![]() the sun, as described above), and negative ones if exposure is prolonged (due to cone cells becoming tired). Healthy patients experience both types: positive ones if looking at particularly bright objects (e.g. a red object creates a blue afterimage), last longer and their duration/intensity is related to the length of exposure. Negative ones have inverted colours (e.g. A classic example of a positive afterimage is when you accidentally look at the sun, look away and then see a small blob/imprint. Positive afterimages last for a short duration, are coloured the same as the original image and their intensity is unrelated to the length of exposure to the original image. Patients may experience both or just one of these forms of palinopsia.Īfterimages describe the phenomena of when an imprint of an object continues to be seen in your vision even though you are no longer looking at the object. There are two types of afterimages – positive and negative – and it is useful to differentiate between the two. Spencer S.Palinopsia refers to either excessive ‘after-images’ or ‘trailing’. For further information regarding the rights to this collection, please visit: Eccles Health Sciences Library, University of UtahĬopyright 2019. So positive visual phenomenon mostly migraine. And you got to differentiate it from photopisas which is just, "I see a flashing light" which is almost always a retinal sign. So if you just knew these three main categories, entoptic phenomenon, migraine aura or an occipital seizure, that's most of the positive phenomena that we see. Lasts seconds at a time they might have mental status changes or generalized. So small colored circles seconds at a time, bilateral, simultaneous, that is almost always occipital in origin and occipital seizures is what we're going to be worried about. In contrast, occipital seizure is usually not this jagged line It usually lasts seconds at a time and its geometric, small, little circles. So a bilateral, geometric, fortification, scintillating, colored or flashing scotoma that starts small and gets bigger lasts about 20 minutes and the headache follows that's going to be compatible with migraine. There might be colors in it and the colors might be flashing off and on and that's what we call a scintillation scotoma. The key differentiating features is the geometric nature of the phenomenon which we call a fortification scotoma because it looked like an old fort would look like in the old days and it typically starts small and gets bigger and moves across the visual field. If its bilateral we'd like to know the character of the phenomenon and migraine is a super common bilateral simultaneous and often hemianoptic positive visual phenomenon. So unilateral we've been thinking about entoptic phenomenon, flashing lights. So the retina cannot make a formed visual image, so it either makes flashing lights or nothing, that's pretty much what it can do. So patients with retinal detachments or posterior detachments or floaters might say I see a flashing light. ![]() Ent mean in and optic means eye and the most common causes of entoptic phenomena are vitreous traction, posterior vitreous detachment, retinal detachment. The most common unilateral visual positive phenomena that we have is called entoptic phenomena. In general, if its unilateral its in the eye and if its bilateral its in your brain. We like to know if its one eye or two eyes. And when patients complain about positive visual phenomena it's good to ask them to draw it. A flashing light, a jagged line, something like that. So positive visual phenomenon the patient will say I see something. So we are going to be covering positive visual phenomenon. Lee lectures medical students on positive visual phenomena. Lee, MD, Chairman, Department of Ophthalmology, The Methodist Hospital, Houston, TX Professor of Ophthalmology, Weill Cornell Medicine Peter Wojcik, Baylor College of Medicine Class of 2020ĭr. Pathology, Signs and Symptoms, Migraines, SeizuresĪndrew G. Positive Visual Phenomena I: Entopic, Migraine Occipital Seizures ![]() Positive_visual_phenomenon_Part_I_Entoptic_Migraine_Occipital_Seizures ![]()
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