This is a follow-up to my brief look at the effects of Lasik surgery on hitting. Going at this from a bit of a different angle this time… There were eleven players in the study who played regularly (400+ PA) in both the Before and After seasons. I took those eleven and identified the most-comparable player in baseball in the Before season. This created a control group against which I could compare the Lasik group. It’s a very flawed study with a tiny sample size, but heck, it’s better than nothing.

I’ll list the players and their comps, and then I’ll present the findings. (Hint: This basically confirmed my initial study.)

Greg Vaughn, age 31, hit .216/.322/.393 in 422 PA.

Jeff Conine, age 31, hit .242/.337/.405 in 466 PA.

Al Martin, age 30, hit .239/.296/.364 in 479 PA.

Ed Sprague, age 30, hit .222/.280/.403 in 510 PA.

Jose Cruz Jr., age 25, hit .241/.358/.433 in 414 PA.

Greg Norton, age 26, hit .255/.358/.424 in 510  PA.

Bernie Williams, age 30, hit .342/.435/.536 in 697 PA.

Roberto Alomar, age 31, hit .323/.422/.533 in 694 PA.

Jeff Bagwell, age 31, hit .304/.454/.591 in 729 PA.

Rafael Palmeiro, age 34, hit .324/.420/.630 in 674 PA.

(As you can see, there were no good comps for Bagwell that year.)

Trot Nixon, age 25, hit .270/.357/.472 in 447 PA.

Ben Grieve, age 23, hit .265/.358/.481 in 558 PA.

Larry Walker, age 35, hit .338/.421/.602 in 553 PA.

Jim Edmonds, age 32, hit .311/.420/.561 in 576 PA.

Rocco Baldelli, age 21, hit .289/.326/.416 in 684 PA.

Sean Burroughs, age 22, hit .286/.352/.402 in 578 PA.

Rich Aurilia, age 31, hit .277/.325/.410 in 545 PA.

Todd Walker, age 30, hit .283/.333/.428 in 647 PA.

Michael Young, age 27, hit .313/.353/.483 in 739 PA.

Mark Kotsay, age 28, hit .314/.370/.459 in 673 PA.

Jhonny Peralta, age 24, hit .257/.323/.385 in 632 PA.

Hank Blalock, age 25, hit .266/.325/.401 in 646 PA.

Obviously, not all of these comps are perfect. But taken together, the match is pretty darned good. The group averages for Year 1:

The Control group batted a few more times and struck out less often, but otherwise, the two groups are virtually identical. Now for Year 2: 

The most obvious difference here is playing time – the Lasik group had over 100 more plate appearances, on average, than their Control counterparts. This is largely attributable to Jeff Conine, Greg Norton, and Hank Blalock, all of whom had fewer than 350 PA in Year 2. I don’t think we can blame that on Lasik.

Anyway, the batting averages and on-base percentages hold steady for both groups, and again are very close matches. But slugging – and more specifically, isolated power – is where the big difference lies. The Lasik group added 35 points of isolated power, while the Control group added just 7. In my original study, the biggest year-to-year change was in isolated power, but I’ve wondered whether that might have been a natural rise, due to increased power with age, or something. The Control group does see a small rise in power, but it’s nothing compared to the spike in the Lasik group.

The other difference of note is in strikeout-to-walk ratio. The Lasik group marginally improved their K:BB, but the Control group got a bit worse.

All of this flies in the face of intuition. I would have assumed that Lasik, with its improved vision, would result in better pitch recognition and thus more walks (and fewer strikeouts), as well as a higher batting average. But my two studies reveal a striking year-to-year consistency in both batting average and walks, and instead, a jump in power. Given the small sample sizes involved, I’m hesitant to come to any conclusions. This study does bolster a bit the findings of my previous one, though – that Lasik surgery seems to affect nothing except for isolated power.