Aniridia Network

Talk by Mr John Brookes, Moorfields Eye Hospital, at Conference 2025

A presentation about aniridia issues, particularly regarding how glaucoma is treated in children and adults with aniridia, from medical to laser and surgery.

Mr Brookes trained in London and qualified in 1993, subsequently specialising in ophthalmology and further, in paediatric glaucoma, for which he has been a consultant at Moorfields Eye Hospital since 2004. His main interest is in secondary glaucomas in children, such as aniridia and their surgical management.

Transcript

[James] Fantastic to have with us now John Brookes, who is also one of our medical advisors for Aniridia Network, recently appointed. Take it away John, thank you very much.

[John] Thank you very much. So thank you for the very kind invitation to come and talk to you today.

So just a bit about me, I’m a consultant at Moorfields Eye Hospital, which I have been for about 22 years, and I also work at the Royal Victoria Hospital in Belfast, and so I spend a day a week in Belfast seeing all the children from Northern Ireland with glaucoma. So I deal with the whole range of paediatric glaucoma. So I’m going to talk a little bit about what my experience is in treating children with aniridic glaucoma.

So as you know aniridia is quite a rare condition. It was first described by somebody called Barratta in 1818. I’ve tried to find out who Barratta is, but have been unsuccessful, but he described it quite a long time ago.

It’s a bilateral condition, as you know, so it affects both eyes. And it’s a pan-ophthalmic disorder, so it’s not only the iris that is involved in the condition. And obviously I’ll show the other clinical effects that aniridia can cause in children.

It’s rare, so it’s estimated to affect between one in 40 to one in 100,000 children. And I’m going to really concentrate this talk on dealing with children, which is what I deal with on a daily basis.

You can see on the clinical photographs on the left, total aniridia, and obviously there are variable degrees of iris hypoplasia. So hypoplasia is an underdevelopment of the iris. And these two photographs show total aniridia. So there’s a complete absence of the iris.

And on the upper slide, you can see these little bobbles here, which are called the ciliary processes, and we’ll come back to those. These are the parts of the eye that manufacture aqueous. This is the fluid that fills the front part of the eye. And that’s very important when we’re talking about raised intraocular pressure, which is what we need to deal with when we’re talking about glaucoma.

I’m sure you’ll have heard about this from Professor Moosajee earlier on this afternoon, that about 85% of cases are familial. So these are autosomal dominant cases. So that means that you only need to inherit one faulty gene from a parent to exhibit the disease itself.

About 15% of cases are thought to be sporadic, so there’s no family history. And it’s important because, as you know, these can be associated with other systemic problems, such as Wilms tumour.

You can see on the lower slide here, this is a case of aniridia, but only partial aniridia. So the absence of the iris is only in the upper part of the eye there. And again, this top slide’s total aniridia. And you can see the ciliary processes, which are the cells that produce the aqueous humour. The incidence of aniridia is the same in boys and girls.

Obviously, photosensitivity is a very important symptom of aniridia. And you can see this child has to have very dark glasses to cope with his photophobia. And we couldn’t really take them off him to have a look at his eyes until he was under general anaesthetic.

But there’s a variety of eye conditions that can stem from aniridia. Nystagmus is an involuntary jerking movement of the eye that happens in children with poor vision from very early on.

Squint is a non-alignment of the eyes, so one eye turns inwards or outwards. That’s usually because of a condition called amblyopia, otherwise a lazy eye. Because children, as they’re developing their vision, often in medical conditions, often have one eye that’s a little bit stronger and sees better than the fellow eye. And if that happens, then the fellow eye, the brain connections don’t develop normally. So they ignore all the vision from the poorer eye. And that’s called a lazy eye or amblyopia. And we have to patch the good eye, the better-seeing eye, to force the fellow eye to start seeing a bit better, to strengthen it up.

And these conditions, squints, amblyopia, refractive errors, are very common in aniridia.

One of the very big problems for vision reasons in aniridia is corneal pannus. This is a progressive fibrovascular scarring around the cornea that affects the peripheral cornea that can spread more centrally.

This is due to the absence of what we call limbal stem cells. So these are specialised cells that develop into corneal epithelial cells. And there’s an absence of this in aniridia. So instead of the clear cornea regenerating itself, the scar tissue replaces it and that can have a very big effect on vision.

It’s also very difficult to treat this, because if it gets to a stage where it needs a corneal transplant, for example, because of the vascularisation of the abnormal blood vessels, that can make the rejection of a new cornea much more likely. So corneal transplants often fail, I’m afraid, in aniridia because of this problem.

Cataracts are very common in aniridia. They account for about 85% cases of aniridia. And we often have to carry out cataract surgery to improve people’s vision.

Optic nerve and foveal hypoplasia, and certainly foveal hypoplasia is almost universal in aniridia. And this is an underdevelopment of the fovea, which is the central part of the retina, which deals with the very fine focusing. And this is the reason why children in infancy have poor vision. Poor vision happens in aniridia in older age because of either cataract, corneal problems or glaucoma.

And this is obviously my main focus. And about 50% of children with aniridia may well develop glaucoma. And it’s probably one of the most important aspects of aniridia to talk about, because this is the condition that is irreversible. Other conditions within aniridia can be treated. And glaucoma can certainly be treated and stabilised, but any damage that happens from glaucoma is irreversible.

A couple of syndromes in aniridia you may well have heard of. WAGR, that occurs because of a deletion on a particular chromosome – chromosome 11. And it’s thought to account for about 30% of sporadic cases of aniridia.

And this is the importance of referring children to paediatricians because we need to screen for Wilms tumour, and do the genetic testing that Professor Moosajee would have talked about earlier.

Gillespie syndrome is quite a rare syndrome associated with aniridia, and this accounts for about 2% of cases of aniridia. And this is an autosomal recessive disease. And so both parents need to be carriers for an affected child to develop Gillespie syndrome. And so one faulty gene needs to be acquired from each parent. But importantly, this is not associated with Wilms tumour.

So I normally go through talks and go through consultations and see children for 10/15 years. And I think the parents and the children know everything about glaucoma. And then somebody will say “What exactly is glaucoma?” So I thought we’d just address that issue first.

It’s an interesting definition, really, because at the end of the day, glaucoma is a disease of the optic nerve. And if you’re in glaucoma clinics, you’ll be very obsessed by intraocular pressure. But in fact, you don’t need to have a high intraocular pressure to have glaucoma.

So glaucoma is an optic neuropathy. So it’s a disease that affects the optic nerve. Now having said that, all children’s types of glaucoma – aniridia, and all other types of paediatric glaucoma – only occur when a child has a high intraocular pressure. And we’ll talk about why that might happen in a minute.

Now, adults can have glaucoma even with a normal eye pressure. But if an adult with aniridia has glaucoma, it’s usually associated with a high intraocular pressure.

And you can see in the clinic, there are different types of measuring the eye pressure, depending on the age and the cooperation of the child. So this is what we call an eye care tonometer. It revolutionised how we manage children, because often we’ve very often had to put children under general anaesthetics to measure their eye pressure. Whereas this eye care is much more acceptable for children and they’re much more cooperative in having it done, having the pressures checked in the clinic.

As they grow up a little bit, we use Goldmann tonometry. And this is a more gold standard type of measurement. So it’s a more accurate measurement of intraocular pressure.

And all our treatments for glaucoma all relate to reducing the intraocular pressure. Whether that’s with medicine, whether it’s with a laser or whether it’s with surgery.

Now when we’re looking at optic nerves, you can see these two photographs on the bottom here. So this is a healthy optic nerve. Why is it healthy? Well, I always describe it as when we’re looking into the back of somebody’s eye, we’re looking at the end of the optic nerve.

So the optic nerve is a stalk. It’s a bundle of over a million individual nerve fibres that connects the eye to the brain. The end of the optic nerve essentially looks like a polo mint. There’s the minty part, which we call the rim, and there’s a hole in the middle.

So here you can see that the pink area is the mint and there’s a paler hole in the middle. And in this photograph, you can see the hole is much bigger and the rim is much thinner. So it’s like you’ve been sucking a polo mint for a long time.

And what we’re looking for is this hole in the middle progressively enlarging. And that’s what we see with glaucoma damage. You’re losing nerve tissue, so the hole in the middle is getting bigger and the rim is getting smaller because of damaged nerve fibres.

The consequence of this is that it damages the peripheral vision. And you can see that one of the tests that we often do are called visual field tests. And there are very characteristic patterns of visual field loss in people with glaucoma.

So essentially, the intraocular pressure increases, that damages the optic nerve, that affects the visual field, and that’s glaucoma.

Well, why does it happen in people with aniridia? Well, in children, it can happen in infancy, although this is much less common than happening at an older age group. If it does happen in infants, it’s because the angle – and I’ll talk about this shortly – has not developed normally.

Now, the angle is where the drainage channel is and fluid, which is continuously made inside the eye, drains out through a little channel in the eye called the angle. And when that hasn’t developed properly, fluid can’t drain out of the eye. It builds up in the front part of the eye and that increases the eye pressure.

The more common type of mechanism for glaucoma happens in older children or in adults. And that’s what we call angle closure glaucoma. Now, even in cases of total aniridia, even if the iris is completely absent, clinically, there is always some rudimentary tissue of iris, which progressively blocks the angle.

So the angle closes, and this is why we call it angle closure. So there’s a blockage to the fluid draining out of the eye, that causes a build-up of pressure, damages the nerve, and that’s how we get glaucoma.

Now with treatments – and we’re talking really the treatment of any type of glaucoma, and there are literally hundreds of different types of glaucoma in children – there are always three options for treatment: medical, laser, and surgical treatments.

And so what we like to do is start at the lower part of that stepwise ladder of increasing invasiveness, and start with medication. And there are multiple treatments now available in the form of eye drops to reduce intraocular pressure, and I’m sure some of you will have heard of these.

Basically, what they’re doing is that some of them are reducing the amount of aqueous produced inside the eye. So remember, I showed those ciliary processes. These are the cells that make the aqueous. Some of these eye drops affect the ciliary processes to reduce the amount of aqueous that’s made inside the eye. Some of the drops increase how much fluid drain out of the eye.

So Latanoprost, which is a very common one, increases how much fluid drains out of the eye. Timolol, which is an extremely common eye drop for glaucoma, reduces the amount of aqueous that’s made inside the eye.

There are increasingly useful eye drops, which are combinations of drops. So Azarga, Cosopt, these are medications that have two drugs in them. And it’s usually one drug that reduces aqueous production and another drug that increases outflow, and they’re mixed together.

And we have lots of drops nowadays, which are especially useful in children, with the combination drops, where they only have to be used once a day. And they also lack preservatives, and these preservatives are chemicals that keep the drop from getting infections in them. But they’re much more comfortable to use when they don’t have preservatives in them. And these are especially useful for children, because they’re comfortable in general, and they only have to be used once a day.

So we would start with one drop, maybe add a drop, or change a drop. And so we’ve got multiple different combinations of medication, before we think about having to move up to the next stage of treatment.

How often do we need to proceed to surgery? Now, as I mentioned, there’s loads of different types of glaucoma in children, and these are the most common types that we see.

The most common childhood glaucoma is called primary congenital glaucoma. So this is the most common glaucoma that we see in infants. And if we diagnose a child with congenital glaucoma, almost all these children will need an operation, because medication is never sufficient to control the intraocular pressure.

All other types of glaucoma, including aniridia, are called secondary glaucomas. And you can see that even though it’s not quite as high as 98%, the majority of children when they’re diagnosed with glaucoma need an operation. And children with aniridia, about 67% of these children, once diagnosed with aniridia, will need surgery at some stage in their lifetime.

Now, you may wonder why I put a cartoon of somebody in a bathtub, because what I want to try and do when I’m trying to explain the surgical treatment is just use a bathtub to try and explain how these surgical operations work.

So if you think of the eyeball like a bathtub, there’s a tap that’s pouring water into the eye, and there’s a plug hole which is draining water out of the eye.

Glaucoma and raised intraocular pressure is when there’s an imbalance between how much water is being poured into the bathtub and how much is draining out. And so, if the plug hole is blocked, the pressure increases. If the tap just continues pouring out fluid and it’s not draining away, the intraocular pressure increases.

So when we’re talking about surgical treatment, or treatment in general, we’re trying to either turn off the tap to have less fluid filling the bathtub, or we’re trying to unblock the plug hole, or find a new way of draining the fluid out of the eyeball.

Now, the treatments can be challenging because glaucoma in children especially is difficult to treat for a whole number of different reasons. It’s difficult because obviously examining babies is difficult and getting accurate pressure readings. It’s difficult trying to get eye drops into children. It’s difficult when you have to operate on them, because they’re not that keen on coming into hospital for surgery, and then they have to use drops very frequently after surgery. So it’s not without its problems.

And if we’ve tried medical treatment, then our next two options are laser treatment or surgery. Now, I’ve listed some of the most common surgical operations that are done for glaucoma in children.

So, angle surgery. This is directly addressing where the abnormality is. It’s the angle, the channel which drains fluid out of the eye. And the operation that we commonly do nowadays is called a trabeculotomy. So, this is where we can open up the channel using a special instrument, which I’ll show you in a moment.

Or a goniotomy, which is slightly out of date now, but a goniotomy is a way of making an incision into the channel to open it up and allowing more fluid to drain out of the eye.

A trabeculectomy is where we’re making a new pathway for draining fluid. We’re making a little hole in the white part of the eye, so there’s a way for fluid to escape.

Glaucoma drainage devices are increasingly commonly used nowadays. It’s probably the most common surgical treatment, otherwise known as tube implants or tube surgery. These are tubes that basically drain the fluid out of the eye continuously. The tube is stitched into the eye. Patients don’t feel it, they don’t see it. But this continually drains fluid out of the eye to lower the intraocular pressure.

So, angle surgery, a little instrument passes through the cornea and makes an incision into the channel to open it up. You can see here, this is a trabeculectomy. So this is done at the top part of the eye. And so the fluid drains out through a little hole that’s made and collects in a little blister on the top of the eye here. And as the pressure goes up, more fluid drains into that little blister and then drains into the circulation.

This is a little catheter which is passed into Schlemm’s canal. Schlemm’s canal is the drainage channel. And when it’s passed into Schlemm’s canal, we can dilate it or open it up to restore that normal drainage.

And this is an example of a type of tube implant. This is called a Baerveldt tube. And you can see that the tube is attached to a large plate. Now, this plate is stitched around the back part of the eye. And then the tube comes forward and the tip of the tube sits just behind the cornea. And as the pressure builds up, the aqueous fluid drains up the tube, collects on top of the plate and then gets reabsorbed into the circulation.

Laser treatment does have an important place in treating glaucoma in children, because it’s a stopgap between the medical treatment of the eye drops and the surgical treatment.

Now, when we’re thinking about surgery and the time when we need to operate, what we’re trying to do is postpone surgery as long as we safely can, because surgical success tends to be increased the older the child is when they have surgery. And when we’re dealing with a lifelong condition, and we’re dealing with operations that are never going to last a lifetime, we want to try and postpone the need for surgery, to stop us getting onto that slippery slope.

And if medical treatment’s not working, cyclodiode laser is a very good option before progressing onto surgery. And what we’re doing with this probe that’s attached to a laser, is that the laser is damaging the ciliary processes which make the aqueous humour. So if you reduce the amount of aqueous humour being produced, then you reduce the amount of fluid, lower the intraocular pressure.

The problem with cyclodiode laser is that it’s only ever seen as a temporary solution, because what will happen is that you destroy the ciliary processes, reduce the pressure, but these ciliary processes will regenerate and then they’ll start pumping aqueous fluid out again. So the pressure will go up. But if this buys some time, then it may be better to operate on a two-year-old than it is on a one-year-old. So it just gives time for the child to get a little bit older before you start surgical treatments.

And the tube implant is one of our mainstays of treatment. So here in these cartoons, you can see how they work. So you can see the plate attached to the tube here, and on this one as well. So the fluid drains along that tube onto the top of the plate, and then gets reabsorbed into the circulation.

There are several different designs of tubes. This is called the Baerveldt tube, and the newer one is called a Paul tube. And the main complication with tube implants is that we don’t want the pressure to drop too low.

Now that sounds a bit odd, but low pressure is actually just as harmful as a high pressure. Because there has to be a certain level of pressure inside the eyeball to keep the eyeball functioning correctly, and keep the retina from detaching or developing any swelling within the retina. So there has to be a lower limit of how low the pressure comes.

And what we do when we’re doing these operations is that we pass a little stitch down the middle of the tube implant, like a little pipe cleaner. So it helps restrict how much fluid is draining up that tube, and that stops the pressure from dropping too low.

But it’s also useful because if in the future the pressure starts to increase again, then that little stitch can simply be pulled out. That allows more fluid to drain along the tube, thus lowering the intraocular pressure.

So we often carry out tube implants. They’re not without other risks, and the particular risk in children and adults with aniridia is that the end of the tube sits behind the cornea. But because there’s an absence of the iris, the lens of the eye is in very close proximity to the tip of the tube implant. And if the tip of the tube is in contact with the lens, that can develop a cataract or can make a cataract worse, and then that might need surgical treatment to remove the cataract.

There has been in recent years, and less so recently in artificial irises, and there are lots of implants which try and replace the iris or give an artificial iris appearance, to try and limit photosensitivity.

I exclusively deal with glaucoma, and these are not a good idea really in children or any adults with glaucoma, because it can actually make glaucoma worse. And even if somebody with aniridia doesn’t have glaucoma, there’s a much increased risk of them subsequently developing glaucoma with these artificial irises. And so this is something that we don’t practice anymore.

So just to summarise, glaucoma secondary to aniridia can be a challenge. That’s not specific to aniridia, it can be challenging for all children with glaucoma. But it can be difficult glaucoma to manage.

And we don’t need to just manage the glaucoma. There’s all the other effects that go with it like the squint, the lazy eye, the high refractive error with spectacles, the patching that we need to do.

And so this has got to be a multidisciplinary approach. And so in our paediatric glaucoma clinics, we have specialist nurses, optometrists, orthoptists, ophthalmologists, family support, who are very important. They deal with the link between the hospital and the outside world and education, schooling and statementing and that sort of thing.

But as is true with any type of glaucoma, early diagnosis is essential, because this is an irreversible process. So if the damage has happened, that cannot be reversed. So if we diagnose it early, we can then hopefully, with the treatments that we’ve got, stop it from progressing. And we do have improving surgical options available. So this is improving prognostic factors, and we hope that that will continue.

So that’s the end of my little talk on aniridia and glaucoma. There were a few questions submitted, which I’ll try and answer as well. And then perhaps, if there’s a little bit of time, I can open the floor for you to ask any other questions really, hopefully related to glaucoma.

But one question was how does vision with aniridia typically change through childhood and then adulthood?

Well, this is a difficult question because every individual is individual and how they progress can be different from child to adulthood. Some people with aniridia have glaucoma and that can be well treated, and they don’t develop any other condition like the cataract and the corneal problem.

I always find the most difficult is the corneal changes, because actually it makes the surgery for the cornea much more challenging and increase graft rejections I mentioned earlier on. But glaucoma is a progressive disease, and so if that does progress from childhood to adulthood, there is a risk that vision can deteriorate along with the addition of all the other clinical factors associated with aniridia.

And that follows very nicely to the next question in the use of preventative eye drops for lubrication.

And I think this is very important, because I think if children and adults with aniridia lubricate the eyes and keep the surface of the eye nice and moist, that enhances the health of the cornea and tries to limit the extent of the corneal changes that can be such a problem later on in life.

There’s another question, does glaucoma differ in PAX6 related aniridia compared with other genetic forms?

Well, PAX6 is the major genetic mutation that causes aniridia. And in actual fact, I deal with a lot of other genetic conditions that develop into glaucoma. And really, whatever the underlying genetic mutation, the treatment’s very much on similar principles – medication, laser treatment, surgery.

Interesting work that’s going on at the moment is trying to correlate genotype with phenotype, meaning that if we know what genetic mutations cause the glaucoma, how does that affect how it affects the patient?

For example, if you have a particular genetic mutation, it may be that that causes a more aggressive type of glaucoma. So you may go for surgery at an earlier stage than if you had a mutation which is known to cause less severe types of glaucoma.

And so this is why genetics is becoming increasingly important. And a lot of the cases of childhood glaucoma, not just aniridia, is now we’re sending them off to Professor Moosajee and taking their DNA, so over time we can have a database that can help in this genotype-phenotype correlation, and then hopefully long term correct these mutations.

How does expertise in aniridia vary across the UK and away from large cities?

Aniridic glaucoma is obviously best dealt with in hospitals which deal with paediatric glaucoma. And these are actually very few and far between. Manchester has a very good department, as does Birmingham and in London at Moorfields and Great Ormond Street.

I think it’s important to be dealt with in a multidisciplinary environment if possible. But I think in general, if glaucoma needs treating as a secondary to aniridia, then you’re better off in one of these more specialised centres who are used to dealing with and operating on people with aniridia if the glaucoma develops.

So thanks very much for your attention and please, I’m happy to answer any other questions that you have.

[James] Wonderful, thank you, John. Very, very interesting. Yeah, we’ve had a few more questions and things come in. Katie.

[Katie] We’ve got a question from Emily. She says “My daughter uses Timolol. Will she definitely have glaucoma or can her IOP just be raised, and they are trying to reduce it?”

[John] Yes, that’s a very good question. If you have an elevated intraocular pressure, that does not necessarily mean you have glaucoma. You have to have nerve damage to be diagnosed with glaucoma.

Now, if somebody with aniridia is being monitored because of the aniridia and they’re being monitored for their visual development or their squint or whatever, and the intraocular pressure is being monitored and it starts to increase, the eye pressure increases before the nerve damage happens.

So if the treatment is started at the point where the pressure has started to increase but not yet damaged the nerve, then that’s not glaucoma. If somebody has a high pressure, that would almost invariably with aniridia lead to glaucoma if it was not treated early on.

So the fact that she’s taking Timolol does not mean that she has glaucoma, but she’d be at high risk if she wasn’t taking Timolol and the pressure remained high. Does that make sense?

[Katie] Yeah, I think so. So maybe a follow-up question then would be for anybody with aniridia who is just being seen because they have aniridia, how often should they get their eye pressure checked?

[John] So in general, while vision’s developing, so this is the 0-7 years of age, they probably need to be seen four-monthly for their vision development, for their glasses check, their patching, that their vision’s optimised.

After that, probably every six months, and as they get older, maybe less frequently. And there may be a point where then the optician can check pressures, so they’re not coming to the hospital all the time. But the younger the child is, the more frequent they need to be checked.

[Katie] So would they actually be having their pressure checked at each of those four-monthly visits?

[John] I think it should be checked at each of those visits, yes, because it’s so closely linked with glaucoma and because the treatment’s best picked up at an early stage. If they’re in the hospital having their vision checked in an ophthalmology department, then they should be having their pressure checked.

[Katie] And if someone was in that position of being able to be checked by the optician, how often should they do that?

[John] So these would normally be older people, older children and adults, I suppose I’d like to say annually, but probably six to twelve-monthly.

[Katie] Okay, so we’ve got another question from Andy here. “Have Moorfields considered doing clinics for people with aniridia with cornea, glaucoma and other specialists there to provide rounded care all in one visit?” We understand that the RVI in Newcastle are doing something like this and patients seem to like them?

[John] I got that question by email earlier and I’ve been thinking about it. I actually googled the RVI in Newcastle and I couldn’t find that they had a specific aniridia clinic. I could be wrong, but I couldn’t find it.

[Katie] We have had feedback from some of our members that go there that it is described as an aniridia clinic, or at least an all-round clinic for the multiple symptoms that can go along with aniridia.

[John] Yeah. I mean, it is in principle a good option, because when you’re dealing with rare conditions, often patients have to travel a long way, and so you don’t want to be travelling several times to different clinics.

So in principle, that’s a good idea. In practice, it’s a little bit more problematic, because very often now clinicians are working not just in one hospital, but in different hospitals. The volume outside the main centre of people with aniridia is quite low to set up particular clinics.

Although it’s not impossible and it doesn’t have to be a weekly clinic. It could be a monthly clinic or a two-monthly clinic and so on. But we’re also competing with other syndromes. A month ago, I was giving a talk at the Sturge-Weber weekend for parents and the same questions come up.

And so from a clinician point of view, it would be difficult to set up clinics in each different type of glaucoma. That’s part of where a multidisciplinary team is needed. So it’s something that I’m really seriously going to think about, but does have some logistical challenges to it.

[Katie] Okay, so we’ve got another question from Elena. So she’s asking “Regarding a viscocanalostomy in children, is it gentle? Or is there a better option? And also, what is the best implant for aniridia patients?”

[John] So a viscocanalostomy is a surgical procedure whereby a viscoelastic material, this is like a jelly consistency, is injected into the canal to dilate the canal, so more fluid can drain out of the eye.

So it is a relatively gentle procedure. And this comes under the angle procedures. So this is affecting how much fluid is draining out of the eye. And so this would be a useful procedure as a first line surgical treatment.

Now, there are other types of angle procedures, and it depends a little bit on the preference of the surgeon. So my preference would not be a viscocanalostomy, it would be a trabeculotomy. Now, you’re doing fairly similar things, just from a different approach, but both of these operations are perfectly acceptable and are quite gentle in their level of invasiveness.

And the second question regarding implants, is the questioner talking about implants after cataract surgery or implants to implant an artificial iris?

[Katie] Well, it could be talking about things like glaucoma tube, the tubes for tube implants. I’ve got a separate question in a moment about the iris implants. So if we assume it’s about glaucoma tubes, which one’s the best one for people with aniridia?

[John] Okay, so not to sound too complicated, but there are two types of tube. One tube has a valve, and that limits how much flow can drain down the tube. They very often fail. So if you’ve heard of an Ahmed valve, we no longer use what we call an Ahmed valve anymore as a tube implant.

The two most common ones nowadays are a Baerveldt tube and a Paul tube. Now my preference, and obviously if it’s my preference I think it’s the best one, is the Paul tube.

The reason being is that with a Baerveldt tube, because the tube is bigger, you have to completely block the tube off with a stitch, which takes up to six weeks for that stitch to dissolve. So you’re left with a high pressure after the surgery for at least six weeks. And further damage could happen while you’re waiting for the stitch to dissolve.

The Paul tube, the lumen is smaller. So you don’t have to block that tube off to prevent the pressure dropping too low. So when you do the operation, the pressure drops almost immediately within a day or two. So you get what you need to get straight away rather than having to wait. So the Paul tube is one that we would favour at Moorfields now.

[Katie] Okay. So yeah, there’s a question about iris implants. So you mentioned that we don’t do them anymore. So was that referring to Moorfields specifically, or would you say ophthalmologists in general in the UK?

And also, there’s mention of the Boston KPro, which I know is not an artificial iris, it’s an artificial cornea, which is something different. But that’s quite popular in the US.

Another thing that’s also quite popular in the US is a type of iris implant, a more modern one than some of the ones that I’ve heard about in the past. So the ones that are made by a company called HumanOptics, and they can be rolled up to be inserted inside the bag, which contains the lens. Or when someone’s having a cataract removed, it can be added in with the artificial lens you put in.

So just your statement about we don’t think that doing iris implants is a good idea. Does that also apply to that newer style of iris implants as well?

[John] Yes. I’m looking at this as a purely glaucoma specialist. And so when we when you get to my clinic and dealing with glaucoma, you really want to try and do everything to reduce the risk of making the glaucoma worse. And certainly the older style of artificial implants did have a much higher risk of not only making the glaucoma worse. But even if children didn’t have it, there was a higher risk of them developing it afterwards.

I have seen the ones that you roll up. I’ve got no experience of it, I’m afraid. In general, we tend to be able to manage the symptoms and I tend to try and avoid carrying out any other unnecessary surgery if possible, because the glaucoma is difficult enough to treat anyway.

Now, I know nobody at Moorfields does any of these artificial implants, either the older ones or the rolled up one. I can’t speak for anybody else. When we get together in… you know, it’s a small world, paediatric glaucoma… these things are not talked about. It’s just something that’s not very frequently done. I’d have to go back and look at the evidence for these other types of implants.

But in general, with the patients I see in my clinic who have glaucoma, I would tend to avoid any extra implantation, I would say. That’s not saying that they don’t have a good role elsewhere or by other people. So it’s worthwhile looking around if that’s something that people want to look into. And I’ll certainly look at the evidence once we’ve finished here.

[Katie] I mean, possibly also related to that is if somebody has cataract surgery, does that increase the risk of developing glaucoma?

[John] It does, I’m afraid, yes. So cataract surgery is actually the most common cause of secondary glaucoma in children. So when I put those on the slide where there were the most common types of glaucoma and the ones that need surgery, aphakic glaucoma is children who’ve had their cataract removed. And the younger that the child is when they have the cataract removed, the higher the risk there is of glaucoma.

So even in children, if they have congenital cataracts, not linked with aniridia or any other associated medical condition, and that is operated on, which it often needs to be, the earlier that they have the surgery, the more risk there is of glaucoma. And that will be true of aniridia as well. So if a cataract needed to be removed, that would increase the risk of glaucoma in children with aniridia.

[Katie] Okay, I think that’s all the questions that we’ve got.

[James] Yep, we’ve not got anything else. So thank you very much for your time John, much appreciated.

[John] Pleasure. Thank you very much.

[James] And we’re looking forward to getting your assistance with other enquiries that may come in, in coming months.

So yeah, just a general advert for the Aniridia Network Enquiries service. You can write into us at enquiries@aniridia.org.uk. We, Katie in particular, we’ll look at those initially. If we can answer them from the information we have to hand already, we will do so. If we need input from someone like John and Mariya Moosajee, then we will pass it on to them and get a real expert answer for you. So if you do have any questions, at any point, do get in touch with us, and we will do our very best to help you out.

So yeah, thank you very much John for your time, much appreciated. And thank you very much to all of our speakers today for their time and their expertise and their insights and inspiration. Really, really grateful for that. I certainly found it really interesting to hear from them all.

This event has been online, of course we are keen to do a physical event again. That requires volunteers. So if you would like to see a physical event happen, and if you would like it to be anywhere near you, step forward and help to organise it.

Yeah, that’s about it. So thanks very much for your time and can I be the first to say Happy Christmas! Bye bye, take care.