How does laser eye surgery work? - Dan Reinstein
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Laser vision correction is a wonderfully complex topic that involves understanding biology, chemistry, physics and psychology! Everything from what a simple glasses prescription means to understanding how lasers work, how lasers interact with corneal tissue, how healing patterns vary, and how to manage people’s anxiety when choosing to have surgery on their eyes while awake is embodied in a specialty called Vision Correction Surgery. Vision Correction Surgery is essentially a branch of eye surgery, performed by ophthalmologists. It is a field that is always innovating as you have seen in the video and you can read more about here. In fact, in 2018 the Nobel Prize in Physics was given based on the principles that were discovered and used in the femtosecond laser that performs SMILE keyhole vision correction today.
There are many ways to break down laser vision correction and a variety of ways to measure how successful it is. But when it comes down to it, the most important measure is, first and foremost, safety. Safety measures include the risk of permanently losing clarity of the ‘best spectacle corrected vision’. Ophthalmologists measure this in terms of lines on the chart of best-corrected visual acuity. For example, if before the surgery you could see down to the 20/16 line with your glasses (fighter jet pilots are required to have 20/16 vision without glasses) and after surgery you were actually 20/20 without glasses, but even glasses couldn’t get you to see the 20/16 line any more would be a loss of one line of best spectacle corrected vision. A comprehensive peer-reviewed journal article published in 2016 showed that, when using a modern laser, the chance of losing 2 lines of vision after treatment is less than 0.1%.
There are also risks such as side effects including glare and halo. In the 1990’s these were relatively common, probably about 30% of all patients who had LASIK experienced them to some extent. But today these side effects are much less common. The Patient Reported Outcomes with LASIK (PROWL) studies looked at patient satisfaction after laser eye surgery. PROWL-1 was conducted at a military center in the USA and PROWL-2 at a variety of private and academic practices in the USA. A questionnaire was provided to participants before and after surgery. While a small number did experience new visual symptoms such as glare and halo, the overall satisfaction rate was greater than 95%.
Finally, on the topic of safety and satisfaction, in the Price survey published in 2016, laser vision correction was compared directly to contact lens wear over a 3 year period in two matched group of individuals.1 The survey found that, compared with contact lens wear, LASIK reduced rates of eye infections, ulcers, and corneal abrasions. The Price survey also showed that people reported less night vision problems after LASIK than in the contact lens group.
In addition to safety, an area of laser vision correction that was not part of the initial offering in the first 15 years since the early 90’s and is still not widely known, is how laser vision correction can help people with presbyopia (decreased ability to read as the eye ages). Probably the safest and most accurate way to improve reading vision now is through laser vision correction as mentioned in the video. Click here to watch a video that dives deeper into the subject and explains the mechanism of how this is accomplished.
There are several laser manufacturers and some surgeons may have a preference to the type of treatment so it can be quite confusing to understand the difference between lasers. Each type of surgery, whether it be Photorefractive keratectomy (PRK), Laser in-situ keratomileusis (LASIK), or Small-incision lenticule extraction (SMILE) has benefits and risks and no one procedure is, globally speaking, better or worse than the others. There are advantages and disadvantages to each procedure type and each potential patient must be evaluated in full and the best and safest option should be offered. Click here for more detail in to each procedure. The eyes are a unique and complicated organ and the great thing is that we have equally unique and complicated lasers that have evolved over time and can now offer the majority of patients a safe and effective solution vision correction solution.
1. Price MO, Price DA, Bucci FA, Jr., Durrie DS, Bond WI, Price FW, Jr. Three-Year Longitudinal Survey Comparing Visual Satisfaction with LASIK and Contact Lenses. Ophthalmology. 2016.
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