Arab patients with POAG. OCT parameters can be important for detecting and monitoring glaucoma cases.

Comparison of retinal nerve fiber layer and macular thickness for discriminating primary open-angle glaucoma and normal-tension glaucoma using optical coherence tomography

PURPOSE

The aim of this study was to evaluate the discrimination capabilities of macular and peripapillary retinal nerve fiber layer (pRNFL) thickness parameters as measured using spectral domain optical coherence tomography (SD-OCT) between primary open-angle glaucoma (POAG) and normal-tension glaucoma (NTG).

METHODS

A total of 90 subjects were enrolled: 30 healthy subjects, 30 subjects with POAG and 30 subjects with NTG, consecutively. Retinal nerve fiber layer thickness, macular thickness and volume measurements were obtained with circular and radial SD-OCT scans. All parameters were compared between groups using an analysis of variance test. Areas under receiver-operating characteristic (AROC) curves with sensitivities at specificities greater than or equal to 90 per cent were generated to compare discrimination capabilities of various parameters between POAG and NTG.

RESULTS

Macular thickness and volume measurements were the highest in normal subjects, followed by NTG and POAG (p < 0.05). Average retinal nerve fiber layer thickness had perfect discrimination for normal-POAG (AROC: 1.000; sensitivity: 100 per cent) and near perfect discrimination for normal-NTG (AROC: 0.979; sensitivity: 93 per cent) as well as NTG-POAG pairs (AROC: 0.900; sensitivity: 60 per cent). Inferior outer macular thickness (IOMT) and total volume were the best macular thickness and volume parameters having similar AROCs and sensitivities between normal and POAG (IOMT, AROC: 0.987; sensitivity: 92 per cent and total volume, AROC: 0.997; sensitivity: 97 per cent), normal and NTG (IOMT, AROC: 0.862, sensitivity: 47 per cent and total volume, AROC: 0.898, sensitivity: 67 per cent) and also between NTG and POAG (IOMT, AROC: 0.910, sensitivity: 53 per cent and total volume, AROC: 0.922, sensitivity: 77 per cent). In each comparison group, there was no statistically significant difference in AROCs between average retinal nerve fiber layer and inferior outer macular thickness, as well as total volume.

CONCLUSIONS

The macular parameters offer comparable performance to pRNFL parameters for the discrimination of NTG and POAG. Average retinal nerve fiber layer thickness, total macular volume and inferior outer macular thickness were the best SD-OCT parameters with superior discriminating capabilities.

Retinal nerve fiber layer and ganglion cell complex thickness in patients with type 2 diabetes mellitus

Aim:

The aim of the following study is to evaluate the retinal nerve fiber layer (RNFL) and ganglion cell complex (GCC) thickness in patients with type 2 diabetes mellitus (DM).

Materials and Methods:

Average, inferior, and superior values of RNFL and GCC thickness were measured in 123 patients using spectral domain optical coherence tomography. The values of participants with DM were compared to controls. Diabetic patients were collected in Groups 1, 2 and 3. Group 1 = 33 participants who had no diabetic retinopathy (DR); Group 2 = 30 participants who had mild nonproliferative DR and Group 3 = 30 participants who had moderate non-proliferative DR. The 30 healthy participants collected in Group 4. Analysis of variance test and a multiple linear regression analysis were used for statistical analysis.

Results:

The values of RNFL and GCC in the type 2 diabetes were thinner than controls, but this difference was not statistically significant.

Conclusions:

This study showed that there is a nonsignificant loss of RNFL and GCC in patients with type 2 diabetes.

Comparison of Ganglion Cell and Retinal Nerve Fiber Layer Thickness in Pigment Dispersion Syndrome, Pigmentary Glaucoma, and Healthy Subjects with Spectral-domain OCT

PURPOSE

To evaluate the ganglion cell complex (GCC) and retinal nerve fiber layer (RNFL) thickness in pigment dispersion syndrome (PDS) and pigmentary glaucoma (PG) with RTVue spectral domain optical coherence tomography (SD-OCT).

METHODS

A total of 102 subjects were enrolled: 29 with PDS, 18 with PG, and 55 normal subjects. Full ophthalmic examination including visual field analysis was performed. SD-OCT was used to analyze GCC superior, GCC inferior, and average RNFL thickness. To compare the discrimination capabilities, the areas under the receiver operating characteristic curves were assessed.

RESULTS

Superior GCC, inferior GCC, and RNFL thickness values of patients with PG were statistically signicantly lower than those of patients with PDS (p < 0.001) and healthy individuals (p < 0.001 for all). No statistically significant difference was found between PDS and normal subjects in same parameters (p > 0.05).

CONCLUSIONS

The SD-OCT-derived GCC and RNFL thickness parameters can be useful to discriminate PG from both PDS and normal subjects.

Macular inner plexiform and retinal nerve fiber layer thickness in glaucoma

PURPOSE

To compare the parameters of the macular ganglion cell-inner plexiform layer (mGCIPL) thickness measured by Cirrus high-definition optical coherence tomography in normal-tension glaucoma (NTG) and primary open-angle glaucoma (POAG).

METHODS

Eighty patients with NTG, 80 patients with POAG, and 100 normal control subjects were enrolled. The mGCIPL and peripapillary retinal nerve fiber layer (pRNFL) thicknesses measured by Cirrus high-definition optical coherence tomography were compared in patients with glaucoma. The areas under the receiver operating characteristic curve (AROCs) were calculated to compare the diagnostic power of the mGCIPL thickness with that of the pRNFL thickness. Pearson correlation coefficients were determined to investigate the correlation between the mGCIPL or pRNFL thickness parameters and the mean deviation (MD) values of visual field tests.

RESULTS

All parameters of the mGCIPL thickness were significantly different between normal control subjects and patients with glaucoma. The superior, superotemporal, and superonasal thickness of mGCIPL and the superior thickness of pRNFL showed significant reductions and significantly higher AROCs for distinguishing between normal eyes and eyes with glaucoma in POAG compared with those in NTG. In NTG or POAG groups, the mGCIPL and pRNFL parameters with the highest AROC were the minimum and average thickness, respectively. The average, minimum, inferior, inferotemporal, and inferonasal thickness of mGCIPL and the average and inferior thickness of pRNFL were correlated with MD in NTG (p < 0.05 for all parameters), whereas all parameters of the mGCIPL thickness except the inferonasal thickness and all parameters of the pRNFL thickness except the temporal thickness were correlated with MD in POAG (p < 0.05 for all parameters).

CONCLUSIONS

The diagnostic ability of the mGCIPL thickness was comparable to that of the pRNFL thickness in patients with NTG or POAG. The mGCIPL loss in NTG was localized and mainly concentrated on the inferior portion compared with diffuse mGCIPL loss in POAG.

Can ganglion cell complex assessment on cirrus HD OCT aid in detection of early glaucoma?

Context

Ganglion cell complex is damaged early in glaucoma. Does this loss of GCC help in early diagnosis of glaucoma.

Aims

To compare the RNFL thickness and ganglion cell complex (GCC) in diagnosed patients of glaucoma, pre-perimetric glaucoma and normal controls.

Settings and design

Case controlled, observational study.

Methods and material

33 glaucoma patients, 45 pre-perimetric glaucoma, and 30 controls were enrolled in the study. ONH parameters on cirrus HD OCT like CD ratio, para papillary RNFL thickness and GCC were calculated for each case.

Statistical analysis used

ANOVA test to analyse differences between groups. ROC for ganglion cell layer.

Results

RNFL thickness was 71.6 μ and GCC was 69.19 μ in glaucoma patients. RNFL thickness was 77.31 μ and GCC was 71 μ in pre-perimetric glaucoma and 99.6 μ and 85.16 μ in controls respectively. The difference of mean for RNFL and GCC by ANOVA was statistically significant for controls, glaucoma patients and pre-perimetric glaucoma patients. RNFL (p < 0.001) and GCC (p < 0.001). Receiver operating characteristic curve for GCC was 0.83 (p < 0.000).

Conclusions

The RNFL analysis is increasingly being used as newer tool in diagnosis of glaucoma. In addition, GCC can be used as a supplementary tool in picking up cases of pre-perimetric glaucoma as loss is significant in pre-perimetric glaucoma also.

Correlation between the ganglion cell complex and structural measures of the optic disc and retinal nerve fiber layer in glaucoma

To correlate the ganglion cell complex (GCC) parameters with structural measures of the optic nerve head (ONH) and retinal nerve fiber layer (RNFL) as evaluated by Fourier-Domain optic coherence tomography (OCT). This retrospective study included patients with glaucoma, ocular hypertensive patients and glaucoma suspects who had previously undergone OCT examination with the RTVue-100. The parameters of GCC (average, superior, inferior, focal loss volume [FLV], global loss volume [GLV]) were correlated with the values of the ONH (cup volume, cup area, horizontal cup-to-disk ratio, vertical cup-to-disk ratio, and rim area) and RNFL (average, superior, and inferior) using Pearson's correlation coefficient. The sample included 74 eyes of 37 patients. All correlations between GCC parameters and RNFL were strong (r > 0.60). The correlation between GCC parameters and ONH were good for most parameters, except that for FLV and cup volume (r = 0.13), GLV and cup volume (r = 0.09), and GLV and cup area (r = 0.21). The GCC parameters can be used as structural measures of the glaucomatous optic neuropathy.

Relation between macular retinal ganglion cell/inner plexiform layer thickness and multifocal electroretinogram measures in experimental glaucoma

PURPOSE

We investigated relations between macular retinal ganglion cell plus inner plexiform layer (RGC+IPL) thickness and macular retinal function revealed by multifocal electroretinonography (mfERG) in a nonhuman primate model of experimental glaucoma.

METHODS

Retinal ganglion cell (RGC) structure and function were followed with spectral-domain optical coherence tomography (SD-OCT) and ERGs in five macaques with unilateral experimental glaucoma. Linear regression was used to study correlations in control (Con) and experimental (Exp) eyes between peripapillary retinal nerve fiber layer (RNFL) thickness, macular RGC+IPL thickness, multifocal photopic negative response (mfPhNR) and high-frequency multifocal oscillatory potentials (mfOP) in slow-sequence mfERG, and low-frequency component (mfLFC) in global-flash mfERG. We used ANOVA and paired t-tests to compare glaucoma-related mfERG changes between superior and inferior hemifields, foveal hexagon, inner three rings, and four quadrants of macula.

RESULTS

Average macular RGC+IPL and temporal RNFL thickness were strongly correlated (r(2) = 0.90, P < 0.001). In hexagon-by-hexagon analysis, all three mfERG measures were correlated (P < 0.001) with RGC+IPL thickness for Con (r(2), 0.33-0.51) and Exp eyes (r(2), 0.17-0.35). The RGC structural and functional metrics decreased as eccentricity increased. The reduction in amplitude of mfERG measures in Exp eyes relative to Con eyes was proportionally greater, in general, than the relative thinning of RGC+IPL at the same location for eyes in which structural loss was not evident, or mild to moderate. Although not statistically significant, percent amplitude reduction of mfERG measures was greatest in the inferior temporal quadrant.

CONCLUSIONS

Macular RGC+IPL thickness and mfERG measures of RGC function can be complementary tools in assessing glaucomatous neuropathy.