Nystagmus is an entity commonly encountered with trepidation in the paediatric clinic. As the cause or result of poor vision, the clinician needs to constantly refresh knowlegde on how best to approach its evaluation and to explore the full range of treatment options which may apply to any individual cases to optimise the gains of management. This lecture will serve as a reminder about its aetiology and provide clear options and steps to it’s management.
Lecturer: Adedayo Adio FWACS, Consultant Pediatric Ophthalmologist
University of Port Harcourt teaching hospital, Nigeria.
Chairperson, Nigerian Pediatric Ophthalmology and Strabismus Society (NIPOSS)
Panelist: Dr. Halima Alimi, Consultant Pediatric Ophthalmologist, An-Nur Eye Centre, Lagos, Nigeria
By way of introduction, NIPOSS is a society of all pediatric ophthalmologists in Nigeria, committed to ensuring overall eye health of the Nigerian child. We’re situated in Africa and Africa is the world’s second largest continent, as well as the second most populated continent after Asia. With a current population estimated to be about 1.3 billion people, which is about a 2.5% increment from last year. And here is where we are, right on the coast of the west Africa. We consist of 36 states that’s in Nigeria. And our capital is Abuja. And currently in the year 2021, it’s estimated our population’s about 211 million people, another 2.5% increment from last years. Now there are 40 pediatric ophthalmologists in Nigeria, constituting about 8% of the 500, just a total number of ophthalmologists, and spread across 21 centers. Slightly more lopsided, more in the south than in the north. And this society has featured topics in the past, academic topics, including: glaucoma following congenital cataract surgery by Dr. Senthil of India, 4th cranial nerve palsy: tips and tricks to understand and treat by Dr. Alan Mulvihill in Glasgow, myopia by Dr. Seo Leo of Singapore, Dr. Lionel Kowal treated abnormal head posture: a new look at an old problem, and cerebral visual impairments: diagnosis and principles of management by Professor George Dutton. That last one, the most recent one, was systematic reviews and meta-analysis in medical research: an introduction by Dr. Tunde Adedokun from the USA. We appreciate Cybersight for robust collaborative educational packages which bring so much knowledge to us.
By way of introduction, nystagmus is a rhythmic involuntary oscillation of the eyes, which may be the cause or the results of poor vision. Although not infrequently encountered, it doesn’t seem to get the sort of attention that it deserves. There’s currently no prevalent data for nystagmus in Nigeria. A few local articles available mention, nystagmus gets a mention either as a symptom of a presentation of disease in clinics or in population studies such as with school children or children in schools of the blind and visually-impaired. Or in association with other congenital anomalies or entities such as cataracts and retinal disease.
However, in the UK in the year 2009, there’s a publication which had a large population, country-wide, hospital-wide prevalence of nystagmus in the UK, specifically the Leicestershire Nystagmus Survey, which established the prevalence to be about 16.6 per 10,000 population. And it revealed that, it concluded that a prevalence of much higher than what was previously supposed. And this study spelt out details on the prevalence of the different types of nystagmus as well as the racial associations and associated disorders.
Similarly in India, the Andhra Pradesh Eye Disease Study also revealed amongst children less than 15 years, that in 8.3% of cases of blindness that nystagmus-related amblyopia was involved. And so these sort of studies establish and bring home to us the fact that nystagmus actually deserves more interest.
Now, what are the reasons why we decided to do this? It’s because we feel there’s a need to stimulate greater interest in creating a systematic approach to nystagmus management and the more familiar we are with this entity, the less trepidation we will feel when we encounter it. Therefore, the management approach will be more robust and we can then individualize it and optimize what each patient we encounter. So it is hoped that this lecture will successfully sow these seeds that will later lead to better clinical attention and research into nystagmus management.
Our guest for this second quarterly NIPOSS webinar for this year, will be Professor Adedayo Omobolanle Adio, Fellow of the West African College of Surgeons, Fellow of the Nigerian College of Ophthalmologists, Fellow of the Charter Institute of Administrators, and Fellow of the Prestigious LV Prasad Eye Institute. And the topic will be Pearls within Nystagmus.
Ladies and gentlemen, we’re in for a treat this morning. Please join me to welcome today’s lecturer for the topic titled: Pearls within Nystagmus, Professor Adedayo Omobolanle Adio. Thank you. She’ll take questions after her lecture.
[Adio] Thank you very much, doctor. I appreciate your nice, kind introduction. We’ll be talking today about pearls within nystagmus. This is a topic that has caused a lot of fear, including myself, at a point in time. And a lot of people generally don’t have much to do, don’t want to really talk about it. And when they need to examine patients they have issues with that because there’s such precious little that you can do. That’s what people think. But to our lecture, eyes to see why nystagmus happens and the effects of nystagmus and how we’re going to manage nystagmus in an effective way within the pearls setting that we have here.
We have about 93 countries joining us and we’re so thrilled about that. That means NIPOSS is making an impact all over the world. We have places like Malaysia, Russian Federation, Mongolia, Botswana, Ukraine, Sweden, Kenya, Ghana, Indonesia, Pakistan, United Kingdom, US of A, Germany, Ecuador, Zambia, the Maldives, Denmark, Nepal, all over the world. The United Arab Emirates, South Africa, Poland, Rwanda, Bosnia and Herzegovina, Guana, Ethiopia, and on and on. So we are all welcome, good morning, good evening, good night, wherever you are. I believe that this is going to help someone, somewhere. I have no financial disclosures.
Now to start. Nystagmus comes from the word nodding. When you are falling asleep, you nod your head, and then you quickly remember that you’re not lying on your bed and you raise up your head rapidly. So it comes from that word nodding, nystati, the Greek word. Other words that we use to describe it, because it’s involuntary, is dancing eyes and jerky eyes. Now this is a condition that causes involuntary, the person that is having this condition cannot control it and does not know how to stop it. It’s rhythmic, also, which makes it different from other types of eye movement disorders. There’s a shaking movement of either one or both eyes. It often occurs with vision problems and one of the things that makes it so difficult, because it cuts across so many specialities, both medical, ENT, and ophthalmology.
In normalized sight, while the head rotates about an axis, distant visual images are sustained by rotating eyes in the opposite direction. So what makes this happen? The semicircular canals in the ear sense the acceleration that is happening in an angular fashion and sends signals to the oculomotor nuclei for eye movements in the brain. So from here a signal is relayed to the extraocular muscles to allow one to fix on an object as the head moves. Nystagmus occurs when the semicircular canals are stimulated while the head is still stationary. And depending on which semicircular canal has been stimulated, the ocular movements go in that direction.
What keeps the eye in steady gaze? There are three things that keeps the eye in steady gaze. One of which is fixation. This needs to develop very quickly, especially in the first six weeks of life. The eye sticks on the object of interest and when there’s any drift, any micro drift, if it is detected, it brings the eye back quickly to look at the object. If the object moves a little bit, the eyes, the fovea, brings it back to the object of interest. So that is the first thing that keeps the eye in steady gaze.
Secondly, we have the vestibulo-ocular reflex. Here, the eye movements compensate for head rotations. As you may want to look to the right, while you’re interested in an object on your left. As you turn your head to the right, while you’re still looking at the left, the vestibulo-ocular reflex ensures that you have a clear vision while your head is moving. So that is a very important reflex that needs to be developed, otherwise the whole world would disappear in a blur while you’re trying to move your head.
The other thing is the oculomotor neural integrators. These are located in the brain stem under the medulla. And they play a role to ensure muscle activity is counteracted. Because there’s a constant push and pull of the extraocular muscles as its eyes are lined within the sockets. And these neural integrators keep the eye in one particular position so that it doesn’t move around aimlessly.
My colleague has talked about prevalence, but we note that it’s actually more in white Europeans than in Asians. We see it quite frequently in our clinics here in Nigeria. And what key things I want you to understand is that there are two key forms of nystagmus, both the pathological and the physiological, and there are variations within each type. Before now we’ve thought they were untreatable, but in recent years a lot of drugs and techniques have now been identified.
Before we go on, we need to dispense of some old terminologies that have been used in the past. One of our fathers of nystagmus, Dr. David Cogan. In 1968, he made some observations and classified nystagmus into two particular classifications. One, sensory, because he saw children who could not see well and had nystagmus. And then motor, because he saw children that could see well and had nystagmus. And he also called it congenital because he observed that they were at birth.
But someone else did some work and published it in 1974, Dr. Bob Daroff. And this made this classification a little bit archaic, showing that eye movement recordings, which are a very important part of present day management of nystagmus, was the same whether it was sensory or motor. So that means that using that classification, sensory and motor, was not really required anymore. But sometimes we still find it in textbooks. You need to take note of this.
Based on the appearance, that is what we have been classifying nystagmus in the past. But now it’s mostly archaic. In fact, one of the classifications is miners nystagmus. Maybe because when someone has been in the mine, underground for some time. So they used the appearance to classify, that was the reason that to classify nystagmus in the past. But no more. We now use mainly eye movements recordings, it’s very important to have one. Unfortunately we don’t have one here, but it’s invaluable in diagnosing and evaluating the effect of any treatment that you want to give to patients who have nystagmus and deciding even which treatments to employ and also the outcome, the prognosis. It’s quite expensive, it ranges between 25 to 70,000 US dollars. It doesn’t take long to do a recording. But if you have one, it’s important to use it for all patients. To help you give it to classify in a better way all these conditions that the patient may present with.
Using this, in 2001 a workshop was held in Bethesda. And they classified all the oculomotor abnormalities that were known in a better way based on these eye movements recordings and in addition to the clinical characteristics. So this was published by Richard Hertle and Susan Cotter in 2001. The link is there, when you’re looking at the presentation at a later date you can look at that.
Using this classification from CEMAS, there were about 11 nystagmus types. Ranging from the acquired ones to the congenital or infantile ones. So we definitely cannot talk about everything. Because we’re mainly pediatric ophthalmologists, we’re going to focusing on more on the infantile nystagmus syndrome, the fusion maldevelopment nystagmus syndrome, and the spasmus nutans syndrome. And then we’ll mention some acquired ones, so that we can have some feel of the adult onset type also.
It’s important for us to differentiate nystagmus from nystagmoid movements. There are disorders, these are disorders of fast eye movements, saccadic intrusions and oscillations. It’s also classified under CEMAS, including square wave jerks, bobbing, double saccadic pulses, dysmetria, flutter, and all that. But this is different because those are fast eye movements where nystagmus are slow eye movements.
Now we’re looking at the different types we’re looking at today. But we’re going to be talking about physiological also, very shortly. For congenital, infantile nystagmus syndrome, we know that it is in children who are less than three months of life. And usually you have eye disorders. So we go into a little bit more detail as we go along. Then we have acquired ones. From three months to six months, or one year, and in adults. Visually, you will find a neurological cause. Then spasmus nutans, which is generally benign. And in this condition you find three features, mainly: nystagmus, head nodding, and torticollis. So we’ll just talk about the physiological nystagmus quickly.
Physiological, everyone uses it every day. Here, the slow phase minimizes the retinal image slip but it’s not pathological. In fact, we use it to be able to help us to make some diagnosis also. The most important ones is the optokinetic, the caloric, or vestibulo-ocular nystagmus, and end gaze nystagmus. They are typically low amplitude, they are not fast, they’re not sustained, they are asymmetric and generally they are horizontal. I will just add as one of the pearls, that if you see vertical nystagmus, visually they are pathological.
So back to physiological, end gaze, as its name, are extremes of gaze. Caloric or vestibulo-ocular nystagmus, if you remember in medical school they talk about cows. When you put cold water injected into, for example, the right ear, the nystagmus goes into the opposite direction. And when you inject warm water, the nystagmus goes in the same direction. The importance of this, when it is not there, that is it is absent, then there’s peripheral vestibular nystagmus in play. It is not central. But when it is there, then the patient has a central vestibular nystagmus. So those are the things that even if they’re not pathological, we’ve seen it with tests and look at all that. So that in the absence of this physiological nystagmus, the caloric one, they can be able to make some level of diagnosis.
Another one is optokinetic nystagmus. That’s rapid movements like when you’re watching a moving train or a rapidly moving object, it’s an initial smooth pursuit and it’s followed by a saccade, which is a fast movement. The important thing about this one is that if it is asymmetric, it is abnormal. That means there’s a greater moment in one direction, when that is moving in one direction, compared to the opposite.
And that brings us to Cogan’s Dictum. Where if you have an asymmetric optokinetic nystagmus, which is abnormal and pathological, along with homonymous hemianopia, then it’s likely that the patient has a mass lesion in the parietal lobe. But if you have a symmetric optokinetic nystagmus, along with homonymous hemianopia, then it’s quite likely that the patient has a vascular lesion in the occipital lobe. You need to know where to look at for that.
All right, before we go further, it’s important for us to describe and understand each other and the terminologies I shall be using in this course of this lecture. Now is the nystagmus in primary position or is it in any particular gaze? Is the gaze evoked? So you have to describe it using the position. Then is it in one eye? Heimann Bielschowsky phenomenon, I like to ask residents that. Or is it bilateral?
Then, what type is it? Is it pendular? That means there’s equal velocity, it’s moving in a pendular fashion equally on both sides or is it jerk? Where you have unequal velocities. It moves slow and then jerks, slow and then jerks. That means that you can use it to describe the nystagmus itself. If you slow-fast, actually, is the pathological one, while the corrective movement is the fast one. Or is it mixed, both pendular and jerked?
Then you want to describe it, also, is it conjugate? Are the two eyes, are they moving in the same direction, the nystagmus or is it in eye different from the other? In which case you talk about it is conjugate. Then you want to look at the trajectory. Is it multiplaner, different directions? Vertical, horizontal, torsional, or is it in one plane, uniplaner? Either it’s vertical or horizontal. Sometimes you see a combination of all these movements to find post on each other.
Now you look at the rate. Is it rapid, is it slow? You look at the direction, also. Like I said earlier, if you need new fast phase, which is the refoveating component, is what you use to describe the nystagmus. The slow phase, which is the defoveating, the abnormal one, is where the pathology is. Then you also want to check for the null zone. In this patient, where is the nystagmus intensity is minimal? Where the nystagmus intensity is minimal, where is it damped down, where it is reduced in amplitude? Some people have it in primary position. So it is not really evident. When we’re talking about how to ensure out to determine where the null zone is very shortly.
We’ll go to the CEMAS classification, where we’re talking about congenital nystagmus syndrome or infantile nystagmus syndrome. In old time terminology, they said it was motor and sensory nystagmus. Generally it’s of infantile onset. The common associated findings is you find is eye’s conjugates. And where the patient tries to fix, it increases as they try to fix. Sometimes there’s a family history of this and then you might find in some cases associated sensory system deficits. In fact, in most cases where you’ll find examples of which congenital cataracts, albinism, achromatopsia. You might even find associated strabismus or refractive errors.
And then when you try and converge, when you try and help make the patients to converge, it decreases. Then you might find null zones and then might find an associated head posture or head shaking. The things that decrease it, like I said, is convergence, increased fusion, extraocular muscle surgery, contact lenses, very important, and sedation or in sleep. And in this particular condition there is no oscillopsia.
We’ll now look at how this infantile nystagmus syndrome, how does it happen? What happens is that to have a stable oculomotor system, which must be developed quickly within the first six weeks of life. When that baby is conceived and within the uterus, I hope you can see my mouse, there is no need to see. It’s developing, the fetus is developing, as a child, as the fetus is growing in utero, is developing. But at birth, the child now needs to see. Both the afferent and the efferent system, both sensory and motor system, are all speaking, are all relating to each other. And by infancy, if there is a problem from birth, if there’s a problem, in infancy is not corrected, then you have instability in the system. That is what makes the infantile nystagmus syndrome develop. For instance, see basic cataracts, there’ll be no vision. The sensory system will be affected and then you now have problems with images landing where they should land. And the nystagmus would develop. If before the six weeks or eight weeks of life, whatever is wrong is corrected, then you now have a stable oculomotor system again and then deficiency does not develop the nystagmus or it reverses.
Now we’ll also talk about fusion mal-developmental nystagmus. The old name is latent nystagmus. In actual fact, we shouldn’t be using that terminology, latent or manifest latent nystagmus. It is called fusion mal-development nystagmus. It’s also infantile onset, there could be strabismus in this condition. It’s also conjugate, it’s horizontal, in this case it’s uniplanar. Usually in this particular FMNS, there is no associated sensory deficits like albinism or achromatopsia. They may change with exaggerated convergence or head posture. In here this is no head shaking. So you can use all these to differentiate it from any other condition. But we know that intensity decreases at patient grows older and it reverses direction on alternate fixation. Meaning that if you cover one eye, there was a right bit of nystagmus initially, it now turns into a left bit of nystagmus. As you move from one eye to the other. So it reverses direction on alternate fixation. And the hallmark of FMNS is when the patient is reading or checking the visual acuity. With both eyes open there’s fairly good vision. But when you cover one eye, poor vision is noticed. So that’s the hallmark of FMNS.
Spasmus nutans syndrome, which is also of infantile onset, sometimes it can be conjugate, it’s variable. Usually it’s small frequency, low amplitude, there’s usually an abnormal head posture and head oscillation, along with torticollis, which improves and appears and disappears during childhood. If you do eye movements recording, you will still see some oscillations. In most cases, I have a series that I’m following now, you find that they have a normal MRI or CT scan of the visual pathways. But sometimes you might find an abnormality, a lesion of the visual pathways in them. Depending on how often you see it, you might need to do an MRI or a CT to examine these patients to make sure there is no mass lesions somewhere.
Disconjugate, it’s asymmetric, it’s multiplanar, there could be a family history of squint in these patients. Sometimes in one eye it is higher, that is the oscillating nystagmus, it’s higher in one eye, it’s generally always there, the head posture. Then also, it spontaneously remits or reduces by the time the child is between two and eight years. When you examine the patient, there is no abnormality in the fundus.
This child is one of my patients. You can see that he has an abnormal head posture with the nystagmus and torticollis.
Generally, we’ll go on to the pathological nystagmus. You find that visually there’s a disease of the brain stem, the cerebellum, and the vestibular system.
The acquired nystagmus from six months of age to one year. Visually there’s blurred vision here, there’s oscillopsia also. Which is the whole world is moving around, you’re stationary, but the whole world is revolving around you, very distressing symptom. The most common causes is multiple sclerosis, tumors, trauma, sometimes it can be drug-induced also. And usually because it’s of neurological origin, you also see signs, typical signs like headache, nausea, vomiting, tinnitus, and vertigo present also.
We’ll look at the downbeat nystagmus. It’s a localizing nystagmus. Here you see a pathologic upward drift and it’s best seen or best induced when the patient is looking down or to the side. There’s crippling oscillopsia in this particular condition. And the cause is Arnold Chiari, platybasia are one of them.
Now upbeat. We have jerk nystagmus with fast phase upwards, it worsens in upgaze. Visually when you examine these patients you won’t see any nystagmus on downgaze. But if it’s present in primary gaze, find that the vermis is present only in upgaze, then you have to look for drug toxicity, one of them being phenytoin.
Bruns nystagmus is also localizing nystagmus. When you look towards the side of the lesion you see nystagmus of high frequency and low amplitude. But when you look at the side opposite the lesion, then you see it becomes a fine, high-frequency nystagmus that increases. Usually you see these with cerebellopontine angled tumors. These are all localizing nystagmus.
Then we also have gaze paretic nystagmus. Patient cannot look in the direction of gaze and he jerks back in eccentric nystagmus. Usually you find that with cerebellar lesions.
We can’t complete this out without talking about see saw nystagmus of Maddox, which is disconjugate, you have vertical and torsional components. The eye looks up and intorts, the other eye looks down and extorts. And there’s also oscillopsia. You have parachiasmal disease, you need to do a radiologic evaluation of this kind of patient.
This patient has see saw. One eye, the right eye is going up and turning in, left eye is going down and turning out. Very interesting condition. I’ll show you one more time.
There are other types of nystagmus which we won’t go into.
Then we also need to talk about periodic alternating nystagmus. This is a nystagmus that changes direction every 120 seconds. And that is the reason why you have to at least spend at least five minutes observing the child before you make up your mind that this is not periodic alternating nystagmus.
The differentials of nystagmus. We have ocular bobbing, oculopalatal myoclonus. As particularly, with oculopalatal myoclonus, there are vertical movement which is synchronous with a palate. We see this in severe brain stem disease. But they are different from nystagmus because they are not rhythmic, they’re not regular, they’re all nystagmoid.
I’ll say one thing about the anomalous head posture that you see in nystagmus. There’s a lot of factors that affect it. It could be static, it could be dynamic, sometimes if the patient is converging it changes, depending on which eye is fixing, whether the eye has good vision, whether there’s a squint, whether there’s a problem with the spine, all these effects. There’s a complex interplay at work with anomalous head posture. It can be corrected but you need to understand this may be some of the reasons why you may have a surprise after you correct an anomalous head posture surgically.
The symptoms that we have, that people that present with nystagmus. Blurred vision, we know that once there’s more than five degrees of movement or retinal image movement degrees per second, usually it will degrade vision. They usually present with blurred vision. Oscillopsia is also there, vertigo also, dizziness or loss of balance, particularly if there’s vestibular nystagmus. And you need to understand or remember these drugs that are causing nystagmus, in case you prescribe or come across them and you understand the history: benzodiazepine, barbiturates, and phenytoin.
The examination techniques you need to employ. Usually if you make the child anxious, it can change, the nystagmus can change. So just observe, about five minutes or less, do a vision testing, not just the acuity, also check the color, vision contrast, stereo vision, the fields. Before you start occluding and doing a close exam, now also do a squint examination. You observe the head turns, the head tilts, while the child is viewing distant or near objects. Examine the fundus. It’s very important because 85% of patients that have this condition have associated optic pathway abnormalities.
It’s also important that you refract, always refract. To refract these kinds of patients, we need to check the binocular uncorrected visual acuity in preferred posture. And then you check again in forced primary. And when you’re checking each eye, that’s the VA in each eye, don’t ever occlude because vision will just drop, use fogging lenses.
Other things that you can do, if you have the faculty, is to use Frenzel glasses, which is up there, to high pulses. This does not allow the patient to see and then the nystagmus is magnified. And then the examiner can see the type of nystagmus in a magnified manner. Then also do visual evoked, ERG, and then do an OCT just to look for optic nerve hyperplasia or fovea hyperplasia if they need to do that.
We’ll look at this diagnosis algorithm whether it’s of infancy or after infancy. You took a quick history, you examine, detailed history, you examine, you check. If there’s no oscillopsia, the developmental milestones are within normal limits, there’s the family history of nystagmus, squint, there’s the head posture and there’s a horizontal and a latent component and there’s other eye disease, then that’s an infantile nystagmus and it’s benign.
But if you don’t see any of these, then you need to go and investigate to look out for the pathological by doing a neuro exam, you image, you do infection serology, metabolic serology, neurodegenerative serology, and also employ genetic testing. These are important things that you need to research.
Now to look at treatment. Sometimes there are many ways to look at this. Treat the underlying etiology, which is actually best, which may not work for every one of them. For instance, lebers, they are injections subretinally that have been given for specific types of lebers, and that how you treat the underlying etiology. You can also look at the sensory system and treat that. For instance, if there’s a cataract, you can do that with corneal opacity, you can do surgery for that. You can treat the motor system by treating/controlling the strabismus. You need surgery for that. You can treat the symptoms, for example, glasses, prisms, eye drops, can offer surgery also. For symptomatic treatment, it’s been classified into non-surgical and surgical.
This involves treating the entire visual system. If there are refractive errors, correct them. If there’s a lazy eye, you treat it. You can give medications, we’ll talk about that a little bit. Then optical, you’ve got prisms also, telescopes, contact lenses and all that.
We’re talking about the medical treatment now, where you have periodic alternate nystagmus, Baclofen, is very, very important. There’s a table here of the pharmacology in nystagmus, where you can use drugs like gabapentin, memantine, to control infantile nystagmus or acquired pendular nystagmus as the case may be. Clonazepam, carbamazepine, and sodium valproate. Then there’s other drugs like acetozolamide and brinzolamiode we’re talking about, and propranolol, so that you can use it to treat different types of nystagmus.
We’ll look at the optical first. For the glasses, you can tint it oculomotor trainers, albinism, or add a little bit of prisms for patients that need that. The contact lenses are very useful, very, very useful, like I said earlier. Because in this case, its visual axis always points sides with the optical axis. And then there’s a tactile feedback from the contact lenses, which has a way of decreasing the nystagmus by itself.
Then, prisms. If you have a downbeat nystagmus, you can put base up prisms to force the eye up, or if you have an upbeat nystagmus, you can put base down to force the eye down. To force the eye where it should go. The general principle is that the apex should always point in the direction of the null. If you want to stimulate convergence, in cases of convergence, know that you put biological base out prisms. You can also employ low vision aids and computer assistive devices for these patients.
Now one of the things that we’ve used in the past, which is no longer in use, is chemodenervation, use of Botox. What they use it for is to reduce the amplitude and to improve foveation time. And also, importantly, it can also improve visual acuity slightly. If the patient also has oscillopsia. Where it’s best used in neurological-acquired nystagmus. For example, in oculopalatal myoclonus, you can do that. The dose is there listed. But it requires repeated injections. And the side effects are sometimes not desirable. Patient could have diplopia, can develop ptosis, among other things.
It’s important to talk about artificial divergence. It’s used in congenital nystagmus syndrome. And here you want to induce extra convergence innervation by weakening the medial rectus. You’re purposely inducing an exophoria. So you can do it by medial recession or you can do a unilateral recess-resect.
Interestingly, acupuncture’s also been employed. One case report by Blechschmidt looked at six patients with a confirmed diagnosis of nystagmus. Both congenital infantile nystagmus and acquired nystagmus. And then they used the standard protocol. Actually they gave the acupuncture on the body and on the ears. And this treatment was scheduled over a period of five weeks. And they discovered there was marked improvement in the visual function of these patients. I think it requires a little bit more studies before we know which particular group of nystagmus patients could benefit more.
Now the surgical principles of eye muscle surgery is to reduce the amplitude of the nystagmus and to increase foveation time. That’s why we use Anderson-Kestenbaum procedure. This has been in place since 40 years or more. Here we have maximal recession of horizontal muscles. That means you move the null point through a recess-resect to primary, like you’re kind of tricking the eye. And then you can also offer tenotomy, that means you cut the muscle and reattach it. This changes the nystagmus by improving the foveation time and this leads to improved vision. You can also augment tenotomy by adding sutures itself, to the muscle itself.
What happens as you’re doing nystagmus eye muscle surgery? When you cut the muscle at the enthesial area,the enthesial area being the area of insertion of the extraocular muscles. Then you now put it right back, you’re not moving it forward or backward, or strengthening or weakening, you’re just putting it right back there. You cut it and you put it back, what happens? Proprioceptive afferent disrupted. That is the principle behind the use. And it interferes with the feedback loop and tells the brain to damp the signal of the extraocular muscle movements and thus the nystagmus is slowed.
So use it mainly for infantile nystagmus syndrome. The beneficial effects is to improve the central visual acuity and gaze dependent visual acuity, null position also gets better, the head posture gets better, among other things.
Looking at the oculomotor recording here. You find that the upper recording was before surgery, you see a lot more fluctuations there compared with the lower one. It doesn’t exactly remove the nystagmus completely, but just makes it better.
Same thing with these eye movements, we can look at the oscillations here. A lot more in five seconds compared with the post op recordings at the bottom here. Much better.
However, what does not get better, of course, is the binocularity, visual vestibular, visual perception, and visual memorym and color. That doesn’t get better. There’s nothing we can do about that for infantile nystagmus syndrome.
Looking at Kestenbaum. He first designed this surgery where the four horizontal recti in both eyes were recessed and resected. So it’s more invasive than the Anderson type. There’s bilateral recession of the yoke muscles opposite the abnormal head posture, combined with bilateral resection or plication of their antagonist. The initial surgery recommended five millimeters for all the four muscles.
For example, you’re treating a left face turn. Surgery to do for the right eye is to recess lateral rectus in that eye and then resect the medial rectus in that eye. And then for the left eye, you recess the medial rectus in that eye and then you resect lateral rectus in that eye. So that’s what is done.
Then Parks came along and modified it. He proposed that to symmetrise these ductions between the two eyes, surgery should be a five millimeter recession of the medial rectus and an eight millimeter resection of the lateral rectus for the eye that is in adduction. And then six millimeter recession of the medial rectus and a seven millimeter recession of the lateral rectus of the other eye. But these are for eyes to just have a head turn of about 25 degrees. You can augment it and increase your dose up to 60% for larger and larger face turns. I’ll just mention that first since I measured using a goniometer, I also use a compass, which you can find in a common mathematical set.
The Anderson procedure you have bilateral recession of the yoke muscles but usually this is best for very small head turns of 15 degrees or less.
If a patient has a squint, and also has a face turn, what you want to do is perform nystagmus surgery in the eye that is fixating while you perform squint surgery in the other eye. For example, if there’s a left face turn and there’s a left esotropia. So you do nystagmus surgery, that means you recess the lateral rectus in the right eye. And then in the left eye that is not preferred, then in the other eye you do 12 millimeters as medial rectus recession and lateral rectus resection in that eye. So that is what you do if you have both of them in the same eye.
There’s an algorithm there that was compiled by Richard Hertle, you can look at this when you’re looking at this presentation later.
For vertical abnormal head posture, the principle is to turn the eye in the direction of the face turn. So if you have a chin up, you do an inferior rectus recession. Before they were doing a superior rectus recession, but now it’s best to do a superior oblique tenectomy. And then you do a chin down, for the chin down, superior rectus recession. Before they were doing an inferior rectus resection, but now you do an inferior oblique myectomy so that you don’t have sudden new squints developing.
We know that there are complications also. You can have a new head position, you can develop new squints, or there might not be any change in the squints, in the abnormal head posture.
All right, talking about the magic drug that has just been discovered a few years ago. Somebody accidently discovered, in a 68-year-old, at that time being reported. He was taking Diamox for something else and accidentally found out his nystagmus was reduced. So he contacted his doctor and explained to him and then it was now studied. looking at the movements of the eyes. So they said okay, if all our Diamox do, let’s try topical Diamox. So that gives rise to brinzolamide/Azort. This was tried and found to do exactly the same thing. A clinical trial was carried out and was found to work on the enthesial area where the proper receptive fibers are located. Using these drugs, they found out there was improved waveforms, improved acuity, and quality of life in this patient.
This is a carbonic anhydrase inhibitor, which has been used for open angle glaucoma and ocular hypertension. This is a brand name that was approved by FDA. Is used three times daily to treat glaucoma. Recently, in November 2020, was approved to be used as a generic, brinzolamide. But we are using this off-label use of reducing nystagmus, especially infantile nystagmus syndrome. That is where it is most useful.
Some people have what we call magnetic oculomotor prosthetics for acquired nystagmus. There they inserted a titanium-encased magnet that was powered to damped nystagmus without interfering with saccades. And they found out when they implanted these devices the visual functions got a lot better.
And of course,there’s also gene analysis, gene counseling for sensory deficit nystagmus, the RP 65 gene is what is associated with it. And therefore congenital idiopathic nystagmus has no associated sensory problems, FRMD 7 gene was discovered to be associated with this. So there’s scope for research in this area.
The prognosis depends on associated conditions because most of these conditions have associated eye disease, work in the retina, the optic nerve, and brain stem.
So to conclude, to take home, the evaluation of nystagmus is multidisciplinary, you can have both localizing and non-localizing nystagmus. Non-localizing doesn’t tell you where the lesion is. For example, the horizontal nystagmus doesn’t tell you where it is or gaze-evoked. But localizing will exactly tell you where the lesion is. For instance, the upbeat, you’ll find that it’s ingrained in the downbeat, is affecting the vernis in the cerebella area. Then you can employ medications, prisms, glasses, surgery, should give the patient a better quality of life. You can look for treatable organic lesions particularly if there’s squint, if there’s a cataract also, you treat all this and the nystagmus could reverse. We’re not there yet, but we are trying. But let’s keep trying to find the pearls in nystagmus and let’s see what we can do for our patients to give them some hope. Thank you very much for listening.
[Halima] Thank you very much, Professor Adio. That was a refreshing hour. We’re really very grateful, certainly improved on our knowledge, and I’m sure we’ll all follow up on this. On behalf of NIPOSS, and powered by Cybersight, we want to say a big thank you to Professor Adio for this time out. And I’d like to ask everyone, thank you for your time, everyone who tuned in. Please tune in again in three months when NIPOSS brings you its third webinar for 2021. Thank you, everyone, and stay safe and have a nice day. Bye.
May 2, 2021