For glasses wearers, most of us have thought about doing surgeries to correct your blurry vision so that you can be glasses-free.
The suitability of doing refractive surgery always rank top of the FAQ during optometric consultation. There are a number of refractive surgeries which aim at correcting the vision and the most popular one is LASIK surgery, but a new generation of refractive surgery named SMILE is steadily gaining popularity.
What is LASIK and what is SMILE? What are the difference between LASIK and SMILE? Are LASIK and SMILE suitable for all patients? Can refractive surgery correct reading difficulties? What are the side effects?
You will find the answers in this article.
The full name of LASIK is ‘laser assisted in-situ keratomileusis’, meaning using laser beam to cut the cornea. Some people call it laser surgery because it actually does use laser, but LASIK is the formal name. For traditional LASIK surgery on shortsighted patients, a very fine blade called microkeratome is used to cut a flap on the cornea. After opening the flap, excimer laser is used to ablate the cornea to reduce its refractive power.
The flap is then flipped back to end the surgical procedure1. According to the American Optometric Association, general side effects of LASIK include dry eye and poor night vision. There are also chances of other complications such as infection and abnormal healing which can leave the vision being poorer than before the surgery2,3. Besides, it is common to have prescription regression for moderate to strong shortsighted patients4.
Nevertheless, in the past years, there are improvements on LASIK surgery such as using femtosecond laser to reduce flap-related complications5 and using wavefront technology to improve visual outcome1.
An alternative surgical method called SMILE which has similar effect as LASIK came to the market recently. SMILE is the short form of ‘Small Incision Lenticule Extraction’, meaning extracting a disc-like corneal tissue from a small incision to correct refractive error.
Different from LASIK, SMILE surgery does not require cutting a flap. During the surgery, femtosecond laser directly focuses at the inner cornea to cut a piece of disc-like tissue within the cornea. The disc is then take out of the cornea from a small incision6,7. SMILE surgery can improve some LASIK-related side effects such as dry eye6,7.
However, sometimes an enhancement surgery is needed after doing refractive surgery to improve the outcome. It is possible for LASIK but currently there is no standard procedure for SMILE surgery8. Also, SMILE is a relatively new technique and requires more long-term studies to confirm its effectiveness.
Successful refractive surgeries can correct refractive error. However, they certainly also have limitations which cannot be overlooked. Preferred LASIK candidates should have stable refractive error, aged over 21 years old, less than -9.00D shortsightedness and less than -2.00D astigmatism2,9,11.
For SMILE surgery, the refractive error should be within -1.00D and -8.00D with minimal astigmatism10. The long term stability of LASIK and SMILE correction for longsightedness is uncertain12,13. Also, presbyopia (near blur) correction by LASIK and SMILE is not ideal because it is irreversible and will increase the difficulty of future cataract surgery14.
Getting refractive surgery at young cannot stop presbyopia from forming, meaning that they still have to wear reading glasses when they get older9. In addition, the patient should be prepared that the glasses-free vision may not always be crystal clear, accompanied by potential dry eyes and glare at night9.
Another point worth mentioning is that these refractive surgeries only mask your prescription at the cornea but will not prevent or cure the retinal problem due to strong prescription. Therefore, it remains vitally important to get annual eye checkups with pupil dilation even after refractive surgeries.
By Paco Chan, Registered (Part I) Optometrist
Eyecare information by Swisscoat Vision Centre
Address : G/F Yuen Yick Building, 27-29 Wellington Street, Central, Hong Kong
Appointment :+852 3579 4763
Website : www.swisscoat.com