Q: I have just turned 40. Recently, I find my vision fluctuating between clear and blur when I wear contact lenses. It is more blurred in dim light conditions. Is LASIK still suitable for me or am I too old for it? Are there any other options?
A: LASIK is a type of refractive surgery that offers patients a permanent alternative to wearing glasses or contact lenses.
It is a life-changing procedure that has been around since 1991 and has been performed on more than 40 million people worldwide.
The procedure is all laser and 100 per cent bladeless. A very thin flap on the cornea is first created using a femtosecond laser, then an excimer laser reshapes the underlying corneal tissue to correct short-sightedness, astigmatism and long-sightedness or presbyopia (“lao hua").
Advanced and safer technology
Technology has advanced greatly, patient satisfaction is at an all-time high, and studies have demonstrated exceptional safety outcomes.
With careful patient selection and ultra-thin flaps made by the bladeless femtosecond laser, post-op dry eyes are only temporary and no longer pose a long-term issue in most patients, while ectasia (loss of corneal strength) is now very rarely seen.
Patients get their vision back the next day and can quickly return to their work and activities.
It is the most commonly performed laser eye surgery worldwide and, at present, remains the mainstay of refractive surgery for the treatment of short-sightedness, astigmatism and long-sightedness/presbyopia.
Suitable age group
The United States Food and Drug Administration (FDA) has approved LASIK for those aged 18 and above, with no upper age limit.
Although the majority of LASIK patients at our eye centre are between 18 and 50 years old, there are also others in their 60s and 70s who come to have presbyopia corrected by LASIK if they did not have the opportunity to get their presbyopia corrected during their previous cataract surgeries.
The FDA approved treatment range for LASIK includes up to -12.00 dioptres (D) of myopia, +6.00D of long-sightedness/presbyopia and -6.00D of astigmatism.
Demand for better visual quality
Patients today not only expect 20/20 vision or better after LASIK surgery, they also demand better quality of vision than what they have with spectacles and contact lenses.
For example, a 20-year-old patient may see well in the daytime but finds that his glasses or contact lenses are associated with glare and haloes at night and generally blurry vision in dim light conditions.
These are visual quality issues rather than visual quantity issues — things that make patients like or dislike their own eyes, enjoy or not enjoy their own vision — and are termed Higher Order Aberrations (HOAs).
HOAs occur mostly in dim light conditions, when the pupil automatically dilates in the dark and allows much more light rays to enter the eye.
These light rays encounter impurities inside the eye’s fluid and get scattered instead of being able to focus onto the retina to provide a clear image, causing night-time optical disturbances such as glare, haloes, starbursts and blur.
The most advanced form of HOA correction is wavefront-guided LASIK.
This technology originated from the National Aeronautics and Space Administration (Nasa) Hubble Space Telescope, considered to be the most powerful optical device ever invented by mankind to date.
Besides reducing or eliminating total dependence on glasses, the technology also has the potential to improve night-time quality of vision.
This was the reason Nasa and the US Navy lifted the ban on LASIK surgery back in 2007, approving specifically wavefront-guided LASIK treatments only to be performed on astronauts and naval pilots.
Scientific evidence in the US showed that for people involved in vision-critical jobs, wavefront-guided LASIK was not only safe and effective, it also enabled many patients to achieve even better improved night-time visual acuity and night-time contrast sensitivity than their glasses or contact lenses.
In 2003, FDA approved the use of customised wavefront-guided technology using VISX CustomVue of iLASIK.
The goal of iDesign iLASIK surgery is no longer to equal the best glasses or contact lenses, but to actually exceed the quality of vision of glasses or contact lenses by treating existing night-time visual disturbances.
The highest form of wavefront-guided LASIK surgery, which applies Fourier algorithm calculations, can offer very high quality or superior night-time quality of vision in different lighting conditions.
Small incision lenticule extraction (SMILE) is a new laser vision procedure, where a piece of carved tissue is removed manually from inside the cornea through a 2mm to 3mm corneal incision.
For patients with a larger amount of myopia, the piece removed will be thicker and deeper compared to a mild correction.
While the incision on the cornea is smaller, the invasion depth in the cornea is the same as LASIK and it should also be avoided for patients with chronic or pathological dry eyes.
Visual recovery from SMILE is longer than LASIK and can even take a month or so.
SMILE is currently FDA-approved to treat between -1.00D and -8.00D of myopia with up to
-3.00D of astigmatism, so it is not yet a solution for patients with long-sightedness/presbyopia or mixed astigmatism.
It is also not able to perform customised treatment for HOAs that affect night vision, and remains a treatment based on spectacle prescription only.
Implantable Collamer Lenses
Implantable Collamer Lenses (ICL) are the ideal solution for patients with high prescriptions not suitable for laser eye surgery.
The FDA-approved age range is 21 to 45 years old, and the FDA-approved treatment range is up to -20.00D of short-sightedness, up to +12.00D of long-sightedness and up to -5.00D of astigmatism.
Dr Natasha Lim
Medical director and ophthalmologist, senior consultant,
Dr Natasha Lim Eye Centre
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A version of this article appeared in the print edition of The Straits Times on Nov 26, 2018, with the headline 'Am I too old for LASIK?'.