What are the criteria that define 3rd, 4th, and 5th generation vision correction surgeries?

 

Vision correction surgery refers to procedures that correct corneal refractive errors to maintain clear vision without the need for glasses or contact lenses.

Representative types of surgery include LASIK, LASEK, SMILE, and ICL (implantable contact lens) surgery.

With advancements in modern medicine and technology, vision correction procedures have become safer and allow for faster recovery. As a result, more people are now considering undergoing these surgeries.

The core of vision correction surgery involves reshaping the corneal stroma using lasers to correct refractive errors. Based on how the epithelial layer (the outermost layer) of the cornea is treated, these surgeries have been categorized into 1st, 2nd, and 3rd generation techniques.

After the introduction of 1st-generation vision correction surgery, LASEK, which corrects refractive errors by removing the corneal epithelium, the field evolved into 2nd-generation surgery, LASIK, which creates and lifts a corneal flap before correcting the stroma beneath.

Then, in 2008, the 3rd-generation vision correction surgery, SMILE, was introduced using the VisuMax device developed by Zeiss. SMILE involves a femtosecond laser passing through the corneal epithelium to isolate only the necessary portion of the stroma (called a lenticule) for refractive correction, which is then extracted through a small incision. This technique is known as "lenticule extraction vision correction."

The 3rd-generation surgery using femtosecond lasers is regarded as a procedure that overcomes the disadvantages of the previous 1st- and 2nd-generation methods. It minimizes corneal damage, offers better resistance to external impact, and allows most patients to return to daily activities the day after surgery. Because of these advantages, Zeiss’s SMILE has become the leading vision correction procedure worldwide.

Since the introduction and widespread adoption of SMILE using Zeiss’s VisuMax, various manufacturers have developed new 3rd-generation laser systems based on femtosecond laser technology. These newer devices are sometimes marketed under terms like 4th-generation or 5th-generation vision correction surgery or as next-generation SMILE, highlighting their advancements beyond VisuMax.

So, are the lenticule extraction procedures that are being referred to as 4th- or 5th-generation completely different from the 3rd-generation SMILE? Can they truly be considered a more advanced form of vision correction surgery compared to 3rd-generation SMILE?

To give you the conclusion upfront: SMILE and the newer procedures using recently developed devices are all part of the same lenticule extraction-based 3rd-generation vision correction surgery.

The newly introduced devices are often described as enabling faster and safer surgeries compared to the VisuMax system, and this is where the terms 4th- and 5th-generation are sometimes applied. However, as previously explained, the classification into generations is based on how the corneal epithelium is treated and the overall surgical method—and in that regard, all of these procedures still fall under the umbrella of 3rd-generation vision correction surgery.

Therefore, we can confidently say that the terms 4th and 5th generation do not refer to entirely new types of vision correction procedures.

We will continue to post more content related to the performance and advancements of the VisuMax system.

Thank you for your time!