Correlation between photopic negative response of focal electroretinograms and local loss of retinal neurons in glaucoma

Correlation Between Optical Coherence Tomography and Photopic Negative Response of Flash Electroretinography in Ganglion Cell Complex Assessment in Glaucoma Patients

Purpose

To investigate the correlation between the photopic negative response (PhNR) of the light-adapted flash electroretinography (ERG) and measurements of standard automated perimetry (SAP) and optical coherence tomography (OCT) in assessment of retinal ganglion cells’ (RGCs) affection in glaucoma.

Patients and Methods

A cross-sectional study included 40 eyes of glaucoma patients and 40 eyes of age- and gender-matched normal subjects. Participants underwent a complete ophthalmologic assessment, SAP, OCT, and light-adapted flash ERG using the extended PhNR protocol of the International Society for Clinical Electrophysiology of Vision (ISCEV). Glaucomatous eyes were divided into 3 subgroups: mild (n = 15), moderate (n = 11) and severe glaucoma (n = 14) according to the mean deviation (MD) of SAP. Measurements of SAP, OCT and ERG parameters were analyzed, and correlations between PhNR measurements and other study measurements were evaluated.

Results

PhNR amplitudes and PhNR/b-wave ratios were significantly reduced in glaucoma cases compared to healthy controls, and they showed a significant and progressive decline across the three glaucoma subgroups (P < 0.05). An exception to this is PT (b-wave peak to PhNR trough) PhNR amplitude where its reduction was statistically non-significant when comparing between controls and mild glaucoma cases (P = 0.178), and between moderate and severe glaucoma cases (P = 0.714). PhNR amplitudes and PhNR/b-wave ratios correlated significantly with SAP and OCT parameters (P < 0.05).

Conclusion

PhNR correlates well with SAP and OCT parameters in glaucoma assessment. PhNR could be a valuable supplementary tool for objective assessment of the RGCs’ function in glaucoma.

Visual function tests for glaucoma practice - What is relevant?

Glaucoma represents one of the most important ocular diseases causing irreversible ganglion cell death. It is one of the most common causes of visual impairment and morbidity in the elderly population. There are various tests for measuring visual function in glaucoma. While visual field remains the undisputed method for screening, diagnosis, and monitoring disease progression, other tests have been studied for their utility in glaucoma practice. This review discusses some of the commonly used tests of visual function that can be routinely used in clinics for glaucoma management. Among the various modalities of testing visual function in glaucoma, this review highlights the tests that are most clinically relevant.

Significant correlations between focal photopic negative response and focal visual sensitivity and ganglion cell complex thickness in glaucomatous eyes

PURPOSE

To determine whether there are significant correlations between the focal photopic negative response (PhNR), the focal visual sensitivity and the ganglion cell complex (GCC) thickness in glaucomatous eyes.

STUDY DESIGN

Single-center observational study.

METHODS

Fifty-two eyes of 52 patients (71.4 ± 9.42 years) with clinically diagnosed open angle glaucoma were studied. Thirty-six age-matched normal subjects served as controls. The focal PhNR of the focal macular electroretinograms (fmERGs) were elicited by a 15° circular, a superior semicircular or an inferior semicircular stimulus centered on the fovea. The thickness of the GCC was measured in the corresponding retinal areas in the spectral-domain optical coherence tomographic images. The visual sensitivities (dB) were measured by microperimetry at the retinal area where the fmERGs were elicited and were converted to liner values (1/Lambert).

RESULTS

The focal PhNR amplitudes were significantly correlated with the visual sensitivities of the full-circle (R = 0.532), the superior (R = 0.530) and inferior (R = 0.526) semicircular responses (P < 0.0001). The GCC thickness was correlated with the visual sensitivities in the same areas with stronger correlations (R = 0.700, 0.759 and 0.650, respectively; P < 0.0001). The focal PhNR amplitudes were proportionally reduced with the thinning of the GCC thickness (R = 0.494, 0.518 and 0.511, respectively; P < 0.0001).

CONCLUSIONS

The significant correlations between the focal PhNR amplitudes, the focal visual sensitivities and the GCC thickness indicate that these may be good biomarkers to track the changes in the physiology and anatomy of the macular area in glaucomatous eyes.

Relationship between structural and functional changes in glaucomatous eyes: a multifocal electroretinogram study

Background

The nasal to temporal amplitudes ratio (N/T) of multifocal electroretinography (mfERG) scans measured within 5° of the macula can be used to detect glaucomatous change. The photopic negative response (PhNR) of mfERG elicited by a circular stimulus centered on the fovea was significantly reduced in eyes with glaucoma. The PhNR to B-wave ratio (PhNR/B) is the optimal measure of the PhNR. However, clinical superiority for evaluating glaucoma patients has not been determined between N/T and PhNR/B yet.

Methods

For morphological assessments, ganglion cell complex (GCC) in six regions and the average were measured by optical coherence tomography (OCT). For functional assessment, Humphrey visual fields (VF) with mean sensitivities (MT) and mfERG scans with parameters of N/T and the multifocal photopic negative response to B-wave ratio (mfPhNR/B) were measured. Sixty-nine eyes of 44 glaucoma patients were included and correlations between mfERG parameters and OCT or VF parameters were evaluated.

Results

The mean age of patients was 59.4 years. The mean deviation for all eyes obtained with the VF 30–2 and VF 10–2 was − 7.00 and − 6.31 dB, respectively. Significant correlations between GCC thickness or VF parameter and the N/T were found, especially in the inferior and inforotemporal retinal areas corresponding to superior and superonasal VF sectors (GCC vs N/T; coefficient = − 7.916 and − 7.857, and MT vs N/T; coefficient = − 4.302 and − 4.437, in the inferior and inforotemporal retinal areas, respectively, all p values < 0.05). However, similar associations were not obtained between mfPhNR/B and OCT or VF parameters. The mfPhNR/B only in the inferotemporal sector was significantly correlated with the average thickness of GCC (coefficient = 4.823, P = 0.012).

Conclusions

The N/T was correlated with GCC and VF in more numbers of measurement areas than the mfPhNR/B in the current study, however, a future study modifying the stimuli and amplitudes to obtain the spatial correspondence to OCT and VF measurement will be required to evaluate the value of mfERG.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12886-021-02061-8.

Comparison of the Humphrey Field Analyzer and Photopic Negative Response of Focal Macular Electroretinograms in the Evaluation of the Relationship Between Macula Structure and Function

Purpose: To investigate the association between macular inner retinal layer thickness and macula visual field (VF) mean deviation as measured by the Humphrey Field Analyzer (HFA) or macular function as measured by focal macular electroretinograms (ERGs) in patients with glaucoma.

Methods: The participants in this cross-sectional study were 71 patients with glaucoma and 10 healthy controls. Macular inner retinal layer thickness and function were measured in all participants using optical coherence tomography (OCT) and HFA or focal macular ERGs, respectively. Macular OCT images were segmented into the macular retinal nerve fiber layer (mRNFL), macular ganglion cell layer/inner plexiform layer (GCL/IPL), and ganglion cell complex (GCC). Spearman correlation analysis was used to assess the relationship between macular inner retinal layer thickness and function.

Results: Focal macular ERGs were composed of a negative wave (N1), a positive wave (P1), and a slow negative wave (N2). The N2 response density was significantly reduced in eyes with glaucoma, and was significantly associated with the thickness of the mRNFL (R = 0.317), GCL/IPL (R = 0.372), or GCC (R = 0.367). The observed structure–function relationship was also significantly correlated with the HFA VF mean deviation for each thickness [mRNFL (R = 0.728), GCL/IPL (R = 0.603), or GCC (R = 0.754)].

Conclusions: Although a significant correlation was found between the N2 response density and the thickness of the macular inner layer, the observed structure–function relationship with the mean deviation of the HFA VF was higher than that of the N2 response density.

Relationships between the vascular structure and neural function of the macula in patients with diabetes mellitus

PURPOSE

To determine the significance of the correlation between the vascular structure and neural function of the macula in patients with diabetes mellitus.

STUDY DESIGN

Single-center observational study.

PATIENTS AND METHODS

Ninety eyes of 90 diabetic patients with an average (SD) age of 63.5 (3.8) years were studied. Fifty of the eyes had no clinically apparent diabetic retinopathy (non-DR), and 40 eyes had mild-to-moderate nonproliferative DR (NPDR). Thirty age-matched healthy individuals were also studied in the same way. Swept-source optical coherence tomography angiography (OCTA) was performed to obtain 3 × 3-mm en face images of the posterior pole of the eye. The vascular densities (VDs) of the superficial capillary plexus (SCP) and the deep capillary plexus (DCP) were determined. The focal macular electroretinograms (ERGs) elicited by a 15° circular stimulus centered on the fovea were recorded. The amplitudes of the a- and b-waves, sum of the oscillatory potentials (ΣOPs), photopic negative response (PhNR), and implicit times of the individual OPs (OP1-OP3) were measured.

RESULTS

The VDs of the SCP and DCP were reduced in eyes with advanced DR (P < .01 for SCP). The implicit times of OP1-OP3 were significantly prolonged in eyes with a lower VD of the SCP and DCP in the non-DR group (P < .05). The amplitudes of the ΣOPs were significantly smaller in eyes with a reduced VD of the SCP and DCP in the NPDR group (P < .05). The correlation coefficients were higher for the OP implicit times than for the ΣOP amplitudes in the non-DR group.

CONCLUSIONS

The OPs of the focal macular ERG are smaller with prolonged implicit times in association with capillary loss in the macula of diabetic patients. The implicit times are the most sensitive functional parameter that reflects the early changes of the microvasculature in the macula caused by diabetes.

The Relationship Between the Photopic Negative Response and Retinal Ganglion Cell Topography

Purpose

To assess the topographic relationship between the photopic negative response (PhNR) and retinal ganglion cell distribution in healthy individuals.

Method

Data was recorded from 16 healthy participants. The amplitude of PhNRs obtained in response to focal long duration (250 ms) and brief flash (5 ms), red (660 nm) on blue (469 nm) stimuli of increasing size (5° - full field) were measured. The number of retinal ganglion cell receptive fields (RGCf) in each stimulus area was established from the literature and regression analysis used to determine the relationships between: PhNR amplitude and number of RGCfs stimulated, PhNR density and the RGCf density and response per RGCf as a function of eccentricity.

Results

The overall amplitude of the PhNR increased with stimulus size and the response density declined from ∼0.1 μV/deg in the macular region to ∼0.003 μV/deg approximately 45° from the fovea. Contrary to expectations, the relationship between the PhNR and number of RGCf was nonlinear, the response from more eccentric neurons being about three times greater than those in the macular region.

Conclusions

Although the amplitude of the PhNR broadly maps on to the topographic distribution of RGCf the increase in PhNR amplitude with increasing eccentricity is only partly explained by RGCf numbers. Increases in the PhNR amplitude may be due to topographic variations in the contributions from other non-RGC neurons, as well as eccentricity-related morphologic and physiologic differences in RGCs.

Correlation between macular structure and function in patients with age-related macular degeneration treated with intravitreal ranibizumab: 12-month-results

PURPOSE

To determine the significance of the correlation between optical coherence tomographic (OCT) findings and focal macular electroretinograms (fmERG) at 12 months after beginning intravitreal injections of ranibizumab (IVR) in eyes with age-related macular degeneration (AMD).

STUDY DESIGN

Prospective, clinical study.

METHOD

We studied 28 eyes of 28 patients with AMD treated with IVR at monthly intervals for the initial three months. Additional IVR was given according to a pro re nata (PRN) regimen. OCT and fmERGs were performed preoperatively and at 3 and 12 months postoperatively. The fmERGs were elicited by a 15° white stimulus spot centered on the fovea. The thickness of the inner, middle, and outer layers of the retina and also of the serous retinal detachment (SRD) and pigment epithelial detachment (PED) in the horizontal and vertical meridians at 1.2 mm from the fovea (parafoveal) were measured in the OCT images.

RESULTS

The b-wave amplitude at 12 months was significantly correlated with the thicknesses of the outer retinal layer, SRD, and PED (P=0.001-0.02). Multiple regression analyses showed that the outer retinal layer thickness was an independent determinant (P= 0.0001). The changes in the b-wave amplitude between the baseline and 12 months were significantly correlated with the changes in the SRD thickness (P=0.006). The changes in the b-wave amplitude during the PRN period were significantly correlated with the changes in the PED thickness (P=0.02).

CONCLUSIONS

At 12 months after beginning treatment, the reduction in the SRD thickness affects macular function recovery. As recurrences of the PED can occur during the PRN period, control of the PED is necessary to obtain good macular function for the long term.

Test-retest reliability of the multifocal photopic negative response

PURPOSE

To assess the test-retest reliability of the multifocal photopic negative response (mfPhNR) of normal human subjects.

METHODS

Multifocal electroretinograms were recorded from one eye of 61 healthy adult subjects on two separate days using a Visual Evoked Response Imaging System software version 4.3 (EDI, San Mateo, California). The visual stimulus delivered on a 75-Hz monitor consisted of seven equal-sized hexagons each subtending 12° of visual angle. The m-step exponent was 9, and the m-sequence was slowed to include at least 30 blank frames after each flash. Only the first slice of the first-order kernel was analyzed. The mfPhNR amplitude was measured at a fixed time in the trough from baseline (BT) as well as at the same fixed time in the trough from the preceding b-wave peak (PT). Additionally, we also analyzed BT normalized either to PT (BT/PT) or to the b-wave amplitude (BT/b-wave). The relative reliability of test-retest differences for each test location was estimated by the Wilcoxon matched-pair signed-rank test and intraclass correlation coefficients (ICC). Absolute test-retest reliability was estimated by Bland-Altman analysis.

RESULTS

The test-retest amplitude differences for neither of the two measurement techniques were statistically significant as determined by Wilcoxon matched-pair signed-rank test. PT measurements showed greater ICC values than BT amplitude measurements for all test locations. For each measurement technique, the ICC value of the macular response was greater than that of the surrounding locations. The mean test-retest difference was close to zero for both techniques at each of the test locations, and while the coefficient of reliability (COR-1.96 times the standard deviation of the test-retest difference) was comparable for the two techniques at each test location when expressed in nanovolts, the %COR (COR normalized to the mean test and retest amplitudes) was superior for PT than BT measurements. The ICC and COR were comparable for the BT/PT and BT/b-wave ratios and were better than the ICC and COR for BT but worse than PT.

CONCLUSION

mfPhNR amplitude measured at a fixed time in the trough from the preceding b-wave peak (PT) shows greater test-retest reliability when compared to amplitude measurement from baseline (BT) or BT amplitude normalized to either the PT or b-wave amplitudes.

Structures affecting recovery of macular function in patients with age-related macular degeneration after intravitreal ranibizumab

PURPOSE

To determine the retinal structures affecting the recovery of macular function in patients with exudative age-related macular degeneration (AMD) treated with intravitreal ranibizumab (IVR).

METHOD

Thirty eyes of 30 patients with exudative AMD who were treated with IVR at monthly intervals for 3 months were studied. Focal macular electroretinograms (fmERGs) and spectral-domain optical coherence tomography (SD-OCT) were performed before and 3 months after beginning the IVR injections. The fmERGs were elicited by a 15° white stimulus spot centered on the fovea. The thickness of different retinal layers, presence of a serous retinal detachment (SRD), and presence of a pigment epithelial detachment (PED) at the fovea was determined in the SD-OCT images. Measurements were made of the inner, middle, and outer layers of the retina and also of the SRD and PED in the horizontal and vertical meridians at 1.2 mm from the fovea (parafoveal regions). The significance of the correlations between these structural parameters and the a-wave amplitude of the fmERG was determined.

RESULTS

There was no significant correlation between the structural parameters of the fovea and the a-wave amplitude. In the parafoveal regions, the thickness of the outer retinal layer was significantly correlated with an increase of the a-wave amplitude (R = 0.56, P = 0.001). In addition, the SRD thickness was negatively and significantly correlated with the a-wave amplitude (R = -0.54, P = 0.002). The change in the parafoveal SRD thickness after IVRs was the only independent determinant of recovery of the a-wave amplitude after the treatments (P < 0.05).

CONCLUSIONS

The macular function measured by the fmERGs was determined by the parafoveal outer layer and SRD thickness in patients with exudative AMD. Of these, changes in the SRD thickness by IVRs most strongly affected the recovery of macular function.

Alterations of photopic negative response of multifocal electroretinogram in patients with glaucoma

PURPOSE

To determine the effect of glaucoma on the multifocal electroretinograms (ERGs) (mfERGs) elicited by low-frequency stimuli.

METHODS

Forty-four patients with open-angle glaucoma and 15 normal subjects were studied. The stimulus frequency was 6.25 Hz, and the stimulus was a circle with a 6.8° radius that was centered on the fovea (center). MfERGs were also elicited by a quarter of an annulus placed around the macula (superior/temporal; inferior/temporal; superior/nasal; and inferior/nasal quadrants). The radius of the inner border of the annulus was 6.8° and that of the outer border was 20°. The actual sensitivity was determined by standard automated perimetry. The thickness of the ganglion cell complex (GCC) was measured by optical coherence tomography.

RESULTS

The mfERGs consisted of a negative wave (N1) followed by a positive wave (P1), and followed by a slow negative wave (N2). There were no significant differences in the response densities of N1 and P1 between the normal control and glaucomatous eyes in any areas. The N2 response density was significantly reduced with the severity of glaucoma in the center. There was a significant reduction even at an early stage of glaucoma compared to control values. In the center, the N2 response density was significantly correlated with the GCC thickness and mean sensitivity. However, in other stimulus areas, there was no significant reduction of any components of the mfERGs.

CONCLUSIONS

These results suggest that the N2 component of the slow-sequence mfERGs is affected by glaucoma in the central retinal area. Regional variations in the contribution of the retinal ganglion cell activity to the N2 should be considered when examining the mfERGs in glaucoma patients.

Differences in functional loss associated with ganglion cell complex thinning between patients with glaucoma and postoperative macular hole

PURPOSE

To compare the changes in the photopic negative response (PhNR) of the focal macular electoretinogram (fmERG) caused by a thinning of the ganglion cell complex (GCC) between patients with open angle glaucoma (OAG) and after successful macular hole (MH) surgery.

METHODS

Twenty-seven eyes of 27 OAG patients (OAG group), 28 eyes of 28 MH patients (MH group) and 23 eyes of 23 normal volunteers (control group) were studied. The OAG patients had early stage of glaucoma. The MH patients had been successfully treated with vitrectomy 12 months earlier. The averaged GCC thickness in the macular area (15 degree in a diameter) was measured by SD-OCT. The fmERGs were elicited by a 15° stimulus centered on the fovea.

RESULTS

The GCC was significantly thinner in the OAG and MH groups than in the control group (p < 0.0001). The PhNR amplitude and PhNR/b-wave amplitude ratio were significantly reduced in the OAG group compared to the control (p < 0.0001), while no significant reduction of the PhNR amplitude was observed in the MH group. The PhNR amplitude and PhNR/b-wave amplitude ratio were significantly correlated with the GCC thickness in the OAG group (R(2 )= 0.741 for the PhNR amplitude, R(2 )= 0.564 for the PhNR/b-wave amplitude ratio, p < 0.0001 for both). There were significant differences in the slopes of regression lines plotting the GCC thickness and the PhNR amplitude (p < 0.05) or the PhNR/b-wave amplitude ratio (p < 0.0005) between the OAG and MH groups.

CONCLUSIONS

The thinning of the GCC affects the RGC function in the macula area differently for patients with OAG and patients after MH closure.

Clinical applications of the photopic negative response to optic nerve and retinal diseases

The photopic negative response (PhNR) in response to a brief flash is a negative-going wave following the b-wave of the cone electroretinogram (ERG) that is driven by retinal ganglion cells (RGCs). The function of RGCs is objectively evaluated by analysing the PhNR. We reviewed articles regarding clinical use of the PhNR. The PhNR was well correlated with the visual sensitivity obtained by standard automated perimetry and morphometric parameters of the inner retina and optic nerve head in optic nerve and retinal diseases. Moreover, combining the PhNR with focal or multifocal ERG techniques enables the objective assessment of local function of RGCs. The PhNR is therefore likely to become established as an objective functional test for optic nerve and retinal diseases involving RGC injury.

Retinal ganglion cell function after repeated intravitreal injections of ranibizumab in patients with age-related macular degeneration

Background

The purpose of this study was to evaluate the safety of intravitreal ranibizumab injection in patients with age-related macular degeneration.

Materials and methods

We examined retinal ganglion cell function using the photopic negative response of the electroretinogram (ERG) in patients with age-related macular degeneration (AMD) treated with intravitreal injections of ranibizumab. We studied 32 eyes of 32 patients with AMD and aged 50–84 years with a mean of 71 years. An intravitreal ranibizumab injection was given three times at monthly intervals. Additional injections were given according to an optical coherence tomography-guided variable dosing regimen. ERG recordings were made before treatment (baseline) and at 3, 6, 9, and 12 months postoperatively. Full-field cone ERGs were elicited by red stimuli on a blue background. The focal macular ERGs were elicited by a 15 degree white stimulus spot centered on the macular region. We measured the amplitudes of the a and b waves, oscillatory potentials, and the photopic negative response of the full-field cone and focal macular ERGs.

Results

Visual acuity was significantly better than the baseline acuity, and macular thickness was significantly reduced after the intravitreal injections of ranibizumab. The amplitudes and implicit times of each wave of the full-field cone ERGs were not significantly changed after intravitreal ranibizumab injections. However, the amplitudes of each wave of the focal macular ERGs were increased after the injections. The implicit times of the a and b waves of the focal macular ERGs were significantly shortened after intravitreal injections of ranibizumab. The ratio of the full-field and focal photopic negative response/b-wave amplitude was not significantly changed after the injections.

Conclusion

The amplitudes of the focal macular ERGs, including the photopic negative response improved after repeated intravitreal ranibizumab injections, accompanied by a recovery of visual acuity and macular structure. The results of the full-field cone ERGs indicate that retinal ganglion cell function was not altered by repeated intravitreal ranibizumab injection.

On- and off-response ERGs elicited by sawtooth stimuli in normal subjects and glaucoma patients

The aim of this study is to measure the on- and off-responses and their response asymmetries elicited by sawtooth stimuli in normal subjects and glaucoma patients. Furthermore, the correlation between the ERGs and other functional and structural parameters are investigated. Full-field stimuli were produced using a Ganzfeld bowl with Light Emitting Diodes (LEDs) as light sources. On- and off-response ERGs were recorded from 17 healthy subjects, 12 pre-perimetric and 15 perimetric glaucoma patients using 4-Hz luminance rapid-on and rapid-off sawtooth stimuli (white light; mean luminance 55 cd/m(2)) at 100% contrast. The on- and off-responses were added to study response asymmetries. In addition, flash ERGs were elicited by red stimuli (200 cd/m(2)) on a blue background (10 cd/m(2)). The mean deviations (MD) of the visual field defects were obtained by standard automated perimetry. The retinal nerve fibre layer thickness (RNFLT) was measured with Spectral Domain Optical Coherence Tomography (SOCT). We studied the correlation between ERG response amplitudes, visual field mean deviation (MDs) and RNFLT values. The on-responses showed an initial negative (N-on) followed by a positive (P-on), a late positive (LP-on) and a late negative responses (LN-on). The off-responses showed an initial positive (P-off) a late positive (LP-off) and a late negative response (LN-off). The addition of on- and off-responses revealed an initial positive (P-add) and a late negative response (LN-add). The on-response components (N-on, P-on and LN-on) in the glaucoma patients were relatively similar to those of the control subjects. However, the LP-on was significantly elevated (p = 0.03) in perimetric patients. The LP-off was significantly elevated (p < 0.001), and the amplitude of LN-off was significantly reduced in perimetric patients (p = 0.02). The LN-add amplitude was significantly reduced (p < 0.001) and delayed (p = 0.03) in perimetric patients. The amplitudes of the LN-off and LN-add ERG components were significantly correlated with the PhNR in the flash ERG (LN-off: p = 0.01; LN-add: p < 0.001) and with RNFLT (LN-off: p = 0.006; LN-add: p = 0.001). On- and off-response ERGs and their response asymmetries, elicited by sawtooth stimuli, are altered in the glaucoma patients. The late components are affected. Changes in the late negative components are correlated with structural and other functional changes.

The photopic negative response of the flash electroretinogram in multiple sclerosis

PURPOSE

To use the photopic electroretinogram (ERG) to evaluate retinal function in eyes of multiple sclerosis (MS) patients with and without a history of optic neuritis (ON) and to compare the functional and structural status of the inner retina.

METHODS

Full-field ERG responses to brief red flashes (0.04-2.8 cd · s/m²) on a rod-saturating blue background were recorded from 51 MS patients and 33 age-matched control subjects. In patients, perimetry was performed and peripapillary retinal nerve fiber layer thickness (RNFLT) was assessed by optical coherence tomography (OCT) and scanning laser polarimetry (SLP). MS eyes were separated into groups: "ON >6" months (n = 25), "ON <6" months (n = 29), and "no ON" (n = 33) based on positive or negative history of ON and time since the last episode. Thirteen ON<6 eyes were re-evaluated 1 year later.

RESULTS

PhNR amplitudes were lower in ON>6, ON<6, and no-ON eyes (mean ± SD, 17.3 ± 7.6, 16.0 ± 6.5, and 23.8 ± 9.3 μV, respectively), than in control eyes (29.8 ± 6.5 μV; P < 0.001) for a standard stimulus of 1.42 cd · s/m²; a- and b-wave amplitudes were unaffected. PhNR amplitudes correlated with visual fields mean deviation (MD) in ON>6 (r² = 0.43; P < 0.001) and no-ON eyes (r² = 0.10; P < 0.05), with similar results for weaker stimuli. PhNR amplitudes correlated with RNFLT in ON>6 eyes: OCT (r² = 0.52; P < 0.0001) and SLP (r² = 0.51; P < 0.01); and in no-ON eyes, OCT (r² = 0.21; P < 0.01) and SLP (r² = 0.17; P < 0.05). ON<6 amplitudes did not correlate significantly with other measures, but increased after 1 year by 5.1 ± 3.1 μV (P < 0.001), visual fields MD increased by 1.8 ± 2.3 dB (P < 0.05), and RNFL loss persisted.

CONCLUSIONS

Photopic ERG PhNR amplitudes in MS patients are significantly reduced in eyes with and without a history of ON.

Hemispherical focal macular photopic negative response and macular inner retinal thickness in open-angle glaucoma

PURPOSE

To investigate in open-angle glaucoma the focal macular photopic negative response and spectral-domain optical coherence tomography measurements of retinal thicknesses in the superior and inferior macula.

DESIGN

Comparative case series.

METHODS

We studied 63 eyes of 63 patients with open-angle glaucoma and 41 normal eyes of 41 volunteers. Photopic negative responses were recorded using a spotlight (diameter of 15 degrees of circle), projected onto the whole or superior or inferior macula. Ganglion cell complex (nerve fiber + ganglion cell + inner plexiform layers) thickness was measured using spectral-domain optical coherence tomography.

RESULTS

Mean photopic negative response amplitude over the entire macula was significantly (P < .001) decreased compared with that of controls in eyes with early (n = 24; to 62.1%), moderate (n = 21; to 57.2%), and severe (n = 18; to 49.3%) open-angle glaucoma, but not significantly different among eyes with various stages of glaucoma. Mean ganglion cell complex thickness was significantly (P < .001) decreased compared with that of controls in eyes with early (86.0%), moderate (78.3%), and severe (71.2%) glaucoma, and thinning correlated positively with glaucoma severity (P < .001). Mean photopic negative response amplitude correlated significantly (P < .001) with ganglion cell complex thickness over the whole, superior, and inferior macular areas (r = 0.57 to 0.74). In 16 eyes without visual field defect in the inferior hemifield, mean photopic negative response amplitude was 56.5% of normal (P < .001), and mean ganglion cell complex thickness in the superior macula was 92.1% of normal (P = .004).

CONCLUSIONS

Focal macular photopic negative response amplitude correlates with ganglion cell complex thickness, but decreases more abruptly in early glaucoma compared with ganglion cell complex thickness.

Comparison of photopic negative response of full-field and focal electroretinograms in detecting glaucomatous eyes

Purpose. To compare the photopic negative response (PhNR) of the full-field electroretinogram (ERG) to the PhNR of the focal ERGs in detecting glaucoma. Methods. One hundred and three eyes with glaucoma and 42 normal eyes were studied. Full-field ERGs were elicited by red stimuli on a blue background. The focal ERGs were elicited by a 15° white stimulus spot centered on the macula, the superotemporal or the inferotemporal areas of the macula. Results. In early glaucoma, the areas under the receiver operating characteristic curves (AUCs) were significantly larger for the focal PhNR (0.863–0.924) than those for the full-field PhNR (0.666–0.748) (P < .05). The sensitivity was significantly higher for the focal PhNR than for the full-field PhNR in early (P < .01) and intermediate glaucoma (P < .05). In advanced glaucoma, there was no difference in the AUCs and sensitivities between the focal and full-field PhNRs. Conclusions. The focal ERG has the diagnostic ability with higher sensitivity in detecting early and intermediate glaucoma than the full-field ERG.