Secrets in the war to stop shortsightedness from increasing

Trying to stop myopia progression is like deciding to go on a diet. Seriously. I'll get to that eventually but before we get too philosophical, let's take a step back.

Currently, more than 50% of twelve year olds in Singapore need to wear glasses because of myopia. And by the time the boys enter the army at 18 years of age, it will have increased to 80%. Unfortunately, myopia is a problem that continues to worsen as children grow up, usually stabilizing by the late teenage years. By this time, it is not uncommon to see patients with myopia of -6D and above. High myopia of course, can give rise to other problems such as an increased risk of retinal detachments and an earlier onset of cataracts.

Myopia or shortsightedness arises because of an imbalance between the focusing power of the cornea and lens of the eye, versus the length of the eyeball. In the type of myopia that arises in children, it is mainly a problem of the eyeball growing too long, ie axial myopia.

For many decades now, research has been ongoing both to find a cause of this abnormal eyeball growth, as well as to find ways to stop it or at least to slow it down. Because the actual cause and mechanism are not known, methods that have been tried are all based on theories or empirical data. Let's take a look at the things that have been tried.

Things that have been tried and failed

1. Timolol eyedrops to lower eye pressure.
Since eye pressure may potentially stretch an eyeball and make it bigger and longer, people tried to see if lowering the eye pressure could stop the eyeball from enlarging. Unfortunately Timolol eyedrops did not work. However, it remains to be seen whether more powerful pressure lowering medications like bimatoprost may have an effect.

Things that may work (either the evidence or effect is weak)
1. Glasses which reduce peripheral hyperopic defocus (Myovision by Zeiss)
These glasses appeared to have an effect in younger children who had myopic parents. Why it would only work in this subgroup of people is unknown but could reflect a weak effect or a chance finding.
Sankaridurg P, Donovan L, Varnas S, et al. Spectacle lenses designed to reduce progression of myopia: 12-month results. Optom Vis Sci 2010; 87: 631–41. 

2. Rigid gas permeable (RGP, or semi hard) contact lenses
At the age of about 11 I was introduced to 'hard' or RGP contact lenses in the hope that it could slow down the rate of increase of my myopia. In fact in my case, it wasn't that successful in this regard. A well conducted trial showed that RGP lenses do not slow down the growth of the eyeball, but may have an effect by reducing the steepening of the cornea.# This may be only a temporary effect from the pressure of the lens on the eyeball.
#Walline et al. A randomized trial of the effects of rigid contact lenses on myopia progression. Arch Ophthalmol. 2004 Dec;122(12):1760-6.

3.Orthokeratology
Orthokeratology (OK or Corneal Refractive Therapy/CRT) takes the concept of corneal flattening using pressure from a lens one step further. In this method, RGP lenses of a special shape are worn to sleep. The lenses press on the patient's cornea during sleep, so that during the day the lens can be removed, and the cornea retains the ideal shape which corrects the long/shortsightedness and astigmatism. After a few days of not wearing the lens to sleep, this effect is lost, so the power lowering effect is temporary.

But does it stop myopia from increasing?

Walline JJ, Jones LA, Sinnott LT. Corneal reshaping and myopia progression. Br J Ophthalmol. 2009 Sep;93(9):1181-5.

The above study showed that yes, it seemed that orthokeratology can slow down the growth of the eyeball compared with soft contact lenses. This effect is not as strong as 1% atropine eyedrops (0.25mm elongation with OK versus -0.02+/-0.35 mm with atropine at 2 years).

In other words, OK lenses had an effect somewhere between soft contact lenses and 1% atropine, but without the side effects of the atropine. Do consider though, that wearing contact lenses to sleep is generally felt to increase the risk of eye infections.

Things that work (with strong evidence and strong effect)

1. Atropine
The idea of using atropine came about because of its well known ability to relax the ciliary muscles in the eye (which are used for near focusing). Since as the theory goes, too much near work is related to shortsightedness, and near work results in prolonged contraction of this muscle, would relaxing the muscle have an effect on myopia progression? The results of well conducted studies show that yes, indeed atropine has a powerful effect on slowing or stopping the worsening of myopia.

There are two concentrations in common usage: 1% (stronger) and 0.01% (weaker). The 1% concentration is very effective but has side effects of causing sensitivity to bright lights and temporary inability to focus for near. These are reduced by using special progressive glasses that turn dark in bright light. With the 0.01% concentration, there are no side effects but the effects of slowing down myopia are not as pronounced. Which specific medicine is used depends on the degree of shortsightedness, how fast it is progressing and the child's tolerance to the side effects of the stronger concentration. Read more about this at my other post on atropine and myopia.

2. Outdoor time
2 generations ago, it was much less common to see a shortsighted person in Singapore, despite people having essentially the same set of genes. Other things have changed, notably our environment and activities.

Increasingly, evidence points to the importance of outdoor activities in reducing the rates of myopia and its progression.# What is it about being outdoors that slows myopia? Many people think it is because we get to see things far away when we step outdoors, but this effect of distance versus near visual work has been shown to be only a weak one.*
#Rose KA, Morgan IG, Ip J, et al. Outdoor activity reduces the prevalence of myopia in children. Ophthalmology 2008; 115: 1279–85.
*Mutti DO, Mitchell GL, Moeschberger ML, Jones LA, Zadnik K. Parental myopia, near work, school achievement, and children’s refractive error. Invest Ophthalmol Vis Sci 2002; 43: 3633–40.

In fact, it is likely to be due to the difference in amount of light being seen by the eye, when comparing being indoors versus outdoors.

When we step outdoors, even at 5 or 6pm in the evening, we are typically being exposed to much more light than we get even with the brightest lamps indoors. It has been shown that bright light leads to the release of more retinal dopamine, a chemical which may play a role in controlling eye growth. It is intriguing that using a chemical to block dopamine in animals can also block the protective effect of bright light.#
#Ashby RS, Schaeff el F. The eff ect of bright light on lens compensation in chicks. Invest Ophthalmol Vis Sci 2010; 51: 5247–53.

SO.....
It is said that in losing weight, '..., you must accept that this is your new lifestyle of eating healthy and being physically active...' http://www.webmd.com/diet/features/10-diet-secrets-lasting-weight-loss-success

And equally, in trying to control myopia, the patient must accept a new lifestyle of regular outdoor activity (in sunlight) and being more active. At least 1-2 hours everyday. As a follow on from that, it's also important to ensure that when indoors/doing near work, that the child has a brightly illuminated environment. It does not matter what type of light it is (eg sunlight by the window, fluorescent, LED etc), as long as it is bright. Failing which, the most effective treatment so far is atropine eyedrops.

No, wait..... Actually it's easier to control myopia than to go on diet. If only our waistlines would stabilise after a certain age (like myopia), so that we don't have to worry about it any more after that!

References:
Lancet 2012; 379: 1739–48
Ophthalmology 2002;109:415–427

Conjunctivitis: What you should do if you get pink/red eye...

Have you ever had one eye inexpicably and rapidly turn red, swollen and sticky in a day or so, and then horror of horrors, the same thing starts to happen in your other eye?

This condition, medically termed conjunctivitis, is also known as 'red eye' or 'pink eye'. It is an eye infection, affecting the outer 'skin' covering the eyeball called the conjunctiva (hence conjunctiv-itis). There are many different germs that can cause this infection. Most cases are caused by viruses, while occasionally we see cases that are caused by bacteria. Among the viruses that cause this condition, the more common ones include adenoviruses and coronaviruses.

Occasionally this condition is mild, and the eye gets better within a few days. However, many cases of viral conjunctivitis can take much longer to recover fully from. In my experience, the eyes can be red, swollen and sticky for up to 2 weeks before improving.

When things go well, usually the stickiness starts to get less, and the swelling improves. The eyes then become less red, and finally everything including vision goes back to normal.

Complications of conjunctivitis

Sometimes though, complications occur. Some patients get a layer of mucus and dead cells stuck to the inner surface of the eyelids. This is called a 'pseudomembrane' (below), and can make the patient feel very uncomfortable as the pseudomembrane, if located at the upper eyelid, rubs the cornea with each blink.

Another complication is unusual in that it actually occurs as the redness is going away and the eye is starting to feel better. This condition is called 'nummular' (coin shaped) keratitis, and consists of little white spots appearing on the cornea of the eye. This condition can cause vision to become hazy/smoky, and can cause glare in bright lights.

How we treat conjunctivitis

The vast majority of cases have a viral cause, and these are typical in having copious discharge that is watery/mildly sticky and whitish to slightly yellowish in colour. The eyes can be very swollen and red, and on the inner surface of the eyelids there can be small bumps called follicles. These cases are typically treated with combined antibiotic and steroid eyedrops. The steroids help to avoid excessive inflammation and reduce the risk of pseudomembranes. Although the antibiotics do not actually kill the virus, they are a commonly prescribed when steroids are used and may help to reduce the risk of secondary infection by bacteria. There is unfortunately not a lot of evidence to support treatment this way, but patients do seem to feel more comfortable using these medications.

If a patient gets nummular keratitis and little white spots that block vision, then steroids are needed to eliminate the white spots. Unfortunately, once the steroids are stopped, the spots can recur sometimes. Occasionally patients with this complication end up needing a little steroids (eg once a day) for many months to avoid blurry vision. Fortunately most patients recover without experiencing this issue.

The other extremely important issue in managing these infections is to break the transmission cycle ie to avoid spreading it. I advise my patients to observe the following:

1. Wash their hands frequently, and especially every time after touching their affected eye eg when they are instilling eyedrops or cleaning the eye

2. Avoid touching the unaffected eye, and 

3. To tell their family members/close contacts not to touch their eye unless they wash their hands first

4. To tell their family members/close contacts not to apply any eyedrops in the hope of 'preventing' an infection. In fact by instilling eyedrops (especially if contaminated) there is the risk of transmitting the infection to that eye!

Sometimes the virus causing conjunctivitis gets into the throat and causes sore throat/flu like symptoms, in which case that is treated as usual with lozenges, paracetamol (panadol/tylenol), and good old rest.

Understanding your spectacle prescription

Have you ever looked at the seemingly random numbers scribbled on a piece of paper that you sometimes get at the optometrists? If you are more familiar talking in terms of hundreds of degrees of short or longsightedness, how come there are all these + and - signs and then all the decimals?

And then there is the funny fraction at the end, which may say 6/6 in most parts of the world (or 20/20 in the US) for good vision. Singapore parents with school going children may remember seeing the note below, as all primary school children undergo vision screening once a year and if vision is less than adequate will be referred to refraction clinics or optometrists.

Oh no! Vision not great on the screening test and it's time to go to the optometrist's again!

Let's take a step back, and look at what your optometrist is trying to do. Basically, the aim is to get the best vision possible using spectacle lenses which bend/focus light.

A slightly blurry Snellen chart, vision ~6/9

A clear ETDRS chart, vision ~6/6

How good is your vision?

Optometrists will first ask the patient to read one of the charts above, to find out what are the smallest letters that can be read without glasses. For most people with normal vision, letters of 6/6 size are visible/distinguishable at 6 meters. So in a way, one could say that 6/6 means being able to see letters at 6 meters that a normally sighted person would be able to see at the same distance. 20/20 is the equivalent notation in feet.

For those interested in mathematical notations, a 6/6 letter on the whole subtends an angle of 5 minutes of arc at the nodal point of the eye. This means that each element of the letter, such as the thickness of the vertical line on a 'D', subtends an angle of 1 minute of arc at the nodal point of the eye. The nodal point refers to the point in the eyeball where the center of an imaginary lens combining all the focusing power of the eye is located.

Sometimes, vision is poorer than 6/6, which means that the person could not read the 6/6 line on the chart at 6 meters. In that case, the smallest letters that could be read would be recorded, such as 6/9 or 6/12.  6/9 means that the patient can see at 6 meters, what a person with 'normal vision' would be able to see at 9 meters, and so on for 6/12 and 6/18. The optometrist will then try different lenses to make the patient's vision (with the lenses) 6/6.

Generally 6/12 and above vision is considered good vision, and this is the threshold which is considered good enough for driving. Generally speaking, vision worse than 6/12 due to a focusing problem (long/shortsightedness/astigmatism) is an indication that glasses are needed. For most people though, the aim is to achieve 6/6 vision.

Spectacle power notation

Having got all of that out of the way, now let's talk about how spectacle power is written down.

Pure long sight or short sight is corrected by lenses called 'spheres', or spherical lenses. Longsightedness is corrected by convex lenses, which we will give a plus ('+') sign to, while shortsightedness is corrected by concave lenses, which we will give a minus ('-') sign to.

An eye with astigmatism has focusing areas (cornea/lens) which are more curved in one direction than the other (see above). This is like the cylinder (below), which is curved in one direction and completely flat in the other direction. In order to correct astigmatism, a lens which is more curved in one direction than the other (called also a cylinder) is placed so that its curved direction is in the same position as the eyes' flat direction (and vice versa), so the lens' astigmatism cancels out the eyes' astigmatism!

Astigmatism is corrected by lenses called 'cylinders', or cylindrical lenses. This can be denoted with either plus or minus cylinders depending on where in the world you are. In places like Singapore, the cylinders tend to go with a minus sign.

For example    Sph       Cyl         Axis
                       -4.00     -1.50     180
or otherwise also written as -4.00/-1.50x180

means 4 dioptres of shortsightedness with -1.50 dioptres of cylinder at an axis of 180 degrees (the long axis of the spectacle cylinder is placed horizontally).

Colloquially, 1 dioptre of spectacle power is called 100 degrees in Singapore and some other parts of the world. So the above example would mean a patient with 400 degrees of shortsightedness and 150 degrees of astigmatism.

Putting it all together

Let's say if you asked somebody to read the chart, and they could only read to the 6/18 line. As a rough rule of thumb, if he/she is shortsighted, then this person is likely to have about 100 degrees of shortsightedness. The 6/36 line corresponds with about 200 degrees of shortsightedness. And anything above that means vision is limited to only the largest letter (6/60) or just counting fingers.

I mentioned earlier that 6/12 and better vision is generally considered good vision. Following from this, most people with unaided (without spectacles) vision of worse than 6/12 (ie~6/18) would benefit from glasses. And as a rough rule of thumb that would be somebody who is about 100 degrees shortsighted. That is my general threshold for starting a child with childhood myopia on glasses. Of course, the decision whether to start wearing glasses also depends on how the child's activities are being affected by their vision, so if for example, the myopia is only 50 degrees but the child is sitting at the back of the classroom and cannot see the teacher's writing on the white board, then glasses may already be necessary even for this small amount of shortsightedness.

Take home points

1. 6/XX indicates the ability to read different size letters at 6 meters (checked with and without glasses)
2. People with 6/12, 6/9, 6/7.5 and 6/6 vision are generally considered to have good vision.
3. Spectacle power can be of the plus sign or minus sign for long and short sight respectively.
4. The numbers for spectacle power indicate the power of the lens required for good vision, ie the higher the number, the higher the degree (the worse) of the long / short sight or astigmatism.
5. For shortsightedness, a general rule for children is to consider starting glasses wear when the spectacle power is 100 degrees and above.

In a future post I will review the methods people have tried to either prevent or delay the onset of shortsightedness, which is a problem of epidemic proportions in many cities around the world.

The best age to have LASIK

So, young, middle, or old? What's the best age?

Is there a best age to have LASIK? I get asked this question quite often when patients enquire about this surgery and the short answer is yes, with some caveats.

I suppose when we decide to have something done (eg surgery), or even when we buy something, we want to get the best that we can get for what we pay. In other words, value. Even more importantly for surgery of course, we want to get a good outcome, and we want to ensure quality and safety, but value is a common factor that pervades many aspects of our lives.

LASIK is somewhat different from other types of surgery, because what you get out of it is influenced by the age when it is done. Let's take a few scenarios.

A typical patient in their 20s comes for LASIK. In such a situation, both eyes are corrected for distance, so everything is clear after surgery, whether it is something far away or something close up that is being looked at. However, when this patient gets to his/her early forties, they are just like any other patient who does not wear glasses for distance, ie near vision for reading slowly starts to get blurry, and they find they have to start holding things further away. This condition is called presbyopia. At some point, reading glasses are needed for comfortable close work like reading.

When a patient comes for LASIK and they are already in their forties or older, presbyopia is an issue that needs to be considered straight off, at the time of the pre-LASIK consultation. This is because LASIK cannot 'cure' presbyopia as such. The usual option offered to patients who desire spectacle independence is monovision, with its attendant compromises. PresbyLASIK is unfortunately unpredictable in its effects, and so far corneal inlays have also shown problems relatively commonly.

Having said this, many presbyopes are very happy with monovision LASIK. The important thing is to allow a trial period of monovison adaptation to see if patients can tolerate it. This simulation is best done with contact lenses. If a patient does not tolerate monovision with contact lenses, then if LASIK is done both eyes should be corrected for distance and then reading glasses worn for near. Therefore it can be seen that LASIK after the age of 40 or so does not provide as much clarity of vision for all distances compared with when it is done earlier, and also involves some compromises, whether it be monovision or reading glasses for near work.

The next group of patients to consider are those 60 and above. Generally speaking, age is associated with an increased incidence of cataracts, especially with those above 60 years of age. The issue with cataract development is that once a patient has cataracts, then they are no longer suitable for LASIK, since the cataract will blur vision even if LASIK is performed. Furthermore, doing cataract surgery is also a way to correct spectacle power, giving an effect like LASIK. In some ways, you could consider cataract surgery as having the ability to reset the power of the eye, therefore, this is the point where the effects of the LASIK surgery are 'lost'.

To cut a long story short, the best age to have LASIK in my opinion is the early twenties, once spectacle power has stabilized and remains unchanged for more than a year. Patients above 40 will still benefit from LASIK, but one might want to consider certain compromises to avoid reading glasses. Generally, patients above 40 who do get LASIK done avoid progressive/bifocal spectacles, which many people find difficult to get used to. Glasses, if needed, tend to be reading glasses, or occasionally distance glasses for monovision patients who drive a lot at night.

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. )

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.

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.

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!

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.

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.

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).

Treatment

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.

From: Myhealth.alberta.ca

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). 

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.