The dubious honour that sees Singapore crowned one of the myopia capitals of the world reflects the visual environment its people are immersed in. Urban-dwellers, now more so than before, are turning to near focus for work and play. The fact is both nature and nurture play a part in shifting the refractive state of entire generations of people to short-sightedness.
Due to dissatisfaction with dependence on optical aids like spectacles and contact lenses, laser vision correction has become increasingly popular in the past two decades. Even though such treatments have become commonplace, they are still a type of surgery, with the attendant considerations that all surgeries should merit.
What then are some of the myths and truths of Lasik surgery?
Myth: Lasik is cosmetic surgery
Photo: The Business Times
There are definite advantages in reducing one’s dependence on spectacles and contact lenses. Spectacles for myopia (short-sightedness) minimise the actual image size, while those for long-sightedness enlarge images. They often cause aberrations with high power corrections. They can fog up in high humidity and may be cumbersome in sports. In comparison, contact lenses can provide excellent quality of vision, but if mishandled, can cause serious eye infections, which can leave the eye with permanent scars and reduced vision.
Lasik stands for laser-assisted in-situ keratomileusis, which means laser-assisted sculpting of the cornea (the clear structure at the front of the eye). By “sculpting” we change the curvature and shape of the cornea, and its focusing power. In most cases, we aim to “neutralise” the errors of the eye’s power of focus, in order to return the eye to a state of zero power.
Lasik surgery when done right can be wonderful in restoring one’s unaided vision, and freeing one from the possible problems associated with spectacles or contact lens wear. It is a fact that the popularity of Lasik contributed to a reduction of contact-lens related serious eye infections in many urban centres, saving many an eye from potential problems.
Myth: Laser eye treatment equals Lasik
Lasik is the most commonly performed refractive (ie pertaining to eye power or refractive errors of the eye) laser vision correction treatment worldwide. However, it is neither the only laser eye treatment available, nor the only refractive laser treatment available.
There are several types of lasers that are utilised for treatment of eye diseases, each with its unique function. Coagulative laser are used for glaucoma and retina diseases, dispersive laser for cataract-related management, while for Lasik usually two sets of lasers are required: the femtosecond dissecting laser and the excimer ablative lasers. So it is indeed true that Lasik is high-tech stuff that makes use of sophisticated technology.
In a nutshell, Lasik is the second generation of refractive laser correction. The first generation treatment is called “surface ablation” utilising the excimer laser alone with minor variation in procedure, variously called PRK, Lasek, epi-Lasik and transPRK.
These treatments sculpt the surface of the cornea, are painful, have a higher risk of infection due to there being an open wound, and have a downtime of at least several days. They declined in popularity when Lasik came into being.
In comparison, Lasik sculpts the cornea under a layer of cornea tissue called a flap, which acts like a thick, natural protective bandage, resulting in a much quicker and comfortable recovery. Lasik uses either a mechanical blade (by now largely obsolete) or a femtosecond laser to fashion the corneal flap. The flap, however, is a weak point that may cause trouble in accidents and trauma.
Constructive criticisms brought conceptual improvement in the form of Relex© Smile (short for refractive lenticule extraction or small incision lenticule extraction), Carl Zeiss’s offering of a third generation of refractive laser correction, in which only the femtosecond laser is required to create an internal mid-layer that is subsequently removed by the surgeon.
The perks of this treatment are reduced vulnerability as it is flapless and better biomechanical and sensory nerve preservation as it is less invasive.
This latest innovation has been gaining traction steadily since its inception in 2011, and with its United States Food and Drug Administration approval in 2016 and adoption by the US defence forces this year, looks set to increase its market share to become a mainstream refractive treatment option.
Myth: Lasik is bad as it causes dry eyes
One of the side effects of Lasik is indeed its effect on the nerves supplying the cornea. In general, the higher the eye power treated, the more the cornea nerves affected. When the nerves are affected, they cause a negative feedback which tricks the eye into thinking that it is not really dry, and hence tear production slows down. This usually recovers with time, but may take longer in those who had larger treatments.
An observation I made over my years in refractive surgery practice is that most candidates for these laser vision corrections are already suffering from dry eyes, often through poor contact lens tolerance, before their laser treatment. Laser treatment does not treat dry eyes, but they do work by getting unsuitable wearers off their ill-fitting contact lenses, which in the long term will contribute to restoration of the ocular surface.
Myth: epiLasik / transPRK / Lasik /Smile / ICL is the best treatment
ICL stands for implantable collamer lens, currently dominated by the Swiss company Staar Visian worldwide. It is a lens made of a biocompatible material that is thin and flexible, hence conceptually much like a contact lens. It is surgically implanted into a very confined space in the back chamber of the eye, between the iris and natural lens. It has its own set of pros and cons, like all other treatment options.
It is not true that one treatment is better than the other. All eyes are unique, and just as square pegs do not fit into round holes, they may not be suitable for a particular treatment. It is better to choose the best treatment for the individual’s eyes, rather than allow the treatment to choose its candidate, no matter how perfect the treatment option is touted to be. It is hence prudent to seek advice from a surgeon who is unbiased regarding the treatment options, or if necessary, ask for a second opinion.
Myth: I already have presbyopia. Lasik is not a good idea
When there is a will, there is a way. Refractive surgery for presbyopia can be had in the form of several options. A common option is monovision Lasik in which one (dominant) eye is aimed for clear distant vision and the other for clear near vision, with small difference in power between the two eyes. This is usually quite tolerable after an initial adjustment period.
Other options such as presbyopic Lasik in which the treatment is modified to provide additional curvature in one eye for improved near vision are less popular due to possible issues with quality of vision.
Inlays which are tiny implants inserted into the centre of cornea are another novel treatment option, with some successful cases. Possible side effects of visual distortion and cornea scarring make their recommendation limited.
Myth: Lasik is for life
Lasik may potentially be repeated, or “enhanced”, if the eye’s measurements permit it. This may arise when the eye power regresses over time. Careful measurement and assessment should be done to rule out potential weakness (ectasia) of the cornea tissue, before such retreatments are performed. Thin corneas may have difficulty for retreatments by laser, but other approaches such as lens implants or exchange may instead be considered.
This article was first published in The Business Times.