 the last presentation. I wanted to talk about a patient that I saw in Dr. Burstein's clinic when I was a second year, year and a half ago, and this is really one of the best patient encounters I've had in residency. So I'll always remember this case. So this is a 16-year-old male with the history of a high myopia was referred to Dr. Burstein's clinic for a workup of RP. So his mom says that since he was a kid, he kept on running into things in the dark and he really didn't like playing outside when it gets dark. It's part of the RP questions. You ask whether he could see the stars and he said he really couldn't. So for the last several years he was told that he likely has retinitis pigmentosa and that his vision will get worse. But he says his vision's been stable for the last several years. You can see well in school and actually does well in school but he was instituted low vision training including braille and mobility for the last several years. So he was learning how to braille, how to cane, after classes he would go to extra classes. The letters were projected to him in like big fonts and he told me that he really didn't think he had any problems seeing the letters. He was just seeing fine. So otherwise pretty healthy kid. He did have a history of a right oral blowout fracture three years ago that did not require any surgeries. He has a high myopia with minus 16 in the right and minus 17 in the left. Where's contact lenses and he has a history of exotropia and stratospotia business surgery. His family history is very interesting. He has a maternal male first degree cousin that was diagnosed with RP at the age of three or four and this is actually the son of his mother's identical twin sister. The patient has four siblings and none have vision problems. I don't know the history of this of this cousin that he has. So his examination in clinic, his visual acuity was 20-30 in both eyes of Pinhosa 2020. The anterior segment examination was unremarkable. The dilated fundus examiner shows tilted in myopic optic disc and there's a mild pigment modeling in the macula. There's these dots that you can see in the mid periphery that's just artifact from the camera that you would usually see in high myops. I talked to Jim about it this and learned as well. But just to point out there are no bone spicules that's characteristic of a retinitis pigmentosa and the vessel seems normal. Macula OCT was normal and the Goldman visual fields were full in both eyes. So as part of the work up we did full field ERGs and just, you know, I think we're all, we've seen this print out and I just wanted to review a couple of things. And just to remind everyone the conditions that Dr. Creole uses. So the first five, one, two, three, four, five are done under scotopic conditions. So the patient is dark adapted for 20-30 minutes and then there's a dim blue flash and then records ERG and then there's a dim red flash and records ERG, a dim white light, a bright white light, and then the oscillatory potentials are measured as well. And then the patient is light adapted for at least five minutes and then you have the photopic ERG measurements which is the single white flash and then you record the ERG from it and then of course the 30 Hertz flicker for cone function. So these are all very important to look at but I'd like to draw your attention to these scotopic condition, the bright white flash. And what we can see is that the A waves are normal but the B waves is highly attenuated. It's about 81 microvolts in the right eye and 91 microvolts in the left eye. You know, this should be around 500 so the B waves are highly attenuated. So, and this suggests that there's abnormality in the bipolar cells. So the differential diagnosis right away with this is on top is congenital stationary night blindness, retinitis pigmentosa, rod cone dystrophy, vitamin A deficiency and especially for the residents and for us to review. What you call when the B waves is gone and what you're left is just the A wave is an electronegative ERG and the differential diagnosis for this is very small including CSNB or congenital stationary night blindness, melanoma associated retinopathy, X-linked juvenile retinoschesis and CRAO and CRVO. These are mostly tested for boards. So we think that this patient has CSNB. So this is a non-progressive disease. X-linked is the most common which, you know, likely explains that his cousin likely also has a X-linked congenital stationary night blindness, but it's also been reported to be inherited autosomal recessive and autosomal dominant. This is a rare class of diseases and we do not know its prevalence, but we do know that it's been reported in all in all races or all racial backgrounds. Visual acuity could be highly variable from being a very, very good visual acuity to 2020 to not very good in 2200. And the important associations include high myopia and stagmus and strabismus. Again, our patient has very high myopia and strabismus. So one of the main points I'd like to point out today is that CSNB is a genetically and phenotypically heterogeneous group of diseases. This is not one disease and you can classify this as types with normal fund disappearance and abnormal fund disappearance. In the normal fund disappearance, we have the Riggs and Schubert Bornstein types and with the fund is abnormal fund disappearance, we have fundus albipuntatus and Oguchi disease. And these are also part of the differential diagnosis as well. And these all carry the classic electronegative ERG response except one of them. So the question that we have is, you know, how can we distinguish the types especially in our patient? And this is mostly an academic exercise. And really it's ERGs. So in the Schubert Bornstein, we know that it's what's hit is by our bipolar cells. And we see the electronegative scotopic ERG again, the normal A wave with a decreased B wave that's shown in here. And, you know, this is really flat B wave. Our patients will hide like a little bit. The Riggs, we know that the mutation is mostly have problems with photoreceptors. And so the ERG shows basically absence of the A wave but have a robust B wave response. And this is all scotopic conditions. And to make it a little bit more complicated CSNB is associated with 17 genes now. And these are all the genes that I found in the literature. And the proteins that encode are localizes to either the RPE rods and bipolar cells. In X-link, which is the most common inheritance pattern, there's only two genes associated. And it's Nix and the CACNA1F. And they're both localized to bipolar cells. So Nix encodes a protein, Nectalupin. We don't know its function, but we know that it's involved in transmission of signal from photoreceptors to on bipolar cells. This is associated, we know that it's associated with a complete form of CSNB, which I'll talk about in the next slide. But this has a preserved cone function. The CACNA1F is encodes a voltage gate and calcium channel sub-unit. And it's associated in contrast to Nix, the incomplete form. And both rods and cone signaling are both affected. You know, we're always tested on this. And it's always a little bit confusing. But just to or yet, you know, especially for the resident, complete CSNB at least historically has been defined electrophysiologically. In scotopic conditions, you see complete CSNB as complete absence of both A and B wave. In the incomplete form, we still have the B wave. And that's, you know, the terminology matches. But when you look at the cones in the complete CSNB, the rods are basically abolished or rod signaling to bipolar cells are abolished, but the cones are not. So you still see a 30 hertz flicker compared to the incomplete CSNB, where both cones and rods signaling are affected. So it's a little confusing the terminology. So the question is, how about our patient? So it's scotopic condition, you know, it's pretty flat, consistent with complete CSNB. In photopic conditions, we do see that, you know, a small B wave, again, consistent with CSNB. In the 30 hertz flicker, we have a normal cone response. So we think that this is a complete form of a CSNB likely associated with NICS. Unfortunately, we do not have the genetic test to confirm this yet as of now. So just to just to finish up my talk, I just want to show you pretty pictures of the types of CSNB with abnormal fundus appearance. The first one is a fundus albipantatus, which you see this, you know, lots of yellow in the periphery. This is associated with RGH5 mutation. And some just important facts to highlight are just it's involved in or the pathophysiology involves delayed regeneration over the opposite, and that the rock, you know, the ERG is abnormal, but it can normalize with extended dark adaptation to hours or even days. And lastly, Oguchi disease, this is the rest in GRK mutation, mostly found in Japanese. And what you can see is this, this is a paper with a five year old kid with this like gold yellow sheen of the fundus. She was dark adapted overnight, basically kept in the dark and then took a picture of her fundus and, you know, it normalized. And after 30 minutes of light adaptation, the fundus goes back again. We do not know the mechanism, but this is called the Mitsuo Nakamura phenomenon. So in summary, CSNB is a non-progressive retinal dystrophy that mostly affects males. The Schubert-Bornstein type has a normal fundus with characteristic electronegative ERG. NYX is associated with complete CSNB and the KACNA1F is incomplete CSNB are both associated with X-linked and full field ERG is important diagnosis of CSNB in the workup of retinal dystrophy. So back to the patient. We ordered a genetic panel, which is not back yet. And, you know, the conversation I had with this patient, telling him that he's that this disease is non-progressive. He's not going blind. And he doesn't really have to do braille or caning that the parents just incredible, like, you know, his life plan dramatically changed after that conversation. So, you know, pretty awesome feeling to tell somebody that he's not going blind. So thank you. Any questions?