Jason went thru a test today called VEP. He was put to sleep after a dose of hydro chlorate. Then electrodes were adhered to his scalp. The flash stimuli were used this time as opposed to the checker patterns done many years ago in Toronto.
It's supposed to measure the time (latency) it took for a stimulus (flash) to travel from the eye to the back of the brain where the visual cortex lies. Jason's result is like this;
P100 latency: 120ms (same for left and right eye)
Amplitude: 4.72uV for the right, 0.89uV for the left
The optometrist said the norm was 110ms so he was not far from the norm. And the fact that there is a recordable amplitude means he doesn't have a strong case of optic atrophy. So he said....
Of course, the inquiring mind of me as usual would search for more info on Google. What I find is that this result is typical of someone with optic dysfunction and not what the optometrist said as "within normal limit" unless there is a different norm in his lab. He did mention that the amplitude for the left eye could be interpreted by some as insignificant. In other words, the response is so weak that it could be considered as negligible. Now that is a concern cuz does that mean Jason doesn't show visual response even to light? He then said some people would repeat this test and may show a different reading. In fact he had to do it three times today to obtain a proper reading. So what does that tell us of Jason's vision? I really have no clue.
By the way, we were supposed to do a similar test for hearing but he woke up so that has to be rescheduled. But I am debating again as to the value of doing it.
First, this is not exact science as there can be factors affecting accuracy of reading. Second, what is this "science" reslly telling us? I know jason's vision is not "normal" per se. Does this quantify anything? Does that tell me how much his visual cortex "receives" and what is being processed? Not at all. The optometrist seems to tell me jason's optic nerve is not too bad (referring to previous observation that it's slightly pale), but the result says it is not "fine". Shall I repeat the test for the purpose of scientific inquiry? Unlikely. Now that I know this optometrist a little more. I guess he is the "half-cup full" type of person who is reluctant to be the bearer of bad news. While I remain "cautiously optimistic" about jason's development, I guess I will wait to see what the neurologist and the paedietric opthalmologist would say in the next appointments.
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