Pattern Electroretinography and Visual Evoked Potentials Provide Clinical Evidence of CNS Modulation of High- and Low-Contrast VEP Latency in Glaucoma

Contributions of Brain Microstructures and Metabolism to Visual Field Loss Patterns in Glaucoma Using Archetypal and Information Gain Analyses

Purpose

To investigate the contributions of the microstructural and metabolic brain environment to glaucoma and their association with visual field (VF) loss patterns by using advanced diffusion magnetic resonance imaging (dMRI), proton magnetic resonance spectroscopy (MRS), and clinical ophthalmic measures.

Methods

Sixty-nine glaucoma and healthy subjects underwent dMRI and/or MRS at 3 Tesla. Ophthalmic data were collected from VF perimetry and optical coherence tomography. dMRI parameters of microstructural integrity in the optic radiation and MRS-derived neurochemical levels in the visual cortex were compared among early glaucoma, advanced glaucoma, and healthy controls. Multivariate regression was used to correlate neuroimaging metrics with 16 archetypal VF loss patterns. We also ranked neuroimaging, ophthalmic, and demographic attributes in terms of their information gain to determine their importance to glaucoma.

Results

In dMRI, decreasing fractional anisotropy, radial kurtosis, and tortuosity and increasing radial diffusivity correlated with greater overall VF loss bilaterally. Regionally, decreasing intra-axonal space and extra-axonal space diffusivities correlated with greater VF loss in the superior-altitudinal area of the right eye and the inferior-altitudinal area of the left eye. In MRS, both early and advanced glaucoma patients had lower gamma-aminobutyric acid (GABA), glutamate, and choline levels than healthy controls. GABA appeared to associate more with superonasal VF loss, and glutamate and choline more with inferior VF loss. Choline ranked third for importance to early glaucoma, whereas radial kurtosis and GABA ranked fourth and fifth for advanced glaucoma.

Conclusions

Our findings highlight the importance of non-invasive neuroimaging biomarkers and analytical modeling for unveiling glaucomatous neurodegeneration and how they reflect complementary VF loss patterns.

Primary Open Angle Glaucoma Diagnosis Using Pattern Electroretinogram Parameters

Background

Glaucoma is the most typical cause of permanent blindness. POAG, or primary open angle glaucoma, is the most common type. The pattern electroretinogram (PERG) has become a promising technique for detecting glaucoma early-on. The goal of this study was to assess the ability of PERG to diagnose POAG, especially in early, difficult-to-diagnose cases in comparison with other already established diagnostic methods.

Methods

150 participants (300 eyes) were enrolled in a cross-sectional study at ophthalmology department at Menoufia University Hospital in August 2022 to February 2023. All recruited participants underwent comprehensive ophthalmological and PERG exams. The studied eyes were divided into three groups as 100 normal eyes (Group I), 100 eyes with preperimetric glaucoma (Group II), and 100 eyes with established perimetric glaucoma (Group III).

Results

OCT-RNFL average thickness had a significant positive correlation with P50 latency (r=0.289, p=0.041) or P50 amplitude (r=0.302, p=0.018) and N95 amplitude (r=0.640, p=0.001) among group (II). Also, RNFL thickness had negative correlation with P50 amplitude (r= -0.268, p=0.043) among group (III). RNFL thickness and P50 and N95 amplitude showed highest AUC values in detecting preperimetric glaucomatous eyes vs normal eyes (AUC=0.927, 0.952, 904), and for detecting established perimetric glaucomatous eyes vs normal eyes (AUC=1.00, 0.957, 0.983 respectively) compared with VF MD which showed AUC (0.458 and 0.901 respectively).

Conclusion

Glaucoma patients exhibit PERG alterations (comparable to RNFL thickness changes) so, it could be used as an accurate diagnostic method in POAG. Because PERG alterations occur before visual field abnormalities, it could be relied on as an early diagnostic tool in preperimetric glaucoma. We can use both RNFL thickness assessment by OCT with PERG parameters as complementary tests for accurate diagnosis of preperimetric glaucoma which represents the most difficult diagnostic challenge in glaucoma diagnosis.

Morphological and Functional Assessment of the Optic Nerve Head and Retinal Ganglion Cells in Dry vs Chronically Treated Wet Age-Related Macular Degeneration

Purpose

The aim of the study comprised the anatomical and functional assessment of the optic nerves and macular ganglion cells in the population of patients with unilateral wet age-related macular degeneration (wAMD) and comparison of its results to those obtained from the fellow eye with non-advanced dry age-related macular degeneration (dAMD). Furthermore, we aimed to determine if the number of administered injections contributed to the potential differences between the examined eyes.

Methods

The study was based on 104 eyes of 52 patients in a cross-sectional study. The eyes with chronically treated wAMD were the main subject of the study, while fellow eyes affected with non-advanced dAMD served as the control group. Primary morphological outcomes comprised differences in peripapillary retinal nerve fiber layer (RNFL) and GCC layers between the studied groups (treated and control). In turn, primary functional outcomes included differences in implicit times and amplitudes of the P100 wave of pattern visual evoked potentials (PVEP) and N95 wave of pattern electroretinogram (PERG) between treated and control groups.

Results

We did not find any differences in total RNFL thickness between wAMD and dAMD groups. The number of injections only affected the RNFL in the nasal quadrant of the optic disc (p = 0.023). We did not find any differences regarding GCL thickness in both groups. In the study group, a longer implicit time of the P100 of PVEP (p = 0.014) and a shorter amplitude of the P50-N95 wave of PERG (p = 0.005) were detected. The total number of injections had no significant effect on these two values.

Conclusion

We detected worse functional parameters of the optic nerve and retinal ganglion cells in eyes with wAMD, with lack of significant differences in anatomical (RNFL, GCL) parameters compared to the control group. However, the number of injections did not contribute to the differences found.

Mechanisms implicated in the contralateral effect in the central nervous system after unilateral injury: focus on the visual system

The retina, as part of the central nervous system is an ideal model to study the response of neurons to injury and disease and to test new treatments. During the last decade is becoming clear that unilateral lesions in bilateral areas of the central nervous system trigger an inflammatory response in the contralateral uninjured site. This effect has been better studied in the visual system where, as a rule, one retina is used as experimental and the other as control. Contralateral retinas in unilateral models of retinal injury show neuronal degeneration and glial activation. The mechanisms by which this adverse response in the central nervous system occurs are discussed in this review, focusing primarily on the visual system.

Neural Conduction Along Postretinal Visual Pathways in Glaucoma

Purpose: This study was conducted in order to evaluate retinal ganglion cell (RCG) function and the neural conduction along the postretinal large and small axons and its correlation with retinal nerve fiber layer thickness (RNFL-T) in open-angle glaucoma (OAG) eyes. Methods: Thirty-seven OAG patients (mean age: 51.68 ± 9.83 years) with 24-2 Humphrey mean deviation (MD) between -2.5 and -20 dB and IOP <21 mmHg on pharmacological treatment (OAG group) and 20 age-matched controls (control group) were enrolled. In both groups, simultaneous pattern electroretinograms (PERG) and visual evoked potentials (VEP), in response to checks stimulating macular or extramacular areas (the check edge subtended 15' and 60' of visual arc, respectively), and RNFL-T (measured in superior, inferior, nasal, and temporal quadrants) were assessed. Results: In the OAG group, a significant (ANOVA, p < 0.01) reduction of 60' and 15' PERG P50-N95 and VEP N75-P100 amplitudes and of RNFL-T [overall (average of all quadrants) or temporal] with respect to controls was found; the values of 60' and 15' PERG P50 and VEP P100 implicit times and of retinocortical time (RCT; difference between VEP P100 and PERG P50 implicit times) were significantly (p < 0.01) increased with respect to control ones. The observed increased RCTs were significantly linearly correlated (Pearson's test, p < 0.01) with the reduced PERG amplitude and MD values, whereas no significant linear correlation (p < 0.01) with RNFL-T (overall or temporal) values was detected. Conclusions: In OAG, there is an impaired postretinal neural conduction along both large and small axons (increased 60' and 15' RCTs) that is related to RGC dysfunction, but independent from the RNFL morphology. This implies that, in OAG, the impairment of postretinal neural structures can be electrophysiologically identified and may contribute to the visual field defects, as suggested by the linear correlation between the increase of RCT and MD reduction.

Diffusion Tensor Imaging of Visual Pathway Abnormalities in Five Glaucoma Animal Models

Purpose

To characterize the visual pathway integrity of five glaucoma animal models using diffusion tensor imaging (DTI).

Methods

Two experimentally induced and three genetically determined models of glaucoma were evaluated. For inducible models, chronic IOP elevation was achieved via intracameral injection of microbeads or laser photocoagulation of the trabecular meshwork in adult rodent eyes. For genetic models, the DBA/2J mouse model of pigmentary glaucoma, the LTBP2 mutant feline model of congenital glaucoma, and the transgenic TBK1 mouse model of normotensive glaucoma were compared with their respective genetically matched healthy controls. DTI parameters, including fractional anisotropy, axial diffusivity, and radial diffusivity, were evaluated along the optic nerve and optic tract.

Results

Significantly elevated IOP relative to controls was observed in each animal model except for the transgenic TBK1 mice. Significantly lower fractional anisotropy and higher radial diffusivity were observed along the visual pathways of the microbead- and laser-induced rodent models, the DBA/2J mice, and the LTBP2-mutant cats compared with their respective healthy controls. The DBA/2J mice also exhibited lower axial diffusivity, which was not observed in the other models examined. No apparent DTI change was observed in the transgenic TBK1 mice compared with controls.

Conclusions

Chronic IOP elevation was accompanied by decreased fractional anisotropy and increased radial diffusivity along the optic nerve or optic tract, suggestive of disrupted microstructural integrity in both inducible and genetic glaucoma animal models. The effects on axial diffusivity differed between models, indicating that this DTI metric may represent different aspects of pathological changes over time and with severity.

The Relationship between Pupillometric Values and Visual Evoked Potential Test Results in Patients with Early Glaucoma

SIGNIFICANCE

Measuring pupil diameter may provide an additional objective method to detect and monitor glaucoma.

PURPOSE

The purposes of this study were to evaluate whether pupillometry can be used in the assessment of glaucomatous damage and to determine whether pupillometer can be used in glaucoma screening.

METHODS

In this retrospective study, patients with early stages of glaucomatous optic neuropathy were tested using visual evoked potential (VEP), standard automated perimetry, and pupillometer. The VEP record was made using two consecutive check sizes (1° and 15') at 1-Hz frequency. Patients with a mean deviation of <-2 and >-6 dB were included in the study. Pupil size measurements were performed under photopic conditions at 60-, 100-, and 130-cd/m luminance levels with the OPD Scan (Nidek, Gamagori, Japan) device.

RESULTS

In all, 24 eyes of 24 patients (14 women and 10 men) with newly diagnosed open-angle glaucoma were included, and 30 eyes of 30 healthy subjects (15 women, 15 men) were used as controls. There was no significant difference between sexes in photopic pupil diameters in either group. Comparing the pupil diameters in different luminance levels, the diameters were significantly larger in the patient group. When age-corrected values in the glaucoma group were compared with an age-matched control group, the differences in P100 latency and amplitudes were statistically significant. There were significant correlations between photopic pupil diameters and timing of VEP waveforms.

CONCLUSIONS

There is a relationship between pupil diameters and VEP results in eyes with early glaucoma.

Nonpenetrating Deep Sclerectomy for Progressive Glaucoma: Long-term (5-year) Follow-up of Intraocular Pressure Control and Visual Field Survival

Purpose

To monitor 5-year outcomes of nonpenetrating deep sclerectomy (NPDS) with mitomycin C (MMC) in a new consecutive patient cohort.

Materials and methods

All eyes undergoing NPDS surgery between 1/08 and 6/12 were monitored for intraocular pressure (IOP), number of antiglaucoma medications (meds), and visual field indices [mean deviation (MD) and corrected pattern standard deviation (CPSD)], relative to the preoperative baseline using the two-tailed paired Student's t test.

Results

Of 106 eyes undergoing NPDS with MMC, mean IOP was 19.7 ± 0.5 [sem] mm Hg preoperatively, 11.9 ± 0.5 at 3 months, 12.5 ± 0.6 at 6 months, 12.4 ± 0.5 at 12 months, 12.6 ± 0.6 at 18 months, 11.1 ± 0.6 at 2 years, 11.8 ± 0.5 at 2.5 years, 11.0 ± 0.5 at 3 years, 11.7 ± 0.5 at 3.5 years, 10.7 ± 0.7 at 4 years, 11.6 ± 0.5 at 4.5 years, and 12.4 ± 0.7 at 5 years (average IOP reduction of 7.8 mm Hg or 37%; p < 10⁻⁶) at 5 years. About 92% of eyes had stable IOP ≥5 and ≤21 mm Hg at 5 years. Mean preoperative meds 2.7 ± 0.1 was reduced to 0.40 ±0.09 at 3 months, 0.51 ± 0.1 at 6 months, 0.38 ± 0.08 at 12 months, 0.49 ± 0.09 at 18 months, 0.41 ± 0.09 at 2 years, 0.39 ± 0.09 at 2.5 years, 0.49 ± 0.1 at 3 years, 0.58 ± 0.1 at 3.5 years, 0.49 ± 0.1 at 4 years, 0.64 ± 0.1 at 4.5 years, and 0.52 ± 0.1 at 5 years, corresponding to mean reduction of 2.2 meds (81%; p < 10⁻²²) at 5 years. Mean deviation and CPSD were stable relative to baseline at all time intervals (R = 0.83–0.94; p < 0.0001).

Conclusion

With appropriate postoperative management, eyes undergoing NPDS can maintain excellent IOP control with minimal medication use and maintain very stable visual fields over an extended time frame.

How to cite this article

Slagle G, Groth SL, Montelongo M, et al. Nonpenetrating Deep Sclerectomy for Progressive Glaucoma: Long-term (5-year) Follow-up of Intraocular Pressure Control and Visual Field Survival. J Curr Glaucoma Pract 2020;14(1):3–9.

Widespread brain reorganization perturbs visuomotor coordination in early glaucoma

Glaucoma is the world's leading cause of irreversible blindness, and falls are a major public health concern in glaucoma patients. Although recent evidence suggests the involvements of the brain toward advanced glaucoma stages, the early brain changes and their clinical and behavioral consequences remain poorly described. This study aims to determine how glaucoma may impair the brain structurally and functionally within and beyond the visual pathway in the early stages, and whether these changes can explain visuomotor impairments in glaucoma. Using multi-parametric magnetic resonance imaging, glaucoma patients presented compromised white matter integrity along the central visual pathway and around the supramarginal gyrus, as well as reduced functional connectivity between the supramarginal gyrus and the visual occipital and superior sensorimotor areas when compared to healthy controls. Furthermore, decreased functional connectivity between the supramarginal gyrus and the visual brain network may negatively impact postural control measured with dynamic posturography in glaucoma patients. Taken together, this study demonstrates that widespread structural and functional brain reorganization is taking place in areas associated with visuomotor coordination in early glaucoma. These results implicate an important central mechanism by which glaucoma patients may be susceptible to visual impairments and increased risk of falls.

Pattern electroretinogram changes in patients with primary open-angle glaucoma in correlation with visual field and optical coherence tomography changes

PURPOSE

To study the pattern electroretinogram changes in primary open-angle glaucoma patients in correlation with visual field changes and optical coherence tomography measurements of retinal nerve fiber layer thickness in the peripapillary region in an attempt to evaluate the clinical value of pattern electroretinogram as an objective test of functional deficit in glaucoma.

PATIENTS AND METHODS

The study included 81 eyes of 81 participants: 50 primary open-angle glaucoma patients, 16 primary open-angle glaucoma suspects, and 15 controls. All subjects underwent visual field testing using 24-2 Humphrey standard automated perimetry, peripapillary retinal nerve fiber layer average thickness using the 3.4-mm circular scan of the Heidelberg OCT spectralis and pattern electroretinogram using CSO RetiMax device in accordance with the International Society for Clinical Electrophysiology of Vision guidelines.

RESULTS

We had three main groups: normal, glaucoma suspect, and primary open-angle glaucoma patients, and the last group included three subgroups: mild, moderate, and severe. There was significant difference in the visual field mean deviation, peripapillary retinal nerve fiber layer average thickness, and most pattern electroretinogram measured parameters between the three main groups and in between primary open-angle glaucoma subgroups. There was significant positive correlation between visual field mean deviation and the peripapillary retinal nerve fiber layer average thickness, P50 amplitude, and P50-N95 amplitude (p < 0.001, p = 0.018, and p < 0.001, respectively). Significant negative correlation was also found between peripapillary retinal nerve fiber layer average thickness and N95 amplitude (p < 0.001). Significant positive correlation was found between retinal nerve fiber layer average thickness and P50-N95 amplitude (p = 0.001). Significant negative correlation was found between peripapillary retinal nerve fiber layer average thickness and N95 amplitude (p = 0.001) and significant positive correlation of retinal nerve fiber layer average thickness with P50-N95 amplitude (p = 0.017) in primary open-angle glaucoma patients.

CONCLUSION

Peripapillary retinal nerve fiber layer average thickness shows significant negative correlation with pattern electroretinogram N95 amplitude and a significant positive correlation with P50-N95 amplitude. In combination with optical coherence tomography, pattern electroretinogram can be used to objectively assess functional loss in glaucoma.

Associations of subjective and objective clinical outcomes of visual functions with quality of life in Chinese glaucoma patients: a cross-sectional study

BACKGROUND

The cost of managing a chronic disease like glaucoma is quite large. A convenient and economical monitoring tool like self-reported measures of Quality of Life (QoL) could have the potential to significantly reduce the health economic burden of this disease. However, evidence about whether QoL can effectively reflect both subjective and objective clinical outcomes of visual functions in glaucoma patients is lacking. In this paper, we examined the relationships between both subjective and objective visual functions and QoL in glaucoma patients.

METHODS

This cross-sectional study enrolled 107 patients with a broad range of glaucomatous visual function loss. Subjective visual function loss was assessed using tests of visual acuity (VA), contrast sensitivity (CS) and visual field (VF). Evaluation of objective visual function was performed using pattern visual evoked potentials (PVEP). National Eye Institute Visual Function Questionnaire 25 (NEI VFQ-25) and Glaucoma Quality of Life-15 (GQL-15) were used to measure QoL. Uni- and multivariable linear regression analyses were performed to investigate the associations between all the clinical variables with Rasch-calibrated QoL scores.

RESULTS

Univariate analysis revealed that worse Rasch-calibrated NEI VFQ and GQL scores were associated with poorer VA and CS in both the better eye (BE) and the worse eye (WE), and with worse VF mean deviation, VF pattern standard deviation and PVEP latency and amplitude in 15 min check size in the WE (P < 0.05). Multivariable linear regression analysis revealed that, after adjusting for age, gender, duration of glaucoma, glaucoma severity and glaucoma type, Rasch-calibrated NEI VFQ-25 person measure scores were significantly associated with PVEP latency in 15 min check size [β = - 0.347, 95% CI: (- 0.618, - 0.118), P = 0.001] in the WE; Rasch-calibrated GQL-15 person measure scores were significantly associated with PVEP amplitude in 15 min check size [β = - 0.338, 95% CI: (- 0.588, - 0.108), P < 0.001] in the WE.

CONCLUSIONS

Self-reported measures of QoL could be supplemental tools for assessing both subjective and objective visual functions in glaucoma patients.