1 00:00:00,000 --> 00:00:12,028 [MUSIC] 2 00:00:12,028 --> 00:00:13,019 Hello, I'm Neil Parry. 3 00:00:13,019 --> 00:00:17,804 I'm a clinical scientist and I work in Manchester Royal Eye Hospital. 4 00:00:17,804 --> 00:00:22,582 I'm mainly involved in electrophysiology of vision which is something that we 5 00:00:22,582 --> 00:00:26,376 use to help diagnose and monitor various sorts of eye disease. 6 00:00:26,376 --> 00:00:30,785 But my main research interest is in color vision. 7 00:00:30,785 --> 00:00:33,474 Some of that has to do with electrophysiology and 8 00:00:33,474 --> 00:00:38,142 some of it has to do with psychophysics of color vision and color vision deficiency. 9 00:00:38,142 --> 00:00:42,373 And particularly how the individual photoreceptor 10 00:00:42,373 --> 00:00:45,167 populations contribute to that. 11 00:00:45,167 --> 00:00:49,769 Well we know that in the normal human eye there are three types of cone 12 00:00:49,769 --> 00:00:51,071 photoreceptors. 13 00:00:51,071 --> 00:00:54,139 These are the cells that work during the day, 14 00:00:54,139 --> 00:00:59,855 have high sensitivity to find patterns but also give us our color vision. 15 00:00:59,855 --> 00:01:04,210 But in actual fact what they have to do is work together in the retina so 16 00:01:04,210 --> 00:01:09,520 that an awful lot of the processing of color vision is done even before 17 00:01:09,520 --> 00:01:12,000 the signals leave the eye. 18 00:01:12,000 --> 00:01:17,310 So we know that there are photoreceptors that are tuned to different wavelengths 19 00:01:17,310 --> 00:01:21,810 of light, down towards the blue and towards the red and one in the middle. 20 00:01:21,810 --> 00:01:24,310 And it's the way they work together 21 00:01:24,310 --> 00:01:29,820 that allows us to have this extremely sensitive color vision that we have. 22 00:01:29,820 --> 00:01:33,960 We've got an opportunity to measure that electrical activity by putting some 23 00:01:33,960 --> 00:01:36,490 comfortable little electrodes around the eye. 24 00:01:36,490 --> 00:01:41,230 And we record something called the electroretinogram. 25 00:01:41,230 --> 00:01:46,230 And we understand from other studies, what's going on within 26 00:01:46,230 --> 00:01:50,180 the eye and how those electrical signals are being propagated. 27 00:01:50,180 --> 00:01:55,650 And so we can see evidence of that activity in the electroretinogram, 28 00:01:55,650 --> 00:02:01,480 which is gotten fairly simple thing to recall, but quite a complicated structure. 29 00:02:01,480 --> 00:02:05,636 And what we've been working on is ways of isolating individual classes of 30 00:02:05,636 --> 00:02:06,660 photoreceptor. 31 00:02:06,660 --> 00:02:09,510 So these are called long wavelength, medium wavelength, and 32 00:02:09,510 --> 00:02:11,440 short wavelength cells. 33 00:02:11,440 --> 00:02:18,200 And as I said already, they work together to give us our color vision. 34 00:02:18,200 --> 00:02:24,780 And so we can look at very specific signatures, each of these photoreceptors. 35 00:02:24,780 --> 00:02:26,380 And we can also include the rods, 36 00:02:26,380 --> 00:02:29,710 which are our night time cells as the fourth class of photoreceptor. 37 00:02:29,710 --> 00:02:33,679 It also has its own signature if you stimulate in these particular ways that 38 00:02:33,679 --> 00:02:35,450 we've been developing. 39 00:02:35,450 --> 00:02:39,750 So that's the eye, then there's an awful lot of activity that goes on from the eye 40 00:02:39,750 --> 00:02:43,170 back to the seeing part of the brain, which is really the back here. 41 00:02:43,170 --> 00:02:46,670 And that's our second opportunity to measure this electrical activity, 42 00:02:46,670 --> 00:02:49,190 using a technique called visual evoked potentials. 43 00:02:49,190 --> 00:02:50,080 And there again, 44 00:02:50,080 --> 00:02:54,250 we will put our electrodes on the site of interest which is at the back of the head. 45 00:02:54,250 --> 00:02:56,170 That's where the seeing part of the brain is. 46 00:02:56,170 --> 00:02:59,930 That's why you see stars if somebody clocks you on the back of the head, okay. 47 00:02:59,930 --> 00:03:03,160 And so again, by stimulating the visual system in particular ways, 48 00:03:03,160 --> 00:03:06,660 we can analyze the electrical activity coming out of the back of the head. 49 00:03:06,660 --> 00:03:11,680 And that tells us about the whole visual pathway, predominantly about what's 50 00:03:11,680 --> 00:03:17,040 going on in the cortex, but obviously about how those signals arrived there. 51 00:03:17,040 --> 00:03:21,799 I wear two hats, I have an interest in clinical electrophysiology, but 52 00:03:21,799 --> 00:03:24,535 also research interest in color vision. 53 00:03:24,535 --> 00:03:29,487 And these have come together in a rather nice way because with these new techniques 54 00:03:29,487 --> 00:03:34,654 we've been developing, we're able to see that each of our photoreceptor classes, 55 00:03:34,654 --> 00:03:39,919 and that's all three of the cones and the rods, have their own particular signature. 56 00:03:39,919 --> 00:03:43,131 What it also turns out is that there are particular sorts of genetic eye 57 00:03:43,131 --> 00:03:45,046 diseases that have their own signature. 58 00:03:45,046 --> 00:03:50,421 And by using these techniques together, we're able to give more accurate 59 00:03:50,421 --> 00:04:05,480 diagnoses and also to monitor the progression of some forms of eye disease.