Nelson: Today we will discuss management issues in adult strabismus. The first patient is a 60-year-old man with increasing exotropia since childhood who has had no previous surgery. His visual acuity is 20/20 in the right eye and 20/25 in the left eye. He has an exotropia that measured 70 prism diopters (PD) that was comitant in all fields of gaze and the same at near. How would you determine the amount of deviation that the patient actually will have to be operated upon?
Wasserman: This is a great patient to operate on. He will finally be able to make eye contact with his peers. Measuring these patients can be challenging when they get past your prisms. I will generally have an assistant hold a 50 base-in prism in front of the dominant eye and then I will add increasing prisms to the nondominant eye and can clear an alternate prism cover test until they are neutralized, adding up the amount of prism to determine their deviation.
Nelson: Once you measure and he is 70 PD, would you operate on the 70?
Wasserman: How I would proceed with the patient has more to do with the history than the measurements. If this was a patient who had a history of intermittent exotropia who was decompensating, I would be less worried if that happened. If he was having only intermittent diplopia with this, I would assume it was a long-term chronic problem that was decompensating. If it was more acute, I would be more concerned about a neurological event and would want a medical and neurological evaluation first.
Wang: I agree with everything Dr. Wasserman said. I would also want to know why this patient waited until he was 60 years old. If his goals are psychosocial, then he may not be happy with the result. You may not be able to straighten out that part of his life, even if his eyes become relatively straight. There have been a lot of articles written on why people wait. Once I decided to proceed with surgery, I would do a forced traction test and then I would leave some room for a second procedure. I would do large recessions (up to 12 mm) on both lateral recti and see where the patient ended up in terms of being happy.
Nelson: You might consider doing a little less than 70 PD with the idea that you'd tell him he might need a second surgery, although he would be much better.
Wang: Right. If I can get into the ballpark and leave the medials, it gives me a lot of options.
Lloyd: I would want to see the patient more than once just to make sure there's no change and would definitely want to make sure that whatever amount of deviation I was correcting for didn't make him diplopic in the clinic.
Nelson: How would you determine whether the patient may have double vision?
Lloyd: If I found that he was exotropic at 70 PD, I would put prisms equaling 70 in front of him if it was possible and make sure that he was still seeing singly at distance and at near. It's possible if he had some anomalous retinal correspondence (ARC), it might give him some double vision if I just corrected him for his full deviation.
Nelson: Let's assume at 70 PD that you did that and he was diplopic. Would you modify your numbers then?
Lloyd: Yes, I'd go up and down to find the combination that had him feeling comfortable.
Nelson: Dr. Wasserman, would you try to determine whether the patient is going to have double vision before you operate on him or would you just go ahead and do the 70 PD?
Wasserman: I think it's certainly reasonable to see if he notices diplopia. I think 70 PD of exotropia is difficult to overcorrect, but you could induce diplopia in that situation and I think the patient would be unhappy. That should also be an important part of your discussion and informed consent because no matter how well you measure and no matter how good your surgery, it's certainly a possibility. Making sure the patient is informed of that and knowing that you can go back and correct it if you have to is important. I would err on the side of trying to get him fully corrected because I think it is likely that he's going to undercorrect in this situation. I would also attempt three muscles on the first surgery. I don't think I can do 70 PD with two muscles. I also would do a recess and resect procedure versus a bilateral lateral recession for this patient, only because I get a more satisfying result long term with less recurrence, assuming that the near and distance measurements are comitant, as you had described.
Nelson: Dr. Wang, when you implied that you probably would do less surgery, was that because you were concerned about diplopia or was there another reason?
Wang: I don't know if that's so conservative if you really do a huge lateral rectus recession. You may get more than you think. I agree with Dr. Wasserman that I'm going for the whole amount. With a large deviation and a chronically exotropic patient, you can hold up prisms and see if you can induce diplopia in the office, but it could be an ARC kind of diplopia at that moment and I think you're going to have to wait to find out, but it is part of the discussion.
Nelson: The second patient is a 19-year-old woman with increasing esotropia and diplopia for 6 months. The family was adamant that there was no previous history of esotropia or diplopia. The patient's visual acuity was 20/20 in each eye and she had a comitant esotropia of 30 PD and the same at near. How would you treat this patient?
Wang: I would be concerned about the etiology in this patient. I would take a careful neurological history and make sure the patient wasn't having headaches or anything like that. This is certainly a patient who I would neuroimage prior to doing anything. You say it's been progressive; I certainly wouldn't do anything surgical until I saw that there was some stability. Besides neuroimaging, I would make sure this patient doesn't have myasthenia. You'd probably see thyroid or a Chiari malformation on the magnetic resonance imaging. I have seen a couple of patients like this who actually had primary monofixation, microtropias that decompensate.
Nelson: Right. But would the fact that the patient is comitant sway you against a neurological problem or with a history that significant and having been around for a short period of time cause you to do a neurological evaluation or refer the patient to a neuro-ophthalmologist?
Wang: Most neurological esotropias that present at 19 years of age are not going to be comitant, but that doesn't mean that the ones that are comitant are not neurological. I think that this is unusual enough. There have certainly been Chiari malformations and brainstem phenomena, especially cerebellar tumors that have presented exactly like this.
Lloyd: I would also do a comprehensive review of systems about recent illness and rashes and hiking, and a refraction before and after dilation, looking for any kind of strange accommodative spasm. I agree the fact that it's comitant makes me less concerned about a neurological issue. I probably would go ahead and image though, just to be safe.
Wasserman: The one thing I didn't hear anyone mention was stereoacuity. If the stereoacuity was less than full or there was any sign of suppression, then that would lead me toward an old monofixation that could be potentially decompensated. I would again look for that full abduction on both sides. Sometimes it can be relatively comitant, but you want to make sure that the extraocular range of motion is full. If it is comitant, I am not certain that I'd feel better in the setting where there is full stereoacuity and there is no reason to believe that it's a monofixation that has de-compensated. As Dr. Wang said, an acute comitant esotropia, not a sixth nerve palsy, is more worrisome for posterior fossa pathology.
Nelson: The next case is a 50-year-old man who sustained closed head trauma approximately 6 months earlier. He has seen several physicians and comes in complaining that he's just not seeing well. Something is out of focus. He's had a difficult time explaining it any better and every physician he's seen says that he seems to be fine and there are no ophthalmologic issues. The patient's visual acuity is 20/20 in each eye. Rotations are full and he has an extremely small right hypertropia. You can barely measure a little flick of a right hypertropia. That is fairly comitant and left gaze couldn't identify anything. Would you ask any other questions about symptoms or is there any other test that you would do that might give you a better idea of what's really going on with this individual?
Lloyd: I'd want to know about the trauma that he had. Did he have a concussion? Did he have any imaging? Because he does have this hypertropia, but some of his symptoms could be due to a post-concussion syndrome. I'd check his saccades, convergence, and stereoacuity to see if there's anything else that might explain some of his symptoms. I could reassure him that will likely continue to improve as he recovers from his concussion. If there's nothing else that I can find and it seems like his symptoms are due to this right hypertropia, then we can talk about typical issues for dealing with these symptoms, like occlusion or a Fresnel prism perhaps, and just observe him to see if there is any change.
Nelson: Let's assume he was involved in an automobile accident, but other than some closed head trauma, he was fine. When you put up any prism, it didn't make a difference. He still seems like he just couldn't see right. It was out of focus. Would you do any other tests?
Lloyd: You could do a double Maddox test. Does he have any kind of atypical head postures or torsion issues?
Wasserman: I had a similar patient this week and the closed head trauma clues you into the fourth nerve, which exits the brainstem posteriorly and is susceptible to this kind of injury. The fourth nerve can give you torsional diplopia, which is harder to describe versus side by side or vertical and can give you these kinds of symptoms. It can also be more difficult to treat.
Nelson: Did your patient present with vague symptoms?
Wasserman: He had diplopia, but he couldn't say that it was horizontal or vertical. He just said that he had difficulty seeing and he had his chin up and slightly tilted and that was about the only place he could find to see comfortably. He didn't have closed head trauma. He had had a pineal tumor, so the dorsal surface of the brainstem alerted me to where his issue was. His double Maddox rod test revealed more than 20 PD of excyclotorsion.
Wang: These patients can come in with very vague torsion. There's a new app out called the iTorsion, which is simple and well done. You can put it on an iPad or on your phone. You put the red-green glasses on and you don't need double Maddox rods anymore.
Nelson: The next case is a 60-year-old man with a long history of exotropia from childhood trauma who had two previous strabismus surgeries as a child. He has no idea whether his eye was in or out at the time, and now he is interested in having further surgery. His visual acuity is 20/20 in the right eye and counting fingers in the left eye and he has a constant exotropia in his left eye that is difficult to measure, but it is certainly noticeable. How would you measure and manage his exotropia?
Wang: I would initially take a 50 diopter prism and have him look across the room at a single opto-type and put it base-in in front of the right eye and see what his eye looks like, just to see where the left eye ends up. This gives me an idea if the 60 estimate is a good one or not. Then I would use a modified Krimsky test, look at his versions, and look for scarring. I would then look at what his eyelid fissures do as he looks around to see if anything looks tight. Do they widen? Do they narrow? If he looks to his right and the left eyelid fissure widens, I presume he has some deficiency of pulling of the left medial rectus. If he looks to his right and the left eyelid fissure narrows, the left lateral rectus is likely tight. I would recheck the traction tests with hooks under the muscles at surgery.
Lloyd: Because the patient doesn't have good vision in that left eye, alternate cover testing is going to be difficult so I would do a Krimsky test. Maddox rod might also be helpful. You'd have to do a careful slit-lamp examination to look for any conjunctival scarring and any clues about where past surgery might be. When you do operate on him, you have to carefully explore before you really decide what you're going to be able to do and then just see what has been done previously to the muscles.
Wasserman: Again, this is a great patient to operate on. He has probably been told for years that this is just a cosmetic issue and his symptoms have been dismissed by other eye physicians. You can make a huge difference in this patient's life. I would measure him by modified Krimsky test and then use that measurement to explore. I think one of the key points for this patient because he's had multiple surgeries is to talk about scar tissue. My approach is to operate from a limbal approach on these patients because I don't know where the muscle is. In an older patient where the techniques might not have been the same 50 years ago and planes might not have been respected, I'd do a limbal approach and really open up the side of the eye to see where each muscle is before I move anything. I will remove any fat adhesion and scar tissue so that I am dealing with just the muscles themselves. I am going to recess a muscle on a polyglactin 910 suture, but not actually reinsert it through the sclera until I've explored the same on the contralateral side of the eye and have a plan as to what I think is going to be best suited for that patient's ultimate result because you can be surprised intraoperatively in these cases.
Nelson: The last patient is a 50-year-old woman who had a scleral buckle done several years ago after several previous retinal surgeries. She is complaining of diplopia since the retinal surgery. She has an exotropia of 20 PD at both distance and near, which is comitant. She has fairly good rotations. Her visual acuity is 20/80 in the right eye, the eye that had a buckle, and 20/20 in the left eye. Unfortunately, the retinal surgeon doesn't feel comfortable removing the buckle, which is encircling. How would you manage this patient's strabismus?
Wang: I would recess the lateral rectus muscle. You have to free it from the band. I would probably put it on an adjustable suture and the amounts and where you measure from have to be figured by a lot of experience, mainly how tight it is and where you can get your sutures because you're going to be putting your sutures a bit further back to start. So, I would put this lateral rectus muscle on an adjustable suture for 20 diopters.
Lloyd: I would probably hang back the muscle over the buckle. I have less experience with adjustable sutures.
Wasserman: In my experience, I don't think removing the buckle has been helpful in these cases. I work around the buckle. I explore both sides in the horizontal case just to see if I can find an area where there's particular restriction. A forced duction test intraoperatively is helpful. I have several plans when I go into the operating room and I see what the best way is to attack that particular case and I have an extended informed consent with the patient. They may require a stepwise procedure, which is perhaps euphemistic for they may need more than one surgery to resolve the diplopia.
Nelson: Do you feel that if you place the muscle around where the buckle is that it's going to be secure? Let's assume it's right around the area where the buckle is, that it would be secure in leaving that muscle in that position and not being able to place it in the sclera because of the buckle interfering with it.
Lloyd: I haven't been involved in many cases, but my understanding is that the muscle tends to scar into place even if the buckle is in the way. From what I hear, it's less of a concern than you'd think it would be.
Wang: I don't like leaving it on the buckle. Usually the fibrous tissue develops over a buckle and hopefully the recession will occur in a position where you start further posterior so you don't end up with the cut end of the muscle on the buckle. You're not going to start at the insertion with your suture. You're going to start close to the back of the buckle so you can get to some of it. You're going to recess that part of the muscle. You have a better chance of ending up with a stretched scar and an unpredictable result, but I think that's the best way to go.
Nelson: Would you be concerned about the muscle being inserted by doing the recession in close proximity to the buckle?
Wasserman: I would. I would make sure that I had good scleral bites. If I was not secure about any type of fixation, I would consider a nonabsorbable suture, which I rarely use but would consider in that scenario. The only other caveat is that, if I was concerned about a stretched muscle situation, I would make sure that I had extra locking bites so I had a lot of tissue in my suture so that at least I knew I was securing the muscle well. I would choose to be either just in front of or just behind that buckle, not on it or in the tissue around it. I want sclera to some degree in my bite.
Nelson: Thank you all for your insight on this topic.
This Eye to Eye session was conducted on March 12, 2020.