0:00:00.000,0:00:02.729 All right, next topic:[br]ocular misalignment. 0:00:02.730,0:00:05.669 If the eyes aren't aligned properly, 0:00:05.670,0:00:08.579 then you might have an exodeviation; 0:00:08.580,0:00:09.989 exo just means outwards, 0:00:09.990,0:00:12.479 or an esodeviation, that's inwards. 0:00:12.480,0:00:15.959 There's also a hyper and a hypo:[br]up and down. 0:00:15.960,0:00:18.389 So let's give a couple examples of this. 0:00:18.390,0:00:20.279 Let's say you have normal eyes,[br]and one of the ways 0:00:20.280,0:00:22.979 you can actually estimate[br]if a young child 0:00:22.980,0:00:25.289 has an eye that's turning in[br]or turning out, 0:00:25.290,0:00:27.329 is by using the Hirschberg test. 0:00:27.330,0:00:29.879 The idea is you shine a light[br]at the eyes, 0:00:29.880,0:00:31.679 and you look at the light reflex, 0:00:31.680,0:00:35.369 the corneal reflex of that light[br]bouncing off the eye, 0:00:35.370,0:00:38.609 and you compare its position[br]to the underlying pupil, 0:00:38.610,0:00:40.379 and normally that reflex ought to be 0:00:40.380,0:00:43.439 laying right on top of that pupil. 0:00:43.440,0:00:45.779 However, if you have one eye[br]that's deviated, 0:00:45.780,0:00:47.999 for example, this left eye[br]is turned inwards, 0:00:48.000,0:00:51.599 it's a left esotropia, then you can see 0:00:51.600,0:00:53.729 that the light reflex is not quite over 0:00:53.730,0:00:55.619 the pupil like it's supposed to be. 0:00:55.620,0:00:58.169 In this case, the right hypertropia, 0:00:58.170,0:01:02.309 the right eye is up a little bit, 0:01:02.310,0:01:05.309 and you can actually estimate[br]the amount of deviation; 0:01:05.310,0:01:07.499 and the rule is for every millimeter 0:01:07.500,0:01:09.869 that this light is off center,[br]so in this case, 0:01:09.870,0:01:13.889 if this was one millimeter[br]off of the pupil, 0:01:13.890,0:01:18.089 equals about seven degrees[br]in misalignment, or 15 prism diopters; 0:01:18.090,0:01:20.129 and this is the measurement[br]that we actually use 0:01:20.130,0:01:22.169 in clinic, prism diopters. 0:01:22.170,0:01:23.879 So we'll go over prisms in a second, 0:01:23.880,0:01:27.809 but the Herschberg test, very useful. 0:01:27.810,0:01:30.419 Now, we just talked about eso/exo, 0:01:30.420,0:01:32.279 tropia/phoria, what does that mean? 0:01:32.280,0:01:35.069 Well, tropia is when the eyes[br]are always deviated. 0:01:35.070,0:01:37.769 So, if you have an exotropia,[br]that means that the eyes 0:01:37.770,0:01:42.569 are deviated out, they're wall-eyed[br]and they're always deviated. 0:01:42.570,0:01:44.189 Now phoria, on the other hand, 0:01:44.190,0:01:47.729 just means that they're only deviated[br]sometimes. 0:01:47.730,0:01:50.789 So, example of a tropia 0:01:50.790,0:01:52.889 would be exotropia or esotropia, 0:01:52.890,0:01:54.779 and of course, the hyper and hypo. 0:01:54.780,0:01:56.069 And of course, of the phorias, 0:01:56.070,0:01:58.589 we would call it something like[br]an exophoria, 0:01:58.590,0:02:00.629 an esophoria, etc, etc. 0:02:00.630,0:02:03.389 So let's show an example of this:[br]this eye, 0:02:03.390,0:02:05.519 looks like this left eye[br]is deviated outwards, 0:02:05.520,0:02:07.409 and we use our paddle to cover the eye; 0:02:07.410,0:02:09.149 this is called the cover uncover test, 0:02:09.150,0:02:11.369 and you look for this eye movement,[br]and that tells you 0:02:11.370,0:02:12.449 that it's there all the time. 0:02:12.450,0:02:14.609 So no eye movement here, 0:02:14.610,0:02:16.859 because it looks like the right eye[br]is the dominant eye, 0:02:16.860,0:02:19.619 this is a left exotropia. 0:02:19.620,0:02:21.209 So let's try to correct it,[br]and to do that, 0:02:21.210,0:02:24.539 we use prisms to try to get things[br]back in alignment. 0:02:24.540,0:02:27.269 Things are still moving, so this isn't[br]quite enough prism 0:02:27.270,0:02:29.489 to get things back in alignment. 0:02:29.490,0:02:32.189 Let's try 20 diopters, and now, 0:02:32.190,0:02:34.469 when you do our cover uncover test, 0:02:34.470,0:02:36.689 we can see that things[br]are back in alignment. 0:02:36.690,0:02:41.789 This was a left exotropia,[br]approximately 20 degrees, 0:02:41.790,0:02:45.389 20 prism diopters, that is,[br]and you pick the tropias up 0:02:45.390,0:02:48.629 with the cover uncover test,[br]which is what we just did. 0:02:48.630,0:02:49.979 So let's try this one. 0:02:49.980,0:02:52.949 These eyes look like they're[br]in reasonably good alignment. 0:02:52.950,0:02:55.919 So let's do our cover uncover test.[br]No movement. 0:02:55.920,0:02:57.929 Things are still nice and stable. 0:02:57.930,0:03:00.929 Let's try the other eye; cover, uncover. 0:03:00.930,0:03:04.139 Things are still in perfect alignment,[br]wonderful. 0:03:04.140,0:03:06.809 But watch this: we'll do a cover 0:03:06.810,0:03:08.819 and we'll do a cross cover test,[br]look at that eye move-- 0:03:08.820,0:03:12.029 Oh, it's moving again-- Oh, that one's[br]moving. 0:03:12.030,0:03:13.619 This is what we call phoria, 0:03:13.620,0:03:17.159 it's there some of the time,[br]basically when we break fusion. 0:03:17.160,0:03:19.319 Let's see if we can get rid[br]of this for you. 0:03:19.320,0:03:23.729 Yep, about 10 diopters a prism[br]is all it took to fix this phoria. 0:03:23.730,0:03:26.219 So this was an exophoria. 0:03:26.220,0:03:28.049 It's there only some of the time, 0:03:28.050,0:03:32.099 and there was about 10 prism diopters[br]of it. 0:03:32.100,0:03:34.619 You pick up phorias with[br]the cross cover test, 0:03:34.620,0:03:37.919 completely different than[br]the cover uncover test. 0:03:37.920,0:03:39.209 Okay. 0:03:39.210,0:03:42.029 So this is a loose prism, 0:03:42.030,0:03:45.449 and certainly with kids, loose prisms[br]are the way to go. 0:03:45.450,0:03:47.189 They also make prism bars, 0:03:47.190,0:03:49.559 basically put a bunch of prisms[br]in a single bar, 0:03:49.560,0:03:51.599 and you just dial this thing up and down 0:03:51.600,0:03:54.389 till you find the right amount[br]of prism to correct. 0:03:54.390,0:03:58.019 I personally hate these bars,[br]I like to use the loose lens prisms, 0:03:58.020,0:04:00.899 they're a lot easier to use;[br]my own personal preference. 0:04:00.900,0:04:02.879 Certainly with children, you want to use 0:04:02.880,0:04:04.979 the loose lenses[br]because they're smaller. 0:04:04.980,0:04:06.929 If you use something this big,[br]kid's gonna try to grab it, 0:04:06.930,0:04:09.359 it's not gonna work well. 0:04:09.360,0:04:12.869 And if you have a tropia[br]that can't be corrected 0:04:12.870,0:04:15.329 by correcting with glasses or patching, 0:04:15.330,0:04:18.179 then you can always go to surgery; 0:04:18.180,0:04:20.398 And basically, when we have eyes[br]out of alignment, 0:04:20.399,0:04:22.018 we get them back in alignment, 0:04:22.019,0:04:23.729 and we do that by either shortening 0:04:23.730,0:04:25.979 or lengthening the rectus muscles. 0:04:25.980,0:04:28.589 In this case, this rectus muscle[br]is cut off 0:04:28.590,0:04:31.109 from its insertion and it's reinserted 0:04:31.110,0:04:35.849 back onto the sclera using suture,[br]and this basically lengthens 0:04:35.850,0:04:38.939 the effective length of this muscle[br]and gets things back in alignment. 0:04:38.940,0:04:40.919 And you can do the opposite,[br]you can also shorten the muscle 0:04:40.920,0:04:44.399 and reattach it back to[br]its original insertion. 0:04:44.400,0:04:46.439 Not an easy surgery to do,[br]because you. could imagine, 0:04:46.440,0:04:49.109 you're trying to do a scleral pass here 0:04:49.110,0:04:51.539 and not perforate into the eye[br]and hit the retina, 0:04:51.540,0:04:54.779 and the sclera is very, very thin. 0:04:54.780,0:04:57.929 I mean, so thin. We're talking about[br]a third of a millimeter 0:04:57.930,0:05:00.239 right underneath this muscle insertion. 0:05:00.240,0:05:02.429 You can very easily perforate[br]into the eye, 0:05:02.430,0:05:05.970 and not an easy surgery,[br]but very effective. 0:05:06.892,0:05:12.120 So that was ocular misalignment.[br]Let's move on.