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Hello, I'm Neil Parry.
I'm a clinical scientist and I work in Manchester Royal Eye Hospital.
I'm mainly involved in electrophysiology of vision which is something that we
use to help diagnose and monitor various sorts of eye disease.
But my main research interest is in color vision.
Some of that has to do with electrophysiology and
some of it has to do with psychophysics of color vision and color vision deficiency.
And particularly how the individual photoreceptor
populations contribute to that.
Well we know that in the normal human eye there are three types of cone
photoreceptors.
These are the cells that work during the day,
have high sensitivity to find patterns but also give us our color vision.
But in actual fact what they have to do is work together in the retina so
that an awful lot of the processing of color vision is done even before
the signals leave the eye.
So we know that there are photoreceptors that are tuned to different wavelengths
of light, down towards the blue and towards the red and one in the middle.
And it's the way they work together
that allows us to have this extremely sensitive color vision that we have.
We've got an opportunity to measure that electrical activity by putting some
comfortable little electrodes around the eye.
And we record something called the electroretinogram.
And we understand from other studies, what's going on within
the eye and how those electrical signals are being propagated.
And so we can see evidence of that activity in the electroretinogram,
which is gotten fairly simple thing to recall, but quite a complicated structure.
And what we've been working on is ways of isolating individual classes of
photoreceptor.
So these are called long wavelength, medium wavelength, and
short wavelength cells.
And as I said already, they work together to give us our color vision.
And so we can look at very specific signatures, each of these photoreceptors.
And we can also include the rods,
which are our night time cells as the fourth class of photoreceptor.
It also has its own signature if you stimulate in these particular ways that
we've been developing.
So that's the eye, then there's an awful lot of activity that goes on from the eye
back to the seeing part of the brain, which is really the back here.
And that's our second opportunity to measure this electrical activity,
using a technique called visual evoked potentials.
And there again,
we will put our electrodes on the site of interest which is at the back of the head.
That's where the seeing part of the brain is.
That's why you see stars if somebody clocks you on the back of the head, okay.
And so again, by stimulating the visual system in particular ways,
we can analyze the electrical activity coming out of the back of the head.
And that tells us about the whole visual pathway, predominantly about what's
going on in the cortex, but obviously about how those signals arrived there.
I wear two hats, I have an interest in clinical electrophysiology, but
also research interest in color vision.
And these have come together in a rather nice way because with these new techniques
we've been developing, we're able to see that each of our photoreceptor classes,
and that's all three of the cones and the rods, have their own particular signature.
What it also turns out is that there are particular sorts of genetic eye
diseases that have their own signature.
And by using these techniques together, we're able to give more accurate
diagnoses and also to monitor the progression of some forms of eye disease.