January 22, 2010

Under The Knife

Frickin' Laser Beams, Part 1

by Will Carroll

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with Chase Gharrity

Fitzgerald said the rich are not like the rest of us. If he'd been around to write about modern baseball players, he'd have learned that not only are they rich, they're not like the rest of us in other ways.

A couple years ago, I was in Arizona for spring training. A player I'd gotten to know a little bit was giving me a tour of the facility when we got to the video room. I asked him about the kind of things he looked for and mentioned that he'd roughed up a highly regarded pitcher just a few days before. "Oh, he was tipping his curve," he said nonchalantly.

He went on to show me how the pitcher's index finger was coming up on a curve. In slow motion, I could see it. At normal speed, even after having had it pointed out, I could barely make it out. I turned to him and said, "You can't see that in time to do anything, can you?" He gave me one of those looks; he could. The guy I know wouldn't be offended by my saying that he's no All-Star and that he's barely hung on in baseball some years. Still, he has eyes that are simply superhuman.

Baseball players have always known that their eyes are their meal ticket. Rogers Hornsby refused to watch movies, thinking the flickering images could damage his eyes. Players have used all kinds of eye trainers, from the low tech to the very high tech, over the course of the game. When radial keratotomy became a surgery that was available, correcting vision was something many players considered. There's no record that a major-league player had this surgery, one that relied entirely on the skill of a surgeon.

In the mid-1990s, advances in medical science brought the miracle of laser eye surgery and, shortly thereafter, the procedure now known as LASIK (Laser in-situ keratomilieusis) was developed and perfected. At a cost that was reachable by many people as a nearly cosmetic procedure, LASIK not only allowed average people to get the procedure, but it also allowed surgeons many more opportunities to perfect the craft. By the mid-2000s, a procedure known as "wavefront-guided LASIK" was the state of the art, and it remains so. In this procedure, the eye is "mapped," and then a precise, personalized surgical procedure is possible, leading not only to 20/20 vision but also, in many cases, the final result is better than that.

As better outcomes and techniques made it into the mainstream, baseball players followed closely. Instead of being on the cutting edge-sports medicine normally is-baseball was a bit behind the curve. Let's face it. The eyes are not only a player's meal ticket, but it's a little bit creepy to lie back on a table and count on a surgeon to use a laser properly. That's a lot of trust for eyes worth millions.

Players began to dip their toes into the LASIK waters in the late '90s, with players such as Wade Boggs and Fred McGriff among the first to try it. There does seem to be some connection here, as players from, or living in, the Tampa area are over-represented in the early LASIK roster. Attempts to reach Boggs, McGriff, and others were not returned, but it's known that the doctor, Antonio Prado, remains a sought-after consultant to many players and teams. Players at this stage tended to be high-level players attempting to hang on a couple more years. Perhaps they were more willing to take a bit of a chance in order to stay in the game a bit longer. It's very difficult to say what, if any, result was gained here, but more than anything, there was no adverse result. If Boggs or McGriff-perennial all-stars-were willing to have surgery, why wouldn't a younger guy who is trying to get a little better?

How much better? There's no list out there of all the players that have had it. In fact, the teams themselves might not be able to compile a complete list. LASIK surgery is an elective procedure in most cases, handled outside the team's purview. There have been cases where the team hasn't been consulted or even informed afterward. This makes testing the effect difficult at best. Actually, it's a lot like trying to find the steroid effect. It requires a lot of legwork and a bit more guesswork than what makes the statistical gurus here at BP very happy. But that's what we did.

To take a quick-and-dirty look at the potential effects of LASIK surgery, we took a look at one of the more famous players to go under the knife-er, excimer laser-for this procedure, Jhonny Peralta. This powerful Indians shortstop-turned-third baseman had always drawn positive reviews for his bat. However, Peralta posted a rough 2006 season in which he posted a .245 EqA (down from .301 EqA the previous season). He decided to have LASIK surgery performed due to his inability to see Victor Martinez's signs from his defensive position, and also due to the hot streak he produced in a trial run with contacts during the final month of the 2006 season. Peralta is no better or worse a test subject here, but he's selected more or less at "random." He's one of the few where we have clear dates and effects.

During the 2007 season, Peralta saw himself bounce back to form, posting a translated EqA .022 points higher than his previous campaign. Furthermore, he improved his home run and ISO numbers by significant margins over the next two years. While there was some regression in 2009, the surface of his performance shows some hints in regards to the potential of LASIK improving player output.

LASIK surgery has become a spring training cliché over the last couple of years for players looking to create buzz and writers looking to have stories during the monotonous pre-season beats. Most quotes from players who've had the surgery say they will "be able to see the spin on the ball better" or "get a better read on the release point of the opposing pitcher." Thus, we can infer that a player who has had his vision significantly enhanced would be able to make contact with the ball more, swing at more balls in the strike zone, and/or lay off pitches that travel outside of the zone.

That leads us first to contact rates. With a disclaimer that we chose to include, the smaller-sized sample of the 2004 season during the following portions of the study is due to the fact that it does not fall outside of the overall form of the data. Below is a table for Peralta's contact percentage during his career, with the asterisks indicating the time the LASIK procedure took place:

Year   Pitches Contact%  # of Pitches Contacted 
2003    1054    73.70%           776.798 
2004     118    76.20%            89.916 
2005    2281    76.70%          1749.527 
2006    2606    73.50%          1915.410
----    ----     ---               --- 
2007    2545    76.90%          1957.105 
2008    2502    78.50%          1964.070
2009    2546    77.60%          1975.696 

Again, on the surface, the pre-surgery contact rates seem to be smaller than the post-surgery rates. This fact is reinforced by looking at the numbers visually:

Oh, but there's more. As sexy as graphs look, we're not going to be able to tell if the change in contact rate is really significant until we do a statistical test. For our purposes, we'll use a 2-Sample Proportion test. This method will allow us to see whether or not the change in contact percentage is really significant. Using the mean pre- and post-LASIK contact rates as our tested proportions, a deeper statistical look gives us this:

Test and CI for Two Proportions

Sample    X    N    CONTACT % 
   1    4532  6059  0.747978 
   2    5897  7593  0.776636 

Difference = p (1) - p (2) 
Estimate for difference:  -0.0286582 
95% upper bound for difference:  -0.0165757 
Test for difference = 0 (vs < 0):  Z = -3.92  P-Value = 0.000 
Fisher's exact test: P-Value = 0.000

The number we want to look at here is the P-Value. This value indicates to us the chances that, given that performance before the offseason of the LASIK surgery should be equal to the performance after the offseason, we observe a contact rate that is more extreme than the contact rate posted in the 2007-2009 seasons. The lower the P-Value, the more support for the significance of our results. Since we received a P-Value of 0, we can conclude that something fairly significant happened during the 2006-2007 offseason. Was it LASIK? We don't know for sure, but let's look at some other factors that could have been effected by the procedure.

Next, let's look at Peralta's Zone Contact %, the percentage of times he made contact with a pitch that was inside the strike zone. If Peralta could see much better from 2007-09 than he could from 2003-06, we'd expect that he would make contact with higher-quality pitches, a.k.a. strikes (or non-balls) more often during his post-surgery tenure. Here are the numbers:

        Pitches     Contact
Year  In the Zone   In Zone    Z-Contact% 
2003    529.108     447.625     84.60% 
2004     60.180      49.588     82.40% 
2005   1220.335    1055.590     86.50% 
2006   1370.756    1129.503     82.40% 
2007   1303.040    1120.614     86.00% 
2008   1268.514    1092.191     86.10% 
2009   1239.902    1058.876     85.40%

Again, we can see the dip in 2006 and significant rise in overall zone contact rates from 2007-2009. More sexy:

Once more, we have our suspicions confirmed by a graph. The interesting thing here is the volatility of the pre-surgery numbers compared to the post-surgery. Even when one excludes the 28 PA season in 2004, Peralta's Z-Contact percentage is all over the place, while the post-surgery numbers are not only high, but also consistent.

Using the ever-useful 2-Sample Proportion Test, we will now test if the change in Z-Contact percentage has been significantly raised during Peralta's post-LASIK seasons:

Test and CI for Two Proportions

Sample    X     N   Sample P 
   1    2683  3180  0.843711
   2    3272  3811  0.858567

Difference = p (1) - p (2)
Estimate for difference: -0.0148566
95% upper bound for difference: -0.000771322
Test for difference = 0 (vs < 0): Z = -1.74  P-Value = 0.041
Fisher's exact test: P-Value = 0.044

As we can see, our P-Value is significant at the 5-percent level, or is below .05. Most stats 101 classes will tell you that .05 is the benchmark number in which one would want their P-Value to be below if statistical significance is observed. Thus, the conclusion can be made that the difference in Z-Contact percentage is significant. While we're unsure is LASIK has anything to do at all with this change, it wouldn't be a stretch to believe there would be some partial influence there.

Finally, we wanted to take a look and see if Jhonny stopped swinging at bad pitches, a.k.a. pitches out of the zone, at a better clip than his pre-LASIK days, denoted in this article as OOZ Swing % (Out Of Zone Swing Percentage). Here are the numbers regarding that (Disclaimer: I decided to exclude the 2004 season due to the its small sample size and potential influence on this portion of the study):

Year  OOZ Pitches    OOZ Swings  O-Swing% 
2003    524.892       137.5217   26.20%
2005   1060.665       197.2837   18.60%
2006   1235.244       261.8717   21.20%
2007   1241.960       305.5222   24.60%
2008   1233.486       345.3761   28.00%
2009   1306.098       342.1977   26.20%

Once more with the sexy chart:

The graphical method shows something very odd: Peralta is actually swinging at more potential OOZ pitches in his post-surgery period than his pre-surgery period. Whether LASIK has something to do with this or he has simply become more aggressive with age, Peralta is taking more hacks at traditionally unfavorable pitches than ever before. Of course, a question we should ask would be: Is this change in OOZ Swing Percentage statistically significant? Let's take a look:

Test and CI for Two Proportions

Sample   X     N   Sample P 
   1    607  2879  0.210837 
   2    994  3782  0.262824 

Difference = p (1) - p (2) 
Estimate for difference: -0.0519868 
95% upper bound for difference: -0.0348123 
Test for difference = 0 (vs < 0): Z = -4.92  P-Value = 0.000 
Fisher's exact test: P-Value = 0.000

Indeed, the rise in OOZ Swing Percentage is very significant. How paradoxical, eh?

Several small-scale studies, like this one, have tried to determine whether or not LASIK surgery has positive effects on players, but there's still no definitive study that would tell us how much, if any, difference it actually makes. While the results have varied, it seems fairly plausible that Peralta probably received some benefit from the LASIK procedure. However, given the wide range of outcomes from players who have had the surgery and because we cannot isolate out other significant variables like age, we can't make any definitive statements.

This all jibes with the 2004 findings of Matthew Namee. Most testing done for LASIK efficacy is focused on simple vision and the lack of "artifacts"-the visual effects, such as halo and ghosting, which are side effects of the procedure. It's no surprise that there's little done in what is a tiny fraction of LASIK cases. Without more data, we're left hoping we can quantify the effects beyond a wide but insignificant range. In fact, while the "why is LASIK all right but steroids aren't" argument actually looks a bit interesting here since both have problems of date, intent, and player quality. No one goes from has-been to All-Star. There's not even a single Henry Rowengartner-style outlier.

So how, then, do we test it? There's nothing like turning yourself into a guinea pig. I'll be having wavefront-guided LASIK surgery at the end of the month. Before and after the surgery, I'll be undergoing a vision test not unlike those used by major leaguers. The first will be the simple before and after testing done by the surgeon. Then, I'll be taking a computerized vision assessment, one that will not only focus on visual acuity, but reaction time and recognition skills. This also will be done before and after. Finally, I'll be standing in the batter's box at Batter's Edge, using specially designed balls. Many teams use this as a drill, using colored dots. Ours will use small numbers, since besides being far-sighted, I'm also a bit colorblind. I'm certainly no major-league hitter, but this is something that we can control. For one man, at least, we'll know just how much of an improvement LASIK surgery is and whether baseball players are truly getting an advantage, or just getting rid of contacts and glasses.

Dan Wade and the 20/20 Institute in Indianapolis provided assistance for this column.