Tuesday, February 14, 2012

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.

Wednesday, January 18, 2012

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.
  1. 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.
  1. 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.
  1. 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.
  1. 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.
  1. 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.
  1. 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.
  1. 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.
  1. 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.
  1. 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.

Friday, January 6, 2012

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!