Electroretinographic evaluation in adult diabetics

Full-field and multifocal electroretinogram in non-diabetic controls and diabetics with and without retinopathy

OBJECTIVE

To compare retinal function assessed by full-field electroretinography (ffERG) and multifocal electroretinography (mfERG) in diabetes without retinopathy, diabetes with moderate non-proliferative diabetic retinopathy (NPDR) and in the absence of diabetes.

METHODS

Scotopic and photopic ffERG and mfERG was made in non-fasting volunteers, including 26 diabetic participants without retinopathy, 22 diabetic participants with moderate NPDR and 22 participants without diabetes using full International Society for Clinical Electrophysiology of Vision protocols.

RESULTS

Of the ffERG responses, significant deviation (p ≤ 0.05, corrected for multiple sampling and other relevant confounders) from the non-diabetic participants was seen in the diabetic participants only for the OP1-OP3 oscillatory amplitudes and the OP2 implicit time. This finding was independent of whether retinopathy was present or not. For the mfERG, minor amplitude or implicit time deviations were found for a small number of rings (R2, R4 and R5). Receiver of operating characteristic analysis showed that the single most prominent abnormality of the ffERG in diabetes, regardless of whether retinopathy was present or not, was the OP2 implicit time (area under the curve ≥ 0.80).

CONCLUSION

This bi-modal study of electroretinographic characteristics found that the most prominent anomaly associated with diabetes was a prolongation of the implicit time of the OP2 of the scotopic ffERG, while the most prominent added effect of non-proliferative diabetic retinopathy was a further prolongation of the OP2 implicit time. Although the variation in ERG characteristics is far too large for diagnostic purposes, the close association of the oscillatory potentials with the amacrine cells of the retina indicate that their function is particularly sensitive to diabetes.

Test-retest repeatability of the pattern electroretinogram and flicker electroretinogram

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Role of a mydriasis-free, full-field flicker ERG device in the detection of diabetic retinopathy

PURPOSE

To determine if the RETeval system can be used for the screening of diabetic retinopathy (DR) to provide early diagnosis.

METHODS

The subjects were 42 diabetic patients selectively recruited by examination of their medical records to have varying severities of DR. The severity of DR was classified into four groups according to the International Clinical Diabetic Retinopathy Disease Severity Scale. Full-field electroretinograms (ERG) without mydriasis were obtained by the DR assessment protocol of the RETeval system. Macular retinal nerve fiber layer (RNFL) thickness was measured by optical coherence tomography. We compared the DR assessment protocol results and the macular RNFL thickness among four groups. Moreover, an analysis was conducted on whether there was any correlation among the DR assessment protocol results, duration of diabetes mellitus, and RNFL thickness individually for each group of patients.

RESULTS

The mean ages and mean duration of diabetes mellitus of the four groups were similar. The DR assessment protocol results in the moderate-severe nonproliferative DR, and proliferative DR groups were significantly higher than those in the other groups (p < 0.001). The mean macular RNFL thickness was similar in all groups. No significant correlation was found between the DR assessment protocol results and duration of DM and the RNFL thickness.

CONCLUSIONS

Our results suggest that the RETeval full-field ERG system can be used as an adjunctive tool for the mass screening of DR, while macular RNFL thickness would not be useful.

A novel device for accurate and efficient testing for vision-threatening diabetic retinopathy

AIMS

To evaluate the performance of the RETeval device, a handheld instrument using flicker electroretinography (ERG) and pupillography on undilated subjects with diabetes, to detect vision-threatening diabetic retinopathy (VTDR).

METHODS

Performance was measured using a cross-sectional, single armed, non-interventional, multi-site study with Early Treatment Diabetic Retinopathy Study 7-standard field, stereo, color fundus photography as the gold standard. The 468 subjects were randomized to a calibration phase (80%), whose ERG and pupillary waveforms were used to formulate an equation correlating with the presence of VTDR, and a validation phase (20%), used to independently validate that equation. The primary outcome was the prevalence-corrected area under the receiver operating characteristic (ROC) curve for the detection of VTDR.

RESULTS

The area under the ROC curve was 0.86 for VTDR. With a sensitivity of 83%, the specificity was 78% and the negative predictive value was 99%. The average testing time was 2.3 min.

CONCLUSIONS

With a VTDR prevalence similar to that in the U.S., the RETeval device will identify about 75% of the population as not having VTDR with 99% accuracy. The device is simple to use, does not require pupil dilation, and has a short testing time.

Effects of 3,4-methylenedioxymethamphetamine administration on retinal physiology in the rat

3,4-Methylenedioxymethamphetamine (MDMA; ecstasy) is known to produce euphoric states, but may also cause adverse consequences in humans, such as hyperthermia and neurocognitive deficits. Although MDMA consumption has been associated with visual problems, the effects of this recreational drug in retinal physiology have not been addressed hitherto. In this work, we evaluated the effect of a single MDMA administration in the rat electroretinogram (ERG). Wistar rats were administered MDMA (15 mg/kg) or saline and ERGs were recorded before (Baseline ERG), and 3 h, 24 h, and 7 days after treatment. A high temperature (HT) saline-treated control group was also included. Overall, significantly augmented and shorter latency ERG responses were found in MDMA and HT groups 3 h after treatment when compared to Baseline. Twenty-four hours after treatment some of the alterations found at 3 h, mainly characterized by shorter latency, tended to return to Baseline values. However, MDMA-treated animals still presented increased scotopic a-wave and b-wave amplitudes compared to Baseline ERGs, which were independent of temperature elevation though the latter might underlie the acute ERG alterations observed 3 h after MDMA administration. Seven days after MDMA administration recovery from these effects had occurred. The effects seem to stem from specific changes observed at the a-wave level, which indicates that MDMA affects subacutely (at 24 h) retinal physiology at the outer retinal (photoreceptor/bipolar) layers. In conclusion, we have found direct evidence that MDMA causes subacute enhancement of the outer retinal responses (most prominent in the a-wave), though ERG alterations resume within one week. These changes in photoreceptor/bipolar cell physiology may have implications for the understanding of the subacute visual manifestations induced by MDMA in humans.

Effect of estrogen on electroretinographic responses in streptozotocin-induced diabetic female rats

The aim of this study is to investigate the effects of estrogen on functional changes in the retinas of streptozotocin (STZ)-induced diabetic rats by using an electroretinography. Female rats were randomly divided into four treatment groups: (1) Control (sham operation and vehicle administration); (2) STZ (sham operation and STZ administration); (3) OVX (ovariectomy and vehicle administration); and (4) OVX + STZ (ovariectomy and STZ administration). Full-field electroretinograms (ERGs) were recorded before OVX and STZ administration and 4 and 12 weeks after STZ administration. At 4 weeks after STZ administration, although there were no differences in the STZ and OVX groups compared with the Control group, the amplitude of the cone-response was significantly lower in the OVX + STZ group than in the Control group (P = 0.013). At 12 weeks after STZ administration, this response showed a similar tendency in the STZ and the OVX + STZ groups. At 12 weeks after STZ administration, the implicit times of OP3 and OP4 and of the cone-response were significantly delayed in the STZ and OVX + STZ groups (OP3: P = 0.030 and 0.050, OP4: P = 0.0060 and 0.0053, cone-response: P = 0.014 and 0.039), compared with in the Control group. Thus, the retinal functions in STZ-induced diabetic female rats were aggravated by OVX. OVX-induced estrogen deficiency resulted in earlier changes in the amplitudes of cone-response, especially in the diabetes, although this is a transient effect and it is difficult to explain. Recognizing the early neurosensory change would enable a better understanding of the effect of estrogen in the retina.

L- and M-cone driven ERGs are differently altered in Best's macular dystrophy

To study the L- and M-cone pathways and their interactions in patients with Best's macular dystrophy (BMD), ERG response thresholds were measured to stimuli which modulated exclusively the L- or the M-cones, or both in various combinations. The ERG threshold data could be described with a vector addition model. Compared with normals, BMD patients showed generally larger amplitudes of the L-cone driven ERGs. However, the M-cone driven ERGs were similar in amplitude but significantly phase advanced. The data confirm our previous observations that L- and M-cone pathways can be affected differently by retinal degeneration, despite their large physiological and biochemical similarities.

A review of current research on the effect of diabetes mellitus on the eye

It is estimated that almost one million Australians will have diabetes by the year 2000. Of those with diabetes a significant proportion will have eye-related conditions, the most debilitating being diabetic retinopathy. Appropriate identification and treatment can result in prevention of visual loss and blindness. The importance of diabetes as a cause of blindness in our community is realised by the commencement of a national program by the National Health and Medical Research Council to develop clinical practice guidelines for the management of diabetic retinopathy. The development of these guidelines was based on available evidence following an extensive review of the literature up to May 1996. This review is a summary of our advances in research on the effect of diabetes on various aspects of the eye and vision over the past two years. This review is a compilation of articles of research on the effect of diabetes on various aspects of the eye and vision. As a result of the enormous amount of effort and work by scientists and clinicians around the world, as well as space restrictions, the review covers the past two years only. Although every effort has been made to include as many research articles as possible, not all articles of research are covered. It is intended that this review provide an overview of the latest trends in research, particularly relating to new techniques and methods in the study of diabetes in ocular tissue as well as the new theories in the development of ocular damage to each of the tissue.