Just wanted to say THANK YOU for your amazing content. I'm a medical assistant who recently started working at a ophthalmology clinic with no previous experience in this specialty, and your videos have been so helpful!
As pointed out by Anton Matvev below!: A RAPD is often observed in the eye contralateral to the optic tract lesion. This is because more fibers in the optic tract come from the opposite eye, having crossed in the chiasm. This greater contribution from the opposite eye is because the nasal retina is bigger than the temporal retina (the temporal visual field is bigger than the nasal visual field in each eye). The resultant RAPD will be in the eye that has contributed the most fibers to the damaged optic tract (i.e., the eye opposite the lesion, on the same side as the homonymous hemianopia).
@majinkobe He moves the arrow back and forth because the arrow's meant to represent bright torchlight. You're not meant to leave the torch shining in the patient's eyes for too long. That's why he shines it in for just long enough to see the constriction, then moves it back out for the patient's comfort.
"when performing the swing light test in a patient who has a mature cataract there should be an "observed RAPD" in the eye without the cataract." Yup, its in the books, but its rare. Have you ever seen it? I haven't. The take home message is never attribute an RAPD to cataract, or you will have a very upset patient after cataract surgery. If you start to worry about "reverse RAPD" you can quickly get tied up in knots about stuff that doesn't matter.
+Annie Li The consensual light reflex is necessary to make sure the the motor portion of the pupil is working, and to rule out a sensory issue. For example, in a normal pupil, a light will be shined in the Right Eye, the right pupil will constrict and the Left eye will constrict as well (even though there was no light shined in it) that is called the consensual response. So you should check each pupil for direct sensory response and consensual response in both eyes.
+Jlricha2 Consensual light reflex is NOT normally required. If you shine a light at the right eye and the pupil constricts, you have demonstrated an intact afferent and efferent pathway on the right eye. Do the same on the left, and you have now shown intact afferent and efferent pathways on both eyes. Finally the swinging RAPD test is to compare the strength of the two afferent pathways. DONE. When is consensual reaction required? Only when the pupil does not respond on that side. You then need to decide whether problem is afferent or efferent. You therefore use the afferent pathway on the other side, while looking for the pupil reaction. Hope that makes sense. In practice you will never fail an exam for checking both direct and consensual response, as many people think it must always be tested, and many books state this too.
so sir u mean to say that the pupils remain dilated all time while u swing the light between the eyes. the optic nerve mediates constriction and if it is affected , the pupils wont constrict /remain dilated{relaxed}. right!
Thanks Neil, I can barely remember now! I was using keynote (mac powerpoint). I think I then exported a video which then edited with scripted audio in iMovie, to adjust times to match transitions. There is a video here ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-RYGcWHDVKL8.html&ab_channel=CreativeLive showing the export options from keynote which I was using. I have considered going back to the original keynote slides to export in 4k, but I'm too busy these days and the videos seem good enough.
Wouldn't it be lesions of the optic nerve? The optic tract is past the crossing of the central nerves and shouldn't manifest in relative differences between the eyes...
@@mrkampfcookie2118 A RAPD is often observed in the eye contralateral to the optic tract lesion. This is because more fibers in the optic tract come from the opposite eye, having crossed in the chiasm. This greater contribution from the opposite eye is because the nasal retina is bigger than the temporal retina (the temporal visual field is bigger than the nasal visual field in each eye). The resultant RAPD will be in the eye that has contributed the most fibers to the damaged optic tract (i.e., the eye opposite the lesion, on the same side as the homonymous hemianopia).
I am sorry I get my left's and right's very confused. When you say the left eye is affected do you mean the patient's left eye or the left side of the screen as I am looking at it?
