Structure-function models for estimating retinal ganglion cell count using steady-state pattern electroretinography and optical coherence tomography in glaucoma suspects and preperimetric glaucoma: an electrophysiological pilot study

Evaluation of additional points in the 24-2C visual field test in pre-perimetric glaucoma

BACKGROUND

Early detection and prevention of glaucoma progression are critical. However, studies of early visual field (VF) changes, particularly those using the 24-2C VF test, are limited. Evaluation of additional points in 2C may help identify glaucoma at an early stage, enabling timely intervention. Pre-perimetric glaucoma (PPG) is characterised by structural damage without noticeable VF loss in standard tests. Assessments of changes in retinal nerve fibre layer (RNFL) and macular ganglion cell complex (mGCC) thickness are valuable, but exploring how these structural changes are related to functional deficits is crucial.

OBJECTIVE

This study focused on the average of the additional points in the 24-2C test to understand their correlation with structural measures in the PPG.

MATERIAL AND METHOD

This study included 59 patients with PPG and 36 healthy individuals. All the patients underwent peripapillary and macular optical coherence tomography (OCT) (Nidek RS-3000 Advance; Nidek, Japan). RNFL thickness was evaluated using peripapillary OCT, and mGCC thickness was evaluated using the macular OCT glaucoma module. The mean deviation (MD), pattern standard deviation (PSD), visual field index (VFI), and average of additional points in the 2C (AAP-2C) were evaluated using the 24-2C SITA Faster VF Humphrey Field Analyser III Model 850 (HFAIII; Zeiss Meditec, Dublin, CA, USA). The relationship between structural and functional parameters was statistically evaluated.

RESULTS

The PPG group showed significantly lower RNFL and mGCC thickness values than the healthy group. The MD, PSD, and VFI did not differ significantly between the groups. For AAP-2C, the PPG group showed significantly lower sensitivity than healthy individuals. A statistically significant positive correlation between was observed between AAP-2C and mGCC thickness (p = 0.003, r = 0.385). However, the RNFL and mGCC thickness values showed no statistically significant correlations with the MD, PSD, and VFI.

CONCLUSION

Although no glaucomatous change was observed in the VF in patients with PPG, these patients showed reduced sensitivity of the additional points. The reduced sensitivity of the additional points in the 24-2C VF test may reflect early macular functional alterations that correlate with structural damage during the pre-perimetric period.

Diagnostic Capability of Pattern Electroretinogram and Three Circumpapillary Retinal Nerve Fiber Layer Thickness Circle Diameter Scans in Glaucoma Suspects

Purpose

To assess the diagnostic capability of pattern electroretinography (PERG) and varying circumpapillary optical coherence tomography (OCT) scan diameters in glaucoma suspects (GS).

Methods

This is a prospective, cross-sectional study. Circumpapillary retinal nerve fiber layer thickness (RNFLT) was measured using spectral domain OCT in 49 eyes from 26 patients (36 normal, 13 GS) in three circle diameters (3.5, 4.1, and 4.7 mm). PERG measurements (Magnitude [Mag], MagnitudeD [MagD], MagnitudeD/Magnitude [MagD/Mag] ratio) were used. Based on clinical examination, participants were classified as controls or GS. Independent t-test and areas under the receiver operating characteristic curve (AUC) were obtained to determine the diagnostic capability of PERG and OCT.

Results

Independent t-test revealed significant differences between controls and GS in age, sex, central corneal thickness (CCT), all PERG parameters, and global RNFLT (gRNFLT) in three circle diameters. All PERG parameters were correlated to all RNFLT sectors (r > 0.291; p < 0.041), except in the temporal and nasal sectors of the three circle scans. Spearman rho was highest in 3.5 and lowest in 4.7 mm circle scan. AUC demonstrated 3.5 mm gRNFLT had the highest diagnostic capability (AUC = 0.877), followed by 4.1 mm gRNFLT (AUC = 0.852), and 4.7 mm gRNFLT (AUC = 0.821). MagD showed the foremost diagnostic capability (AUC = 0.81), followed by Mag (AUC = 0.799) and MagD/Mag (AUC = 0.762).

Conclusion

Global, superior, and inferior RNFLT in 3.5 and 4.1 mm diameters, and MagD performed best in discriminating GS from controls, suggesting that a larger scan of 4.1 mm may be equally useful in glaucoma diagnosis as the conventional 3.5 mm diameter. We recommend using PERG with OCT of 3.5 or 4.1 mm diameters for glaucoma suspect diagnosis.

Resveratrol protects against diabetic retinal ganglion cell damage by activating the Nrf2 signaling pathway

Objective

Oxidative stress-induced retinal neurodegenerative changes are among the pathological alterations observed in diabetic retinopathy. Resveratrol (RSV), a polyphenolic compound with diverse pharmacological effects, has shown preventive qualities in several neurodegenerative illnesses, including anti-inflammatory, anti-aging, and antioxidant benefits. However, its therapeutic efficacy in diabetic retinal neurodegeneration has not yet been thoroughly elucidated. Our study aimed to explore the protective mechanisms and therapeutic benefits of RSV on diabetic retinal neurodegeneration alterations.

Materials and methods

Using streptozotocin, we created a diabetic mouse model and conducted visual electrophysiological examinations on mice from the normal group, diabetic group, and diabetic group treated with RSV. Retinas were harvested for histological staining. Additionally, primary retinal ganglion cells cultured in high glucose conditions were used to assess malondialdehyde (MDA) levels and superoxide dismutase (SOD) levels upon siRNA-mediated nuclear factor erythroid 2-related factor 2 (Nrf2) interference. Protein levels of Nrf-2, heme oxygenase-1 (HO-1), and transcriptional levels of them were also measured.

Results

We demonstrated that RSV significantly improved the retinal morphology and function in the diabetic retinopathy model mice. The treated mice exhibited notable improvements in visual electrophysiology, with a significant reduction in retinal ganglion cell apoptosis. Following RSV treatment, the high glucose-cultured ganglion cells demonstrated a considerable rise in SOD levels and a substantial drop in MOD. Moreover, the protein expression of solute carrier family 7 member 11 (SLC7A11) and Nrf2 significantly increased. RT-PCR and Western blot results indicated a significant attenuation of RSV's therapeutic effects upon Nrf2 inhibition.

Conclusion

Our findings suggest that RSV may reduce oxidative stress levels in the retina and inhibit retinal ganglion cell apoptosis via reducing the Nrf2/HO-1 pathway, which lessens the harm that excessive glucose causes to the retina.

Correlations between Steady-State Pattern Electroretinogram and Humphrey Visual Field Analyzer Global Indices and Their Associations with Retinal Ganglion Cell Layer-Inner Plexiform Layer Thickness in Glaucoma Suspects

Purpose

The purpose of this study was to investigate the utility of steady state pattern electroretinogram (ss-PERG) in detecting retinal ganglion cell (RGC) dysfunction in glaucoma suspects (GS) who had normal 24-2 Humphrey Visual Fields (HFA).

Materials and Methods

This was a prospective cohort study of GS patients who were identified based on optic disc appearance with normal HFAs. Patients received a complete eye examination, standard automated perimetry (SAP), optical coherence tomography (OCT), and ss-PERG measurements. The ss-PERG parameters, Magnitude (Mag), Magnitude D (MagD), and MagD/Mag ratio, were examined, along with their relationships between HFA and OCT measurements.

Results

Twenty-five patients were included in this study, with a total of 49 eyes. Fifteen eyes had abnormal ss-PERG parameters and when compared to GS eyes with normal ss-PERG parameters, there were significant differences in HFA 24-2, retinal nerve fiber layer (RNFL) thickness, and ganglion cell layer and inner plexiform layer (GCL + IPL) thickness. All ss-PERG parameters were significantly correlated with 24-2 VF mean deviation (MD) and visual field index (VFI), as well as 10-2 VF MD after controlling for age, sex, intraocular pressure, central corneal thickness, and spherical equivalent. When controlled for age, spherical equivalent, and IOP, MagD/Mag ratio significantly contributed to the variance in average GCL + IPL thicknesses, whereas 24-2 VF MD and 10-2 VF MD did not. MagD/Mag ratio also significantly accounted for variance in all macular GCL + IPL sectors, while 10-2 VF MD did not.

Conclusions

ss-PERG has significant correlations with HFA global indices and was predictive of GCL + IPL thickness in GS patients. Clinical Significance. ss-PERG may serve as a useful functional tool for detecting and measuring RGC dysfunction in GS. It appears to be more sensitive than HFA in the detection of early changes in GCL + IPL thicknesses and may be helpful to use in conjunction with current diagnostic studies to improve the ability of monitoring GS progression.

Retinal Ganglion Cell Functional Recovery after Intraocular Pressure Lowering Treatment Using Prostaglandin Analogs in Glaucoma Suspects: A Prospective Pilot Study

Aim and background

To evaluate the ability of pattern electroretinogram (PERG) to detect improvement of retinal ganglion cell (RGC) function in glaucoma suspects (GS) after medically reducing intraocular pressure (IOP) using prostaglandin analog drops.

Materials and methods

Six subjects (eight eyes) received topical IOP lowering treatment based on their clinical examination and were observed at Manhattan Eye, Ear & Throat Hospital over an average of 3.1 ± 2.2 months. During this time, participants underwent a full ophthalmologic exam and were evaluated with a Humphrey visual field analyzer (HFA) 24-2 [24-2 mean deviation (MD), 24-2 pattern standard deviation (PSD), and 24-2 visual field indices (VFI)], Diopsys NOVA PERG optimized for glaucoma [magnitude (Mag), magnitudeD (MagD), and magnitudeD/magnitude ratio (MagD/Mag ratio)] and optical coherence tomography (OCT)-derived average retinal nerve fiber layer thickness (avRNFLT) and average ganglion cell layer + inner plexiform layer (avGCL + IPL) thicknesses at baseline visit (pretreatment) and 3 months later (posttreatment). Goldman applanation tonometry was used to measure IOP at each visit. Paired sample t-tests were conducted to determine the statistical significance of the change in IOP, HFA indices, PERG parameters, and OCT thickness measurements between the two visits.

Results

Lowering IOP by 22.29% resulted in a significant increase (32.98 and 15.49%) in MagD [t (7) = -3.174, 95% confidence interval (CI) = -0.53, -0.08, p = 0.016] and MagD/Mag ratio [t (7) = -3.233, 95% CI = -0.20, -0.03, p = 0.014], respectively. There was a positive percentage change for all variables of interest, however, 24-2 MD, Mag, avRNFLT, and GCL+ IPLT did not reach statistical significance.

Conclusion

After reducing IOP by 22.29% for a duration of 3.1 months, the PERG parameters, MagD and MagD/Mag ratio, significantly improved by 32.98 and 15.49%, respectively.

Clinical significance

Pattern electroretinogram (PERG) may be a crucial tool for clinicians to locate a window of opportunity in which degenerating yet viable RGCs could be rescued from irreversible damage. We suggest consideration of PERG as a tool in early retinal ganglion cell (RGC) dysfunction detection as well as for monitoring IOP lowering treatment.

How to cite this article

Tirsi A, Gliagias V, Sheha H, et al. Retinal Ganglion Cell Functional Recovery after Intraocular Pressure Lowering Treatment Using Prostaglandin Analogs in Glaucoma Suspects: A Prospective Pilot Study. J Curr Glaucoma Pract 2023;17(4):178-190.

The Discriminatory Ability of Ganglion Cell Inner Plexiform Layer Complex Thickness in Patients with Preperimetric Glaucoma

Purpose

To evaluate diagnostic performance of ganglion cell inner plexiform layer (GCIPL) and retinal nerve fiber layer (RNFL) parameters measured with Cirrus high-definition optical coherence tomography (OCT) in patients with preperimetric glaucoma.

Methods

In this multicenter cross-sectional study, 150 eyes of 83 patients with preperimetric glaucoma were compared with 200 eyes of age and sex matched healthy subjects. All patients had visual field testing and OCT scanning of GCIPL and RNFL in all quadrants. The independent Samples t-test was used to determine if a difference exists between the means of two independent groups on a continuous dependent variable. The area under the receiver operating characteristic (ROC) curve (AUC) of each parameter was calculated for discriminatory ability between normal controls and preperimetric glaucoma. The sensitivity and specificity were estimated by point coordinates on ROC curve.

Results

The best parameters for distinguishing preperimetric glaucoma from healthy eyes were the combined average GCIPL + average RNFL, followed by average RNFL + GCIPL (inferotemporal), and average RNFL + GCIPL (minimum). The GCIPL parameters with the highest to lowest AUC (in decreasing order) were inferotemporal, followed by average, minimum, superior, inferior, superonasal, inferonasal, superotemporal, and quadrants. The RNFL parameters with the highest to lowest AUC (in decreasing order) were average, followed by nasal, temporal, superior, and inferior quadrants. The sensitivity of combined GCIPL + RNFL parameters ranged 85%-88% and the specificity ranged 76%-88%. The sensitivity for RNFL parameters ranged 80%-90% and the specificity ranged 64%-88%.

Conclusion

GCIPL and RNFL have good discriminatory ability; the sensitivity and specificity increase when both parameters are combined for early detection of glaucoma.

Posterior Pole Asymmetry Analysis as a Diagnostic Tool in Glaucoma Suspects: An Electrophysiological Approach

Purpose

Spectral domain optical coherence tomography (SD-OCT) with posterior pole asymmetry analysis (PPAA) provides a mapping of posterior pole retinal thickness with asymmetry analysis between hemispheres of each eye. We investigated whether these structural abnormalities were correlated with functional retinal ganglion cell (RGC) loss, quantified by steady state pattern electroretinogram (ssPERG), in glaucoma suspects (GS).

Methods

Twenty GS (34 eyes) were enrolled in a prospective study at the Manhattan Eye, Ear, and Throat Hospital. All subjects underwent ophthalmological examination, including Humphrey visual field, Spectralis Glaucoma Module Premium Edition (GMPE) SD-OCT PPAA, and ssPERG testing. The ability of ssPERG parameters (Magnitude [Mag, µv], MagnitudeD [MagD, µv], and MagD/Mag ratio) to predict PPAA thickness (total, superior, and inferior thickness, [µm]) was tested via adjusted multivariate linear regression analysis.

Results

Mag explained 8% of variance in total PPAA change (F(1,29)=6.33, B=6.86, 95% CI: 1.29-12.44, p=0.018), 8% in superior PPAA change (F(1,29)=5.57, B=6.92, 95% CI: 0.92-12.92, p=0.025), and 7.1% in inferior PPAA change (F(1,29)=5.83, B=6.80, 95% CI: 1.04-12.56, p=0.022). Similarly, MagD explained 9.7% of variance in total PPAA change (F(1,29)=8.09, B=6.47, 95% CI: 1.82-11.13, p=0.008), 10% in superior PPAA change (F(1,29)=7.33, B=6.63, 95% CI: 1.62-11.63, p=0.011), and 8.5% in inferior PPAA change (F(1,29)=7.25, B=6.36, 95% CI: 1.53-11.18, p=0.012). MagD/Mag ratio and PPAA were not significantly associated.

Conclusion

To the best of our knowledge, this is the first study demonstrating a positive relationship between RGC dysfunction and retinal thickness changes between the superior and inferior hemispheres. The detection of asymmetrical structural loss, combined with functional RGC assessment using ssPERG, may be an informative tool for early glaucoma diagnosis.