||Andrew G. Lee, MD, Chairman, Department of Ophthalmology, The Methodist Hospital, Houston, TX, Professor of Ophthalmology, Weill Cornell Medicine; Sami Younes, Baylor College of Medicine, Class of 2022
||Summary: • Diplopia (seeing two images) can be grouped into being binocular or monocular o Binocular diplopia involves both eyes being open -One eye looks at target while the other does not -Covering one of either eye makes double vision disappear -Treatment requires neuro-ophthalmology • Can affect many parts of the visual pathway (i.e. nerve, neuromuscular junction, muscle) o Monocular diplopia involves one eye being affected -Only covering affected eye makes double vision go away • Covering unaffected eye results in double vision remaining (way to differentiate the two types of diplopia) -Etiology is usually ocular • i.e. dry eyes, corneal disease, refractive disease, cataracts -Can be unilateral or bilateral -Can be corrected using the pinhole test • Central beam of light passing through pinhole does not require much refraction • Eliminates stray light beams to eliminate monocular diplopia [Transcript of video] "So, we're going to be talking about diplopia. Diplo means two and opia means see (see two). So, when a patient has diplopia, they're seeing two. We'd like to know whether it is monocular or binocular, and binocular means we are viewing with both eyes open. It's not the same as bilateral. Monocular means you're viewing with only one eye and so when we have binocular diplopia, what that means is, the two eyes are not obviating the targets. So, this eye is looking at the target and this eye is not looking at the target, and you're going to have two images. When you have ocular misalignment in this case, an esotropia, if you cover either eye the double vision will go away. So, if I cover this eye, single vision, if I cover this eye, single vision. And so, the key question in any patient whose complaint is diplopia is whether it is monocular or binocular, but you can't ask it like that. You have to ask the patient, does the double vision go away if you cover either eye? And the key word is either eye. And the reason you can't just say "does it go away if you cover one eye?" is because if they happen to cover the eye with the monocular diplopia, they'll say yes to your question. And that is not what we're trying to achieve. So if you have monocular diplopia in your right eye and you just happen to cover the monocular diplopia right eye, they'll say yes so the question "does it go away if you cover one eye?" but it will be no if you cover either eye because if they cover the left eye, which is uninvolved, they'll still have the monocular diplopia. So monocular diplopia is almost always ocular. Most common things are dry eye, corneal disease, refractive error, cataract. If someone has monocular diplopia, that can either be unilateral or bilateral. And if you have monocular diplopia, we'd like to use the pinhole to see if we can make it go away. So, as you know, when you have rays of light entering into the eye, they have to be refracted to fall onto the retina. However, this particular central beam of light that is passing through the pinhole, actually its blur circle doesn't need as much refraction, and so it will eliminate the stray light beams and therefore it will reduce the monocular diplopia. So, the pinhole test is both useful for determining if someone's vision is refractive or not because we don't have to refract the peripheral rays. They're blocked. And it's also useful for monocular diplopia. It's a very quick, low-tech, no cost test to decide if someone's monocular diplopia can be made to go away with the pinhole. So monocular diplopia, that is not neuro-ophthalmology. Binocular diplopia, now we have a differential. It could be supranuclear, it could be nuclear, it could be infranuclear. It could be the nerve, the muscle, or the neuromuscular junction. Binocular diplopia patients do need to see us. But monocular, that's for general ophthalmology, and you can prove it with the pinhole." [Questions] Q: I see 2 images of anything that's not in focus. Like if I focus on my hand, everything in the background I see as 2 images, and vice versa. Is that diplopia? A: Yes, but it is a normal form of diplopia termed physiological diplopia. Though the brain can usually suppress this effect, some people notice the diplopia on unfocused objects, resulting in this.