Mapping of retinal function in Best macular dystrophy using multifocal electroretinography

Vitelliform maculopathy: Diverse etiologies originating from one common pathway

Vitelliform lesions (VLs) are associated with a wide array of macular disorders but are the result of one common pathway: retinal pigment epithelium (RPE) impairment and phagocytic dysfunction. VLs are defined by the accumulation of yellowish subretinal material. In the era of multimodal advanced retinal imaging, VLs can be further characterized by subretinal hyperreflectivity with optical coherence tomography and hyperautofluorescence with fundus autofluorescence. VLs can be the result of genetic or acquired retinal diseases. In younger patients, VLs usually occur in the setting of Best disease. Additional genetic causes of VL include pattern dystrophy or adult-onset vitelliform macular dystrophy. In older patients, acquired VLs can be associated with a broad spectrum of etiologies, including tractional, paraneoplastic, toxic, and degenerative disorders. The main cause of visual morbidity in eyes with VLs is the onset of macular atrophy and macular neovascularization. Histopathological studies have provided new insights into the location, nature, and lifecycle of the vitelliform material comprised of melanosomes, lipofuscin, melanolipofuscin, and outer segment debris located between the RPE and photoreceptor layer. Impaired phagocytosis by the RPE cells is the unifying pathway leading to VL development. We discuss and summarize the nature, pathogenesis, multimodal imaging characteristics, etiologies, and natural course of vitelliform maculopathies.

A pathogenic in-frame deletion-insertion variant in BEST1 phenocopies Stargardt disease

Here, we describe affected members of a 2-generation family with a Stargardt disease-like phenotype caused by a 2-base pair deletion insertion, c.1014_1015delGAinsCT;p.(Trp338_Asn339delinsCysTyr), in BEST1. The variant was identified by whole-exome sequencing, and its pathogenicity was verified through chloride channel recording using WT and transfected mutant HEK293 cells. Clinical examination of both patients revealed similar phenotypes at 2 different disease stages that were attributable to differences in their age at presentation. Hyperautofluorescent flecks along the arcades were observed in the proband, while the affected mother exhibited more advanced retinal pigment epithelium (RPE) loss in the central macula. Full-field electroretinogram testing was unremarkable in the daughter; however, moderate attenuation of generalized cone function was detected in the mother. Results from electrooculogram testing in the daughter were consistent with widespread dysfunction of the RPE characteristic of Best disease. Whole-cell patch-clamp recordings revealed a statistically significant decrease in chloride conductance of the mutant compared with WT cells. This report on a mother and daughter with a BEST1 genotype that phenocopies Stargardt disease broadens the clinical spectrum of BEST1-associated retinopathy.

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.

Multifocal electroretinography in amblyopia

PURPOSE

To identify whether there are functional abnormalities in the retina of amblyopic eyes using multifocal electroretinography (mfERG).

METHODS

This is a prospective study of patients ≥ 7 years of age identified with unilateral amblyopia (strabismic or anisometropic). Multifocal ERG and flash ERG were performed to compare parameters between the amblyopic and non-amblyopic fellow eyes. A complete analysis of the five ring averages was done including the central ring.

RESULTS

Thirty-eight patients were included: mean age was 14.3 ± 7.3 years; 18 patients were strabismic and 20 were anisometropic. Amblyopic eye responses across the rings in multifocal ERG were diminished compared with fellow non-amblyopic eyes with significant differences detected in the central rings (p = 0.001). On the other hand, flash ERG did not show any consistently significant differences. When divided by severity, amplitudes of central rings were significantly lower in severely amblyopic eyes compared with non-amblyopic eyes (p = 0.001), while in mild amblyopia, no significant differences were observed. No significant difference was observed between anisometropic and strabismic amblyopic eyes.

CONCLUSIONS

Using multifocal ERG, significantly decreased amplitudes were observed in amblyopic eyes compared with normal fellow eyes in the central ring. This correlated with the severity of amblyopia. No difference was observed when comparing the two groups of amblyopia (strabismic and anisometropic). Those findings may help clarify the pathophysiology of amblyopia better and open the door for new objective ways to monitor the response to amblyopia treatment but this needs to be further studied.

Genetic testing for Best vitelliform macular dystrophy

We studied the scientific literature and disease guidelines in order to summarize the clinical utility of the genetic test for Best vitelliform macular dystrophy (BVMD). BVMD is mostly inherited in an autosomal dominant manner (autosomal recessive transmission is rare). The overall prevalence is currently unknown. BVMD is caused by mutations in the BEST1 gene. Clinical diagnosis is based on clinical findings, ophthalmological examination, optical coherence tomography, electrooculography and electroretinography. The genetic test is useful for confirming diagnosis, and for differential diagnosis, couple risk assessment and access to clinical trials.

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.

Best vitelliform macular dystrophy: literature review

Best vitelliform macular dystrophy (BVD) is a slowly progressive form of macular dystrophy. In most cases this disease begins in childhood although sometimes it can develop in later age. The diagnosis of BVD is based on family history, clinical and electrophysiological findings. Clinical signs are variable, yet the majority of patients have a typical yellow yolk-like macular lesion in the eye fundus. Lesions are usually bilateral, but in rare cases can be unilateral. Atrophy of the macula may develop after many years. The mutations responsible for Best vitelliform macular dystrophy are found in a gene called VMD2, which encodes a transmembrane protein named bestrophin-1 (hBest1) that is a Ca2+-sensitive chloride channel. Most reported cases causing the disease are in exons 2, 4, 6 and 8 in patients with BVD. In this article we discuss the etiology of Best’s vitelliform macular dystrophy, clinical presentation, diagnostics, genetic and current treatment possibilities.

Effect of docosahexaenoic acid supplementation on the macular function of patients with Best vitelliform macular dystrophy: randomized clinical trial

OBJECTIVE

Best disease is a slowly progressive macular dystrophy that typically has an onset in early childhood. Multiple lines of evidence suggest that dietary docosahexaenoic acid (DHA) protects against the development of macular degeneration. Our trial tested the effect of an oral supplement of DHA on visual function in patients with Best disease.

DESIGN

Double-masked, randomized, placebo-controlled, crossover clinical trial.

PARTICIPANTS

Eight patients with Best disease.

METHODS

Patients were given either an oral supplement of DHA (20 mg/kg daily) or placebo. Primary outcome measures were the multifocal electroretinogram (mfERG) and electro-oculogram (EOG). Plasma DHA was tracked along with visual acuity (Early Treatment Diabetic Retinopathy Study chart), VF-14 scores, and Humphrey visual fields.

RESULTS

All 8 patients had increased plasma DHA levels (2-3 fold) during periods of DHA supplementation compared with periods without supplementation. Differences in visual acuity, VF-14 scores, and EOG Arden ratios during periods with and without DHA supplementation were all statistically insignificant. A positive correlation was found between the plasma concentration of DHA and mfERG amplitudes, but amplitude changes during the treatment periods were not significant. A carryover effect of DHA supplementation was a confounding error.

CONCLUSIONS

Our pilot trial of DHA supplementation in 8 patients with Best disease did not demonstrate an improvement in macular function. An expanded trial would be needed to examine the full effects of DHA supplementation on visual function in Best disease.

Visual acuity and multifocal electroretinographic changes after arteriovenous crossing sheathotomy for macular edema associated with branch retinal vein occlusion

PURPOSE

To evaluate the influence of arteriovenous (AV) sheathotomy on retinal function with central multifocal electroretinography (mfERG) in eyes with macular edema secondary to branch retinal vein occlusion (BRVO).

METHODS

Fifteen patients (15 eyes) who underwent AV sheathotomy for macular edema secondary to BRVO were included in the study. Best-corrected visual acuity and mfERG responses from the most central seven hexagons were analyzed before and 6 months after the operation.

RESULTS

The mean preoperative Early Treatment Diabetic Retinopathy Study (ETDRS) score +/- SD was 34.1 +/- 12.7 letters (Snellen equivalent, 20/50) and significantly improved up to 40.5 +/- 10.9 letters (Snellen equivalent, 20/40) at 6 months after AV sheathotomy (P = 0.027, Wilcoxon signed rank test). The mean preoperative P1 amplitude +/- SD of the most central 7 hexagons was 39.30 +/- 10.86 nV/deg(2) for the affected eye versus 47.72 +/- 6.67 nV/deg(2) for the normal fellow (control) eye (P = 0.013, Mann-Whitney U test) and significantly increased up to 50.71 +/- 15.58 nV/deg at 6 months after the operation (P = 0.014, Wilcoxon signed rank test). Significant correlations between preoperative and postoperative ETDRS score and preoperative P1 amplitude were present (r = 0.929, P < 0.001; r = 0.768, P = 0.001; respectively [Spearman correlation]).

CONCLUSIONS

AV sheathotomy improved macular function and anatomical outcome as measured by ETDRS score and mfERG responses in patients with macular edema due to BRVO.

First and second-order kernel multifocal electroretinography abnormalities in acute central serous chorioretinopathy

PURPOSE

To evaluate the first and second-order kernel multifocal electroretinogram (mfERG) response abnormalities in patients with acute central serous chorioretinopathy (CSC).

METHODS

This was a cross-sectional observational study in which 45 eyes of 45 patients with acute CSC underwent mfERG recordings. Peak amplitudes and implicit times of the first and second-order kernel responses were analyzed and compared with 20 age-matched normal controls. Correlation analyses were performed between the patients' visual acuity and the first and second-order amplitudes and implicit times.

RESULTS

The first-order N1 and P1 mfERG amplitudes in the central three concentric rings were reduced in eyes with acute CSC compared with controls (P < 0.05). The first-order P1 implicit times of the central four rings were also delayed (P < 0.05). For the second-order mfERG response, there were significant reductions in the second-order P1 and N1 amplitudes in rings 3-5 compared with controls (P < 0.05). No significant difference between the second-order P1 and N1 implicit times was found compared with controls (P > 0.05). Correlation analyses showed significant correlations between visual acuity and the first-order N1 response amplitudes of rings 1 and 2, and for the first-order N1 and P1 implicit times of rings 1-4 (P < 0.05).

CONCLUSION

Both first and second-order mfERG response abnormalities occur in eyes with acute CSC. These results suggest that in acute CSC, while outer retinal dysfunction is mostly localized to the central macula, there might be more widespread impairment in adaptive mechanisms of the inner retina or outer plexiform layer dysfunction in the more peripheral macula.

A Korean family with an early-onset autosomal dominant macular dystrophy resembling North Carolina macular dystrophy

Purpose

To characterize and report the phenotype of a Korean family with an early-onset autosomal dominant macular dystrophy resembling North Carolina macular dystrophy (NCMD).

Methods

Five members of a Korean family were examined clinically and underwent fundus photography, fluorescein angiography, indocyanine green angiography, optical coherence tomography, full field electroretinogram (ERG), multifocal ERG, electro-oculography (EOG), a color vision test, and a visual field test.

Results

Visual acuity ranged from 20/200 to 20/20. Fundus findings demonstrated varying degrees of involvement ranging from drusen only to chorioretinal involvement. Central scotoma corresponded to retinal lesions in two patients. Full field ERG was normal but multifocal ERG showed decreased amplitude and delayed implicit time in the macular area. EOG was normal except in one patient. Color vision tests were also normal.

Conclusions

The phenotype of this Korean family is consistent with NCMD. Linkage analysis is required to confirm the diagnosis.

The clinical applications of multifocal electroretinography: a systematic review

Multifocal electroretinography (mfERG) is an investigation that can simultaneously measure multiple electroretinographic responses at different retinal locations by cross-correlation techniques. mfERG therefore allows topographic mapping of retinal function in the central 40-50 degrees of the retina. The strength of mfERG lies in its ability to provide objective assessment of the central retinal function at different retinal areas within a short duration of time. Since the introduction of mfERG in 1992, mfERG has been applied in a large variety of clinical settings. This article reviews the clinical applications of mfERG based on the currently available evidence. mfERG has been found to be useful in the assessment of localized retinal dysfunction caused by various acquired or hereditary retinal disorders. The use of mfERG also enabled clinicians to objectively monitor the treatment outcomes as the changes in visual functions might not be reflected by subjective methods of assessment. By changing the stimulus, recording, and analysis parameters, investigation of specific retinal electrophysiological components can be performed topographically. Further developments and consolidations of these parameters will likely broaden the use of mfERG in the clinical setting.

New VMD2 gene mutations identified in patients affected by Best vitelliform macular dystrophy

PURPOSE

The mutations responsible for Best vitelliform macular dystrophy (BVMD) are found in a gene called VMD2. The VMD2 gene encodes a transmembrane protein named bestrophin-1 (hBest1) which is a Ca(2+)-sensitive chloride channel. This study was performed to identify disease-specific mutations in 27 patients with BVMD. Because this disease is characterised by an alteration in Cl(-) channel function, patch clamp analysis was used to test the hypothesis that one of the VMD2 mutated variants causes the disease.

METHODS

Direct sequencing analysis of the 11 VMD2 exons was performed to detect new abnormal sequences. The mutant of hBest1 was expressed in HEK-293 cells and the associated Cl(-) current was examined using whole-cell patch clamp analysis.

RESULTS

Six new VMD2 mutations were identified, located exclusively in exons four, six and eight. One of these mutations (Q293H) was particularly severe. Patch clamp analysis of human embryonic kidney cells expressing the Q293H mutant showed that this mutant channel is non-functional. Furthermore, the Q293H mutant inhibited the function of wild-type bestrophin-1 channels in a dominant negative manner.

CONCLUSIONS

This study provides further support for the idea that mutations in VMD2 are a necessary factor for Best disease. However, because variable expressivity of VMD2 was observed in a family with the Q293H mutation, it is also clear that a disease-linked mutation in VMD2 is not sufficient to produce BVMD. The finding that the Q293H mutant does not form functional channels in the membrane could be explained either by disruption of channel conductance or gating mechanisms or by improper trafficking of the protein to the plasma membrane.

A comparison of pattern and multifocal electroretinography in the evaluation of age-related macular degeneration and its treatment with photodynamic therapy

This study compares pattern electroretinography (PERG) and multifocal electroretinography (mfERG) measures in 13 patients with predominantly classic choroidal neovascularisation (CNV) associated with age-related macular degeneration (ARMD, 9/13 unilateral, 4/13 bilateral), assesses the usefulness of each test in monitoring disease progression, and identifies electrophysiological predictors of outcome following treatment with photodynamic therapy (PDT). PERG and mfERGs were recorded at presentation, 2 weeks post-treatment, and at 3 monthly intervals for 2 years. The PERG was detectable in 8/13 patients with unilateral disease; the mfERG was detectable in 12/13 patients. P50 and N95 amplitudes increased in 6/8 patients and mfERG p1 increased in 7/13 patients at 2 years. PERG amplitudes correlated strongly with mfERG amplitudes in patients with unilateral disease. PERG P50 and mfERG p1 amplitude correlated with visual acuity at 2 years (R = 0.68, R = 0.82, respectively). The largest PERG P50 and mfERG p1 amplitude difference between treated and fellow eyes of all the groups on initial visit was associated with a poor visual outcome (P50 64% difference; p1 29% difference) whereas those with the smallest P50 and p1 amplitude difference was associated with improved vision at 2 years (P50 30% difference; p1 21% difference). The PERG and mfERG provide an objective measure of central retinal function in the progression of ARMD. A detectable PERG on presentation was the single best indicator of improved function and visual acuity at 2 years. The mfERG demonstrated disease progression from central retina into the paramacular regions over 2 years. Patients with poor visual outcomes had the largest inter-ocular amplitude difference on presentation, suggesting that such patients may have a worse prognosis following treatment.

Variant phenotype of Best vitelliform macular dystrophy associated with compound heterozygous mutations in VMD2

PURPOSE

To characterize the phenotype of members of a Swedish family with Best macular dystrophy and two distinct mutations in VMD2.

METHODS

Venous blood samples were obtained from six family members and screened for mutations in VMD2. Six individuals were examined clinically, four of whom were further investigated with full-field electroretinography (ERG), electro-oculography (EOG), multifocal electroretinography (mfERG), and optical coherence tomography (OCT).

RESULTS

The VMD2 mutations resulting in Arg141His and Tyr29stop were identified in family members. Two individuals harbored both mutations, one mutation in each VMD2 allele. These two family members had an abnormal EOG and their full-field ERG demonstrated widespread degeneration with a prolonged implicit time in the cone 30-Hz flicker ERG. MfERG verified reduction of the central retinal function and OCT demonstrated intraretinal fluid, swelling, and thickening of the outer retina-RPE-choroid complex (ORCC).

CONCLUSION

A previously undescribed severe form of Best macular dystrophy is associated with compound heterozygous mutations in VMD2.

Multifocal electroretinography and fluorescein angiography in retinal vein occlusion

PURPOSE

To interpret the responses of multifocal electroretinography (mfERG) of the central macula in retinal vein occlusion and correlate them with findings of fluorescein angiography, optical coherence tomography (OCT), and visual acuity.

METHODS

In a prospective observational case series, 25 patients with branch or hemiretinal vein occlusion were examined by means of mfERG, fluorescein angiography, OCT, and visual acuity.

RESULTS

In eyes with macular ischemia shown by fluorescein angiography, the implicit time was significantly longer than that in eyes without macular ischemia (P = 0.006; Mann-Whitney test). The amplitudes in the first-order kernel responses in the ischemic eyes were more reduced (P = 0.04; Mann-Whitney test), and the amplitudes in the central macula correlated well with visual acuity (P = 0.006; Pearson correlation). There was no significant correlation between the degree of retinal thickening as measured by OCT and the mfERG responses, although there was a trend toward reduced amplitudes in the maculae with central retinal thickening (P = 0.08; Pearson correlation).

CONCLUSION

Macular ischemia as measured by fluorescein angiography correlates well with the prolonged implicit time on the first-order kernel response in mfERG, but no significant correlation was detected between the responses of mfERG and the OCT findings. Further investigations will demonstrate if this can be used as a prognostic instrument in the selection of patients, who will most likely benefit from future treatments.

Topographic mapping of retinal function with the SLO-mfERG under simultaneous control of fixation in Best's disease

PURPOSE

To introduce the scanning laser ophthalmoscope-evoked mfERG (SLO-mfERG) as a new method to measure focal retinal function.

METHODS

Sixty-two healthy individuals and 12 patients with Best's disease were examined. mfERGs were recorded using a scanning laser ophthalmoscope as a stimulator and trigger device (He-Neon 632.8 nm) as well as a fundus-monitoring system (Infrared 730 nm).

RESULTS

Amplitudes in the central concentric area were found to be significantly lower in patients with Best's disease than in healthy controls, while no significant differences were found for the more peripheral areas.

CONCLUSION

SLO-mfERG is a reliable new technique for topographic mapping of retinal function under simultaneous control of fixation.