Flash visual evoked potentials in patients with periventricular leucomalacia in children less than 1 year of age

Periventricular leukomalacia: an ophthalmic perspective

Periventricular leukomalacia (PVL) is a common magnetic resonance imaging (MRI) finding in cases of hypoxic ischemic encephalopathy. PVL, in MRI, is identified by the increased signal intensity of periventricular white matter on T2-weighted sequences which is more conspicuous in the posterior cortex. It occurs because of perinatal damage to the cerebral cortex. This insult is in the form of hypoxia, metabolic insults, prematurity, seizures, or infection. Periventricular area is most prone to damage owing to its immaturity and vascular supply. PVL is proven to affect vision in children. Depending on the area and cause of affection, PVL is associated with variable ophthalmic manifestations. It is known that visual function is closely linked to the overall neurodevelopment of a child. A multidisciplinary approach is required to promote the growth and development of these children, and in the midst of multiple disabilities, visual function should not be overlooked. A comprehensive knowledge of the ophthalmological presentation in the developing world can aid us in an early and accurate diagnosis and in intervention for better therapeutic recovery and rehabilitation of these children.

Flash visual evoked potentials (FVEP) in various stimulation conditions

Aim

To compare flash visual evoked potentials (FVEP) elicited using a Ganzfeld bowl (G), Mini Ganzfeld (MG) and Flash Goggles (GG) with eyes open and closed.

Patients and method

The study group comprised 17 volunteers with mean age of 30 years; all of them were examined with the Roland Consult electrophysiological diagnostic system. Active electrodes were placed at O₁ and O₂. With the G and MG stimulators, the flash generated by white-light-emitting diodes (LEDs) presented standard flash of 3 cd s m⁻². The GG used red LED flash of 3 cd s m⁻². Stimulus frequency of 1.0 Hz, low-pass filter of 1.0 Hz and high-pass filters of 100 Hz (G); 50 Hz (MG); 30 Hz (GG) were used. P2 amplitude and latency were compared by the means of the Wilcoxon matched-pairs signed-rank test.

Results

After right eye stimulation (from O₁; n = 17), the mean amplitudes of P2, elicited with the G, MG and GG, were 13, 7 and 10 µV, respectively. The respective latencies were 129, 114 and 110 ms. Hence, the difference between the results obtained with these stimulators was statistically significant (p < 0.05). The mean P2 amplitudes, acquired by the means of the G, MG and GG, were 13 µV, 7 µV and 10 µV for open eyes, and 11 µV, 8 µV and 8 µV for closed eyes. The respective latencies were 129, 114 and 110 ms for eyes open, and 127, 125 and 121 ms for eyes closed. These results of the MG (latency only) and GG (latency and amplitude) stimulation differed significantly (p < 0.05).

Conclusion

The amplitudes and latencies of the FVEP P2 elicited with different stimulators are not suitable for comparison. Closing the eye during the examination had a significant effect on the components of FVEP waveform elicited with the Flash Goggle and on the latency of P2 elicited with the MG.