Refractive Surgeries – Glasses-free Soultion?

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.

LASIK Surgery

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 surgery^2,3. 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.

SMILE Surgery

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 incision^6,7. SMILE surgery can improve some LASIK-related side effects such as dry eye^6,7.

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.

Considerations of Refractive Surgeries

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 astigmatism^2,9,11.

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 uncertain^12,13. 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

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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

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Reference:

1. R., Steinert, A., McColgin, & S., Garg. (2013, December 11). Laser in situ Keratomileusis (LASIK). American Academy of Ophthalmology. Retrieved June 18, 2017, from https://www.aao.org/munnerlyn-laser-surgery-center/laser-in-situ-keratomileusis-lasik-3
2. Clinical Practice Recommendations. Optometric Co-Management of Refractive Surgery: Laser Assisted In Situ Keratomileusis, Advanced Surface Ablation, Conductive Keratoplasty For Hyperopia. American Optometric Association. Retrieved from https://www.aoa.org/Documents/optometrists/co-management-of-refractive-surgery.pdf
3. Bromley, J. G., Albright, T. D., Kharod-Dholakia, B., & Kim, J. Y. (2012). Intraoperative and postoperative complications of laser in situ keratomileusis. Expert Review of Ophthalmology, 7(1), 25-31.
4. Lim, S. A., Park, Y., Cheong, Y. J., Na, K. S., & Joo, C.-K. (2016). Factors Affecting Long-term Myopic Regression after Laser In Situ Keratomileusis and Laser-assisted Subepithelial Keratectomy for Moderate Myopia. Korean Journal of Ophthalmology : KJO, 30(2), 92–100. http://doi.org/10.3341/kjo.2016.30.2.92
5. M., Goel, A., Pathak, & N., Afshari. (n.d.). Femtosecond lasers and laser assisted in situ keratomileusis (LASIK). American Academy of Ophthalmology. Retrieved June 18, 2017, from http://eyewiki.aao.org/Femtosecond_lasers_and_laser_assisted_in_situ_keratomileusis_(LASIK)
6. J., Harvey, H., Fukuoka, N., Afshari, & B., Feldman. (2015). Small Incision Lenticule Extraction (SMILE). American Academy of Ophthalmology. Retrieved June 18, 2017, from http://eyewiki.aao.org/Small_Incision_Lenticule_Extraction_(SMILE)
7. Reinstein, D. Z., Archer, T. J., & Gobbe, M. (2014). Small incision lenticule extraction (SMILE) history, fundamentals of a new refractive surgery technique and clinical outcomes. Eye and Vision, 1, 3. http://doi.org/10.1186/s40662-014-0003-1
8. W., Tullo, & J., Owen. (2016, May 10). Will the SMILE procedure replace LASIK? Small-incision lenticule extraction is new application for femto laser. Optometry Times. Retrieved June 18, 2017, from http://optometrytimes.modernmedicine.com/optometrytimes/news/will-smile-procedure-replace-lasik?page=0,0
9. Is LASIK for Me? A Patient’s Guide to Refractive Surgery. (2008, October). Retrieved June 18, 2017, from https://www.aao.org/Assets/e890eb55-9bfa-465a-8422-8fdbd828518e/635854347414670000/lasik-patient-guide-pdf?inline=1
10. VisuMax SMILE Procedure Wins FDA Approval. (2016, October 05). Review of Ophthalmology. Retrieved June 18, 2017, from https://www.reviewofophthalmology.com/article/visumax-smile-procedure-wins-fda-approval
11. D., Huang, B., Feldman, & N., Afshari (2015). LASIK for Myopia and Astigmatism: Safety and Efficacy. American Academy of Ophthalmology. Retrieved June 18, 2017, from http://eyewiki.aao.org/LASIK_for_Myopia_and_Astigmatism%3A_Safety_and_Efficacy
12. Jaycock, P. D., O’Brart, D. P., Rajan, M. S., & Marshall, J. (2005). 5-year follow-up of LASIK for hyperopia. Ophthalmology, 112(2), 191-199.
13. Liu, Y. C., Ang, H. P., Teo, E. P. W., Lwin, N. C., Yam, G. H. F., & Mehta, J. S. (2016). Wound healing profiles of hyperopic-small incision lenticule extraction (SMILE). Scientific Reports, 6.
14. M., Stephenson. (2015, February 05). The Future of Presbyopia Correction. Review of Ophthalmology. Retrieved June 18, 2017, from https://www.reviewofophthalmology.com/article/the-future-of–presbyopia-correction