LASIK surgery-Spectacle freedom with precision laser treatments

Around the world, millions of people have undergone LASIK surgery. It is a very effective procedure, which uses a laser beam to reshape the transparent covering at the front of the eye called the cornea. LASIK was introduced in the late 1990s, and essentially involves creating a very thin ‘corneal flap’, and then using a special ‘excimer’ laser on the cornea under the flap.

The LASIK procedure

Although LASIK is a very successful procedure, many people are concerned about undergoing surgery. Some patients have reported problems such as difficulty seeing at night and dry eyes after surgery. There is the potential of leaving behind some of the spectacle power that was to be treated, and a very small risk of infection.

Before Surgery

Such issues are of foremost importance at Jerry Tan Eye Surgery. Prospective patients undergo a comprehensive assessment to check their spectacle power, corneal shape and general health of the eye. Spectacle power is checked both without and with special eyedrops which relax the muscles of the eye so that the reading is as accurate as possible. Once the assessment is complete, careful planning of the procedure is performed.

The LASIK Procedure

Surgery at Jerry Tan Eye Surgery is normally performed one eye at a time. This enhances safety because there is no chance of infection in both eyes at the same time, even though the risk of this happening is extremely small. Furthermore, it allows fine adjustment of the treatment for the second eye, for a more accurate result.

The traditional method of creating a corneal flap made use of a special blade called a ‘microkeratome’. However, the corneal flap that was created was sometimes uneven, resulting in less optimal outcomes. At our clinic, most cases now have their corneal flaps made by a special laser - the femtosecond laser. It creates a series of bubbles in a perfectly uniform plane in the cornea. This allows a flap to be lifted, much like how a stamp can be torn in a straight line. The resulting flap is much more even in thickness and diameter. Older femtosecond lasers worked very slowly, but the iFS laser at Jerry Tan Eye Surgery creates corneal flaps in 10-15 seconds, minimizing patient discomfort while ensuring better vision after surgery.



How a femtosecond laser creates a corneal flap

The iFS femtosecond laser





After a corneal flap is created and lifted, an excimer laser is used to reshape the cornea. Modern lasers work very fast, and the new Schwind Amaris laser at Jerry Tan Eye Surgery works at 750 times a second. This means that 100 degrees of short-sightedness is corrected in 1.5 seconds. The Amaris laser also tracks eye movements at 1050 times a second in 6 dimensions, ensuring very accurate placement of the laser treatment. For most patients, the actual surgery takes a surprisingly short time in comparison to the time spent on assessment and planning.

Our Results

LASIK results

 At Jerry Tan Eye Surgery our results show that for patients with between 100-700 degrees of shortsightedness, 89% achieved perfect vision (6/6) or better. 55% achieved better than perfect vision.  After LASIK, 84% achieved refraction within 25 degrees of 0, and 97% were within 50 degrees of the intended final power.

Customised PerfectShape® LASIK

In order to avoid night time glare and haloes after surgery, we have developed ‘PerfectShape®’ LASIK at Jerry Tan Eye Surgery. In most traditional ways of performing LASIK, the cornea becomes more curved at the sides after treatment, and this causes poor focusing of light in the dark, when the pupils of the eye become big. PerfectShape® LASIK preserves the natural corneal contour as much as possible while using special corneal maps to guide the laser to smooth out any unevenness of the corneal surface. With PerfectShape® LASIK, night vision was the same or better after LASIK in 90% of our patients, which is remarkable considering that only a few years ago standard LASIK was causing glare and halos in many patients. In fact, PerfectShape® LASIK can be used to reduce night vision problems in many patients who had their LASIK done with older lasers.

A common problem encountered by LASIK patients after surgery is dry eyes. This is related to a disturbance of the eye’s surface caused by surgery. While it normally improves over several months as the eye heals, it can cause blurred vision and eye irritation. In our practice, this problem is less serious because we temporarily plug one of the tear drainage channels. This helps preserve the patient’s own tears on the surface of the eye.

Patients who are older than 40 years of age and undergo LASIK will have good vision for things far away, but near vision is not as good. This is due to presbyopia or ‘old sight’ (rabun tua). This cannot be cured by LASIK. We believe that the best way to reduce the need for reading glasses is ‘monovision’, which means that the LASIK is performed so that some shortsightedness is purposely left behind in one eye. Although with monovision only one eye has clear vision for distance and the other eye has clear vision for near, when both eyes are open all distances are generally sharp.

In summary, LASIK as a method for correcting vision continues to be refined, leading to better outcomes and fewer side effects for patients. Femtosecond laser corneal flaps and customised excimer treatments with the latest excimer lasers bring us closer to the goal of giving perfect vision to all our patients. The future of refractive surgery will bring further innovations, however, they will have to be compared to the gold standard which is current LASIK surgery.

Contact lens FAQs

Problems such as shortsightedness have become so common in Singapore that by 12 years of age, about 60% of children are already wearing glasses. Although spectacle wearing is effective and safe, they are not always the most convenient of things to use.

At my clinic, we often come across patients who are either keen to start wearing contact lenses or are already wearing them but have some nagging questions about them that they just thought of. Hopefully this post, which is in a Q+A format, will help to answer those queries.

1. Can my contact lenses get lost in my eyes?

Contact lenses cannot be lost in the eyes, because there are natural pockets at the side of the eyes which prevent the lenses from going further backwards. However, they may sometimes slip off the cornea onto the white part of the eye. If this is noticed, you may reposition it yourself, or see an eye care professional for help.

2. If I’m playing soccer and the ball hits me near or on my eye, will my lenses break or tear in my eyes?

Direct impact by the soccer ball onto the eyeball will cause injury of varying severity depending on the force of the trauma. A soft contact lens will not generally break or tear due to its flexibility. A hard contact lens could theoretically break although that is also very unlikely due to the softness of the surrounding tissues. What happens more commonly is the lens is knocked or rubbed off the eye. Surface abrasions of the cornea may be caused as a result.

4. I want to wear coloured lenses to look different sometimes... Will these lenses damage my eyes?

Coloured or tinted lenses are available from major manufacturers such as Cibavision. These are generally safe to use but like all contact lenses should be dispensed only after fitting by an eye care professional. Buying these lenses from internet sources, or from manufacturers with an unknown reputation risks severe damage to the eye from problems such as infection, irritation from chemicals in the soaking solution, or poorly fitting lenses.

5. I heard that I could catch Acanthamoeba infection by swimming without removing my contact lenses. This parasite can burrow into my eyes and make me blind. Is this true?

Acanthamoeba is a one-celled protozoan parasite that is found in many places in our environment, including tap water. If contaminated water from the swimming pool enters the eye, Acanthamoeba can stick to the contact lens and establish an infection on the surface of the eye. If not treated, a severe corneal ulcer can develop causing blindness. In general contact lenses should be removed before swimming and they should not be cleaned with tap water or home made saline to avoid this infection.

6. I have no access to saline solution and even tap water. There is a problem with one of my lenses (the edge has curled inwards slightly and is causing me pain). What can I do? Can I remove the affected lens and re-wet it with saliva?

The best thing to do is to remove the contact lens and discard it. Saliva should not be used because the mouth is filled with bacteria and using saliva is going to contaminate the lens, thereby making it very likely for a corneal infection to occur.

7. I fell asleep overnight with my lenses on. Will they get stuck to my eyes?

Sleeping with contact lenses on for any length of time raises the risk of infection and should not be done for any length of time. Even without an infection, lens adherence or sticking to the eye is very common after sleeping with them on and is due to a combination of dryness and the pressure of the eyelids. This sticking is not permanent, and if it happens, the wearer should wet the eyes with re-wetting solution or artificial tears, and then attempt to remove the lens after a few minutes. If this cannot be done, then an eye care professional should be consulted for removal of the lens.

8. I use daily disposables. However, I’ve been wearing them continuously for a week (I don’t remove them). How long can I overuse disposable lenses?

It is very dangerous to wear daily disposable lenses in such a fashion. The lenses become coated with deposits and sooner or later an infection develops or the eye becomes red and irritated from the lack of oxygen and deposits. Disposable contact lenses should be changed strictly according to the schedule recommended by the manufacturer.

9. I was travelling overseas when I ran out of saline solution. I used tap water to rinse my lenses instead. After a few days, I started noticing coloured spots on my lenses. What is happening to my lenses?

It is not possible to say with certainty what these spots are but they could be mineral deposits if the tap water was hard (with a high concentration of dissolved substances). Worse, they could even be fungus growing on the contact lens. These lenses should be discarded immediately.

11. Do the new “HD” soft lenses work for people with astigmatism? Can people with severe astigmatism wear such “HD” lenses? Are RGP lenses still preferred for people with astigmatism?

“HD” refers to optimized optics which include aspheric designs but it does not necessarily mean that the lens will have a toric component to correct astigmatism. A person with severe astigmatism needs either a toric soft lens or a rigid gas permeable (RGP, otherwise known as hard) lens. RGP lenses correct astigmatism very well and possibly provide the sharpest vision among the types of contact lenses. However this must also be balanced with comfort issues.

12. I have lazy eyes. Will contact lenses help my condition? What types of contact lenses are best suited for my condition?

Lazy eyes (amblyopia) develop during childhood because a disturbance of vision prevents normal development of the nerve pathways between the eye and brain. Later on in life, vision remains blurred in the lazy eye even when glasses or contact lenses are worn, because the problem has to do with the nerves and brain, and is not related only to spectacle power. If lazy eyes are detected in childhood, the better eye is patched and the child is forced to use the lazy eye to see, with the use of glasses or contact lenses as appropriate. Beyond the age of about 10 years, patching is no longer useful. Older children and adults with lazy eye are now treatable with a revolutionary computer based training program called Neurovision (see http://www.neurovision.com.sg/). This presents customised images to the patient and over a period of several months improves nerve connections and vision even in adults with lazy eye. As such, lazy eyes are not treated by particular contact lenses per se, but the contact lenses or glasses will help with any long/short-sightedness or astigmatism that is present.

One year already

Time flies. It's been one year since I first started posting and it's been a bit like my paper diaries!!

Eye-wise, interesting things have happened. A year ago I posted about Demodex and using Tea Tree oil or systemic Ivermectin to kill them. If you can compound Ivermectin cream that works even better and does not sting.

I have found a few patients with what appears to be seborrhoeic dermatitis and also happened to have lots of Demodex in their eyelashes. Somehow I managed to cure their skin problem which had usually been causing trouble for years. The Ivermectin cream killed the mites in the lashes as well as in the skin and the rash disappeared. This rash was typically erythematous (reddish) macules and sometimes could be slightly scaly. it was often in the brow and nasolabial fold and had not responded to previous courses of steroids and other treatments. In the picture below you can see the rash between the brows and at the side of the left upper eyelid in one patient.

Recently also we have been seeing a spate of microsporidial keratoconjunctivitis. Often the story was of playing rugby or football on a muddy field (it has been raining a lot over the past one month) and getting muddy water splashed into the eye. Gardeners have also been affected. Their eye became red and teary about a week after contact with the contaminated water. On the front surface of the eye (cornea) the patients developed tiny white spots like in the picture below.

So far all our patients have recovered with antibiotic eyedrops. I think the main issue is not to confuse it with viral conjunctivitis and start with steroid eyedrops too early, since this can prolong the infection somewhat. Viral conjunctivitis is usually redder, with more discharge and stickiness in the morning and there is usually no history of contact with dirty water.

The rugby players at Turf City have gotten so familiar with this that they are going to see the doctor, and telling the doctor the diagnosis even before being seen!

Improving visual quality after previous LASIK

About 2 months ago I saw a patient who had LASIK done in another clinic a few months previously. His vision when measured on the reading chart was actually very good-it was 6/6 without glasses in both eyes. However, he was very disturbed by his vision at night. He was unable to recognize faces when the surroundings got a little dark, and vision in such situations was just generally blurred. Before his LASIK, his power was only about 500 degrees short-sighted.

When we did his corneal maps (topography), it was obvious why he had such problems. The previously treated zone was small, and it was also slightly decentered upwards. Our aberrometer shows clearly his predicament. When his pupil is 3mm in diameter (in bright light), you can see the image of the 'E' is sharp. When his pupil enlarges to 6mm, all you see is a shapeless smudge.

Last week I performed topography guided enhancement LASIK for his left eye. A comparison of the pre and post-operative corneal topographies shows that the central blue/green area is now larger. Subjectively, his night vision is much improved and best of all, his daytime vision also improved to 6/4.8 without glasses.

This case highlights an important aspect of LASIK which is often overlooked, sometimes because of the limitations of technology at a particular clinic. And that is-the quality of vision, on top of the spectacle power issues. In this day and age, we aim not just for minimal spectacle power after LASIK, but also the best quality of vision in all situations. There are limitations, such as for those with very high powers, because there will be issues with corneal thickness. But customizing a 'perfect shape' cornea should be possible for all those with low to moderate degrees of shortsightedness and astigmatism, such as in this case.

Asia ARVO 2011

For the benefit of non eye doctors, Asia ARVO is essentially one of many conferences cum trade exhibitions for eye professionals. By attending these events, we hope to keep up to date and abreast of new developments. For the organisers, a successful event garners brownie points and prestige.

This event was held over the last 4 days at Resorts World Sentosa. I went without expecting too much in the way of new developments. But I was peasantly surprised. For me, these were the highlights:

1. Rho kinase inhibitor (ROCK inhibitor) Y-27632 has been found to be able to cause corneal endothelial cells to proliferate both in vitro and in vivo. To put you in the picture, corneal endothelial cells keep the cornea transparent but the unfortunate thing is-once they are damaged, to date, they have behaved like nerve cells-showing no inclination to repair themselves. So the traditional treatment for conditions where they are too damaged has been corneal transplants. Now we may have a medicine so that many can avoid these surgeries!
2. Intravitreal Avastin has been found useful for all stages of CRVO. Avastin blocks a vascular growth factor, which causes many of the complications of central retinal vein occlusion (CRVO). Finally, we have a clearer picture of the role of avastin in this condition.
3. Richard Spaide has done some remarkable work with OCT and choroidal vessel imaging. Apparently there are cases of unexplained visual loss which have now been shown to be correlated to loss of the choriocapillaris. And guess what? Viagra has been shown to increase the thickness of the choriocapillaris! On a more serious note we now need to see if other vasodilators like glyceryl trinitrate can do the trick on a more prolonged basis without too much in the way of complications...
4. Lenticule extraction with the Visumax laser (FLEX procedure) is associated with a fairly prolonged loss of best vision in 25% of patients! I have a feeling this is not going to work out too well...

Wavefront-guided and topography-guided customized LASIK: What do they mean and what's the big deal?

In recent years, the word 'customized' has become ubiquitous in LASIK treatments. If you're not doing customised treatments, if you're only doing standard treatments, you're out. But aren't all treatments customised, since they're customised according to the refractive error you have? Let me explain.

There are 2 things that so called customised treatments aim to control for, that so called standard treatments do not. One is ocular 'aberrations'. Most of us know that vision is affected by short or long sightedness, or astigmatism. But our vision is also affected by other irregularities of the cornea and lens, called aberrations. The chief ones which cause problems are 'coma' and 'spherical aberration'. When present in large degrees, they can cause glare and halos especially when the pupil is large at night. So these 'customised' treatments aim to treat the particular aberrations of the individual eye.

Now, when most people talk about 'wavefront-guided', they are talking about 'whole eye' wavefront. But whole eye wavefront is affected by a few different things. It is affected by pupil diameter, it is affected by the state of focus of the eye (accomodation), and it constantly changes as the eye ages, primarily due to changes in the shape of the lens. Furthermore, most measuring systems for whole eye wavefront only measure several hundred points at most through the pupil.

Topography-guided LASIK, or more precisely 'corneal wavefront guided' LASIK, is LASIK based only on measurements of the cornea.This is advantageous, because the cornea does not change as much in shape throughout life-definitely less so than the lens. It does not change in response to pupil shape, nor does it change in response  to accommodation. Topographers measure corneal shape right out to the periphery, and typically measure in excess of 20,000 points. In most cases, corneal aberrations account for a majority of whole eye aberrations. It would thus appear that topography or corneal wavefront guided LASIK is the way to go.

Customised treatments also take your corneal curvature into account when delivering the treatment. Why is this important? Well, imagine yourself standing in the sun at noon, at the equator. Your shadow would be tiny, directly under yourself. If you were standing in London in winter at noon, your shadow would be much longer, because the sun's rays are coming at an angle. In a similar way, the laser's rays strike the cornea at an angle at the periphery of the cornea. If a cornea is of relatively standard shape, that's not a problem, because the laser has been programmed to treat relatively 'standard' eyes. However, if your cornea is more curved than normal, ie steeper at the sides, then the laser would strike your corneal periphery at a larger angle than normal and work less effectively. You could end up with a smaller optical zone than expected. You could end up with lots of night glare and halos.

So, go for customized LASIK if you can. Better still, go for Topography Guided/Corneal Wavefront Guided LASIK for best visual quality.

Itchy eyelids? Crusty eyelids? The reality of Demodex

What's Demodex? They are mites, which are microscopic little critters with eight legs. They belong in the same class  of animals as spiders. While most have heard of house dust mites, few have heard or come across demodex, except maybe dog owners. This is despite Demodex infesting many of us, only we are unaware of their presence most of the time.

Demodex are readily accessible to inspection by most ophthalmologists, only many ophthalmologists are also unaware of their presence. When they infest the lash follicles, they are readily visible on high power with the slit lamp microscope. The video shows how I look for them-by pulling lightly and twirling the eyelashes. Before I do this I clean away all debris and dandruff like material with an alcohol swab. Then, pulling lightly on the lashes causes their tails to poke out, and further twirling the lash will cause the mass of demodeces to come out and lie on the skin surface. They look like tiny shiny rod shaped objects. They can then be scooped up with the tip of a forceps and I touch them lightly on the sticky side of a cellophane tape. I then stick them on a microscope slide and have a look on a compound microscope. The picture shows one that I caught recently. However, now that I've seen quite a few of them, I can readily identify them on the slit lamp alone.

So what? It seems to me that most people with blepharitis, especially anterior blepharitis and lots of debris near the eyelashes also have lots of demodex. Coincidence? Some people say demodeces are commensals. Well, I would say it's too much of a coincidence. Several papers by Scheffer Tseng have now come out about the pathological role of demodex in ocular surface disease. I still wonder about posterior blepharitis and meibomian gland disease. I often see this without demodex infestation of the lashes. It could be that there is deeper infestation within the Meibomian gland itself, by D Brevis, but we won't know for sure unless we can somehow put a scope up the gland or maybe test the Meibum by PCR for the demodex.

If you see Demodex, what do you do? Some would do nothing. I think that is reasonable if you see one or two of them in the odd follicle, and the patient is not symptomatic. But if there are lots, and the patient is itching like crazy or the lids are inflamed, then steps should be taken. Tea tree oil has been touted as being a great mite killer-but that would only work for the ones on the lashes. If there are any in the Meibomian glands one might have to resort to something  systemic like ivermectin. I don't see how the tea tree oil would get into the Meibomian glands. So there you have it-in a nutshell. My thoughts on Demodex and blepharitis. I do welcome your comments.