Normative data for a user-friendly paradigm for pattern electroretinogram recording

Sensitivity and specificity of the uniform field electroretinogram in glaucoma detection in comparison to the pattern electroretinogram

PURPOSE

To determine the ability of the photopic negative response (PhNR) of the uniform field electroretinogram (UF-ERG) to identify early glaucomatous changes in comparison to the checkerboard and bar stimuli of the pattern electroretinogram (PERG).

METHODS

Forty-nine glaucoma patients were classified into two groups: glaucoma-suspect (23 eyes) and early to moderate glaucoma (30 eyes), based on their clinical examination and the results of standard automated perimetry. Thirty patients (30 eyes) with intraocular pressures (IOP) of 21 mmHg or less, with no history of reported high IOP, were included as controls. PERG and UF-ERG recordings were obtained on a Diagnosys D-341 Attaché-Envoy System. Visual field testing was done only for glaucoma-suspect and glaucoma patients.

RESULTS

All three tests (PERG bar stimulus, PERG checkerboard stimulus and PhNR) displayed significantly prolonged peak times for glaucoma and glaucoma-suspect patients, with delays ranging from 7.8 to 14.8%, depending on the test. The PERG bar stimulus also showed a significantly lower N95 amplitude for both glaucoma groups (with reductions of 26.0% and 33.0% for glaucoma-suspect and glaucoma groups, respectively). The PERG checkerboard N95 amplitude component had high sensitivity for detecting glaucoma patients but a low specificity (97% and 37%, respectively; AUC = 0.61). Overall, the PhNR peak time showed the highest sensitivity and specificity (77% and 90%, respectively; AUC = 0.87).

CONCLUSIONS

PERG bar stimuli and the PhNR of the UF-ERG can be used in the clinical setting to detect glaucoma-related changes in glaucoma-suspect and glaucoma patients. However, our data confirm that the PhNR peak time has the best combined sensitivity and specificity.

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.

Leber Hereditary Optic Neuropathy Gene Therapy: Longitudinal Relationships Among Visual Function and Anatomical Measures

PURPOSE

To assess longitudinal relationships among visual function and anatomical measures of gene therapy in G11778A Leber hereditary optic neuropathy (LHON).

DESIGN

Phase 1 clinical trial.

METHODS

This was a single-institution study of patients with G11778A LHON. Patients with chronic bilateral visual loss >12 months (group 1, n = 11), acute bilateral visual loss <12 months (group 2, n = 9), or unilateral visual loss (group 3, n = 8) were administered unilateral intravitreal AAV2(Y444,500,730F)-P1ND4v2 injection with low, medium, high, and higher doses to worse eye for groups 1 and 2 and better eye for group 3. Oucome measures were best-corrected visual acuity (BCVA), visual field mean deviation (VF MD), steady-state pattern electroretinogram (SS-PERG), optical coherence tomography (OCT) retinal nerve fiber layer (RNFL) thickness and ganglion cell+inner plexiform layer (GCIPL) thickness, and National Eye Institute Visual Function Questionnaire (NEI-VFQ-25) scores. Mean follow-up was 33.6 months (range = 18-36 months).

RESULTS

Baseline SS-PERG amplitude was much reduced in both eyes of all groups including asymptomatic eyes of group 3, and showed no appreciable changes irrespective of disease stage and treatment. Significant and progressive GCIPL and RNFL thinning occurred in all eyes; BCVA and VF MD fluctuated in treated and fellow eyes, with some eyes having modest improvement that may be related to natural history or to gene therapy. Mean NEI-VFQ-25 scores declined in group 3 subjects (P = .023), CONCLUSION: Asymptomatic eyes in LHON patients with unilateral visual loss may be beyond the window of effective neuroprotection given reduced GCIPL and SS-PERG. Randomization of patients to an untreated control group would help to assess treatment effect by accounting for variable natural history. NOTE: Publication of this article is sponsored by the American Ophthalmological Society.

Pattern Electroretinogram in Ocular Hypertension, Glaucoma Suspect and Early Manifest Glaucoma Eyes: A Systematic Review and Meta-analysis

Topic

To provide standardized confidence limits of the transient pattern electroretinogram (tPERG) P50 and N95 and steady state pattern electroretinogram (ssPERG) amplitudes in normal controls as compared to ocular hypertension (OHT), glaucoma suspect (GS), or early manifest glaucoma (EMG) eyes.

Clinical Relevance

The identification of standardized confidence limits in the context of pattern electroretinogram (PERG) might overcome the high intrinsic variability of the measure, and it might lead to a more intuitive understanding of the results as well as to an easier comparison of data from multiple tests, sites, and operators.

Methods

The study protocol was prospectively registered on the International Prospective Register of Systematic Reviews (ID: CRD42022370032). A literature search was conducted on PubMed, Web of Science, and Scopus. Studies comparing PERG raw data in normal control eyes as compared to OHT, GS, or EMG were included. The risk of bias was assessed using the National Institute for Health and Clinical Excellence quality assessment tool. The main outcome was the P50, N95, and ssPERG amplitude difference between the control and the study groups' eyes. The standardized mean difference was calculated as a measure of the effect size for the primary outcome. A subanalysis was conducted based on the type of electrodes adopted for the PERG measurements (invasive vs. noninvasive).

Results

Of the 4580 eligible papers, only 23 were included (1754 eyes). Statistically significant amplitude differences were found in the P50, N95, and ssPERG amplitudes between normal controls and OHT, GS, and EMG eyes. The highest standardized mean difference values were observed in the ssPERG amplitude in all 3 sets of comparison. The subanalysis did not reveal any statistically significant differences between invasive and noninvasive recording strategies.

Conclusions

The use of standardized values as the main outcome measures in the context of the PERG data analysis is a valid approach, normalizing several confounding factors which have affected the clinical utility of PERG both for individual patients and in clinical trials. Steady state PERG apparently better discriminates diseased eyes compared to tPERG. The adoption of skin-active electrodes is able to adequately discriminate between healthy and diseased statuses.

Financial Disclosures

Proprietary or commercial disclosure may be found after the references.

Full-field electroretinogram recorded with skin electrodes in 6- to 12-year-old children

PURPOSE

To determine the full-field electroretinogram (ffERG) parameters, including the light-adapted (LA) 3 ERG and the photopic negative response (PhNR), in 6- to 12-year-old children.

METHODS

ffERG data were obtained from 214 eyes of 214 healthy subjects. The amplitudes and peak time of the ffERG responses were obtained from children divided into 6- to 8-year-old and 9- to 12-year-old groups. Using a skin electrode, electrical signals were measured in response to white stimulating light and white background light (LA 3 ERG). A blue background light and red flashes were then used to elicit the PhNR.

RESULTS

The a-wave amplitude ranged from 0.40 to 9.20 μV, the b-wave ranged from 4.70 to 30.80 μV, and the PhNR ranged from 1.30 to 39.90 μV. The b-wave peak time (33.20 ms) of 6- to 8-year-old groups was slightly shorter than that of the 9- to 12-year-old groups (33.60 ms, P = 0.01), but no differences in amplitudes or in peak time of other components. There were significant correlations between the amplitudes (a-wave and b-wave: r = 0.43, p < 0.001; a-wave and PhNR: r = 0.25, p < 0.001; b-wave and PhNR: r = 0.45, p < 0.001). There was a moderate correlation between the a-wave and b-wave peak time (r = 0.31, P < 0.001).

CONCLUSIONS

We determined the largest dataset of the LA 3 ERG and PhNR parameters in a population of healthy children, aged 6-12 years, which may provide a useful reference value when evaluating children with potential retinal defects.

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.

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.

Pattern Electroretinogram Parameters and their Associations with Optical Coherence Tomography in Glaucoma Suspects

Aim

To investigate whether steady state pattern electroretinogram (ssPERG) could identify retinal ganglion cell (RGC) dysfunction, and to assess the relationship between ssPERG with optical coherence tomography (OCT) measurements in glaucoma suspects (GS).

Materials and methods

This was a prospective cohort study of GS, identified based on suspicious optic disk appearance and glaucoma risk factors. Complete eye exam, Standard automated perimetry, OCT, and ssPERG were performed. Magnitude (Mag), Magnitude D (MagD), and MagD/Mag ratio were subsequently used in the correlation and linear regression analyses between ssPERG parameters and the RNFL, GCL/IPL, and macular thicknesses measurements.

Results

Forty-nine eyes of 26 patients were included. Mag and MagD were significantly correlated with the superior, inferior, and average RNFL thicknesses (avRNFLT). All ssPERG parameters were significantly correlated with the average and minimum GCL/IPL thicknesses and the inner macular sector thicknesses. Mag and MagD significantly predicted the superior, inferior, and avRNFLT in the regression analysis. All ssPERG parameters were predictive of GCL/IPL thickness in all sectors as well as the average and minimum GCL/IPL thicknesses. All ssPERG parameters were predictive of all inner macular sector thicknesses and MagD was also predictive of some outer macular sector thicknesses as well.

Conclusion

ssPERG has significant correlations with and is predictive of RNFL, GCL/IPL, and macular thicknesses in glaucoma suspects.

Clinical significance

ssPERG may serve as a useful objective functional tool for identifying and following the progression of disease in glaucoma suspects.

How to cite this article

Tirsi A, Wong A, Zhu D, et al. Pattern Electroretinogram Parameters and their Associations with Optical Coherence Tomography in Glaucoma Suspects. J Curr Glaucoma Pract 2022;16(2):96-104.

Associations between steady-state pattern electroretinography and estimated retinal ganglion cell count in glaucoma suspects

Purpose

To estimate retinal ganglion cell (RGC) count in glaucoma suspects (GS) and ascertain its relationships with steady-state pattern electroretinography (ssPERG) parameters.

Methods

In this prospective cross-sectional study, 22 subjects (44 eyes) were recruited at the Manhattan Eye, Ear, and Throat Hospital. Subjects underwent complete eye examinations, optical coherence tomography, standard automated perimetry, and ssPERG testing. Eyes were divided into two groups based upon clinical data: healthy subjects and GS. RGC count was estimated using the combined structure–function index.

Results

Estimated RGC count, average retinal nerve fiber layer thickness (ARNFLT), and average ganglion cell layer and inner plexiform layer thickness (GCIPLT) were reduced in GS eyes (p ≤ 0.001 for all parameters). Pearson correlations revealed that ssPERG magnitude and magnitudeD correlated with ARNFLT (r ≥ 0.53, p < 0.001), GCIPLT (r > 0.38, p < 0.011), and estimated RGC count (r > 0.46, p < 0.002). Six mediation analyses revealed that estimated RGC count mediated the relationships among ssPERG parameters, ARNFLT, and GCIPLT.

Conclusion

Steady-state PERG parameters demonstrated linear correlations with estimated RGC count. The associations among ssPERG parameters and structural measures were mediated by estimated RGC count.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10633-022-09869-9.

The Relationship Between Stage of Leber's Hereditary Optic Neuropathy and Pattern Electroretinogram Latency

Purpose

The purpose of this study was to compare the baseline steady-state pattern electroretinogram (SS-PERG) of patients with G11778A Leber hereditary optic neuropathy (LHON) with different stages of visual acuity (VA) loss before allotopic gene therapy (GT).

Methods

Patients (n = 28) were enrolled into groups (GT I: chronic bilateral VA ≤35 Early Treatment Diabetic Retinopathy Study [ETDRS]; GT II: acute bilateral VA ≤35 ETDRS; GT III: acute unilateral, VA ≤35 ETDRS, and better eye VA ≥70 ETDRS) and tested with SS-PERG together with 210 age-matched normal controls (NCs). SS-PERG amplitude (nV) and latency (ms) of each eye were averaged for groups GT I, GT II, and NC. Symptomatic eyes (GT III-S) and asymptomatic eyes (GT III-A) of group GT III were included separately and accounted for by using generalized estimating equation (GEE) methods.

Results

Compared to NC, SS-PERG amplitudes were reduced similarly by approximately 50% (P < 0.001) among all GT groups (NC > GT I, GT II, GT III-S, and GT III-A). SS-PERG latencies were shorter by ≥3.5 ms in all LHON groups and differed by disease stage (G III-A < NC, P = 0.002; GT III-S < GT III-A, P = 0.01; GT II < GT III-S, P = 0.03; GT I < NC, P < 0.001, but not different from other GT groups, all P > 0.1).

Conclusions

Although SS-PERG amplitude reduction did not distinguish between disease stages, SS-PERG latency shortening occurred in asymptomatic eyes and symptomatic eyes and distinguished between disease stages.

Translational Relevance

SS-PERG latency shortening is consistent with primary damage of smaller/slower axons and sparing of larger/faster axons and may provide an objective staging of LHON, which may be helpful to determine efficacy in LHON trials.

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

PURPOSE

To derive and validate structure-function models for estimating retinal ganglion cell (RGC) count using optical coherence tomography (OCT) and steady-state pattern electroretinography (ssPERG) parameters in glaucoma suspects (GS) and preperimetric glaucoma (PPG).

METHODS

In this prospective cross-sectional study, 25 subjects (50 eyes) were recruited at the Manhattan Eye, Ear, and Throat Hospital. Subjects underwent comprehensive eye examinations, OCT, standard automated perimetry (SAP), and ssPERG testing. Eyes were divided into three groups based on the Global Glaucoma Staging System: healthy (N = 30), GS (N = 10), and PPG (N = 10) eyes. The combined structure-function index (CSFI), which estimates retinal ganglion cell count (eRGC_CSFI) from SAP and OCT parameters, was calculated in each study subject. Two prediction formulas were derived using a generalized linear mixed model (GLMM) to predict eRGC_CSFI from ssPERG parameters, age, and average retinal nerve fiber layer thickness (ARNFLT) in 30 eyes selected at random (training group). GLMM predicted values were cross-validated with the remaining 20 eyes (validation group).

RESULTS

The ARNFLT, ssPERG parameters magnitude (Mag) and magnitudeD (MagD), and eRGC_CSFI were significantly different among study groups (ANOVA p ≤ 0.001). Pearson correlations demonstrated significant associations among ARNFLT, ssPERG parameters, and eRGC_CSFI (r² ≥ 0.31, p < 0.001). Two GLMMs predicted eRGC_CSFI from Mag (eRGC_Mag) and MagD (eRGC_MagD), respectively, with significant equations (F(3,18), F(3,19) ≥  58.37, R² = 0.90, p < 0.001). eRGC_Mag and eRGC_MagD in the validation group (R² = 0.89) correlated with eRGC_CSFI similarly to the training group. Multivariate pairwise comparisons revealed that eRGC_Mag and eRGC_MagD distinguished between healthy, GS, and PPG eyes (p ≤ 0.035), whereas independent Mag, MagD, and ARNFLT measures did not distinguish between GS and PPG eyes.

CONCLUSION

This pilot study offers the first combined structure-function models for estimating RGC count using ssPERG parameters. RGC counts estimated with these models were generalizable, strongly associated with CSFI estimates, and performed better than individual ssPERG and OCT measures in distinguishing healthy, GS, and PPG eyes.

Case Report: Off-Label Liraglutide Use in Children With Wolfram Syndrome Type 1: Extensive Characterization of Four Patients

Aims: Wolfram syndrome type 1 is a rare recessive monogenic form of insulin-dependent diabetes mellitus with progressive neurodegeneration, poor prognosis, and no cure. Based on preclinical evidence we hypothesized that liraglutide, a glucagon-like peptide-1 receptor agonist, may be repurposed for the off-label treatment of Wolfram Syndrome type 1. We initiated an off-label treatment to investigate the safety, tolerability, and efficacy of liraglutide in pediatric patients with Wolfram Syndrome type 1. Methods: Pediatric patients with genetically confirmed Wolfram Syndrome type 1 were offered off-label treatment approved by The Regional Network Coordination Center for Rare Diseases, Pharmacological Research IRCCS Mario Negri, and the internal ethics committee. Four patients were enrolled; none refused nor were excluded or lost during follow-up. Liraglutide was administered as a daily subcutaneous injection. Starting dose was 0.3 mg/day. The dose was progressively increased as tolerated, up to the maximum dose of 1.8 mg/day. The primary outcome was evaluating the safety, tolerability, and efficacy of liraglutide in Wolfram Syndrome type 1 patients. Secondary endpoints were stabilization or improvement of C-peptide secretion as assessed by the mixed meal tolerance test. Exploratory endpoints were stabilization of neurological and neuro-ophthalmological degeneration, assessed by optical coherence tomography, electroretinogram, visual evoked potentials, and magnetic resonance imaging. Results: Four patients aged between 10 and 14 years at baseline were treated with liraglutide for 8-27 months. Liraglutide was well-tolerated: all patients reached and maintained the maximum dose, and none withdrew from the study. Only minor transient gastrointestinal symptoms were reported. No alterations in pancreatic enzymes, calcitonin, or thyroid hormones were observed. At the latest follow-up, the C-peptide area under the curve ranged from 81 to 171% of baseline. Time in range improved in two patients. Neuro-ophthalmological and neurophysiological disease parameters remained stable at the latest follow-up. Conclusions: We report preliminary data on the safety, tolerability, and efficacy of liraglutide in four pediatric patients with Wolfram Syndrome type 1. The apparent benefits both in terms of residual C-peptide secretion and neuro-ophthalmological disease progression warrant further studies on the repurposing of glucagon-like peptide-1 receptor agonists as disease-modifying agents for Wolfram Syndrome type 1.

Pattern Electroretinogram Parameters Are Associated with Optic Nerve Morphology in Preperimetric Glaucoma after Adjusting for Disc Area

Purpose

We examined the relationships between pattern electroretinogram and optical coherence tomography derived optic nerve head measurements, after controlling for disc area.

Methods

Thirty-two eyes from 20 subjects with preperimetric glaucoma underwent pattern electroretinogram and optical coherence tomography. Pattern electroretinogram parameters (Magnitude, MagnitudeD, and MagnitudeD/Magnitude ratio) and optic nerve head measurements (rim area, average cup to disc ratio, vertical cup to disc ratio, cup volume, retinal nerve fiber layer thickness sectors, and Bruch's membrane opening-minimum rim width thickness sectors) were analyzed after controlling for disc area.

Results

Magnitude and MagnitudeD were significantly associated with rim area (r ≥ 0.503, p ≤ 0.004). All pattern electroretinogram parameters significantly correlated with Bruch's membrane opening-minimum rim width sectors—temporal superior and nasal inferior (r = 0.400, p=0.039)—and retinal nerve fiber layer sectors—superior, nasal superior, and inferior (r ≥ 0.428, p ≤ 0.026). Magnitude and MagnitudeD explained an additional 26.8% and 25.2% of variance in rim area (B = 0.174 (95% CI: 0.065, 0.283), p=0.003, and B = 0.160 (95% CI: 0.056, 0.265), p=0.004), respectively. MagnitudeD and MagnitudeD/Magnitude ratio explained an additional 13.4% and 12.8% of the variance in Bruch's membrane opening-minimum rim width global (B = 38.921 [95% CI: 3.872, 73.970], p=0.031, and B = 129.024 (95% CI: 9.589, 248.460), p=0.035), respectively. All Bruch's membrane opening-minimum rim width sectors and retinal nerve fiber layer sectors (nasal superior, nasal inferior, and inferior) were significantly correlated with rim area (r ≥ 0.389, p ≤ 0.045).

Conclusion

PERG abnormalities can predict rim area loss in preperimetric glaucoma after controlling for disc area. We recommend controlling for disc area to increase diagnostic accuracy in early glaucoma.

PERG adaptation for detection of retinal ganglion cell dysfunction in glaucoma: a pilot diagnostic accuracy study

It has been previously demonstrated that the adaptive phase changes of steady-state pattern electroretinogram (SS-PERG), recorded during 4-min presentation of patterned stimuli, are reduced in glaucoma suspects and patients compared to normal subjects. Our study aims at testing the hypothesis that adaptive changes of SS-PERG, recorded using the novel optimized Next Generation PERG (PERGx) protocol, differ between glaucoma patients and controls. In this pilot cross-sectional study, we included 28 glaucoma patients and 17 age-matched normal subjects. Both patients and controls underwent a full ophthalmologic examination, visual field testing, OCT and PERGx. The PERGx signal was sampled over 2 min (providing 1 noise and 9 signal packets) in response to alternating gratings generated on an OLED display. PERGx amplitude and phase were analyzed to quantify adaptive changes over recording time. Receiver operating characteristic (ROC) curves were used to study the diagnostic accuracy of PERGx parameters in distinguishing glaucoma patients from normal subjects. PERGx amplitude and phase data showed declining trends in both groups. PERGx amplitude slope and grand-average vector amplitude and phase were significantly different in patients compared to controls (p < 0.01), whereas phase angular dispersion was greater in patients but not significantly different between the two groups. The area under the ROC curves were 0.87 and 0.76 for PERGx amplitude slope and grand-average vector amplitude, and 0.62 and 0.87 for PERGx angular dispersion and grand-average vector phase, respectively. The PERGx paradigm resulted highly accurate in detecting the reduction of amplitude adaptive changes in glaucoma patients, presumably due to the loss of functional retinal ganglion cell autoregulation. Thus, PERG adaptation, recorded by this new protocol, might be helpful in the identification and diagnosis of early glaucomatous dysfunction.

Retinal microvascular and neuronal function in patients with multiple sclerosis: 2-year follow-up

OBJECTIVE

To determine the longitudinal changes in retinal microstructure, microvasculature, microcirculation, and axonal and neuronal functions in patients with relapsing-remitting multiple sclerosis (RRMS) over the time course of about two years.

METHODS

A total of 30 patients (60 eyes) with RRMS were followed for a period of 27 ± 6 months and evaluated with a battery of clinical tests including low contrast letter acuity (LCLA), intraretinal layer thicknesses by optical coherence tomography (OCT), ganglion cell function by steady-state pattern electroretinography (PERG), axonal function by polarization-sensitive OCT, volumetric vessel density (VVD) by OCT angiography, and retinal tissue perfusion (RTP) by retinal function imager.

RESULTS

Axonal function measured as retinal nerve fiber layer birefringence in the temporal quadrant and vessel density in the deep vascular plexus were significantly decreased at 2-year follow-up (P < 0.05). Subgroup analyses showed that the increased retinal blood flow volume occurred in patients with no evidence of disease activity (NEDA), and with stable or improved visual function (P < 0.05). There was no significant difference in the expanded disability state scale, LCLA, RTP, VVD, or PERG measures between the two visits (P > 0.05).

CONCLUSION

To our best knowledge, this is the first 2-year prospective comprehensive study with a detailed assessment of retinal microstructure and neuronal functions in patients with RRMS. The recovery of retinal microcirculation occurred in patients with NEDA, and stable or improved visual function, suggesting these measurements as potential imaging biomarkers for monitoring disease progression.

Impact of femtosecond laser-assisted in situ keratomileusis on retinal ganglion cell function

PURPOSE

To analyse the effect of femtosecond laser-assisted in situ keratomileusis (FS-LASIK) on the electrical response of retinal ganglion cells using pattern electroretinography (pERG).

METHODS

This was a longitudinal, prospective, observational pilot study. We included consecutive myopic patients who underwent FS-LASIK to correct up to 6 dioptres of myopia and up to 2 dioptres of astigmatism. Patients with excessive blinking or tearing and those with Snellen uncorrected visual acuity less than 0.9 dec on postop day 1 were excluded. Diopsys NOVA^® (Diopsys Inc., NJ) pERG records, using high- and low-contrast patterns, were obtained 16 h and 1 month after FS-LASIK was performed. Magnitude (μV), Magnitude D (μV), Magnitude D/Magnitude ratio and signal-to-noise ratio (dB) were analysed. Wilcoxon test for nonparametric paired data was employed.

RESULTS

pERG data from 24 eyes were analysed from 24 patients who underwent FS-LASIK. Mean age was 35.79 ± 9.86 years. Mean preoperative refraction was -2.69 ± 7.6 D (spherical) and -0.38 ± 0.40 D (cylinder). Mean surgical time was 56.88 ± 7.6 s. No statistically significant differences were obtained for any of the studied parameters when comparing 16 h with 1 month after FS-LASIK, with the exception of Magnitude with low contrast, which increased from 1.21 ± 0.2 to 1.39 ± 0.29 µV at 16 h and 1 month postoperatively, respectively (p = 0.03).

CONCLUSIONS

FS-LASIK seems to induce a mild and transitory defect in retinal ganglion cell function. Only a mild decrease was detected in the magnitude value for low-contrast stimuli when pERG was performed 16 h postoperatively, and it returned to normal 1 month after surgery.

Comparison of structural and functional tests in primary open angle glaucoma

Purpose:

To comparatively analyze the structural and functional tests used in the diagnosis and follow-up of glaucoma.

Methods:

Eighty eyes of 40 patients with primary open angle glaucoma (POAG) and 46 eyes of 23 healthy individuals were included in the study. Transient pattern electroretinography (PERG), steady-state PERG (ssPERG), computerized visual field (VF) screening, and examination of retinal nerve fiber layer (RNFL) and macular thickness on optical coherence tomography (OCT) were undertaken. The results were compared between the groups.

Results:

80 eyes belonging to 40 patients with a diagnosis of POAG (23 female, 17 male) (18 mild 22 moderate POAG) with a mean of 57.37 (±8.6) years, and 46 eyes of 23 healthy individuals (14 female, 9 male) with a mean age of 55.30 (±8.09) years were included in the study. PERG P50 and N95 and ssPERG latency revealed a significant delay in the POAG group. When the wave amplitudes were examined, they were found to be significantly lower in both PERG and sSPERG tests for the POAG group, but the results were more pronounced in ssPERG. The latency values of PERG and ssPERG tests were not significantly correlated with any of the parameters of the remaining tests. However, the amplitude values of these tests had a positive correlation with the mean deviation value and negative correlation with the pattern standard deviation value of VF. All associated parameters were significant for the amplitude value of the ssPERG test.

Conclusion:

For the proper management of glaucoma, rather than approaching damage simply as the loss of retinal ganglion cells or the neuroretinal rim, it is necessary to focus on the ongoing anatomical and functional relationship and evaluate structural and functional tests together. In addition, ssPERG test, which is not widely adopted in routine practice, provides valuable information and is significantly correlated with OCT parameters.

Shortened Pattern Electroretinogram Latency and Impaired Autoregulatory Dynamics to Steady-State Stimuli in Patients With Multiple Sclerosis

BACKGROUND

The steady-state pattern electroretinogram (PERG) is a sensitive measure of retinal ganglion cell (RGC) function that includes within-test progressive changes-adaptation-reflecting RGC autoregulatory dynamics. Comprehensive PERG assessment in patients with multiple sclerosis (MS) (with or without optic neuritis [ON]) may provide unique information about RGC dysfunction and its progression, as well as a comparison between functional loss and structural loss as measured by optical coherence tomography (OCT). The goal of this project was to measure steady-state PERG components and their associations with intraretinal layer thicknesses in MS.

METHODS

One hundred forty eyes of 70 patients with relapsing-remitting MS and 126 eyes of 63 age- and sex-matched healthy control subjects (HC) were investigated using a new-generation PERG method and ultrahigh-resolution OCT. Of MS eyes, there were 30 eyes with ON (MSON), 22 non-ON fellow eyes (MSFE), and 88 non-ON MS eyes (MSNON). PERG amplitude, phase (latency), and adaptation of amplitude and phase were measured and correlated with OCT-determined thicknesses of intraretinal layers.

RESULTS

The average PERG amplitude in MSON eyes was significantly lower than MSFE (P = 0.007), MSNON (P = 0.002), and HC (P < 0.001). The PERG amplitude in MSFE eyes was also significantly lower than HC (P = 0.039). The PERG latency in MSON eyes was significantly shorter than in MSFE (P = 0.001), MSNON (P = 0.002), and HC (P < 0.001). The PERG latency in MSFE (P = 0.007) and MSNON (P = 0.002) was significantly shorter than in HC. However, no significant differences were found between MSFE and MSNON (P > 0.05). PERG adaptation of amplitude in MSON was significantly lower than that in MSNON (P = 0.039) and HC (P = 0.037). Both the amplitude and latency in the MS eyes were significantly correlated with the thicknesses of the macular retinal nerve fiber layer (mRNFL) and ganglion cell-inner plexiform layer (GCIPL).

CONCLUSIONS

Shortened PERG latency and impaired autoregulatory dynamics occurred in MS, suggesting preferential dysfunction of small, slower RGC axons and decreased ability of RGC to autoregulate their gain in response to PERG stimulus. The established relations of PERG measurements with intraretinal thickness measurements suggested that PERG losses were primarily associated with GCIPL and mRNFL thinning.

RE-PERG in early-onset Alzheimer's disease: A double-blind, electrophysiological pilot study

PURPOSE

To evaluate the ability of re-test pattern electroretinogram (RE-PERG), a non-invasive and fast steady-state PERG, to detect inner retinal bioelectric function anomalies in patients with early-onset Alzheimer's disease (AD).

METHODS

The study population consisted of 17 patients with AD-related mild cognitive impairment (MCI), 16 patients with vascular dementia (VD)-related MCI, both assessed using the neuropsychological Mini-Mental State Examination (MMSE) and by structural magnetic resonance imaging, and 19 healthy, age-matched normal controls (NC). All participants were visually asymptomatic, had normal or near-normal general cognitive functioning and no or minimal impairments in daily life activities. Visual field (VF) test, optical coherence tomography (OCT) and RE-PERG, sampled in five consecutive blocks of 130 events, were performed.

RESULTS

There was no statistically significant difference among the three groups with respect to age, VF parameters (mean and pattern standard deviations) and OCT parameters (ganglion cell complex thickness and retinal nerve fiber layer thickness). The mean amplitude in the RE-PERG was significantly lower, but only weakly in the AD group than in NC (p = 0.1) whereas the intrinsic variability of the 2nd harmonic phase was significantly higher in the AD group than in either the VD or NC group (p<0.001).

CONCLUSIONS

RE-PERG is altered in early-stage AD, showing a reduced amplitude with high intrinsic phase variability. It also allows the discrimination of AD from VD. A high intrinsic variability in the PERG signal, determined using RE-PERG, may thus be a new promising test for neurodegenerative diseases.

Use of a novel telemetric sensor to study interactions of intraocular pressure and ganglion-cell function in glaucoma

Aims

(1) To test the feasibility of simultaneous steady-state pattern electroretinogram (ssPERG) and intraocular pressure (IOP) measurements with an implanted IOP sensor. (2) To explore the scope of this approach for detecting PERG changes during IOP manipulation in a model of lateral decubitus positioning (LDP; lateral position).

Methods

15 healthy controls and 15 treated glaucoma patients participated in the study. 8 patients had an IOP sensor (Eyemate-IO, Implandata Ophthalmic Products GmbH) in the right eye (GLAIMP) and 7 had no sensor and with glaucoma in the left eye. (1) We compared PERGs with and without simultaneous IOP read-out in GLAIMP. (2) All participants were positioned in the following order: sitting1 (S1), right LDP (LDR), sitting2 (S2), left LDP (LDL) and sitting3 (S3). For each position, PERG amplitudes and IOP were determined with rebound tonometry (Icare TA01i) in all participants without the IOP sensor.

Results

Electromagnetic intrusions of IOP sensor read-out onto ssPERG recordings had, due to different frequency ranges, no relevant effect on PERG amplitudes. IOP and PERG measures were affected by LDP, for example, IOP was increased during LDR versus S1 in the lower eyes of GLAIMP and controls (5.1±0.6 mmHg, P0.025=0.00004 and 1.6±0.6 mmHg, P0.025=0.02, respectively) and PERG amplitude was reversibly decreased (−25±10%, P0.025=0.02 and −17±5%, P0.025, respectively).

Conclusions

During LDP, both IOP and PERG changed predominantly in the lower eye. IOP changes induced by LDP may be a model for studying the interaction of IOP and ganglion-cell function.

Pattern Electroretinograms in Preperimetric and Perimetric Glaucoma

PURPOSE

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

DESIGN

Cross-sectional observational study.

METHODS

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

RESULTS

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

CONCLUSIONS

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

Long-term PERG monitoring of untreated and treated glaucoma suspects

PURPOSE

To investigate long-term structural and functional progression of untreated and treated glaucoma suspects (UGS and TGS).

METHODS

Retrospective analysis of serial steady-state pattern electroretinogram (PERG), mean retinal nerve fiber layer thickness (RNFLT), and standard automated perimetry mean deviation (SAP-MD) in UGS (N = 20) and TGS (N = 18). Outcome measures were the rates of change (linear regression slopes) of PERG amplitude, PERG phase, mean RNFLT, and SAP-MD over 9.8 ± 1.3 years (15.6 ± 4.2 visits).

RESULTS

The number of patients with significant (P < 0.05) progression slopes for PERG amplitude, PERG phase, RNFLT, and SAP-MD was, respectively, UGS: 5, 0, 4, 2; TGS: 8, 2, 6, 5. In UGS, outcome measures were not correlated with each other. In TGS, both PERG amplitude and RNFLT were significantly (P < 0.05) correlated with SAP-MD (R ≥ 0.58), while PERG amplitude and RNFLT were not correlated with each other (R = 0.43, P = 0.064). The rate of change of SAP-MD was predicted (P < 0.05) by a linear combination of RNFLT slope and PERG amplitude slope.

CONCLUSIONS

Results substantiate and extend previous results showing that steady-state PERG amplitude progressively decreased over time in a proportion of glaucoma suspects, with relatively steeper slope in TGS compared to UGS. RNFLT progression also had a steeper slope in TGS compared to UGS; however, progressions of PERG amplitude and RNFLT were not significantly correlated. Both PERG progression and RNFLT progression independently contribute to prediction of visual field progression.

Antioxidant Saffron and Central Retinal Function in ABCA4-Related Stargardt Macular Dystrophy

Retinal oxidative damage, associated with an ATP-binding cassette, sub-family A, member 4, also known as ABCA4 gene mutation, has been implicated as a major underlying mechanism for Stargardt disease/fundus flavimaculatus (STG/FF). Recent findings indicate that saffron carotenoid constituents crocins and crocetin may counteract retinal oxidative damage, inflammation and protect retinal cells from apoptosis. This pilot study aimed to evaluate central retinal function following saffron supplementation in STG/FF patients carrying ABCA4 mutations. Methods: in a randomized, double-blind, placebo-controlled study (clinicaltrials.gov: NCT01278277), 31 patients with ABCA4-related STG/FF and a visual acuity >0.25 were randomly assigned to assume oral saffron (20 mg) or placebo over a six month period and then reverted to P or S for a further six month period. Full ophthalmic examinations, as well as central 18° focal electroretinogram (fERG) recordings, were performed at baseline and after six months of either saffron or placebo. The fERG fundamental harmonic component was isolated by Fourier analysis. Main outcome measures were fERG amplitude (in µV) and phase (in degrees). The secondary outcome measure was visual acuity. Results: supplement was well tolerated by all patients throughout follow-up. After saffron, fERG amplitude was unchanged; after placebo, amplitude tended to decrease from baseline (mean change: −0.18 log µV, p < 0.05). Reverting the treatments, amplitude did not change significantly. fERG phase and visual acuity were unchanged throughout follow-up. Conclusions: short-term saffron supplementation was well tolerated and had no detrimental effects on the electroretinographic responses of the central retina and visual acuity. The current findings warrant further long-term clinical trials to assess the efficacy of saffron supplementation in slowing down the progression of central retinal dysfunction in ABCA4-related STG/FF.

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

PURPOSE

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

PATIENTS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

Test-retest repeatability of the pattern electroretinogram and flicker electroretinogram

PURPOSE

To evaluate the repeatability of the steady-state pattern electroretinogram (PERG) and full-field flicker electroretinogram (Flicker ERG) protocols, delivered by the office-based Neuro Optic Vision Assessment (NOVA)™ testing platform, in healthy subjects.

METHODS

Healthy individuals underwent PERG (16° and 24°) and Flicker ERG [fixed luminance (FL) and multi-luminance (ML)] testing protocols. Test-retest repeatability of protocols was calculated using intra-class correlation coefficients (ICC). Reference values of the parameters of the aforementioned tests were also calculated.

RESULTS

The ICCs for the PERG parameters ranged from 0.793 to 0.911 (p < 0.001). The ICCs for the Flicker ERG parameters ranged from 0.968 to 0.994 (p < 0.001). A linear regression analysis was applied to assess the impact of age on ERG responses. Age had a significant impact on all PERG parameters (16° or 24°). The phase response of the FL Flicker ERG significantly decreased with age (β = - 0.837, p ≤ 0.001). The FL Flicker ERG Magnitude was also impacted with a significant quadratic effect of age (β = - 0.0047, p = 0.0004). Similarly, the Phase Area Under the Curve (Phase AUC) of the ML Flicker ERG significantly declined with age (β = - 0.007, p = 0.009), and the impact on the Magnitude AUC was significant as well, with a negative quadratic age effect.

CONCLUSIONS

The PERG and Flicker ERG protocols, delivered by an office-based testing platform, were shown to have good-to-excellent test-retest repeatability when tests were performed in the same order and in immediate succession.

Comparison of pattern electroretinograms of glaucoma patients with parafoveal scotoma versus peripheral nasal step

Retinal ganglion cells are distributed disproportionately with retinal eccentricity. Pattern electroretinogram (PERG) stimuli resulted in reduced responses with more eccentric stimuli. Therefore, we investigated whether PERG amplitude is associated with the location of visual field (VF) defect in primary open-angle glaucoma. Data from Twenty-nine glaucoma patients with a parafoveal scotoma (PFS) within the central 10° of fixation, 23 glaucoma patients with a peripheral nasal step (PNS), and 27 normal control subjects were analyzed in this study. Electroretinograms (ERGs) were obtained using a commercial ERG stimulator (Neuro-ERG). The thickness of the ganglion cell-inner plexiform layer (GCIPL) was measured using spectral-domain optical coherence tomography. A lower N95 amplitude was observed in both PFS and PNS compared to the normal control (Both P < 0.001). The N95 amplitude of the PFS group was significantly lower than that of the PNS group (P = 0.034). Average GCIPL thickness correlated positively with N95 amplitude (r = 0.368, P = 0.002), but did not correlate significantly with global mean sensitivity (r = 0.228, P = 0.073) or mean deviation on 24-2 standard automated perimetry (r = 0.173, P = 0.176). In conclusion, parafoveal VF defects were associated with the lower PERG amplitude. Therefore, it is necessary to take into account the location of VF defects in evaluating PERGs of glaucoma patients.

Applications of Isolated-Check Visual Evoked Potential in Early Stage of Open-Angle Glaucoma Patients

Background:

Standard automated perimetry does not sufficiently detect early open-angle glaucoma (OAG) in the clinic. New visual function tests for early glaucoma damage are therefore needed. The present study evaluated whether an isolated-check visual evoked potential (icVEP) could be used to detect visual function abnormalities in early-stage OAG and to explore potential related factors.

Methods:

This was a cross-sectional study. Thirty-seven OAG patients with early-stage visual field loss (mean deviation ≥ −6.00 dB) detected by the Humphrey Field Analyzer (30-2 SITA program) and 26 controls were included in this study. Optical coherence tomography (OCT) was used to detect retinal nerve fiber layer (RNFL) defects. The icVEP preferentially evaluates the magnocellular-ON pathway. VEPs were recorded and signal-to-noise ratios (SNRs) were derived based on multivariate analysis. Eyes that yielded an SNR ≤1 were considered abnormal. Receiver operating characteristic (ROC) curve analysis was used to estimate the accuracy of group classification. Correlations between SNRs and related factors were analyzed.

Results:

Based on an SNR criterion of 1, the icVEP had a sensitivity of 62.2% and a specificity of 92.3% for diagnosing early-stage OAG with 74.6% classification accuracy. The ROC curve analysis, however, suggested that an SNR criterion of 0.93 would produce the highest classification accuracy (77.3%). Both RNFL thinning in the temporal superior quadrant on OCT and number of abnormal test points in the central 11° visual field (pattern deviation, P < 0.5%) significantly correlated with the SNR (P < 0.05).

Conclusions:

The icVEP detected visual function abnormalities in approximately 3/5 of eyes with early-stage OAG with greater than 90% specificity. SNR correlated with both a decrease in RNFL thickness and severity of central visual field loss.

A Comparison of the RETeval Sensor Strip and DTL Electrode for Recording the Photopic Negative Response

PURPOSE

To compare the RETeval sensor strip and Dawson-Trick-Litzkow (DTL) electrodes for recording the photopic negative response (PhNR) using a portable electroretinogram (ERG) device in eyes with and without glaucoma.

METHODS

Twenty-six control and 31 glaucoma or glaucoma-suspect participants were recruited. Photopic ERGs were recorded with sensor strip and DTL electrodes in random order using the LKC RETeval device. Stimuli consisted of brief, red flashes (1.7 cd.s/m2) on a blue background (photopic 10 cd/m2). The PhNR amplitude was measured from baseline to trough and also expressed as a ratio over the b-wave amplitude.

RESULTS

The sensor strip-recorded PhNR amplitude was significantly attenuated (mean ± standard deviation [SD], 4.8 ± 2.1 vs. 12.7 ± 4.8 μV, P < 0.0001), with lower signal-to-noise ratio (SNR; 5.5 ± 2.1 vs. 8.1 ± 3.9, P < 0.0001), and a trend toward a larger PhNR/b-wave ratio compared with DTL electrodes. The PhNR amplitude, implicit time and PhNR/b-wave ratio correlated with visual field mean light sensitivity, although this fell short of significance for the sensor strip recorded PhNR amplitude. The electrodes demonstrated similar intersession repeatability with a coefficient of repeatability of ±27% and ±28% for the DTL and sensor strip, respectively.

CONCLUSIONS

Sensor strip electrodes are a viable alternative for recording reproducible PhNRs, especially when values are normalized to the b-wave. However, DTL electrodes should be considered in cases of attenuated PhNR, or in elevated noise levels, due to its better signal-to-noise quality.

TRANSLATIONAL RELEVANCE

Sensor strip electrodes can simplify PhNR recordings in the clinic, potentially eliminating the need for an experienced operator.

Pattern Electroretinogram Detects Localized Glaucoma Defects

Purpose

We evaluated the clinical ability of pattern electroretinogram (PERG) to detect functional losses in the affected hemifield of open-angle glaucoma patients with localized perimetric defects.

Methods

Hemifield (horizontally-defined) steady-state PERGs (h-PERGs) were recorded in response to 1.7 c/deg alternating gratings from 32 eyes of 29 glaucomatous patients with a perimetric, focal one-hemifield defect, 10 eyes of 10 glaucomatous patients with a diffuse perimetric defect, and 18 eyes of 18 age-matched normal subjects. Standard automated perimetry (SAP) and spectral-domain optical coherence tomography (SD-OCT) for retinal nerve fiber layer (RNFL) thickness also were performed. h-PERG amplitudes and ratios, calculated corresponding hemifield perimetric deviations, as well as hemiretina RNFL thicknesses were analyzed.

Results

h-PERG amplitudes, perimetric deviations, and RNFL thicknesses showed losses (P < 0.001) when comparing affected with unaffected hemifields of localized glaucomatous eyes. No differences were found in h-PERG amplitudes between hemifields of normal or diffuse glaucomatous eyes. h-PERG amplitude ratios (affected/unaffected hemifield) in localized glaucoma were lower (P < 0.001) than the ratios from normal or diffuse glaucomatous eyes. The areas under the receiver operating characteristic curves for h-PERG amplitude ratios, comparing localized-defect glaucomatous eyes with normal or diffuse glaucomatous eyes, were 0.93 and 0.91, respectively.

Conclusions

h-PERG assessment showed good diagnostic accuracy to confirm localized glaucomatous defects detected perimetrically. This test may be particularly useful in cognitively impaired patients or young/nonverbal patients unable to provide reliable visual fields.

Translational Relevance

h-PERG provides a sensitive objective measure to confirm focal losses detected with SAP and/or RNFL thickness analysis.

Visual Evoked Potentials and Glaucoma

Visual evoked potentials (VEP) can be used to assess the function of the visual system objectively. Research on VEP testing as a method of glaucoma evaluation has been performed for many years. Pattern VEP has shown good specificity and sensitivity in the detection of glaucoma in some studies, but other studies have not shown similar efficacy. Multifocal VEP can produce a topographical measure of glaucomatous damage and has been shown to be able to detect a similar number of defects in patients with glaucoma or ocular hypertension as compared with the visual field test. Despite promising data on these VEP test modalities in the assessment of glaucoma, multiple aspects of test administration make their routine use impractical in a clinical setting. New VEP testing modalities, such as short-duration transient VEP and isolated-check VEP, allow the test to be performed more quickly and easily. Further research on these more recent technologies may allow us to use VEP effectively in the diagnosis and management of glaucoma.

Steady-state PERG adaptation: a conspicuous component of response variability with clinical significance

PURPOSE

To investigate within-test variability of the steady-state PERG (SS-PERG).

METHODS

SS-PERGs were recorded in response to black-white horizontal gratings (1.6 cycles/deg, 98% contrast, 15.63 reversals/s, LED display, 25 deg square field, 800 cd/sqm mean luminance) using skin electrodes. PERG and noise (± reference) signals were averaged over 1024 epochs (~ 2.2 min) and Fourier analyzed to retrieve SS-PERG amplitude and phase. SS-PERGs were split into 16 partial averages (samples) of 64 epochs each, and corresponding amplitudes and phases combined in polar coordinates to assess their dispersion (within-test variability). To assess time-dependent variability, samples were clustered in four successive time segments of ~ 33 s each. Amplitude adaptation was defined as amplitude difference between initial and final clusters, and PERG phase adaptation as the corresponding phase difference. To determine the dynamic range of SS-PERG adaptation, recording was performed in normal controls of different age (n = 32) and patients with different severity of optic nerve dysfunction (early manifest glaucoma, EMG, n = 7; non-arteritic ischemic optic neuropathy, NAION, n = 5).

RESULTS

Amplitude adaptation was largest in younger controls (amplitude adaptation ÷ noise, SNR = 9.5, 95% CI 13.1, 5.9) and progressively decreased with increasing age (older subjects, SNR = 5.5, 95% CI 9.2, 1.8) and presence of disease (EMG: SNR = 2.4, 95% CI 3.5, 1.4; NAION: SNR = 1.9, 95% CI 6.5,-2.2). In 11 young subjects, amplitude adaptation was repeatable (test-retest in two sessions a week apart; intraclass correlation coefficient = 0.59). Phase adaptation was not significantly different from zero in all groups.

CONCLUSIONS

SS-PERG adaptation accounts for a sizeable portion of the within-test variability. As it has robust SNR, sufficient test-retest variability, and is altered in disease, it may have physiological and clinical significance. This study suggests that SS-PERG protocols should include adaptation in addition to SS-PERG amplitude and phase/latency.

Improved retinal and visual function following panmacular subthreshold diode micropulse laser for retinitis pigmentosa

Objectives

To examine the effect of subthreshold diode micropulse laser (SDM) on pattern electroretinography (PERG) and visual function in retinitis pigmentosa (RP).

Methods

The records of all patients (pts) undergoing SDM in a vitreoretinal subspecialty practice were reviewed. Inclusion criteria included the presence of RP evaluated before and after SDM by PERG. As a secondary outcome measure, the results of automated omnifield resolution perimetry (ORP) were also reviewed.

Results

All eyes undergoing SDM for RP were eligible study, including 26 eyes of 15 pts; seven male and eight female, aged 16–69 (avg. 47) years. Retinal function by PERG improved by all indices, with significant improvements in the 24° field signal latency measures; the MagD(µV)/ Mag(µV) ratio (P < 0.0001) and the MagD(µV) amplitude (P = 0.0003). ORP significantly improved by all indices (p = 0.02–0.002). Average best-corrected chart visual acuities improved from 0.6 to 0.4 logMAR units (p = 0.02). There were no adverse treatment effects.

Conclusions

SDM significantly improved chart visual acuity, mesopic logMAR visual acuity perimetry, and retinal function by PERG in RP without adverse treatment effects. Treatment responses indicate a significant capacity for rescue of dysfunctional retina. These results suggest that early and periodic treatment with SDM might slow disease progression and reduce long-term vision loss.

Three Dimensional Stimulus Source for Pattern Electroretinography in Mid- and Far-peripheral Retina

Purpose

The pattern electroretinogram (pERG) response reflects, in part, ganglion cell function. However, probing retinal ganglion cell (RGC) function in the mid- and far peripheral retina is difficult with conventional flat-panel pERG stimulus sources. A pattern stimulus source is presented for probing the peripheral retina. Peripheral pERG (ppERG) responses were evaluated versus luminance, reversal rate, and field subtended, and were compared with conventional pERG in healthy eyes.

Methods

Eleven normally-sighted subjects were recruited. A hemispherical surface was used to present a reversing checkerboard pattern to the peripheral retina, from approximately 35° to 85° of visual field, in all directions. Responses to stimuli presented to peripheral field sectors (superior, nasal, inferior, temporal) were also recorded. Conventional pERG responses were recorded on the same day. Amplitudes and implicit times of waveform peaks were evaluated.

Results

Robust pERG responses from peripheral retina resemble conventional pERG responses but with shorter implicit times and reduced positive component. Responses to high-luminance patterns include high-frequency components resembling flash ERG oscillatory potentials. Negative response component amplitudes increased with increasing pattern luminance, and decreased with increasing reversal rate.

Conclusions

Peripheral-field pERG responses are robust and repeatable; the unique response properties reflect differences between central and peripheral retina. Field-sector response ratios can be used to probe for sectoral dysfunction associated with disease.

Translational Relevance

The ppERG approach provides direct measurement of proximal retinal function beyond the fields probed by conventional perimetry and pERG, providing access to a relatively under studied part of the retina relevant to early stage glaucoma.

Head-down Posture in Glaucoma Suspects Induces Changes in IOP, Systemic Pressure, and PERG That Predict Future Loss of Optic Nerve Tissue

PURPOSE

To obtain pilot data on posture-induced changes of intraocular pressure (IOP), systemic pressure, and pattern electroretinogram (PERG) predictive of future optic nerve tissue loss glaucoma suspects (GSs).

METHODS

Mean peripapillary retinal fiber layer thickness (RNFLT) was measured with optical coherence tomography 2 times/year in 28 GS aged 58±8.9 years over 5.0±0.73 years. All patients had a baseline PERG, IOP, and brachial blood pressure measurements in the seated and -10 degrees head-down-body-tilt (HDT) position. Outcome measures were seated/HDT PERG amplitude and phase, IOP, mean arterial blood pressure, and estimated ocular perfusion pressure. An additional group of 11 similarly aged controls aged 56.9±13 years was tested for comparison.

RESULTS

Although all GS had initial RNFLT in the normal range, 9/28 of them developed significant (P<0.05) loss of mean RNFLT [thinners (T)] over the follow-up period as opposed to 19/28 who did not [nonthinners (NT)]. Significant (P<0.05) differences between similarly aged controls, NT, and T were found in PERG amplitude, PERG phase, mean arterial blood pressure, IOP, and ocular perfusion pressure. A nominal logistic regression using baseline PERG and hemodynamic variables was able to distinguish T from NT with an area under receiving operator characteristic of 0.89 (SE, 0.07).

CONCLUSIONS

Baseline PERG, IOP, and systemic blood pressure, together with their changes upon HDT, may have predictive value for future loss of optic nerve tissue in GS. This study supports the rationale for a full-scale clinical trial to identify patients at high risk of development of glaucoma.

Gene Therapy for Leber Hereditary Optic Neuropathy: Low- and Medium-Dose Visual Results

PURPOSE

To determine the effects of AAV2(Y444,500,730F)-P1ND4v2 in patients with Leber hereditary optic neuropathy (LHON).

DESIGN

Prospective open-label, unilateral single-dose, intravitreal injection of AAV2(Y444,500,730F)-P1ND4v2 per participant.

PARTICIPANTS

Fourteen patients with visual loss and mutated G11778A mitochondrial DNA.

METHODS

Intravitreal injection with the gene therapy vector AAV2(Y444,500,730F)-P1ND4v2 into 1 eye. Six participants with chronic bilateral visual loss lasting more than 12 months (group 1), 6 participants with bilateral visual loss lasting less than 12 months (group 2), and 2 participants with unilateral visual loss (group 3) were treated. Nine patients had at least 12 months of follow-up. Clinical testing included visual acuity, visual fields, optical coherence tomography, pattern electroretinography, and neuro-ophthalmic examinations. Generalized estimating equation methods were used for longitudinal analyses.

MAIN OUTCOME MEASURE

Loss of visual acuity.

RESULTS

For groups 1 and 2, month 12 average acuity improvements with treatment relative to baseline were 0.24 logarithm of the minimum angle of resolution (logMAR). Fellow eyes had a 0.09-logMAR improvement. A post hoc comparison found that at month 12, the difference between study eye minus fellow eye improvement in group 2 patients of 0.53 logMAR was greater than that observed in our prior acute natural history patients of 0.21 logMAR (P = 0.053). At month 18, the difference between study eye minus fellow eye improvement in our acute group 2 gene therapy patients of 0.96 was more than that observed in our prior acute natural history patients (0.17 logMAR; P < 0.001). Two patients demonstrated asymptomatic uveitis that resolved without treatment. Optical coherence tomography of treated eyes showed an average temporal retinal nerve fiber layer thickness of 54 μm before injection and 55 μm at month 12. For fellow eyes before injection, it was 56 μm, decreasing to 50 μm at month 12 (P = 0.013). Generalized estimating equations suggested that PERG amplitudes worsened more in treated eyes than in fellow eyes by approximately 0.05 μV (P = 0.009 exchangeable). No difference between eyes in outcomes of other visual function measures was evident.

CONCLUSIONS

Allotopic gene therapy for LHON at low and medium doses seems to be safe and does not damage the temporal retinal nerve fiber layer, opening the door next for testing of the high dose.

Next Generation PERG Method: Expanding the Response Dynamic Range and Capturing Response Adaptation

Purpose

To compare a new method for steady-state pattern electroretinogram (PERGx) with a validated method (PERGLA) in normal controls and in patients with optic neuropathy.

Methods

PERGx and PERGLA were recorded in a mixed population (n = 33, 66 eyes) of younger controls (C1; n = 10, age 38 ± 8.3 years), older controls (C2; n = 11, 57.9 ± 8.09 years), patients with early manifest glaucoma (G; n = 7, 65.7 ±11.6 years), and patients with nonarteritic ischemic optic neuropathy (N; n = 5, mean age 59.4 ± 8.6 years). The PERGx stimulus was a black-white horizontal grating generated on a 14 × 14 cm LED display (1.6 cycles/deg, 15.63 reversals/s, 98% contrast, 800 cd/m² mean luminance, 25° field). PERGx signal and noise were averaged over 1024 epochs (∼2 minutes) and Fourier analyzed to retrieve amplitude and phase. Partial averages (16 successive samples of 64 epochs each) were also analyzed to quantify progressive changes over recording time (adaptation).

Results

PERGLA and PERGx amplitudes and latencies were correlated (Amplitude R² = 0.59, Latency R² = 0.39, both P < 0.0001) and were similarly altered in disease. Compared to PERGLA, however, PERGx had shorter (16 ms) latency, higher (1.39×) amplitude, lower (0.37×) noise, and higher (4.2×) signal-to-noise ratio. PERGx displayed marked amplitude adaptation in C1 and C2 groups and no significant adaptation in G and N groups.

Conclusions

The PERGx high signal-to-noise ratio may allow meaningful recording in advanced stages of optic nerve disorders. In addition, it quantifies response adaptation, which may be selectively altered in glaucoma and optic neuropathy.

Translational Relevance

A new PERG method with increased dynamic range allows recording of retinal ganglion cell function in advanced stages of optic nerve disorders. It also quantifies the response decline during the test, an autoregulatory adaptation to metabolic challenge that decreases with age and presence of disease.

RE-PERG, a new procedure for electrophysiologic diagnosis of glaucoma that may improve PERG specificity

PURPOSE

A significant variability of the second harmonic (2ndH) phase of steady-state pattern electroretinogram (SS-PERG) in intrasession retest has been recently described in glaucoma patients (GP), which has not been found in healthy subjects. To evaluate the reliability of phase variability in retest (a procedure called RE-PERG or REPERG) in the presence of cataract, which is known to affect standard PERG, we tested this procedure in GP, normal controls (NC), and cataract patients (CP).

METHODS

The procedure was performed on 50 GP, 35 NC, and 27 CP. All subjects were examined with RE-PERG and SS-PERG and also with spectral domain optical coherence tomography and standard automated perimetry. Standard deviation of phase and amplitude value of 2ndH were correlated by means of one-way analysis of variance and Pearson correlation, with the mean deviation and pattern standard deviation assessed by standard automated perimetry and retinal nerve fiber layer and the ganglion cell complex thickness assessed by spectral domain optical coherence tomography. Receiver operating characteristics were calculated in cohort populations with and without cataract.

RESULTS

Standard deviation of phase of 2ndH was significantly higher in GP with respect to NC (P<0.001) and CP (P<0.001), and it correlated with retinal nerve fiber layer (r=-0.5, P<0.001) and ganglion cell complex (r=-0.6, P<0.001) defects in GP. Receiver operating characteristic evaluation showed higher specificity of RE-PERG (86.4%; area under the curve 0.93) with respect to SS-PERG (54.5%; area under the curve 0.68) in CP.

CONCLUSION

RE-PERG may improve the specificity of SS-PERG in clinical practice in the discrimination of GP.

Photopic Negative Response Obtained Using a Handheld Electroretinogram Device: Determining the Optimal Measure and Repeatability

Purpose

To determine the measure of the photopic negative response (PhNR) of the full-field electroretinogram (ERG) that exhibits the optimal level of test-retest repeatability, and examine its repeatability under different conditions using a handheld, nonmydriatic ERG system and self-adhering skin electrodes.

Methods

Multiple ERG recordings (using 200 sweeps each) were performed in both eyes of 20 normal participants at two different sessions to compare its coefficient of repeatability (CoR; where 95% of the test-retest difference is expected to lie) between different PhNR measures and under different testing conditions (within and between examiners, and between sessions).

Results

The ratio between the PhNR trough to b-wave peak and b-wave peak to a-wave trough amplitude (PhNR/B ratio) exhibited the lowest CoR relative to its effective dynamic range (30 ± 4%) when including three recordings. There were no significant changes in the PhNR/B ratio over seven measurements (4 right and 3 left eyes) at either session (P ≥ 0.100), or significant difference in its CoR between different testing conditions (P = 0.314).

Conclusion

The PhNR/B ratio was the measure that minimized variability, and its measurements using a novel handheld ERG system with self-adhering skin electrodes and the protocols described in this study were comparable under different testing conditions and over multiple recordings.

Translational Relevance

The PhNR can be measured for clinical and research purposes using a simple-to-implement technique that is consistent within and between visits, and also between examiners.

Bilateral Glaucomatous Optic Neuropathy Caused by Eye Rubbing

In this report, we describe a particular condition of a 52-year-old man who showed advanced bilateral glaucomatous-like optic disc damage, even though the intraocular pressure resulted normal during all examinations performed. Visual field test, steady-state pattern electroretinogram, retinal nerve fiber layer and retinal tomographic evaluations were performed to evaluate the optic disc damage. Over a 4-year observational period, his visual acuity decreased to 12/20 in the right eye and counting fingers in the left eye. Visual fields were severely compromised, and intraocular pressure values were not superior to 14 mm Hg during routine examinations. An accurate anamnesis and the suspicion of this disease represent a crucial aspect to establish the correct diagnosis. In fact, our patient strongly rubbed his eyes for more than 10 h per day. Recurrent and continuous eye rubbing can induce progressive optic neuropathy, causing severe visual field damage similar to the pathology of advanced glaucoma.

Can Variability of Pattern ERG Signal Help to Detect Retinal Ganglion Cells Dysfunction in Glaucomatous Eyes?

Objective. To evaluate variability of steady-state pattern electroretinogram (SS-PERG) signal in normal, suspected, and glaucomatous eyes. Methods. Twenty-one subjects with suspected glaucoma due to disc abnormalities (GS), 37 patients with early glaucoma (EG), and 24 normal control (NC) were tested with spectral-domain optical coherence tomography (SD-OCT), standard automated perimetry (SAP), and SS-PERG. Mean deviation (MD), pattern standard deviation (PSD), retinal nerve fiber layer (RNFL), and ganglionar complex cells (GCC) were evaluated. The SS-PERG was recorded five consecutive times and the amplitude and phase of second harmonic were measured. PERG amplitude and coefficient of variation of phase (CVphase) were recorded, and correlation with structural and functional parameters of disease, by means of one-way ANOVA and Pearson's correlation, was analysed. Results. PERG amplitude was reduced, as expression of retinal ganglion cells (RGCs) dysfunction, in EG patients and GS subjects compared to NC patients (P < 0.0001). CVphase was significantly increased in EG patients and GS subjects, compared to healthy (P < 0.0001), and it was also correlated with PSD (P = 0.0009), GCC (P = 0.028), and RNFL (P = 0.0078) only in EG patients. Conclusions. Increased intrasession variability of phase in suspected glaucomatous eyes may be a sign of RGCs dysfunction.

Retinal Neurodegeneration in db/db Mice at the Early Period of Diabetes

Purpose. To describe both the functional and pathological alternations in neurosensory retina in a murine model of spontaneous type 2 diabetes (db/db mouse). Methods. db/db (BKS/DB-/-) mice and heterozygous littermates (as control group) at various ages (12, 16, 20, 24, and 28 weeks) were inspected with pattern electroretinogram (PERG), fundus fluorescein angiography (FFA), and optical coherence tomography (OCT). Histological markers of neuroinflammation (IBA-1 and F4/80) were evaluated by immunohistochemistry. In addition, levels of retinal ganglion cell death were measured by terminal dUTP nick-end labeling (TUNEL). Results. Significant alternations of PERG responses and increased retinal ganglion cells (RGCs) apoptosis were observed in diabetic db/db mice for 20-week period when compared with control group. IBA-1 and F4/80 expression in microglia/macrophages became evidently for 24-week period, thus supporting the PERG findings. Furthermore, obvious thinning of nasal and dorsal retina in 28-week-old db/db mice was also revealed by OCT. No visible retinal microvascular changes were detected by FFA throughout the experiments on db/db mice. Conclusions. Diabetic retina underwent neurodegenerative changes in db/db mice, which happened at retinal ganglion cell layer and inner nuclear layer. But there was no obvious abnormality in retinal vasculature on db/db mice.

Adaptation of the steady-state PERG in early glaucoma

PURPOSE

Previous studies have shown that the onset of high-contrast, fast reversing patterned stimuli induces rapid blood flow increase in retinal vessels in association with slow changes of the steady-state pattern electroretinogram (PERG) signal. We tested the hypothesis that adaptive PERG changes of normal controls differed from those of glaucoma suspects and patients with early manifest glaucoma.

METHODS

Subjects were 42 glaucoma suspects (Standard Automated Perimetry-MD -0.89±1.8 dB), 22 early manifest glaucoma (MD -2.12±2.4 dB) with visual acuity of ≥20/20 and 16 age-matched normal controls from a previous study. The PERG signal was sampled every ~15 seconds over 4 minutes in response to gratings (1.6 cyc/degree, 100% contrast) reversing 16.28 times/s. Amplitude/phase values of successive PERG samples were fitted with a nonparametric locally weighted polynomial regression smoothing function to retrieve the initial and final values and calculate their difference (δ) and the residual SD around the fitted function. The magnitude of PERG adaptive change compared to random variability was calculated as log10 of percentage coefficient of variation (CoV)=100×residual SDr÷δ. Grand-average PERGs were also obtained by averaging all samples of the same series.

RESULTS

The grand-average PERG amplitude [analysis of variance (ANOVA), P=0.02], but not phase (ANOVA, P=0.63), decreased with increasing severity of disease. Adaptive changes [log10 (CoV)] of PERG amplitude were not significantly associated with disease severity (ANOVA, P=0.27) but adaptive changes [log10 (CoV)] of PERG phase were (ANOVA, P=0.037; linear trend, P=0.011).

CONCLUSIONS

The steady-state PERG signal displayed slow adaptive changes over time that could be isolated from random variability. PERG adaptive changes differed from those of grand-average PERGs (corresponding the standard steady-state PERG), thus representing a new source of biological information about retinal ganglion cell function that may have potential in the study of glaucoma and optic nerve diseases.

Relationship between transient and steady-state pattern electroretinograms: theoretical and experimental assessment

PURPOSE

We determined if the overlap of transient (tr) pattern electroretinograms (PERG(tr)) can explain the generation of the steady-state (SS) pattern electroretinogram (PERG(SS)), and investigated the relationship between the two types of responses.

METHODS

Slightly jittered pattern reversals were used to generate quasi SS (QSS) PERG(SS) responses from eight normal subjects, recorded using lower eyelid skin electrodes, at rates between 6.9 and 26.5 reversals per second (rps). Jittered quasi PERG(SS) were deconvolved using the frequency domain continuous loop averaging deconvolution method. Additionally, conventional PERG(tr) at 2.2 rps and PERG(SS) at each of the QSS stimulation rates were obtained from all subjects. Two synthetic PERG(SS) responses were constructed at each stimulation rate, one using the PERG(tr) obtained at that rate, and the other using the conventional 2.2 rps PERG(tr). Synthetic responses then were compared to the recorded PERG(SS) using amplitude, latency, and spectral measurements.

RESULTS

Findings indicate that the PERG(SS) obtained at SS rates can be predicted using the superposition of deconvolved tr PERGs at each particular rate. Although conventional PERG(tr) can explain PERG(SS) obtained at rates below 15.4 rps (≥ 97% correlation), for higher reversal rates only deconvolved responses obtained at that rate can produce the recorded SS responses (96% vs. 65% correlation at 26.5 rps).

CONCLUSIONS

The study shows that PERG(SS) results from the overlapping of tr PERG(tr) waveforms generated at that reversal rate. The first two peaks (N(SS) and P(SS)) of the PERG(SS) reflect N35 and P50 waves of the tr PERG(tr). The N95 amplitude is reduced at conventional (16 rps) SS rates, but contributes to the overall PERG(SS) amplitude.

Trial end points and natural history in patients with G11778A Leber hereditary optic neuropathy : preparation for gene therapy clinical trial

IMPORTANCE Establishing the natural history of G11778A Leber hereditary optic neuropathy (LHON) is important to determine the optimal end points to assess the safety and efficacy of a planned gene therapy trial. OBJECTIVE To use the results of the present natural history study of patients with G11778A LHON to plan a gene therapy clinical trial that will use allotopic expression by delivering a normal nuclear-encoded ND4 gene into the nuclei of retinal ganglion cells via an adeno-associated virus vector injected into the vitreous. DESIGN, SETTING, AND PARTICIPANTS A prospective observational study initiated in 2008 was conducted in primary and referral institutional practice settings. Participants included 44 individuals with G11778A LHON, recruited between September 2008 and March 2012, who were evaluated every 6 months and returned for 1 or more follow-up visits (6-36 months) as of August 2012. EXPOSURES Complete neuro-ophthalmic examination and main measures. MAIN OUTCOMES AND MEASURES Visual acuity, automated visual field testing, pattern electroretinogram, and spectral-domain optical coherence tomography. RESULTS Clinical measures were stable during the follow-up period, and visual acuity was as good as or better than the other visual factors used for monitoring patients. Based on a criterion of 15 or more letters from the Early Treatment Diabetic Retinopathy Study chart, 13 eyes of 8 patients (18%) improved, but 24 months after the onset of symptoms, any further improvements were to no better than 20/100. Acuity recovery occurred in some patients despite continued marked retinal nerve fiber layer thinning indistinguishable from that in patients who did not recover visual acuity. CONCLUSIONS AND RELEVANCE Spontaneous improvement of visual acuity in patients with G11778A LHON is not common and is partial and limited when it occurs, so improvements in vision with adeno-associated virus-mediated gene therapy of a synthetic wild-type ND4 subunit gene should be possible to detect with a reasonable sample size. Visual acuity appears to be the most suitable primary end point for the planned clinical trial.

Interocular amplitude and latency differences of pattern ERG and pattern VEP parameters

PURPOSE

To determine the normal interocular differences in amplitudes and peak times of the pattern electroretinograms (PERGs) and pattern visual evoked potentials (PVEPs) and to investigate whether the PERG and PVEP parameters correspond in lateral dominance or whether the eye-side distributions of the functional parameters are similar.

METHODS

The PERGs and PVEPs were recorded in healthy subjects (N = 77) according to the standards of the International Society for Clinical Electrophysiology of Vision, with the modification of the check size of the PERG to 0.5 degrees. This allows stimulation of the macular ganglion cells and their corresponding visual pathways in healthy subjects.

RESULTS

Comparison of the averaged higher and lower response amplitudes and the shorter and longer response peak times showed significant differences (p < 0.001) in both the PERG and the PVEP parameters (median [5 to 95%]): the P50 (1.92% [0 to 5.48%]) and N95 (2.06% [0 to 13.95%]) peak times and the P50 (11.82% [1.32 to 29.93%) and N95 (9.45% [1.17 to 30.38%]) amplitudes of the PERGs and the P100 (1.04% [0 to 4.15%]) and N135 (1.96% [0 to 12.36%]) peak times and the P100 (9.86% [1.26 to 29.76%]) and N135 (11.19% [1.18 to 29.99%]) amplitudes of the PVEPs. No significant correlation was found concerning the eye dominance of the PERG and PVEP parameters.

CONCLUSIONS

Our results reveal a significant interocular difference on PERG and PVEP recording, but this could not be ascribed to the anatomy of the retina and related visual pathways. If the difference between the eyes is not taken into account, misinterpretation may occur in a pathological process.

Unwrapping of transient responses from high rate overlapping pattern electroretinograms by deconvolution

OBJECTIVE

Due to overlapping, temporal information is mostly lost in high rate steady-state pattern electroretinograms (PERGSS). This study develops a deconvolution method and a display/recording system to "unwrap" PERGSS and obtain a transient, "per stimulus" response (PERGtr) regardless of reversal rate.

METHODS

Processing and instrumentation, including high temporal resolution display and acquisition were developed for deconvolving PERGs acquired at high rates by slight jittering of reversal onsets at a given mean rate.

RESULTS

The system was successfully tested at eight rates from 2.2 to 78.1rps. At medium rates (17.4-41.2rps) recordings with conventional morphology (N35-P50-N95) but earlier peaks and higher amplitudes were extracted up to 40rps. At higher rates, smaller triphasic responses were obtained, exhibiting similar peak latencies, but reversed polarity. Oscillating potentials (OPs) were also recorded at all rates after deconvolution.

CONCLUSIONS

Transient PERGs and OPs can be extracted from quasi steady-state PERG recordings obtained at high rates with a deconvolution algorithm using high temporal resolution display and acquisition systems.

SIGNIFICANCE

The methodology to extract transient and oscillatory responses from steady-state PERGs could be useful in understanding high rate responses and diagnosis of various retinal diseases by revealing temporal information on waveform components which cannot be normally observed.