Dark-adapted Oscillatory Potentials Research Articles

Retinal Functional Impairment in Diabetic Retinopathy.

Diabetic retinopathy (DR) is a neurodegenerative disease of the retina. The aim of our study was to analyze latency changes in a full-field electroretinogram (ERG) in patients with type 2 diabetes. This prospective study included 15 diabetic patients without DR, 16 diabetic patients with non-proliferative DR, 14 patients with pre-proliferative DR, 15 patients with proliferative DR, and 14 age-matched controls. All the participants underwent ophthalmologic examination and full-field ERGs. The ERGs were recorded with the Metrovision MonPackOne system. The latencies were analyzed for "a"- and "b"-waves in the dark-adapted (DA) 0.01 ERG, DA 3.0 ERG, DA oscillatory potentials, light-adapted (LA) 3.0 ERG, and 30 Hz flicker ERG. The delayed responses of healthy subjects compared to diabetic patients without DR were the DA oscillatory potentials (25.45 ± 1.04 ms vs. 26.15 ± 0.96 ms, p = 0.027). When comparing diabetic patients without DR and with non-proliferative DR, we did not obtain statistically significant delays. Significant delays in the DA 0.01 "b"-wave (61.91 ± 5.52 ms vs. 66.36 ± 8.12 ms, p = 0.029), DA 3.0 "b"-wave (41.01 ± 2.50 ms vs. 44.16 ± 3.78 ms, p = 0.035), and LA 3.0 "a"-wave (16.21 ± 0.91 ms vs. 16.99 ± 1.16 ms, p = 0.045) were found between non-proliferative DR and pre-proliferative DR. When comparing the groups of patients with pre-proliferative DR and proliferative DR, the LA 3.0 ERG "b"-wave (32. 63 ± 2.53 ms vs. 36.19 ± 3.21 ms, p < 0.0001), LA 30 Hz flicker ERG "a"-wave (19.56 ± 3.59 vs. 21.75 ± 4.74 ms, p= 0.025), and "b"-wave (32.23 ± 4.02 vs. 36.68 ± 3.48 ms, p = 0.017) were delayed. the electrophysiological findings from our study indicate that there is a substantial dysfunction of the neural retina in all stages of DR.

ISCEV Standard for full-field clinical electroretinography (2022 update)

The full-field electroretinogram (ERG) is a mass electrophysiological response to diffuse flashes of light and is used widely to assess generalized retinal function. This document, from the International Society for Clinical Electrophysiology of Vision (ISCEV), presents an updated and revised ISCEV Standard for clinical ERG testing. Minimum protocols for basic ERG stimuli, recording methods and reporting are specified, to promote consistency of methods for diagnosis, monitoring and inter-laboratory comparisons, while also responding to evolving clinical practices and technology. The main changes in this updated ISCEV Standard for clinical ERGs include specifying that ERGs may meet the Standard without mydriasis, providing stimuli adequately compensate for non-dilated pupils. There is more detail about analysis of dark-adapted oscillatory potentials (OPs) and the document format has been updated and supplementary content reduced. There is a more detailed review of the origins of the major ERG components. Several tests previously tabulated as additional ERG protocols are now cited as published ISCEV extended protocols. A non-standard abbreviated ERG protocol is described, for use when patient age, compliance or other circumstances preclude ISCEV Standard ERG testing.

Effects of fixed cutoff filtering on dark- and light-adapted ERG components and the application of variable cutoff filter

PurposeHuman oscillatory potentials (OPs) are derived from dark-adapted (DA) electroretinograms (ERGs) with fixed frequency cutoff filters while light-adapted (LA) OPs are generally not isolated from ERGs. Our purpose was to analyze the effect of cutoff frequencies on DA and LA ERG components using a series of fixed and variable filters.MethodsDA and LA ERGs were recorded from 10 healthy eyes of 10 subjects (mean age = 20.5 ± 6.7 years) following ISCEV standards. Each signal was filtered in the Fourier domain to acquire slow (a- and b-waves; below cutoff frequency) and fast (OPs; above cutoff frequency) components. Fixed cutoff frequencies ranged from 60 to 105 Hz and a variable cutoff frequency was calculated. Results were analyzed with statistical tests and specific models.ResultsDA ERG components were slightly influenced by the filter cutoff frequency. In contrast, fixed and variable filters significantly changed LA components: the lower the cutoff frequency the smaller the b-wave and OP3 and the higher the OP2/OP4 amplitudes. Analyzing the filter frequency limits a transition range between 68.9 Hz and 83.9 Hz was observed where amplitudes vary.ConclusionsThe present report shows that DA OPs may be isolated from ERGs using filtering procedures with high-pass cutoff frequency at about 75 Hz as recommended by ISCEV. On the other hand, the spectral distribution of low-frequency and high-frequency LA ERG components may overlap. Accordingly, filtering the signal using different cutoff frequencies is not necessarily separating b-wave and OPs.

A novel method for electroretinogram assessment in patients with central retinal vein occlusion.

Central retinal vein occlusion (CRVO) is the second most common retinal vascular disorder after diabetic retinopathy that affects the eyes. We propose a method for distinction of normal and central CRVO eyes based on electroretinogram (ERG). Seventeen patients with CRVO in one eye were analyzed. Their ERG signals were collected in six different stimuli, including four records in the darkness (dark-adapted 0.01, dark-adapted 3.0, dark-adapted oscillatory potentials, and dark-adapted 10) and two records in brightness (light-adapted 3.0 and light-adapted 30Hz flicker). Nonlinear features such as Hurst exponent (HE) and approximate entropy (ApEn) were extracted from healthy and CRVO eyes. Finally, a parabolic mapping and two criteria (theta angle and the density of points) were proposed to distinguish the groups. For ApEn, the P values of dark-adapted 3.0 oscillatory (P = 0.0433) and flicker (P = 0.0425) confirmed significant differences between the groups. For HE, the P values of dark-adapted 3.0 oscillatory (P = 0.0421) and flicker 30Hz (P = 0.0402) confirmed differences between the healthy and CRVO groups. The P values of theta angle for dark-adapted 3.0 (P = 0.0199), dark-adapted oscillatory (P = 0.0265), dark-adapted 10.0 (P = 0.0166), light-adapted 3.0 (P = 0.0411), and flicker (P = 0.0361) showed significant differences. Using the density criterion, the statistical test demonstrated a significant difference between the groups in dark-adapted 3 (P = 0.0038), dark-adapted oscillatory (P = 0.0102), dark-adapted 10.0 (P = 0.0071), light-adapted 3.0 (P = 0.0319), and flicker 30Hz (P = 0.0076). The proposed features have made it possible to distinguish between healthy and CRVO eyes. This method could be helpful in some cases with no definite diagnosis or to estimate the severity of CRVO.

Contribution of GABAa, GABAc and glycine receptors to rat dark-adapted oscillatory potentials in the time and frequency domain.

Retinal oscillatory potentials (OPs) consist of a series of relatively high-frequency rhythmic wavelets, superimposed onto the ascending phase of the b-wave of the electroretinogram (ERG). However, the origin of OPs is uncertain and methods of measurement of OPs are diverse. In this study, we first isolated OPs from the rat ERG and fitted them with Gabor functions and found that the envelope of the OP contained information about maximum amplitude and time-to-peak to enable satisfactory quantification of the later OPs. And the OP/b-wave ratio should be evaluated to exclude an effect of the b-wave on the OPs. Next, we recorded OPs after intravitreal injection of 2-amino-4-phosphonobutyric acid (APB), tetrodotoxin (TTX), γ-aminobutyric acid (GABA), strychnine (STR), SR95531 (SR), isoguvacine (ISO), (1,2,5,6-tetrahydropyridin-4-yl) methylphosphinic acid (TPMPA) and GABA+TPMPA. We showed that GABA and APB only removed the later OPs, when compared to control eyes. TTX delayed the peak time, and STR, SR and ISO reduced the amplitude of OPs. TPMPA delayed the peak time but increased the ratio of OPs to b-wave. Furthermore, administration of combined GABA and TPMPA caused the later OPs to increase in amplitude with time, compared with those after delivery of GABA alone. Finally, we observed that GABAc and glycine receptors contributed to a low-frequency component of the OPs, while GABAa contributed to both components. These results suggest that the early components of the OPs are mainly generated by the photoreceptors, whilst the later components are mainly regulated by GABAa, GABAc and glycine receptors.

Features of full field electroretinogram responses in children with early type 1 diabetes

Objective To observe the features of the full field electroretinogram (FF-ERG) in type 1 diabetes (T1D) children without diabetic retinopathy (DR). Methods Retrospective case study. Forty-one T1D children and 25 age-matched normal controls underwent a complete ophthalmic examination, including best-corrected visual acuity, refraction, intraocular pressure, slit lamp, fundus photography, indirect ophthalmoscopy, and spectral domain optical coherence tomography to exclude DR. All FF-ERG tests were performed by an experienced technician. The ERG series includes six protocols: dark-adapted 0.01 ERG (r-b 0.01); dark-adapted 3 ERG (mix-a 3.0, mix-b 3.0); dark-adapted 10 ERG (mix-a 10.0, mix-b 10.0); dark-adapted oscillatory potentials (OPS); light-adapted 3 ERG (c-a 3.0, c-b 3.0); light-adapted 30 Hz flicker (30 Hz FP) ERG. To compare the amplitudes and implicit times of the FF-ERG between the T1D and control group children. Results Compared with the control subjects , the FF-ERG amplitudes decreased and the implicit times increased in T1D. Except for r-b 0.01 (t=-0.228, P>0.05), the amplitudes of other FF-ERGs were all significantly attenuated (t=-1.664, -3.645, -4.324, -6.123, -5.846, -12.9, -14.4, -5.23; P 0.05). Conclusion The FF-ERG amplitudes decreased and implicit times increased in T1D children compared with the control normal subjects. Key words: Diabetes mellitus, type 1; Child; Electroretinography

Contributions of human rods and cones pathway to different components of oscillatory potentials in time and frequency domain

To investigate the contributions of human rods and cones pathway to different components of oscillatory potentials (OP) in time and frequency domain. Case-control study. Twenty subjects were divided into two groups, normal groups (NG) and cones pathway abnormal groups (CAG). All eyes were investigated by dark-adapted (DA) and light-adapted (LA) 3.0 ERG recommended by ISCEV. Data were output into the computer and processed and analyzed by the software Matlab7.0. First, to extract the OP by filter, then to get the frequency-amplitude relationship by FFT, after that the relationship was fitted by equations and lastly we statistic and analyze the parameters gotten from the equations. Compared with normal group [(48.63 ± 4.29), (158.00 ± 32.75), (69.27 ± 30.31), (38.5 ± 15.28) µV], the amplitudes of the first two components of dark-adapted OP in the CAG [(4.12 ± 3.20), (71.25 ± 25.43), (48.96 ± 20.05), (36.84 ± 14.26) µV] were significant decreased (t = 16.68, 5.77, P < 0.01). Frequency domain of LA and DA OP in the two groups was comprised with two components (harmonic and subharmonic). Compared with normal group, harmonic components of CAG were dramatic decreased (t = 2.72, P < 0.05; Z = -2.24, P < 0.05). The value of subharmonic component in CAG was lowest in DA OP compared with NG (t = 4.20, P < 0.005). Cones and rods pathway all contributed to the DA and LA OP Cones pathway mainly contributes to the earlier and faster components of OP while the rods pathway to the later and slower components.

Variability of Normal Values of Electroretinogram Parameters Due to Aging in Healthy Individuals.

Aim- To find normal values of implicit time and amplitudes of full-field electroretinogram and to determine their changes with age in healthy Romanian subjects. Material and Methods- The prospective study included 59 healthy subjects aged between 20 and 80 years old; in the end, we had valid ERG recordings for all tests from 54 subjects. All of the participants underwent full-field ERG, recorded with Metrovision MonPack One system. The implicit times and amplitudes were analyzed for a and b waves in dark-adapted 0.01 ERG, dark-adapted 3.0 ERG, dark-adapted oscillatory potentials, light-adapted 3.0 ERG, and 30Hz flicker ERG according to International Society for Clinical Electrophysiology of Vision (ISCEV) protocols. Results- ERG latency values were bigger in subjects above 50 years old than in younger subjects for b wave in dark adapted 0.01, dark adapted 3.0, light adapted 3.0 and dark adapted 3.0 flicker and for a wave in dark adapted 0.01 and dark adapted 3.0 ERG. There was no significant difference in latency values for dark adapted 3.0 oscillatory potentials between young and old subjects. Because of increased variability, we could not prove that observed differences for amplitudes held statistical significance. Conclusions- This study proves there is a major loss in retinal activity due to aging, most of it being caused by the rod cells delayed response. Also, oscillatory potentials do not seem to be affected by age, and could prove a valuable test to investigate for changes in patients with Diabetes mellitus.

Dark-adapted oscillatory potentials in preterm infants with and without retinopathy of prematurity

To describe the appearance and maturation of dark-adapted oscillatory potentials (OPs) in electroretinograms (ERGs) recorded from preterm infants, and to determine any effect of retinopathy of prematurity (ROP). Dark-adapted ERGs were recorded in conjunction with screening for ROP and at outpatient follow-up, using a flash luminance of 11.3 scot cdsm(-2) (4.06 phot cdsm(-2)). Eligible infants were born before 31weeks' gestation and/or weighed ≤1,250grams at birth. Presence or absence of OPs was established for 68 ERG recordings from 38 infants at maturities ranging from 30weeks' postmenstrual age (PMA) to 28weeks' post-term corrected age. 20 infants did not develop ROP, eight developed stage 1, one stage 2 and one stage 3 disease which regressed spontaneously. Eight infants received treatment for threshold ROP. OPs were present in 50% of infants at 36weeks' PMA and in all by 50weeks' PMA. The earliest appearance of OPs was at 30+5 weeks' PMA. Individual OP amplitudes increased and peak time of individual OPs decreased with increasing maturity. For infants with threshold ROP summed OP amplitudes tended to be smaller prior to treatment (6.5 vs 9.9μV, P=0.09) and were significantly smaller by 50weeks' PMA (14 vs 30μV, P=0.007). OP1 was less likely to be present in infants who developed stage 3 or worse ROP (P=0.000). Dark-adapted OPs are recordable in some preterm infants from 30weeks' PMA. Relative suppression of early OPs is a potential marker for developing ROP.

Study of Rod- and Cone-Driven Oscillatory Potentials in Mice

To characterize rod- and cone-driven oscillatory potentials (OPs) in mice. Dark- and light-adapted electroretinograms (ERGs) were obtained in three mouse models: wild-type C57BL/6J mouse, cone photoreceptor function loss 1 (cpfl1) mouse, and rhodopsin knockout (rho-/-) mouse. A Butterworth filter was used to extract OPs from ERG signals. Latencies were calculated from the extracted OPs. Major frequency components were determined from OP power spectra computed using fast Fourier transform (FFT). The total power of the OP signal (an alternative measurement of amplitude) was calculated by numerically integrating the area enclosed by its frequency spectra, which is analogous to the total energy of mechanical vibration. In C57BL/6J mice, dark- and light-adapted OPs had distinctly different peak frequencies (100 to 120 Hz and 70 to 85 Hz, respectively). In cpfl1 mice which possess pure rod ERGs, dark-adapted OPs had a peak frequency similar to those of the wild-type mice, whereas light-adapted ERGs and OPs were not detectable. In rho-/- mice with pure cone functions, both dark-adapted and light-adapted OPs had peak frequencies of 70 to 90 Hz, which were similar to those obtained from light-adapted OPs in wild-type mice. The total power of cone-driven OPs was less than 5% that of rod-driven OPs. In time-domain, cone-driven OPs occurred approximately 13 ms after rod-driven OPs. Cone- and rod-driven OPs exhibit significantly different characteristics in peak frequency, latency, and total power. By using these characteristics, it is possible to differentiate cone- and rod-driven OPs in mouse models. Understanding these OP features is essential for analyzing OPs.

Persistent functional and structural retinal anomalies in newborn rats exposed to hyperoxia

Previous studies have shown that newborn rats exposed postnatally to hyperoxia will develop a permanent impairment of the retinal function as determined with the electroretinogram (ERG). The purpose of our study was to examine whether postnatal hyperoxia equally alters the light- and dark-adapted ERGs and oscillatory potentials (OPs) as well as leads to permanent structural modification of the retina. During the first 14 days of life, cohorts of Sprague-Dawley rats were exposed to a hyperoxic environment, and ERGs were recorded at mean ages of approximately 25 and 55 days. Our results indicate that both light- and dark-adapted ERGs and OPs are already significantly altered within a few days following exposure to hyperoxia. None of the ERG and (or) OP parameters, with the exception of the a-wave, returned to normal values by 55 days of age. In fact some dark-adapted OPs were completely abolished following postnatal O2 exposure. Histological analysis revealed that the retina of rats exposed to hyperoxia failed to develop an outer plexiform layer and had a reduced count of horizontal cells, consistent with the permanent postreceptoral anomalies seen in the ERG responses. Our results suggest that postnatal hyperoxia causes a generalized retinal disorder leading to permanent structural modifications of the retinal cytoarchitecture and lasting anomalies of the rod and cone functions.Key words: rods, cones, electroretinography, oscillatory potentials, hyperoxia, retina, development.

Oscillatory Potentials and Light Microscopic Changes Demonstrate an Interaction between Zinc and Taurine in the Developing Rat Retina , ,

Our objective was to investigate whether zinc interacts with taurine to influence the development of retinal structure and function. Virgin female Sprague-Dawley rats were bred overnight and assigned to one of four treatments in a 2 × 2 factorial design with two levels of zinc (50 μg/g through gestation and 50 μg/g after parturition; 15 μg/g through gestation and 7.5 μg/g after parturition) and two levels of taurine (2 or 0 μmol/g). The control diet contained 50 μg/g zinc and 2 μmol/g taurine. Guanidinoethyl sulfonate (10 g/L), a taurine transport inhibitor, was added to the drinking water of the rats receiving 0 μmol/g taurine. At postnatal d 23, male pups (n = 10) were weaned onto their respective diets. Pup eyes were examined by biomicroscope and indirect ophthalmoscope at 4 and 7 wk; retinal folds and choroidal atrophy were detected in the pups deficient in zinc and taurine. Analysis of plasma zinc and tibial zinc concentrations revealed a significant interaction in these tissues (P < 0.05). Dark-adapted oscillatory potentials (OP) were recorded at 7.5–8.5 wk. Two-way ANOVA showed a significant interaction between zinc and taurine for OP2 and OP3 amplitudes; marginal zinc deficiency decreased the amplitude of the OP only when rats were also deficient in taurine. A significant depressing effect of marginal zinc deficiency was noted for OP1 amplitude. Taurine deficiency significantly depressed the amplitude of OP1 and OP4 . Histological examination of the retinas from rats deficient in both zinc and taurine revealed photoreceptor degeneration and confirmed retinal dysplasia. These data provide evidence for an interaction between zinc and taurine in retinal morphology and function.