Watching the game the other day, it was mentioned on the broadcast that one of Rob Johnson's countless offseason surgeries was performed on his eyes. I forgot about this almost as quickly as I learned it, but SSI jogged my memory. Rob Johnson is one of the latest Major Leaguers to get LASIK.

Now, I'm not going to use this as an opportunity to post another thread about whether or not vision enhancement is the same as taking PEDs. (It is.) Instead, I got curious about whether or not we can observe any trend in the performance of LASIK patients. So I went to my Google machine and put together a list of big league position players to get the operation. Result? The following 26 names:

Wade Boggs, Jeff Bagwell, Jeff Cirillo, Jeff Conine, Jose Cruz Jr., Wally Joyner, Larry Walker, Bernie Williams, Jason Kendall, Bernard Gilkey, Greg Vaughn, Al Martin, Mike Lansing, Todd Dunwoody, Trot Nixon, Frank Catalanotto, Cristian Guzman, Ryan Sweeney, Troy Glaus, Justin Morneau, Michael Cuddyer, Bill Hall, David Dellucci, Jhonny Peralta, Rocco Baldelli, Aaron Guiel

It's not a complete list, but it's the best I felt like doing, because there's no master list of players who've gotten their eyes zapped and tracking down names is hard and annoying.

I only looked at position players, by the way, because they're the ones who, it seems, would benefit the most. I don't know how it would help pitchers a whole lot, so I ignored them.

Stat of choice? wRC+. Captures the magic of wOBA, park adjustments, and league adjustments all in one. It's not perfect, and it'd be nice to have additional info like contact rate and all that, but I wanted to keep this quick and easy.

Results of the group?

Year before LASIK: 97 wRC+
Year after LASIK: 109 wRC+

Now that looks pretty significant. However, you figure that players would be more likely to get something fixed after a bad season than a good season, right? Let's narrow this group to the 24 players for whom we have three years of big league data.

Two years before LASIK: 112 wRC+
One year before LASIK: 96 wRC+
Year after LASIK: 109 wRC+

Well there you go. Definitely a response to frustrating seasons. Going on, the best way to do this would be to compare the YAL numbers to projected numbers, but I don't have those, so again, in keeping with the simplicity:

Average, years before LASIK: 104 wRC+
Year after LASIK: 109 wRC+

Hooray! Mildly interesting. Based on our very limited sample, it seems that LASIK eye surgery can indeed help hitters perform at a higher level. Which we'd expect, given that a good hitter has to be able to, you know, see.

But let's not go repeating these numbers as gospel. It's time for Important Caveats!

• This is a small sample. A very small sample. As such, the errors are going to be pretty big, and we can't assume that all the variables (like age) balance out. This isn't a direct measure of the effect of LASIK surgery on hitters. This is an estimation based on a limited pool of names and imperfect analysis.
  
• Not all LASIK surgery is alike. Some players improve their vision by a lot. Some players improve their vision by a little. Some players don't improve their vision at all. There are degrees, here, and if LASIK does have a beneficial effect, we'd expect to see it in the more extreme cases than in the minor ones. Alternatively or additionally, there may be diminishing returns beyond 20/20 or 20/15.
  
• (Somehow forgot this one) Some/most/all LASIK patients may have worn lenses, glasses, or goggles before their procedures. In this case the LASIK may not actually enhance their on-field vision.
• I'm sure there are other caveats, too, but it's almost 7 on a Friday and I can't think of them.

Assorted other bits and pieces:

• This doesn't include minor leaguers like Denard Span or Bobby Kielty. Both players credit their operations for helping get them to the bigs.
• Brian McCann is one of the few players to get LASIK done and then suffer from a complication. He has since opted for glasses.
• I would've loved to include players like Mark McGwire who wear crazy effective contact lenses, since that's another form of vision enhancement, but that information is even harder to track down, so I stuck with LASIK. Players talk about LASIK a lot.
• There's actually a journal article on this very topic from 2005, published in the Journal of the American Optometric Association. Based on their even more limited sample of players, they did not find any statistically significant effect on BA, OBP, SLG, or OPS.
• According to an article in the St. Paul Pioneer Press in October 2002, Troy Glaus was "adamant about keeping the [eye] surgeons away from his means of making a living." Glaus had LASIK done the next offseason.