||Andrew G. Lee, MD, Chairman, Department of Ophthalmology, The Methodist Hospital, Houston, TX, Professor of Ophthalmology, Weill Cornell Medicine; Smruti Rath, Baylor College of Medicine, Class of 2022
||Summary: • Refraction o Myopia - light beam focuses in front of the retina o eye is too long o myopic shift - lens thickens o Hyperopia - light beam focuses behind the retina o eye is too short o hyperopic shift - retina pushed forward • Change in lens - Myopic Shift o Diabetes o hyperglycemia drives sugar into the lens causing it to swell o don't give glasses if sugar is not under control o Medications o sulfa derived medications: Topamax and Diamox • anteriorly rotate the ciliary body o Causes myopic shift o shift the lens iris staff forward and cause angle closure • Change in retina - Hyperopic Shift o Subretinal fluid o steroids causing central serous retinopathy o shift retina forward o Choroidal Folds o caused by idiopathic intracranial hypertension o space flight associated neuro-ocular syndrome o any causes of papilledema or choroidal folds due to fluid pressing on the black of the globe o Choroidal Thickening o electrolyte abnormalities - hyponatremia • inappropriate anti-diuretic use • SIADH - can occur transiently after pituitary surgery [Transcription of video] "So, we're going to cover today something that's very unusual, which is a refractive shift; which is common in other specialties, but a refractive shift in neuro-ophthalmology. So, when would a neuro-ophthalmologist need to know about a transient hyperopic or transient myopic shift? So as you know, the whole point of the front of the eyes is to refract the light and we're going to be focusing it; and if the beam is in front of the retina, that means the eye is too long, and that's what typically what happens in myopes who have axial myopia. But if the beam is being focused behind the retina, that means we're too short an eye, and that is a hyperopic shift. So, we can have hyperopia or myopia and the way that the shift can occur is if the retina is pushed forward. That will make the eye shorter and that will cause a hyperopic shift. Or if the lens thickens, that will cause a myopic shift. So, we have two ways to change the refractive error, and those could be from neuro-ophthalmic disorders; either a change in the lens or change in the position of the retina. So, starting with the change in the lens, the thing we see most often in neuro-op with a transient myopic shift is diabetes from the sugar: the hyperglycemia drives the sugar into the lens and through various mechanisms involving the polyol pathway and sorbitol; sugar gets trapped inside the lens, the lens swells, and that can lead to a myopic shift. And we never want to give glasses to someone whose sugar is not under control. With the front of the eye, we also have medicines that can anteriorly rotate the ciliary body and make the eye get a myopic shift and that's medications that are sulfa derived medications, especially Topamax, but also Diamox. These things can cause a myopic shift, they can shift the lens iris staff forward and cause angle closure. So, Topamax is one of the most common medicines that we see causing this. In the posterior segment, hyperopic shift is caused because the retina is moving forward, usually from subretinal fluid; and for neuro-op, that's steroids causing central serous retinopathy. But anything that causes a serous detachment can do this. We also have the hyperopic shift from fluid in the sheath pressing on the back of the globe and that causes choroidal folds, so we can see a hyperopic shift in idiopathic intracranial hypertension or any cause of papilledema or any cause of choroidal folds; including the space flight associated neuro-ocular syndrome, which you can read about more on your own, and we can get a hyperopic shift if we have choroidal thickening. And that choroidal change can occur from electrolyte abnormalities including the hyponatremia of the syndrome of inappropriate anti-diuretic or SIADH, which occurs transiently sometimes after patients have had pituitary surgery or have SIADH for any number of different reasons. So, you really need to know about the refractive shifts in neuro-ophthalmology producing transient myopia or transient hyperopia. It can either be the front of the eye, the lens, or the back of the eye, the choroid, and under the retina."