A comparison of multifocal ERG and frequency domain OCT changes in patients with abnormalities of the retina

A simplification of intricate multifocal electroretinogram understanding: A mini-review

Variation of multifocal electroretinogram (mfERG) data presentation in existing scientific publications is a challenge for eye care practitioners to apply the scientific information for evidence-based practice in patient management. This review offers an overview of the mfERG data presentation types. Eight types of data presentation in the form of a table, scatter plot, line graph, bar graph/box plot, single waveform/a group of waveforms, trace array topography, three-dimensional topography, and two-dimensional topography are identified. The table format is used to provide the exact values. Line graphs, scatter, and box plots offer information about the relationship of mfERG values. Waveforms are helpful for comparison between groups or conditions. Topographies outline the retinal, especially the specific localized retinal abnormalities. An infographic of fundamental mfERG electrical response with definitions and clinical indications is provided to bridge the gap between researchers and clinicians to facilitate efficient clinical application.

Novel Machine-Learning Based Framework Using Electroretinography Data for the Detection of Early-Stage Glaucoma

Purpose

Early-stage glaucoma diagnosis has been a challenging problem in ophthalmology. The current state-of-the-art glaucoma diagnosis techniques do not completely leverage the functional measures' such as electroretinogram's immense potential; instead, focus is on structural measures like optical coherence tomography. The current study aims to take a foundational step toward the development of a novel and reliable predictive framework for early detection of glaucoma using machine-learning-based algorithm capable of leveraging medically relevant information that ERG signals contain.

Methods

ERG signals from 60 eyes of DBA/2 mice were grouped for binary classification based on age. The signals were also grouped based on intraocular pressure (IOP) for multiclass classification. Statistical and wavelet-based features were engineered and extracted. Important predictors (ERG tests and features) were determined, and the performance of five machine learning-based methods were evaluated.

Results

Random forest (bagged trees) ensemble classifier provided the best performance in both binary and multiclass classification of ERG signals. An accuracy of 91.7 and 80% was achieved for binary and multiclass classification, respectively, suggesting that machine-learning-based models can detect subtle changes in ERG signals if trained using advanced features such as those based on wavelet analyses.

Conclusions

The present study describes a novel, machine-learning-based method to analyze ERG signals providing additional information that may be used to detect early-stage glaucoma. Based on promising performance metrics obtained using the proposed machine-learning-based framework leveraging an established ERG data set, we conclude that the novel framework allows for detection of functional deficits of early/various stages of glaucoma in mice.

Impacts of intravitreal anti-VEGF therapy on retinal anatomy and neurophysiology in diabetic macular edema

PURPOSE

To evaluate anatomical and neuroretinal functional aspects in patients with diabetic macular edema (DME) after intravitreal anti-vascular endothelial growth factor (VEGF) therapy, in particular aflibercept.

MATERIALS AND METHODS

This prospective single-centered interventional study was performed at Afyonkarahisar Health Science University Faculty of Medicine, Department of Ophthalmology, where 32 eyes of 32 patients with DME were investigated. All patients received five intravitreal aflibercept injections on a monthly basis and were followed up for ≥ 6 months. After a comprehensive ophthalmological examination, including the measurements of visual acuity and intraocular pressure, and an antero-posterior segment slit-lamp biomicroscopy before and after full pupil dilation, fundus fluorescein angiography and optical coherence tomography were performed at baseline and during the third and sixth months post-therapy. Microperimetry and multifocal electroretinography were also performed at baseline and during the sixth months.

RESULTS

Mean visual acuity increased from 0.73 to 0.57 and 0.33 logarithm of the minimum angle of resolution (logMAR) during the third and sixth months, respectively (p < 0.001). Changes in intraocular pressure were not statistically significant (p = 0.472). There was statistically significantly decreased mean central macular thickness from 390.2 μm to 242.6 and 289.7 μm during the third and sixth months, respectively (p < 0.001). Significantly improved fixation patterns during the sixth month, along with significantly increased macular sensitivity from 8.2 to 14.2 dB (p < 0.001) and significantly decreased local deficit from - 10.3 to 5.5 dB (p < 0.001) were observed. Further, there was a significantly increased N1 amplitude in the first ring and significantly increased P1 amplitude in all rings (p for each parameter < 0.05). There was also significantly decreased N1 wave implicit time in all rings and significantly decreased P1 wave in the second, third, fourth and fifth rings (p for each parameter < 0.05).

CONCLUSIONS

Patients with DME showed profound improvement in the retinal neurophysiological function, which was also accompanied by anatomical and ultrastructural integrity recovery after intravitreal aflibercept therapy. In the pathogenesis of DME, the influence of neurodegeneration has been increasingly gaining significant attention. Consequently, the need to assess neurophysiological effects of anti-VEGF therapy using a variety of diagnostic measures like electrophysiological studies and multimodal imaging technologies is undeniably growing.

Anatomical and functional outcomes of subthreshold micropulse laser versus intravitreal ranibizumab injection in treatment of diabetic macular edema

Background

To compare the therapeutic effects of subthreshold micropulse laser (SML) versus intravitreal injection of ranibizumab in treatment of diabetic macular edema (DME) both anatomically using optical coherence tomography (OCT) and functionally using best corrected visual acuity (BCVA) and multifocal electroretinogram (mfERG).

Methods

his study was an interventional prospective randomized comparative study. The study included 120 eyes classified into 3 groups: Group 1 included 40 eyes of 28 patients treated by SML laser, group 2 included 40 eyes of 32 patients treated by intravitreal injection of ranibizumab, and group 3 (control group for mfERG) included 40 eyes of 20 patients with diabetes mellitus (DM) of more than 10 year duration with no signs of diabetic retinopathy (DR). BCVA measurements, OCT and mfERG were done for the cases before and after interference and were followed up for 6 months

Results

By the end of the follow up period, BCVA significantly improved by 31% in group 1 vs 93% in group 2 with a statistically highly significant difference between the two groups (p value < 0.001). There was also a significant decrease in central subfield thickness in both groups with more reduction in group 2 compared with group 1 (p value < 0.001). There was a significant improvement in P1 amplitude of mf-ERG in group 2 (p value < 0.002) with no significant improvement in group 1. There was a significant decrease in P1 implicit time in group 2 (p value < 0.001) while there was no significant decrease in group1.

Conclusions

Intravitreal injection of ranibizumab is a superior treatment modality for DME compared with SML regarding both anatomical and functional outcomes.

Trial registration: This study has been approved by the local ethical committee of faculty of medicine of Minia University and retrospectively registered at the clinical trial gov. with Identifier: NCT04332133.

Correlation between optical coherence tomography, multifocal electroretinogram findings and visual acuity in diabetic macular edema

AIM

To analyze the correlation between macular morphology and function in eyes with diabetic macular edema (DME).

METHODS

Fifty-five eyes with different visual acuity (VA) of 32 patients who suffered from DME were analyzed using multifocal electroretinography (mfERG) and optical coherence tomography (OCT). The parameters of mfERG including implicit times and response amplitude were compared to those of 50 normal eyes of 36 age-matched subjects. Correlation analysis was performed between VA, the parameters of mfERG including implicit times and response amplitude, and the central macular thickness (CMT).

RESULTS

The amplitude of N1 and P1 were significantly decreased and their latency were significantly increased in five ring regions of the retina in patients with DME. There was statistically significant correlation between logMAR BCVA and P1 amplitude densities in rings 1-4 (r=-0.306, -0.536, -0.470, -0.362; P=0.023, <0.01, <0.01, 0.007 respectively), N1 amplitude in ring 2 and ring 3 (r=-0.035, -0.286; P=0.019, 0.034 respectively). There was poor correlation between the CMT and best-corrected visual acuity (BCVA; r=0.288, P=0.033), but there was no significant correlation between CMT and amplitude or implicit time of N1 and P1 (P>0.05) in the central macular ring. Multiple stepwise regression analysis showed that P1 amplitude density in ring 2 was the only contributor to the VA.

CONCLUSION

It seems to be more appropriate of combining use of mfERG with OCT for the evaluation of macular function in eyes with DME.

Multifocal electroretinogram in diabetic macular edema and its correlation with different optical coherence tomography features

PURPOSE

To evaluate multifocal electroretinogram (mfERG) parameters in eyes with diabetic macular edema (DME) and its correlation with vision and optical coherence tomography (OCT) features.

METHODS

Fifty-four eyes of 27 subjects with DME due to nonproliferative diabetic retinopathy were evaluated. MfERG responses were measured in three concentric rings. Macular thickness was measured by OCT in each segment of the three concentric rings, and mfERG rings were superimposed on the macular thickness map. The correlation between macular thickness in specific points of the thickness map and changes of the mfERG parameters in the corresponding points of the mfERG field map was evaluated and the relationship between the OCT and mfERG changes and changes of best-corrected visual acuity (BCVA) was investigated. The central foveal B-scans of SD-OCT were used to evaluate any correlation between the external limiting membrane (ELM) status, ellipsoid zone (EZ) status, presence of cysts or disorganization of retinal inner layers (DRIL), and mfERG parameters at the central corresponding area.

RESULTS

The mean of BCVA was 0.5 ± 0.3 in logMAR, and the central macular thickness was 392.6 ± 123.4 microns. The central ring P1 and N2 amplitudes had a significant correlation with BCVA in univariate and multivariate analyses (P = 0.001 for both, r = - 0.346 and r = - 0.646, respectively). There was a significant correlation between retinal thickness and the N1 amplitude in the central ring (P = 0.02, r = - 0.343). Outer retinal layer disruption (ELM and EZ) correlated with prolonged P1 implicit time at the corresponding location (P = 0.005, r = 0.068). The presence of the DRIL was associated with reduced P1 and N2 amplitudes (P = 0.037, r = - 0.284 and P = 0.019, r = - 0.562, respectively). A significant correlation was also found between the presence of cysts and a lower central P1 amplitude (P = 0.033, r = - 0.376).

CONCLUSION

In diabetic patients, discrete changes of some parameters in the central ring of the mfERG field map (e.g., P1 and N2 amplitudes) have a significant correlation with both structural OCT abnormalities in the corresponding points of the thickness map (like DRIL, intraretinal cyst and ELM/EZ disruption) and BCVA. Predictive models such as those described in this report may make it possible to identify the relationship between specific anatomical and functional characteristics in diabetic retinopathy.

Assessment of macular function in patients with idiopathic Epiretinal membrane by multifocal Electroretinography: correlation with visual acuity and optical coherence tomography

Background

This study evaluates the macular function changes in patients with idiopathic macular epiretinal membrane (ERM) by multifocal electroretinography (mfERG) and their correlations with visual acuity and central macular thickness (CMT) by optical coherence tomography (OCT).

Methods

Twenty eyes of 20 patients with ERM underwent OCT and mfERG examinations. The response amplitude densities and implicit times of mfERG were compared to the control fellow eyes. Correlation analyses among visual acuity, central macular thickness and mfERG values in the central two concentric rings were performed.

Results

The mfERG P1 response amplitude densities in ring 1–2 and P1 implicit time in ring1 were significantly changed in epiretinal membrane eyes compared with controls (P < 0.05). Multivariate stepwise linear regression analyses showed LogMAR visual acuity was significantly correlated with CMT (P = 0.004), and also with the P1 amplitude density in ring 1 (P = 0.002). CMT showed significant correlation with P1 implicit time in ring 2 (P = 0.013).

Conclusions

The mfERG abnormalities show macular function changes and correlate with visual acuity and central macular thickness in eyes with ERM. In first-order mfERG responses, P1 wave changes may be a sensitive functional measurement for ERM patients.

Ganglion cell layer segmentation and the two-flash multifocal electroretinogram improve structure function analysis in early glaucoma

Purpose

To improve structure-function analysis in primary open-angle glaucoma (POAG) by including the two-global flash multifocal electroretinogram (2F–mfERG) and macular ganglion cell layer segmentation.

Methods

Twenty-five glaucoma patients (six pre-perimetric (PPG), 19 POAG) and 16 controls underwent 2F–mfERG, optical coherence tomography (OCT), and standard automated perimetry (SAP). For 2F–mfERG, the root mean square was calculated for the focal flash response at 15–45 ms (DC) and the global flash responses at 45–75 ms (IC1) and 75–105 ms (IC2). For OCT, macular total thickness (mT) and ganglion cell-inner plexiform layer (GCIPL) thickness were analysed. Values from the central 10° and 15° of 2F-mfERG were compared to the corresponding areas from OCT and visual field.

Results

Both PPG and POAG had significantly lower mfERG responses in the central 10° and 15° than the control group. Of the glaucoma patients, 30.7% (three PPG, five POAG) showed central mfERG and GCIPL reduction without a SAP defect in the central 15 degrees. Four patients had a central SAP defect associated with a reduced GCIPL without any detectable dysfunction on mfERG. MfERG DC and IC2 were larger with increased mT (p ≤ 0.02), but GCIPL only related positively to IC2 (p = 0.027). SAP sensitivity also increased with thicker mT but not with GCIPL (p < 0.03 and p = 0.35). DC, IC2, and GCIPL could best differentiate glaucoma from control (AUC values: 0.897, 0.903, and 0.905).

Conclusions

Structure function analysis in glaucoma can be improved when the GCIPL thickness as well as the 2F–mfERG is included as these measures complement information obtained by SAP.

Assessing Photoreceptor Structure in Retinitis Pigmentosa and Usher Syndrome

Purpose

The purpose of this study was to examine cone photoreceptor structure in retinitis pigmentosa (RP) and Usher syndrome using confocal and nonconfocal split-detector adaptive optics scanning light ophthalmoscopy (AOSLO).

Methods

Nineteen subjects (11 RP, 8 Usher syndrome) underwent ophthalmic and genetic testing, spectral-domain optical coherence tomography (SD-OCT), and AOSLO imaging. Split-detector images obtained in 11 subjects (7 RP, 4 Usher syndrome) were used to assess remnant cone structure in areas of altered cone reflectivity on confocal AOSLO.

Results

Despite normal interdigitation zone and ellipsoid zone appearance on OCT, foveal and parafoveal cone densities derived from confocal AOSLO images were significantly lower in Usher syndrome compared with RP. This was due in large part to an increased prevalence of non-waveguiding cones in the Usher syndrome retina. Although significantly correlated to best-corrected visual acuity and foveal sensitivity, cone density can decrease by nearly 38% before visual acuity becomes abnormal. Aberrantly waveguiding cones were noted within the transition zone of all eyes and corresponded to intact inner segment structures. These remnant cones decreased in density and increased in diameter across the transition zone and disappeared with external limiting membrane collapse.

Conclusions

Foveal cone density can be decreased in RP and Usher syndrome before visible changes on OCT or a decline in visual function. Thus, AOSLO imaging may allow more sensitive monitoring of disease than current methods. However, confocal AOSLO is limited by dependence on cone waveguiding, whereas split-detector AOSLO offers unambiguous and quantifiable visualization of remnant cone inner segment structure. Confocal and split-detector thus offer complementary insights into retinal pathology.

The assessment of multifocal ERG responses in school-age children with history of prematurity

PURPOSE

The authors examined macular function in preterm-born children, using multifocal ERG (mfERG). Possible alterations in P1 amplitudes, P1 amplitudes density and P1 implicit time between school-age children with history of prematurity and their peers were researched. The correlations between parameters of mfERG responses and birth weight, gestational age, macular volume and central macular thickness were verified.

METHODS

A group of 18 preterm-born school-age children were analyzed (mean age 10.18 ± 1.21 years). The study group was compared to the group of 15 peers born appropriate for gestational age (mean age 10.8 ± 1.52 years). The mfERG was evaluated in all children.

RESULTS

There were statistically significant differences for P1 amplitudes from ring 1 (p = 0.0001) and P1 amplitudes density from ring 1 (p = 0.0001). Calculating the correlation coefficients, we receive significant results for P1 amplitudes from ring 1 versus gestational age (r = 0.54; p = 0.026), birth weight (r = 0.54; p = 0.026) and central macular thickness (r = -0.62; p = 0.008), and for P1 amplitudes density from ring 1 versus central macular thickness (r = -0.51; p = 0.034).

CONCLUSIONS

The study suggests that P1 amplitudes and P1 amplitudes density vary in preterm-born children in comparison with their peers born appropriate for gestational age, which might suggest discreet macular dysfunction. The correlation between low birth weight, early gestational age, central macular thickness and mFERG components from ring 1 might evidence that decreased bipolar cells density caused by premature birth is the result of altered development of central retina reflecting in structural anomalies of the fovea.

Defining the Relationships Among Retinal Function, Layer Thickness and Visual Behavior During Oxidative Stress-Induced Retinal Degeneration

PURPOSE

The purpose of this study was to identify how changes in retinal structure and function correlate with visual deficits during increasing amounts of retinal degeneration.

MATERIALS AND METHODS

Retinal degeneration was induced in adult mice by subretinal injections of paraquat (PQ) (0.2-1 mM). Retinal anatomy and photoreceptor layer thickness were quantified by histology and optical coherence tomography (OCT), retinal function was measured using electroretinography (ERG), and visual behavior were measured by optokinetic tracking, at 1 to 3 week post-injury.

RESULTS

Photoreceptor layer structure, function and visual behavior declined at a linear rate over time following PQ-induced degeneration, with the correlations between outcome measures being lowest at mild injury levels and increasing with injury severity. Overall reductions in visual acuity were highly correlated with declines in retinal thickness (r(2) = 0.78) and function (r(2) = 0.67) and retinal thickness correlated with photoreceptor function (r(2) = 0.72). ERG a-wave scotopic amplitudes showed a stronger correspondence to retinal structure and visual behavior than b-waves.

CONCLUSIONS

Measurements of photoreceptor loss at the structural and functional levels showed good correspondence with degeneration-associated changes in visual behavior after oxidative stress injury. The results provide new insight about the relative kinetics of measurements of retinal degeneration induced by oxidative stress, which could guide the choice of optimal outcome measurements for other retinal diseases.

Macular function measured by binocular mfERG and compared with macular structure in healthy children

PURPOSE

To create normative data in children from binocular multifocal ERG (mfERG) recordings and compare results with the macular thickness.

METHODS

Forty-nine 5- to 15-year-old healthy, full-term children were examined with Espion Multifocal System, using DTL electrodes. The stimulus matrix consisted of 37 hexagonal elements. Amplitudes, implicit times and response densities (presented in three rings) of the first-order component P1 were analyzed. Measurements of macular thickness were performed with spectral-domain Cirrus OCT.

RESULTS

There were no significant differences between right and left eyes regarding mfERG recordings. Median P1 implicit times of Rings 1-3 of the 46 right eyes were 30.0, 30.0 and 30.8 ms and response densities 20.5, 10.9 and 7.6 nV/deg(2), respectively. Implicit time was longer in boys than in girls (p = 0.009, 0.039, 0.005 in Rings 1-3) and was correlated with age (r s = 0.417, 0.316, 0.274 in Rings 1-3). Implicit time in Ring 1 correlated significantly with the inner circle of the OCT measurements (p = 0.014).

CONCLUSION

Binocular mfERG with DTL electrodes is a reliable test of the central macular function in children and correlates with macular structure. As previously not shown, there was a significant difference in implicit time between boys and girls.

Multifocal Electroretinogram in Diabetic Macular Edema; Correlation with Visual Acuity and Optical Coherence Tomography

Purpose:

To evaluate multifocal electroretinogram (mfERG) changes in eyes with diabetic macular edema (DME) and investigate any possible correlation with optical coherence tomography (OCT) features and visual acuity (VA).

Methods:

Twenty-nine right eyes of 29 subjects with DME due to non-proliferative diabetic retinopathy and 30 eyes of 30 normal subjects were evaluated. All patients underwent a complete ophthalmic examination. Sixty-one scaled hexagon mfERG responses were recorded. Components of the first order kernel of N1, N2, and P1 in five concentric rings centered on the fovea, were measured in both groups. Correlation and regression analyses were performed among VA, central macular thickness (CMT) based on OCT, mfERG amplitude, and latency of the N1, N2 and P1 waves.

Results:

Significant differences were observed in all mfERG parameters in five-ring regions of the retina between eyes with DME versus controls (P < 0.05). There were significant correlations among VA with N2 (P = 0,001, b = 0.73) and P1 amplitudes (P = 0.001, b = −0.84) in the central macular area, and there was a borderline association between VA and CMT (P = 0.042, b = 0.392).

Conclusion:

Amplitudes of mfERG components (N1, P1, and N2) are significantly reduced and their latencies are delayed in eyes with DME indicating functional impairment in the outer retina. The mfERG total amplitude was significantly correlated with VA even more than CMT, therefore the combined use of OCT and mfERG for macular evaluation may better evaluate visual status in DME patients.

Structural and functional changes in glaucoma: comparing the two-flash multifocal electroretinogram to optical coherence tomography and visual fields

PURPOSE

To correlate multifocal electroretinogram (mfERG) findings in the macular area of glaucoma patients with automated perimetry (visual fields) and with optical coherence tomography (OCT).

METHODS

A two-global flash mfERG (VERIS™) was recorded in 20 eyes with primary open-angle glaucoma. The root mean square was calculated, and three response epochs were analysed: the direct component (15-45 ms) and two induced components (IC-1 at 45-75 ms and IC-2 at 75-105 ms). The central 10° of the mfERG was compared to the central 10° of the OCT and of the visual field. Responses grouped in a superior and in an inferior semicircle, extending between 10° and 20°, were also compared to the corresponding areas of the OCT and of the visual fields. In addition, the area of the papillomacular bundle was also analysed separately.

RESULTS

In glaucoma patients, mfERG responses showed a significant positive association with retinal thickness in the central 10° for IC2 (p = 0.001) and a trend for IC1 (p = 0.066). A significant association was found between the central IC1 and IC2 of the mfERG and corresponding perimetric sensitivities expressed in linear units (p < 0.01). The OCT showed a positive association with visual field sensitivities (p < 0.05) in all areas examined (p < 0.05). Separation of the papillomacular bundle area did not improve structure-function association further.

CONCLUSIONS

In our study, mfERG showed a statistically significant correlation with perimetric sensitivity measured in linear units and with structural macular changes detected with time-domain OCT.

[Importance of morphological and functional diagnostics of the vitreoretinal interface]

Optical coherence tomography (OCT) is the standard examination for assessment of the vitreoretinal interface (VRI); therefore, it is essential to select the appropriate scan modalities to detect the total amount of morphological changes, not only at the VRI but also in all layers of the retina and in both the foveal and parafoveal areas. For the success of a surgical intervention in the treatment of vitreomacular interface disorders, morphological changes, especially in the outer retinal layers, have been determined to be of prognostic interest in high-resolution OCT. This article gives an overview of current OCT examination procedures as well as correlative aspects of morphological and functional findings.

A comparison of structural and functional changes in patients screened for hydroxychloroquine retinopathy

PURPOSE

The aims of this retrospective study were to compare the results of recommended screening tests for hydroxychloroquine-related retinal toxicity and analyze disparities between the structural and functional findings.

METHODS

Thirty-four patients (31 women and 3 men) were included in the study. All were evaluated with standard automated perimetry using the 10-2 and/or 24-2 visual field program (Zeiss, Meditec), multifocal electroretinography (mfERG), spectral-domain optical coherence tomography (SD-OCT), and short-wavelength fundus autofluorescent imaging (SW-FAF). The results for the right eye from each patient were analyzed. Visual fields were classified as normal or abnormal based on pattern deviation plots, and mfERGs based on a comparison of R5 ring ratios to values from 20 controls. The SW-FAF images were examined for areas/rings of abnormal hypo- and/or hyperautofluorescence, and the SD-OCT line scans were classified as abnormal based on visual inspection and thickness measurements of the outer segment plus retinal pigment epithelial layer and total receptor layers compared to mean thicknesses from 35 controls.

RESULTS

Fifteen patients had abnormal results on at least one test; however, only two patients had abnormal results on all four tests. Excluding SW-FAF, seven of the 15 had abnormal visual fields, mfERG ring ratios, and SD-OCTs. The remaining eight had either abnormal mfERGs and/or visual fields and normal SD-OCTs. We found no evidence of abnormal SD-OCTs in the presence of normal mfERG and visual field results.

CONCLUSIONS

The findings suggest that functional deficits precede structural changes seen on SD-OCT in these patients.

Inverse pattern of photoreceptor abnormalities in retinitis pigmentosa and cone-rod dystrophy

PURPOSE

To determine the characteristics of the photoreceptor abnormalities in retinitis pigmentosa (RP) and cone-rod dystrophy (CRD).

METHODS

We evaluated the photoreceptor abnormalities using spectral-domain optical coherence tomography (SD-OCT) in 28 patients with RP and 17 patients with CRD. The OCT images and full-field electroretinograms were obtained from 21 eyes in normal subjects who were age-matched to patients with RP and CRD and served as controls.

RESULTS

Eyes with RP and CRD had markedly decreased rod responses (6.5 and 57.5 % of normal value), maximal responses (9.6 and 51.6 %), cone (16.5 and 25.8 %), and 30-Hz flicker responses (17.8 and 30.1 % of normal value), and their P values were smaller than 0.0003. On comparison of ERG data between RP and CRD, they had statistically significant differences in rod responses (P < 0.0003) and maximal responses (P < 0.0003). However, there were no statistical differences in cone response and a weak difference in 30-Hz flicker responses (P < 0.017). The best-corrected visual acuity was -0.03 ± 0.09 (logMAR, mean ± standard deviation [SD]) in eyes with RP, but 0.57 ± 0.54 in eyes with CRD. SD-OCT showed that eyes with RP had an intact reflective line at the junction between the photoreceptor inner and outer segment (IS/OS) at the fovea, while eyes with CRD had no IS/OS. The extent of the central visual field was correlated with the IS/OS length at the macula in eyes with RP.

CONCLUSION

The distribution patterns of the IS/OS line help to differentiate between RP and CRD.

Relationships among multifocal electroretinogram amplitude, visual field sensitivity, and SD-OCT receptor layer thicknesses in patients with retinitis pigmentosa

PURPOSE

To compare local functional measures, the multifocal electroretinogram (mfERG) and visual field sensitivity, with a local structural measure, spectral domain (SD) optical coherence tomography (OCT), of receptor damage in patients with retinitis pigmentosa (RP).

METHODS

MfERGs, visual fields, and SD-OCT scans were obtained from 10 patients with RP, ranging in age from 23 to 59 years. Average amplitudes, average linear sensitivities, and average layer thicknesses were measured from within the central 3° and from three concentric annuli located between 3° and 8°, 8° and 15°, and 15° and 24°. A computer program aided manual segmentation and calculated OCT thickness in the scans.

RESULTS

Within each patient with RP, mfERG amplitude for each circle/annulus was highly correlated with corresponding layer thicknesses in the outer retina (r = 0.88 to 0.99), but not at all correlated with thickness of the inner nuclear layer or total retina. Across all ring eccentricities, relative mfERG amplitude and relative visual field sensitivity were correlated with relative SD-OCT outer retinal thickness.

CONCLUSIONS

In patients with RP, preserved cone photoreceptor function measured by mfERG amplitude and visual field sensitivity correlate well with the remaining thickness of the photoreceptor layer. All three measures show comparable relative loss beyond 3° eccentricity. In the fovea, SD-OCT outer retina thickness showed less relative loss than either mfERG or visual field sensitivity.

The inner segment/outer segment border seen on optical coherence tomography is less intense in patients with diminished cone function

PURPOSE; The integrity of the inner segment ellipsoid (ISe) band, previously called the inner segment/outer segment (IS/OS) border, seen on optical coherence tomography (OCT) scans is of clinical significance. To better understand the influence of cones on the appearance of this band, the intensity of its signal in patients with diminished cone function was examined.

METHODS

Horizontal line scans through the fovea of 30 healthy controls, 10 patients with achromatopsia (A), and six with cone dystrophy (CD) were obtained with frequency domain (fd) OCT. The fdOCT borders were segmented with a computer-aided manual technique. The ISe was divided into regions 60.1 μm wide and 19.5 μm deep. The relative ISe intensity of each region was defined as its intensity divided by the intensity of a local region, which extended in depth from the choroid to the retinal ganglion cell/retinal nerve fiber layer.

RESULTS

Except for the central fovea, all patients had a clear ISe band across the region studied, ± 3 mm from the foveal center. However, the relative ISe intensity was significantly lower (P < 0.0001) in patients (A: 1.14 ± 0.14; CD: 1.27 ± 0.14), than in controls (1.61 ± 0.16). There were no differences in the relative intensity of the other retinal layers.

CONCLUSIONS

Although present, the intensity of this ISe band is lower in patients with diminished cone function than it is in healthy controls. This is consistent with the hypothesis that both rod and cone receptors must be absent or damaged for the ISe band to be missing.

Multifocal electroretinograms

A limitation of traditional full-field electroretinograms (ERG) for the diagnosis of retinopathy is lack of sensitivity. Generally, ERG results are normal unless more than approximately 20% of the retina is affected. In practical terms, a patient might be legally blind as a result of macular degeneration or other scotomas and still appear normal, according to traditional full field ERG. An important development in ERGs is the multifocal ERG (mfERG). Erich Sutter adapted the mathematical sequences called binary m-sequences enabling the isolation from a single electrical signal an electroretinogram representing less than each square millimeter of retina in response to a visual stimulus. Results that are generated by mfERG appear similar to those generated by flash ERG. In contrast to flash ERG, which best generates data appropriate for whole-eye disorders. The basic mfERG result is based on the calculated mathematical average of an approximation of the positive deflection component of traditional ERG response, known as the b-wave. Multifocal ERG programs measure electrical activity from more than a hundred retinal areas per eye, in a few minutes. The enhanced spatial resolution enables scotomas and retinal dysfunction to be mapped and quantified. In the protocol below, we describe the recording of mfERGs using a bipolar speculum contact lens. Components of mfERG systems vary between manufacturers. For the presentation of visible stimulus, some suitable CRT monitors are available but most systems have adopted the use of flat-panel liquid crystal displays (LCD). The visual stimuli depicted here, were produced by a LCD microdisplay subtending 35-40 degrees horizontally and 30-35 degrees vertically of visual field, and calibrated to produce multifocal flash intensities of 2.7 cd s m(-2). Amplification was 50K. Lower and upper bandpass limits were 10 and 300 Hz. The software packages used were VERIS versions 5 and 6.

Abnormal multifocal ERG findings in patients with normal-appearing retinal anatomy

To evaluate eyes with abnormal visual fields and multifocal electroretinograms (mfERGs) but normal-appearing frequency-domain optical coherence tomography (fdOCT) scans, the thicknesses of the outer retinal layers were measured. A total of 25 eyes from 17 patients, including 15 eyes previously tested (Dale et al. in Doc Ophthalmol 120(2):175-186, 2009) were examined. All patients were evaluated with standard automated perimetry (SAP) using the 24-2 and/or 10-2 program (Zeiss Meditec), mfERG with 103 hexagons (Veris, EDI), and fdOCT imaging (3DOCT-2000, Topcon) with scans of the macula. All patients had reliable visual fields showing macular defects and good quality mfERG and fdOCT results. The mfERG results were classified as abnormal based on decreased amplitudes and/or increased latencies corresponding to the abnormal visual field. Based on visual inspection, three experienced observers classified the fdOCT scans as normal or inconclusive, as opposed to clearly abnormal. Retinal layers of the fdOCT scans were manually segmented with the aid of a computer program and compared to mean thicknesses from 20 controls. The thicknesses of the outer segment plus retinal pigment epithelium, total receptor, and inner nuclear layers were measured. Quantitative analysis of fdOCT scans demonstrated thinning of the outer retina in some scans that was not readily apparent on visual inspection. One or more of the outer retinal layers was significantly thinner in 15 of the 25 eyes. The absence of significant thinning in the other 10 eyes represents instances in which functional loss measured by visual fields and mfERGs can precede clear structural changes on fdOCT.

Association between photoreceptor integrity and visual outcome in diabetic macular edema

PURPOSE

To investigate the correlation between foveal photoreceptor integrity and final visual acuity (VA) after treatment of eyes with diabetic macular edema (DME), and to determine the visual prognostic factors.

METHODS

We retrospectively studied 61 eyes of 52 patients with DME who were treated successfully with intravitreal triamcinolone injection (IVTA). Using spectral domain optical coherence tomography (SD-OCT), the eyes were categorized into three groups at the final visit according to restoration of the photoreceptor inner and outer segment junction (IS/OS) and the external limiting membrane (ELM): (1) the A group, with a completely visible IS/OS and ELM, (2) the B group, with a disrupted IS/OS and intact ELM, and (3) the C group, with a disrupted or loss of the IS/OS and ELM. Disrupted IS/OS length (DIL), disrupted ELM length (DEL), and mean disrupted IS/OS and ELM length (DIEL) were measured at the initial and final visits. Foveal thickness (FT), macular center thickness (MCT), and outer nuclear layer (ONL) thickness were also measured at the initial and final visits. Multivariate analysis testing was performed over the measured SD OCT variables.

RESULTS

Final VA was closely associated with IS/OS integrity at the final visit; final VA (logMAR) in the A group (0.21 ± 0.14; 31 eyes) or B group (0.31 ± 0.21; 15 eyes) was significantly better than that in the C group (0.45 ± 0.33; 15 eyes) (p < 0.001). Shorter DIL, DEL, and DIEL at the final visit were associated with better final VA. Multivariate analysis showed that DIEL (r = 0.564) have the greatest correlation coefficient with final VA compared to DIL (r = 0.561) and DEL (r = 0.540). Better VA, preservation of the IS/OS and ELM at the initial visit were associated with intact photoreceptor integrity after resolution of DME. However, MCT, FT, and ONL thickness had no significant correlation with photoreceptor integrity.

CONCLUSION

IS/OS and ELM are useful hallmarks for use in evaluation of foveal photoreceptor layer integrity, and are closely associated with final VA in DME. Pretreatment VA and photoreceptor status can predict potential restoration of photoreceptor integrity and subsequent visual recovery in DME.

Primary retinal pathology in multiple sclerosis as detected by optical coherence tomography

Optical coherence tomography studies in multiple sclerosis have primarily focused on evaluation of the retinal nerve fibre layer. The aetiology of retinal changes in multiple sclerosis is thought to be secondary to optic nerve demyelination. The objective of this study was to use optical coherence tomography to determine if a subset of patients with multiple sclerosis exhibit primary retinal neuronopathy, in the absence of retrograde degeneration of the retinal nerve fibre layer and to ascertain if such patients may have any distinguishing clinical characteristics. We identified 50 patients with multiple sclerosis with predominantly macular thinning (normal retinal nerve fibre-layer thickness with average macular thickness < 5th percentile), a previously undescribed optical coherence tomography defined phenotype in multiple sclerosis, and compared them with 48 patients with multiple sclerosis with normal optical coherence tomography findings, 48 patients with multiple sclerosis with abnormal optical coherence tomography findings (typical for multiple sclerosis) and 86 healthy controls. Utilizing a novel retinal segmentation protocol, we found that those with predominant macular thinning had significant thinning of both the inner and outer nuclear layers, when compared with other patients with multiple sclerosis (P < 0.001 for both), with relative sparing of the ganglion cell layer. Inner and outer nuclear layer thicknesses in patients with non-macular thinning predominant multiple sclerosis were not different from healthy controls. Segmentation analyses thereby demonstrated extensive deeper disruption of retinal architecture in this subtype than may be expected due to retrograde degeneration from either typical clinical or sub-clinical optic neuropathy. Functional corroboration of retinal dysfunction was provided through multi-focal electroretinography in a subset of such patients. These findings support the possibility of primary retinal pathology in a subset of patients with multiple sclerosis. Multiple sclerosis-severity scores were also significantly increased in patients with the macular thinning predominant phenotype, compared with those without this phenotype (n = 96, P=0.006). We have identified a unique subset of patients with multiple sclerosis in whom there appears to be disproportionate thinning of the inner and outer nuclear layers, which may be occurring as a primary process independent of optic nerve pathology. In vivo analyses of retinal layers in multiple sclerosis have not been previously performed, and structural demonstration of pathology in the deeper retinal layers, such as the outer nuclear layer, has not been previously described in multiple sclerosis. Patients with inner and outer nuclear layer pathology have more rapid disability progression and thus retinal neuronal pathology may be a harbinger of a more aggressive form of multiple sclerosis.