Safety and efficacy evaluation of a new electrode (the LVP electrode) part I. Pattern ERG pilot study

The DTL ERG electrode comes in different shapes and sizes: Are they all good?

PURPOSE

Although the DTL fiber electrode has been in use in the ERG field for more than four decades, its composition was never clearly defined. We compared five different types of conductive (DTL type) yarn (differing in terms of mass, number of filaments, and crimping degree) in order to determine whether we could identify one that would be better suited for the recording of ERGs.

METHODS

Photopic flash ERGs were recorded from five subjects using the following DTL electrodes: 27/7, 22/1, 11/1, 11/1*2, and 22/1*2. Data analysis included amplitude and peak time measurements of the a- and b-waves in the time domain (TD) as well as measurements of specific frequency descriptors of the ERG waveform in the time-frequency domain using the discrete wavelet transform (DWT) approach. The degree of comfortableness was also assessed in 12 subjects with two surveys (Likert 5-point and the ranking scale).

RESULTS

Comparisons of TD and DWT parameters did not permit to identify the best DTL electrode, all yielding comparable measures. There was a slight trend for the largest electrode (22/1*2) to yield the largest response, but this was at the expense of comfort, the 22/1*2 electrode being rated as the least comfortable.

CONCLUSIONS

Given the minimal impact the different electrodes had on the amplitude of the signal, we believe that comfort should dictate our choice. It would appear from our results that use of a multifilament electrode is the best choice since one can get an electrode whose size is optimized for the recording of large responses while minimizing the foreign-body sensation due to the small size of each of the filaments that compose this multifilament electrode.

Pattern Electroretinography Changes in Patients with Established or Suspected Primary Open Angle Glaucoma

PURPOSE

To assess pattern electroretinogram (PERG) changes in patients with established or suspected primary open angle glaucoma (POAG).

MATERIALS AND METHODS

Transient PERG using LV Prasad eye electrodes were performed in 76 normal, 32 glaucomatous and 22 glaucoma suspect eyes. The P50 amplitude, N95 amplitude and P50 latency were analyzed. The results were further analyzed with receiver operating characteristic (ROC) curves and discriminant function analysis (DFA).

RESULTS

The P50 and N95 amplitude of the POAG and glaucoma suspect groups were significantly reduced. There was significant shortening in the P50 latency in the POAG and glaucoma suspect groups. DFA using the P50 amplitude, N95 amplitude and P50 latency waveform parameters showed a sensitivity and specificity of 76.67 and 88.57% respectively.

CONCLUSION

Pattern ERG demonstrated significant changes in POAG patients and suspects. ROC curves for the three wave parameters demonstrated that N95 amplitude was the better indicator for diagnosis of POAG when used individually. How to cite this article: Ganekal S, Dorairaj S, Jhanji V. Pattern Electroretinography Changes in Patients with Established or Suspected Primary Open Angle Glaucoma. J Current Glau Prac 2013;7(2):39-42.

Multifocal electroretinography in type 2 idiopathic macular telangiectasia

BACKGROUND

To characterize the electroretinographic response of the macula by multifocal electroretinography (mfERG) in patients with type 2 idiopathic macular telangiectasia (MacTel).

METHODS

A prospective study of mfERG in patients with type 2 MacTel was conducted from April 2009 to November 2009. mfERGs were recorded using a visual evoked response imaging system (MonElec2, Metrovision, Perenchies, France). The International Society for Clinical Electrophysiology of Vision (ISCEV) guidelines were followed. Patients with type 2 MacTel confirmed by fundus fluorescein angiography without subretinal neovascularisation were included. For recording purposes, 61 stimulus hexagonal elements were used. The first-order kernel mfERG responses were analyzed. Individual mfERG responses for the hexagons were grouped into concentric rings centered on the fovea for analysis (< 2, 5-10, 10-15 and >15°). Student's t-test and Mann-Whitney U test and linear regression analysis was performed with STATA ver 11.1 (StataCorp, College Station , TX, USA).

RESULTS

Twenty eight eyes of 14 patients and 20 eyes of ten normal controls were included in the study. The mean logMAR visual acuity of the patients was 0.51 (Snellen equivalent 20/63). The mean N1 amplitude (nv/deg(2)) of patients were significantly reduced compared to controls and were as follows: 8.91 ± 14.00 vs 43.44 ± 9.55 (p < 0.0001) in less than 2°, 9.24 ± 10.47 vs 22.00 ± 3.87 (p < 0.0001) in 5-10°, 8.57 ± 10.02 vs 15.24 ± 1.89 (p < 0.0001) in 10-15°, and 7.03 ± 6.52 vs 12.47 ± 2.62 in > 15° (p < 0.001). The mean P1 amplitude (nv/deg(2)) was also significantly reduced in patients compared to controls and was as follows: 27.66 ± 37.44 vs 96.20 ± 12.41 (p < 0.0001) in less than 2°, 22.61 ± 19.38 vs 53.78 ± 9.79 (p < 0.0001) in 5-10°, 18.75 ± 20.21 vs 35.22 ± 4.16 (p < 0.001) in 10-15°, and 17.10 ± 12.54 vs 25.71 ± 3.93 (p < 0.001). The implicit time of N1 and P1 were also delayed significantly in all the rings. The mean central foveal thickness assessed by optical coherence tomography (OCT) scan was 84.78 ± 45.12 μm. There was poor correlation between mfERG amplitudes or implicit times with either the visual acuity or OCT central thickness.

CONCLUSION

mfERG showed significant reduction in amplitudes and implicit times of the waveforms in patients with type 2 MacTel in all the rings, suggesting a more generalized affection of the macula. The maximum reductions were seen in the <2(o) rings. Although there was poor correlation between the visual acuity and the amplitudes a of the waveforms, mfERG is a useful investigative modality for functional assessment of macula in type 2 MacTel patients.

Safety and efficacy evaluation of a new ERG electrode (the LVP electrode) part II. Flash ERG pilot study

A new disposable, non-contact electrode (LVP electrode) was evaluated for use in recording flash ERG. A comparison of DTL and LVP electrodes showed reproducible waveforms for all components analysed. There was a good correlation obtained between the DTL and LVP electrodes. The LVP electrode is safe, less expensive and has less movement of the fiber due to its rigidity.