Sunday, July 27, 2014

Stories of stubborn grit in the eye

A middle aged man was on his way to Bangkok from Singapore when he felt something blow into his eye at the airport. Trying to clear the irritation, he rubbed his eyes. The irritation persisted and while in Bangkok a doctor could not find anything wrong and patched the eye up. Unfortunately, this did not help much.

He returned to Singapore the next day at the end of the work trip and when I saw him the eye was obviously red and tearing. The picture below shows a green area with surrounding green dots and lines. These represent raw areas on the surface of the eye where the surface cells (epithelium) have been scratched away. 
(Note: I have put some fluorescein drops into the eye-this vegetable based dye tends to stick to raw areas, and gives off a green light when blue light is shone onto it. This makes it very valuable for highlighting abrasions/scratches ont he eye. )

Corneal abrasion

Even before I did anything else, I knew there was something still in the eye. The green lines indicated that very fresh scratches were occurring at the time itself by blinking and eye movements. I automatically 'everted' the eyelid (turned it so that the inner surface faces outwards-some small children like my youngest daughter can do it as a trick to look like a ghoul [below]!)

The picture below shows a tiny yellow spot just to the left of center. The yellowness is actually from the fluorescein dye-if I had not put fluorescein in, it would have been invisible as it was transparent.

Subtarsal foreign body

Having found the culprit, it was a simple thing to get a pair of jeweller's forceps (mini tweezers) to grab and remove the foreign body. Most of the time when we remove such things, it is impossible to say what it was or where it came from. The picture below shows the offending object at the end of the forceps-a nondescript, fluorescein stained stiff strand-I suspect some little bit of plastic.

Foreign body at the tip of forceps

When looking for such things, I am fortunate enough to have a slit lamp microscope and of course, the good ol' fluorescein. Very few things escape such scrutiny. Except...

There was a similar case that initially flummoxed me a couple of years ago. A Japanese lady went to the Accident and Emergency Department of a local hospital and I was called to see her. She similarly complained of a stubborn, persisting scratchy sensation in her eye. I did my usual, but try as I might, I could not see a foreign body. She certainly did have scratches on the cornea, but with no sign of a foreign body even with fluorescein eyedrops instilled, I thought the foreign body had been washed out by her tears. I inserted a bandage contact lens and she felt better.

I checked on her a couple of days later and she said she was feeling fine, so I removed the bandage contact lens. Almost immediately, she started tearing and as I looked, scratches were starting to appear on the cornea again! (See pic below) So I everted the eyelid at the slit lamp, but still could not see anything. OK, this calls for plan B...

I brought her to our small treatment room and used an operating microscope this time. With her lying down I could 'double evert' the eyelid-lo and behold-there was a small stitch protruding from the inner surface of the upper eyelid!
NB: In double eversion we evert the eyelid a second time to expose things even higher up in the little pocket called the 'conjunctival fornix'. This stitch was at the upper end of the stiff 'skeleton' of the eyelid, the tarsus.

It turned out that she had double eyelid surgery some years ago, and the person doing it had used a method utilising just stitches. These stitches are often permanent, and do not dissolve on their own. Over time, it had slowly eroded out through the inner surface of the eyelid and the ends of the stitch were now poking the cornea. With that, it was a simple matter to cut the stitch and remove it-problem solved.

Did the double eyelid disappear? No, because after some months collagenous 'scar' tissue forms around the stitch and anchors the skin around the eyelid fold down to the underlying tissues, thus creating a permanent effect that persists even if the stitch is taken out.

I guess the message is, if there is any stubborn grit/irritation in the eye, firstly don't rub the eye, and secondly don't hesitate to visit your friendly eye doctor!

Sunday, July 20, 2014

Floaters, flashes of light and retina detachments

One of the most common reasons people seek an eye consult is the sudden onset of floaters or flashes of light.

Those of us who've never experienced this might be scratching our heads wondering if these people were hallucinating...:)

In actual fact, this series of symptoms are natural phenomena which will affect most if not all people at some point in their life.

What our eyes contain

Most of our eyeball is filled with a jelly like substance called the vitreous, and this is a solid blob at the time we are born. It is made of a number of molecules including hyaluronic acid (the substance that lubricates our joints) interspersed in a collagen matrix.

With age, these molecules separate out from the collagen, leading to the formation of liquid filled cavities within the vitreous. Usually, a thin layer of the vitreous gel continues to line the retina of the eyeball for many years, even though the centre has turned into liquid. For some people at this stage, floaters are noted already. These are generally perceived as 'transparent', and look like little bubbles/circles that may be arranged in string like patterns. I've even sometimes had children of 9 or 10 years old tell me that they see these things.

As a person gets older, even more of the jelly in the center liquefies. At some point, the remaining solid vitreous lining the retina at the sides collapses inwards towards the fluid filled center-this is called a 'posterior vitreous detachment' or PVD. When this happens, there is a dramatic change in the floaters. Instead of transparent bubbles in clumps or a string, more obvious gray or black floaters like a cobweb or mosquito can appear. Sometimes these are associated with flashing streaks of light at the side especially in the dark, when turning the head. That's why the term 'floaters and flashes' came about.

As the layer of vitreous jelly peels away from the retina, nothing happens most of the time. However, if that layer happens to be stuck firmly at some point to the retina, this area of retina can get torn as the jelly peels away. Imagine peeling the skin of an onion. If the layers are not stuck together, they can come off nicely layer by layer. However, if the layers are stuck together, peeling one layer off will tear the underlying layer.

A retinal hole with operculum floating above it

A retinal hole after laser treatment

In the pictures above you can see a retinal hole before and after it is lasered. The white blob floating to the right of the arrow is the piece of retina that has been torn off. In the bottom picture, there is a white circle around the hole. This is retina that has been treated with laser, which causes the retina to stick to the wall of the eye. Even though the hole is still there and cannot be closed, the retina is now much less likely to detach.

Retinal 'U' tear

Multiple retinal breaks and retinal detachment
The picture above shows a large U shaped tear on the right but no retinal detachment yet, while the picture below shows 2 retinal breaks (one oval hole and one curvy tear on the right) with most of the retina already detached (greyish areas).


How do we treat these problems? As with all the things we deal with, some things we can treat well, and other things-well, are still looking for a solution. Unfortunately for many people, the annoying floaters continue to be a problem for many months or even years, although they do generally get less obvious with time as they drift out to the periphery somewhere. They are more obvious in bright situations, so I tell my patients to wear sunglasses when they go outdoors and perhaps to dim their computer screens. But there is no medication to clear them. Some surgeons do 'floaterectomy' operations, but these are generally frowned upon by most eye doctors because manipulating the vitreous gel confers a risk in itself of retinal tears and retinal detachment. Plus a risk of early onset cataracts associated with removing the vitreous gel.

Wherever a retinal break (hole or tear) is seen and the retina is not yet detached, laser treatment is done. This takes 5-10 minutes, and the chance of future problems is very significantly reduced. Unfortunately by the time some patients arrive at the doctor's office, the retina is already detached, by which stage it is too late to solve the problem with laser treatment alone.

There are basically 2 ways to repair detached retinas. The first involves stitching and fixing a band of plastic around the circumference of the eye like a belt. This presses the wall of the eye inwards, and by doing so brings it closer to the detached retina. It also reduces the pull of the vitreous on the retinal tear. This can be combined with drainage of the fluid under the detached retina, and also freezing or laser treatment to form a permanent seal around the laser tear. In the picture below, the ridge at the top part of the picture is the view from inside the eye of the band pressing inwards.

Scleral buckle

The second method involves removing the vitreous gel (vitrectomy) and then replacing the gel with a gas or silicone oil. This second method can actually also be combined with the first in complicated cases.

There are pros and cons with each type of surgery, which perhaps should be addressed in a later post. Suffice to say that wherever possible, most surgeons in Singapore prefer to do the first method (Scleral buckling) as it is an external procedure, with no requirement to posture face down (as the patient would have to do if it was vitrectomy with gas) and no need for a second operation to remove silicone oil (as is sometimes done with vitrectomy and silicone oil). 

Monday, July 14, 2014

Soft contact lenses or hard contact lenses?

Contact lenses are a very popular form of vision correction. In Singapore, it is estimated that 600000 people wear them (ST, Sep 1 2012 'Contact lenses safe, provided proper care is taken'), with a very low risk of complications.

Generally, contact lenses can be divided into soft and hard varieties. Soft lenses tend to be large in diameter and are flexible, so they can be folded. They are much more comfortable to wear, and currently the most commonly used ones are of the disposable type. Although soft contact lenses first became available in 1971, the disposable type only became available from 1987 onwards.

Nowadays, there are daily disposable, 2 weekly disposable, and monthly disposable types. And of course, there are the longer term, permanent lenses which actually are used for about 1 year before they need to be replaced. Daily disposable lenses are expensive, but they are least likely among soft contact lenses to cause problems such as allergies or infections, unless the user does not wear them according to instructions. Daily disposable lenses also are thinner, and so less likely to cause or exacerbate dry eye situations. Even 2 weekly or monthly disposable types are worn successfully by many people, and are most cost efficient for those who wear lenses on a daily basis.

Current 'hard' or 'semi-hard' lenses usually refer to corneal rigid gas permeable lenses (RGP), and these were first introduced in 1978. In actual fact there are other types of hard lenses, such as scleral lenses, and there are even hybrid hard lenses with a soft skirt at the edge, but these are more rarely used.

In 2012, RGP lenses made up 9% of contact lenses worn in the US. Source: Contact Lens Spectrum, January 2013. 

They are less widely used than soft lenses, because there is an initial period when RGP wearers will feel the lens in their eye. This uncomfortable sensation is akin to having an eyelash in the eye-ie it is not very painful but in the initial stages can cause tearing and bother the wearer. Once over this period (up to 2-3 weeks), the lens is as comfortable as soft lenses, and the RGP lens really begins to shine. Occasionally, if a bit of dust gets under the contact lens, that can cause eye pain, but a quick rinse with even tap water will clear this easily.

The benefits of RGP lens wear are many, among which are sharp vision (usually sharper than soft contact lenses or spectacles), very good oxygen permeability (yes, your cornea needs to breathe oxygen in the air!), less tendency to be affected by dry eyes, and very good durability.

One reason why some young children used to be started on RGP lenses was a belief that wearing them could slow the progression of shortsightedness (Myopia). However, a study done 10 years ago (Arch Ophthalmol. 2004;122(12):1760-1766) showed that there was no difference in growth of eyeball length between the soft contact lens wearers vs the RGP lens wearers. This suggests that RGP lenses have no real ability to  retard the progression of shortsightedness.

There is a special class of RGP lenses called orthokeratology lenses which are worn to sleep, and are worn with the intention to flatten an area of the cornea. I will cover these lenses in a future post as they are used in a radically different way compared to other contact lenses.

Should one go for soft lenses or hard lenses? I would say that for the majority of people, soft contact lenses are best because of the comfort, ease of wear and care. They are good for occasional wearers and those with otherwise healthy eyes.

RGP lenses would be especially useful for those with the desire or need to see with very sharp vision, and those for whom the extra thickness of soft contact lenses might give rise to problems eg those with very high spectacle power, or those with dry eyes.

I guess I am partial to RGP lenses, having worn them myself for over 30 years. The only thing I avoid doing with any regularity is swimming, even though it is possible to wear goggles with them on. I have gotten so used to them that I actually find it easier to wear them than soft contact lenses.

Tuesday, July 1, 2014

Blood is thicker than water

Mr C is an old patient of mine. I first met him 3 years ago, soon after moving to Singapore from Penang.

His is a story of survival, of successfully battling leukemia and unfortunately then losing vision in one eye from complications of graft vs host disease. At the time of his leukemia treatment, he was fortunate enough to receive a bone marrow transplant from one of his sisters, and he subsequently went into remission. The bone marrow unfortunately produced cells which started attacking parts of his body. Some scarring developed in his mouth, but it was his right eye which bore the brunt of it. Treatment with high doses of steroids produced steroid induced glaucoma in the eye, for which he underwent transscleral cyclodiode laser treatment. Unfortunately, that eye became phthisical.

When I first met him, he was just starting to develop inflammation in his other eye. We managed to control that with oral steroids at the beginning, but soon a tongue of fibrovascular tissue started growing inexorably towards the centre of his cornea from under his upper eyelid.

We got him a haematology referral, put him on other immunosuppressants, searched the literature for graft vs host disease, and got nowhere. His vision was soon obscured by the fibrovascular ingrowth. At first, I did a simple excision of this tissue, but ominously it grew back within a matter of months.

I had read reports of oral mucosal transplantation to the ocular surface, but had up to this time been somewhat skeptical of the reported benefits. For this patient, there were not many alternatives. The superior fibrovascular tissue had obliterated the superior conjunctival fornix, and at a minimum I would need some tissue to resurface that. There was no significant tissue to take from his other, phthisical eye. I got my plastic surgeon brother and together we worked on Mr C. He harvested a rectangle of oral mucosa, following which I dissected Mr C's upper lid free of the cornea. I then transplanted the oral mucosa to the uppermost part of the tarsal surface of the upper lid. The surface of the eyeball I covered with a layer of amniotic membrane.

It was with dismay that I noticed fibrovascular tissue creeping across the amniotic membrane a few weeks after surgery. Before long we would be back to square one!

I took Mr C to the treatment room, and slightly out of desperation took a very thin layer (split thickness, see pic below) of the transplanted oral mucosa from the superior forniceal area and retransplanted this to his superior limbal area, hoping that this would act as a barrier to further fibrovascular ingrowth. Amazingly, it did just that! The fibrous tissue regressed into a small red granuloma (see below), which I easily excised in clinic. Epithelium from the oral mucosa in the limbal area also started growing over the cornea, which was soon epithelialised. Amazing, and here we are with so much research done trying to grow oral mucosal epithelium in the lab.

And we all live happily forever after? Unfortunately, no.

After about a year, it became apparent that things were still unstable. Firstly, blood vessels started growing into the superior part of the cornea (see below). Obviously, the oral mucosal cells do nothing to stop blood vessels from growing in. Anytime I tried to reduce his oral steroids and immunosuppression, his conjunctiva and even cornea would get inflamed, with epithelial defects and even more alarmingly, slowly progressive corneal thinning. Secondly, his long term usage of oral steroids had caused a very dense posterior subcapsular cataract. We got by, by keeping him dilated with atropine so he could still see out of the less affected peripheral lens.

But we knew that things were not getting any better. And I was worried that one day his cornea would melt and perforate (as has happened to one of my Stevens Johnson patients before). What he really needed was limbal stem cells that were immune to attack from the transplanted bone marrow. A light bulb went off-I would use limbal tissue from the sister who had donated the bone marrow in the first place! As the immune cells and the limbal tissue are from the same donor, the limbal tissue would naturally be immune from attack!

We discussed this a number of times, and finally about a month ago I sat down and spoke to quite a few of the siblings (they are a large family). As expected, the sister involved wanted to know how the limbal stem cell harvest would affect her. I replied that it was a very safe procedure that would cause very temporary and mild discomfort, although it could cause some changes in spectacle power/astigmatism.

Last week I performed the operation to remove the cataract as well as transplant the limbal stem cells from the sister to Mr C. Both are doing great. The limbal stem cells are taking well and today donor corneal epithelium had grown to cover most of the corneal stroma. Hopefully this is the last operation I have to do for Mr C!

Even though Mr C was unfortunate to get leukemia and then graft vs host disease, he was very lucky to have such a supportive family and sister. You really know who are the people you can count on when the going gets tough!

Update (13 August 2014)
Mr C continues to do well with clear corneas and vision of 6/12 unaided. Driving vision!