Nelson: Today's topic is management of diplopia issues. The first case is a 50-year-old man with a scleral buckle in the right eye for several years, and the retina surgeon said the buckle cannot be removed. He's had diplopia since the buckle has been in place and currently wears a patch over his right eye because of this diplopia. His exotropia is fairly comitant and 20 prism diopters (PD). Visual acuity is 20/80 in the right eye and 20/20 in the left eye. How would you manage the diplopia and exotropia in this patient?
O'Hara: The first question I have is whether this patient can fuse. I will put him in Fresnel prisms to see if he can fuse, in either all or some of the gazes. If he can't fuse at all with prisms in place, then surgery is probably not going to help. If he can fuse in all gazes, surgery is an option. If he can fuse in a couple of gazes, the prisms demonstrate to him what the outcomes of surgery might be.
Nelson: How long would you keep Fresnel prisms on before you see him and see if it has made a difference?
O'Hara: I like patients to have time to use the prisms in a lot of different situations. I don't think an hour or a day is enough. They need to go out into the world. They need to see if they are fusing when they are in a car or reading. I think a week is a good amount of time to try to test drive the prisms.
Nelson: Let's assume that the patient does have some functional areas of single binocular vision and is happy to proceed with surgery if that can possibly be done. What type of surgery would you do?
O'Hara: Before I do any surgery, I would counsel him that he still might have diplopia afterward and he might have a different type of diplopia. Just because the Fresnel prisms gave us some idea of the outcome, there is no guarantee. I would do horizontal surgery, possibly only on one muscle. I would probably explore the medial rectus muscle first. When I do a reoperation, I usually look at the two muscles that I might be operating on before beginning the surgery because you never know what you have until you are in the operating room.
Nelson: Let's assume that both muscles are in the normal position.
O'Hara: So they're over the buckle and the retina surgeon told me that he cannot remove the buckle. Whatever surgical plan I choose, I'm going to have to keep the buckle in place. You could recess or advance the medial rectus muscle. If this is a patient with other heath problems, rather than taking the muscle off, you could tuck the muscle. Because this is only a 20 PD exotropia, you could tuck the muscle the same amount for 20 PD of exotropia that you would do for a resection of the muscle. I hesitate to use adjustable sutures for these cases because I think that there are too many variables.
Bacal: I agree with many of Dr. O'Hara's points. In this patient, it is possible that even if you align the eyes with prisms or surgery, he may not be able to fuse those two images, because of the quality of the vision and any associated distortion. So that needs to be determined first. Also, if you are going to contemplate surgery because of the discrepancy of the vision, you're going to only want to operate on the eye with the buckle. Twenty prism diopters is the maximum deviation where I would consider a large unilateral-lateral recession versus two-muscle surgery. Typically I would avoid the buckle and use that part of the muscle just behind the buckle as my consideration of the insertion.
Nelson: Let's assume that you explored that right lateral rectus muscle at the beginning of your procedure and found that the buckle was out a bit and probably right near where you would place the muscle for a recession. Would that change what you would do?
Bacal: I don't think the buckle would be back so far that I couldn't reattach the muscle posterior to it, but it may force me to operate on the medial rectus muscle.
Nelson: If you did the medial rectus muscle, would you do a re-section or a tuck?
Bacal: I would typically perform a resection if possible, as long as the scarring is not significant.
Wang: As Dr. O'Hara said, I would try to find out if the patient can fuse using Fresnel prisms. I assume a forced traction test is going to be normal because the patient is comitant. I would explore the lateral rectus muscle and probably put it on an adjustable suture, because I agree with Dr. Bacal that I'm probably going to put it past where the encircling band is. If it looked like it was going to end up right on a piece of silicone, then I would tack it behind there.
Nelson: Let's say that you did your adjustable procedure and you were relatively close and did not have to make any real adjustment. Would you be concerned that the sutures are over the buckle?
Wang: Not necessarily. There's usually a lot of fibrosis just around the buckle and muscles can attach there. It would not be ideal. You would have more scarring later. It may be a rare case, but I think I would take that risk to get good alignment if I'm looking for fusion.
Nelson: The second patient is a 30-year-old man who had accommodative esotropia and, for some reason, had LASIK surgery for his hyperopia. He is now complaining about diplopia after the LASIK surgery. His visual acuity is 20/20 in the right eye and 20/25 in the left eye. He has a comitant esotropia of 25 PD. How would you manage the diplopia and the esotropia?
Bacal: I would hope that the patient was counseled about this before considering LASIK surgery. Sometimes the LASIK surgeon is not going to consider these factors. What is his current refraction?
Nelson: Fairly close to plano.
Bacal: If he is plano, we are somewhat limited in options as far as manipulating the refractive correction and then the prism that would be needed to remove the double vision is going to be a high level for grinding. That is unlikely to be feasible and he is unlikely to be satisfied with a Fresnel prism in the long term, although you could try that temporarily just to relieve the symptoms. Ultimately, this patient will require a medial rectus recession in both eyes.
Nelson: He won't be happy because he had the LASIK surgery so he wouldn't need glasses and now you're saying he needs glasses. How would you proceed with the surgery?
Bacal: I would perform medial rectus recessions and consider an adjustable suture on one of them.
O'Hara: My first step would be to do a refraction pushing as much plus as possible, and also possibly a cycloplegic refraction just to make sure that there isn't any hyperopia. I would perform a bimedial recession with an adjustable suture.
Wang: I agree with my colleagues. I would also try to find out whether this patient fused in the spectacles prior to the LASIK surgery and which was the preferred eye. This patient may have fixation-switch diplopia and may now be using the right eye. If the left eye was dominant prior to the LASIK surgery, he may now be out of his suppression scotoma that he had all of his life with the accommodative esotropia.
Nelson: Would that alter your treatment?
Wang: It depends on how much the diplopia was bothering the patient. I would operate. If he still had diplopia after surgery, I might give him a contact lens to switch fixation back to the left eye.
Nelson: The next case is 50-year-old woman who had glaucoma, had a tube shunt implanted at the 4-o'clock position of her right eye, and now has vertical diplopia postoperatively. Her visual acuity is 20/100 in the right eye and 20/25 in the left eye. She has a mild depression deficit and diplopia that has persisted for 7 months. She has a right hypertropia of 18 PD. How would you manage this patient's diplopia and right hyperopia?
Wang: I assume the patient has a valve that's restricting up above so there's a depression issue. The patient is worse in down gaze?
Nelson: Yes, she's had a mild depression deficit and has a slightly larger right hypertropia in down gaze. But her main concern is that she can't function straight ahead.
Wang: I would start with Fresnel prisms to see what the fusional ability is. This is another good example of the fact that visual acuity doesn't obviate diplopia. To go to the right eye, you would have to relieve that restriction and I don't think that will be possible. I don't think you can go superiorly in the right eye to where the implant is. Resection of the inferior rectus muscle on that side doesn't work well and most surgeons would be reluctant to go to the left eye in this circumstance. Is this patient wearing spectacles?
Wang: I would start with the Fresnel prisms and try to treat this non-surgically, to see if the patient can continue to tolerate prisms. You may be able to split them between the eyes.
Nelson: Let's assume that the patient comes back at the required time and says there is not as much double vision but she cannot tolerate the prisms. By splitting the prisms, both eyes are now blurry.
Wang: I wouldn't use the Fresnel prism in the left eye. If the Fresnel prism worked, I would grind it in the glasses.
O'Hara: The 2-o'clock position is an unusual position to place the glaucoma drainage device; most valves are placed superotemporally but that's beside the point. I would check forced duction to see how much restriction the patient had. If there was a lot of restriction, I would probably explore the superior rectus muscle in the right eye to see if there's some scarring from the glaucoma drainage device and if it could be relieved. If I found that, and certainly I wouldn't go in on the nasal side, I would make a temporal conjunctival incision and then I would explore the superior rectus muscle. If I found some significant scarring, I would try to free that up and possibly recess the superior rectus muscle. There's some incomitance in measurements where the right hyperopia is worse in down gaze. If that persisted after surgery, I might consider placing a Faden on the left inferior rectus muscle to limit its down gaze and match it to the other side.
Nelson: Would you have the glaucoma surgeon involved in the surgery? Or would you feel comfortable enough to just go ahead and relieve any scarring?
O'Hara: It would be ideal to have the glaucoma surgeon there. If it's not possible, you have to be extremely conservative. If you think that you're going to in any way compromise the glaucoma drainage device, you stay away from it.
Bacal: For an adult-acquired vertical strabismus, there are a couple of key concepts you have to use as your starting point. Because this patient did not have childhood strabismus, her vertical fusional amplitudes are going to be minimal. When I discuss surgery with a patient like this, I explain that it is difficult to relieve the double vision completely. She may still require some amount of prism after the surgery, but it is likely to be reduced.
Nelson: Would you give the patient prisms preoperatively and see how she does or would you proceed with surgery?
Bacal: An 18 PD vertical strabismus with incomitance in down gaze is going to limit the effectiveness of a prism. You might be able to get her diplopia free in primary position watching television, but it is going to really limit her functionality. I would tell this patient she most likely will need surgery, but with the understanding that there may be some need for a prism postoperatively. If we could make her misalignment more comitant, that will also help benefit the use of prisms. In this case, there is likely restriction in down gaze. My goal surgically would be to recess the superior rectus muscle and try to free up some scar tissue if possible.
Wang: If the prisms that I gave were not tolerated and I had to go back to the superior rectus muscle, I would have to overcorrect the patient a little, really recess it so that in down gaze she may be able to fuse.
Nelson: Would you use an adjustable suture in that case?
Wang: No. At that age down gaze is her functional position, so I would want to put it back far enough that she might fuse.
Nelson: The next case is a 70-year-old man with a history of amblyopia and cataract surgery in the left eye. His visual acuity is 20/20 in the right eye and 20/60 in the left eye. He noted the onset of diplopia following the cataract surgery and has a comitant esotropia of 20 PD. How would you manage this patient's diplopia and esotropia?
Bacal: Did you say the patient was esotropic?
Nelson: We know he has been observed since he was young for a lazy eye. His vision was poor in the left eye compared to the right eye and he has worn glasses since he was a young boy. He's never had diplopia before.
Bacal: I would try to learn the refraction he had before the cataract surgery and see what his refraction is now. I've seen some patients who had a cataract with poor vision and they were not aware that they had double vision until after the cataract surgery. Then I would see if he could fuse with prisms. If he can, I would consider strabismus surgery. A visual acuity of 20/60 is on the edge for considering medial rectus recession in both eyes or a recess-resect procedure in the left eye.
Nelson: What if the patient asks why he suddenly developed double vision when he never had it before?
Bacal: That's why knowing the prior refraction is important. I've seen patients with bad cataracts develop a sensory exotropia and then after cataract surgery have diplopia for the first time. It could be a change in his refractive status or his vision improved and he can now notice the diplopia.
Wang: What kind of anesthesia did this patient have?
Wang: No injections?
Wang: Because injections could cause problems with diplopia. Did he have any strabismus before?
Nelson: The patient is vague and says he's had a lazy eye his whole life. He had normal vision in the left eye and wore glasses. He's not sure if he ever patched in the right eye.
Wang: He may have drifted outside of an old suppression scotoma at this point after the cataract surgery. I would focus my surgery primarily on the left medial rectus muscle, but I wouldn't mind staging the procedures and doing a large left medial rectus recession.
O'Hara: My colleagues have made excellent points. I've had several patients with that sort of vague history who did not remember having strabismus surgery, but on careful examination of their conjunctiva, I've found scarring consistent with strabismus surgery. When I tell them that, it can trigger their memory of previous surgery when very young.
Nelson: It sounds familiar.
O'Hara: It's important to look carefully at the conjunctiva under the slit lamp to make sure that you don't have a surprise on the operating table.
Nelson: Let's assume that you did that and it doesn't appear that there is any evidence that he's had previous surgery. How would you proceed?
O'Hara: I would use prisms before surgery to make sure that he can fuse and check to see if he has a suppression scotoma. Before proceeding with surgery, I would determine how much of an emotional investment he has in that left eye versus the right eye. Some patients with poor vision in one eye become upset when you suggest operating on both eyes. This patient would perceive his right eye to be his “good” eye and his left eye to be his “bad” eye and may not want any surgery on his right eye. If he did not want bilateral surgery, I would do a recess-resect procedure on the left eye. Before I operated on either of those two muscles, I would look at them first to make sure that one of them had not been operated on before.
Nelson: The last case is a 50-year-old woman with vertical diplopia for 6 months. The neurological evaluation was completely normal. She doesn't normally wear glasses and prisms were unsuccessful in correcting her diplopia. Her visual acuity is 20/25 in the right eye and 20/25 in the left eye. She has a comitant right hypertropia of only 5 PD. How would you manage the patient's diplopia and right hypertropia?
Wang: There are many things that would cause a right hypertropia. I would make sure that she did not have thyroid disease or any other diseases. It could be related to pulleys, but age 50 is pretty young. She did not tolerate the prisms?
Nelson: She just doesn't want to wear glasses full time.
Wang: I've never done this, but I've heard that you can do an increasing tenotomy of the right superior rectus muscle under topical anesthesia until the small deviation like this patient has is corrected. But I would try to talk her into not having any surgery. As Dr. Bacal pointed out earlier, not being able to fuse 5 PD is a problem. If she insisted on surgery, I would try to do a very small recession of the right superior rectus muscle and put it on an adjustable suture.
O'Hara: It bothers me that she can't fuse with prisms. I'd try to determine if she cannot physically fuse with prisms or if the prisms are just such a pain that she doesn't want to use them.
Nelson: She says the prisms may help a little, but she doesn't want to wear glasses.
O'Hara: Then I would try to fuse her in free space with prisms in the office. If I could, then I would proceed with a solution. If I could not, then I would look at her retina to make sure that there's not a confounding retinal disorder. If she could fuse in the office and doesn't want to use prisms, I think a small tenotomy might be an option.
Bacal: I see a lot of senior citizens with 1 or 2 PD vertical deviations that I don't work up, but I would be uncomfortable with not having a diagnosis at 5 PD, so I really would explore that first. Also, I would check to see if there is a primary and secondary deviation based on which eye she fixates with. If surgery is needed, I have had good success with these small deviation cases. I would consider either a very small right superior rectus recession or a left inferior rectus recession.
Nelson: And how much would you recess it in this case if you did the recession of the superior rectus?
Bacal: My guideline is 3 PD for a vertical deviation per millimeter.
Nelson: So you would do a very small recession and you've been happy with the results in most of these cases?
Nelson: Thank you all for participating.
This Eye to Eye session was conducted on April 3, 2020.