Lasering eyes for acute vision: how I wish medical information was presented to me
As of 2017 three main types of corneal interventions to correct myopia are available. (Cornea is the transparent front-most part of the eye). In the order of technological maturity, these are: Photorefractive keratectomy (PRK), for which the first laser devices were approved by the US Food and Drug administration (FDA) in 1995; Laser-assisted in situ Keratomileusis (LASIK) — FDA-approved since 1998; and Small Incision Lenticule Extraction (SMILE) — FDA-approved since 2016. All three are surgical interventions with the decreasing degree of invasiveness.
Refractive surgeries are elective procedures with small risk of serious irreversible complications. Typically they are not covered by health insurance, and are performed commerically.
The most commonly performed refractive surgery is LASIK. Given its scale, the FDA, the National Eye Institute (NEI), and the Department of Defense (DoD) launched the LASIK Quality of Life Collaboration Project (LQOLCP) in 2009 “to help better understand the potential risk of severe problems that can result from LASIK”. Two resulting studies, enrolling a total of 574 patients, were published in 2014. Summary of the findings is presented below:
- Up to 46% of participants, who had no visual symptoms before surgery, reported at least one visual symptom at three months after surgery.
- Up to 28% of participants with no symptoms of dry eyes before LASIK, reported dry eye symptoms at three months after their surgery. This is consistent with previous studies.
- Less than 1% of study participants experienced “a lot of difficulty” with or inability to do usual activities without corrective lenses because of any one visual symptom (starbursts, ghosting, halos, glare) after LASIK surgery.
PRK has similar outcomes, compared to LASIK (Source: Cochrane). SMILE, in contrast, is a newer technology. The first 5-year follow-up on SMILE intereventions in only 30 patients was reported in the BMJ in 2016. While being less invasive than LASIK, it still involves a corneal incision. Possible injuries resulting from the SMILE procedure can be tracked in the FDA’s MAUDE (Manufacturer and User Facility Device Experience) Adverse Events database, and include difficulty in extracting the lenticule, which can result in additional surgery that may or may not be successful, as well as post-operative severe dry eye, blurred vision and pain. Such complications are rare. In the absence of a large scale study comparable to FDA’s LQOLCP on LASIK, quantification is difficult. Remember that SMILE was only approved by FDA last year. More studies are underway.
While more than 95% of participants were satisfied with their vision following LASIK surgery (according to LQOLCP), the burden of disease for postoperative complications has been sufficient to create a market for the development of treatment for “corneal ectasia following refractive surgery” — approved by FDA in April 2016. The company, which received marketing authorisation — Avedro, — is now conducting clinical trials to test the safety and efficacy of their non-invasive procedure — Corneal Cross Linking — for the treatment of myopia. The clinical studies in Sweden and France are expected to be completed in 2018–2020. The procedure involves application of ultraviolet light to reshape cornea. It is not FDA-approved as of today.
Summary. Corneal interventions to correct vision as performed today are surgeries, and all surgeries involve risk or irreversible damage. As of 2017, the level of technology is such that the risk could be expected to be at ~5% of being dissatisfied with the procedure; and ~1% of facing severe complications. These risk are not negligible, and so are to be weighted against the obvious benefit of corrected vision. Importantly, however, the technology is evolving, and so less invasive, safer technologies become available in one’s lifetime. As a result, in some situations it may be a better choice to wait for the next generation technologies; surgeries cannot be reversed.
Disclaimer. I’m not a doctor, I’m a patient. I’m not giving medical advice, I’m synthesising the medical information in such a form, in which I would like to have had it received, with ephasis on data, sources, quality of evidence and absence of conflict of interersts when presenting information. Accordingly, I too, report no finanical or other ties to commercial ophthalmology.