The Impact of Laser Assisted in Situ Keratomileusis (LASIK) on MLB Batting Performance

Catcher Wilson Ramos is one of many athletes who have undergone LASIK surgery during their professional careers. He had the surgery performed in 2016, according to published reports. (Trading Card Database)

 

Since the 1990s there have been increased reports of prominent athletes undergoing refractive surgery including laser assisted in situ keratomileusis (LASIK). Some refractive surgery practices advertise the benefits of LASIK for athletes, including enhanced vision and contrast sensitivity, improved convenience, improved eye safety, reduced fluctuations associated with glasses or contact lenses, and many more.1 Several top athletes in different sports have publicly declared LASIK to be beneficial to their careers.2

Despite these claims, there remains a paucity of current and peer-reviewed literature on the impact of LASIK for professional baseball players. A prior study by Laby et al. in 2005 concluded that LASIK did not have a statistically significant effect on the hitting performance of baseball players by evaluating 12 players who underwent the procedure.3 More recently, non-peer-reviewed sources, such as baseball fan blogs, have analyzed this same question and come to a variety of conclusions, including that LASIK improves hitting power, but not batting average or plate discipline, which are hypothesized to be more highly associated with visual acuity.4

To better understand the impact of LASIK on athletic performance, we sought to evaluate the impact of LASIK for Major League Baseball (MLB) players. MLB batters were chosen for a multitude of reasons. Primarily, professional baseball players have been shown to have incredibly high visual acuity because exceptional visual function is required to succeed in the sport.5 Specifically, hitting a baseball requires excellent visual function, as modern-day pitchers can throw up to 105 miles per hour and hitters only have approximately 0.25 seconds to make a swing decision and execute it.6 In addition, average velocities and pitch movement profiles continue to improve annually in MLB as players and teams continue to optimize pitching training techniques. In addition, a significant number of MLB players have publicly acknowledged their history of LASIK, increasing the potential sample size for analysis.7 Finally, the extraordinary amount of statistical data on MLB player performance allows for direct analyses of consistent performance metrics.

While there is no consensus on the effect of LASIK on MLB performance, players continue to undergo LASIK, and some ophthalmology practices continue to advertise it as a means for improved athletic performance. Our study sought to answer the question of whether LASIK improves baseball player hitting performance. We examined an updated list of players who have had LASIK and multiple seasons of traditional and advanced batting statistics.

Methods

Player Identification. MLB players who had a history of LASIK were identified through online records, primarily through articles about LASIK in professional athletes, ophthalmology practice websites, and news articles about individual players. Additionally, a Google search of each team using the keywords “[Team Name]+ LASIK” was conducted to find relevant web pages for lesser-known players. Google searches including “[Team Name]+PRK” and “[Team Name]+Refractive Surgery” were conducted as well but did not yield additional players. Finally, the year of each player’s procedure was obtained through further use of web-based public sources. Players that underwent LASIK between the years of 1996 and 2022 were included. With these new data, we hoped to clarify the effects of LASIK on batting performance in MLB.

Batting Statistics. Statistics for each player and season were gathered from FanGraphs. These included player age, at-bats, batting average (BA), on-base average (OBA), walk percentage (BB%), strikeout percentage (K%), walk to strikeout ratio (BB/K), slugging average (SLG), on-base plus slugging (OPS), weighted runs created plus (wRC+), weighted runs above average (wRAA), weighted on base average (wOBA), and wins above replacement (WAR).

The “traditional” batting statistics analyzed included BA, OBA, SLG, OPS, and BB/K (ratio of a hitter’s walks to strikeouts). OBA, BB, K, and BB/K were analyzed to evaluate plate discipline because it is established in the baseball sabermetrics field that a player’s walk rates, strikeout rates, and walk to strikeout ratio correlate with plate discipline, and stabilize well for a given player’s level of hitting ability.8

The advanced performance metrics analyzed were wRC+, wRAA, wOBA, and WAR. WAR was chosen as it assesses a player’s aggregate on-field contribution by comparing them to a replacement-level player at his position and estimates the number of incremental wins during a season that the player adds to (or subtracts from) his respective team. A WAR value greater than zero means a player added value to the team beyond the level of an average replacement player, a WAR of zero means the player was as valuable as the average replacement player, and less than zero means a player impacted his team more negatively than an average replacement player. To adjust each player’s performance for seasonal league-wide offensive performance differences, we included wRC+ and wRAA to indicate how each player’s overall offensive performance compares to league-average performance that season. Similarly, wOBA was used as an advanced metric incorporating plate discipline.

The statistics from two seasons prior to the LASIK procedure and the two seasons following the procedure were included for analysis. Seasons in which the player had less than 130 at bats were excluded from analysis.9

Statistical Analysis. Data were compiled and analyzed using Microsoft Excel. Batting statistics were compared across seasons for individual players. Paired t-tests (2-tailed) were used to analyze differences in statistics from one season to another. Paired two sample t-tests with equal variance were used to assess for differences in statistics from baseline season. A P-value of less than 0.05 was considered significant. All data in this study were accessed through publicly available resources; thus, no institutional review board approval was necessary.

RESULTS

Forty-four unique position players were identified who qualified with enough at bats in the season prior to and after LASIK, and for whom a timetable of when LASIK occurred was found. One player had LASIK at two different times in his career separated by multiple years; his statistics before and after were included for each surgery. Three players had mid-season LASIK approximately three quarters of the way through the season. For these cases, the partial season preceding the surgery was defined as the season “prior to LASIK.” Finally, one player had mid-season LASIK surgery approximately one seventh of the way through the season. For this player, statistics for the partial season before surgery were added to the previous season due to the small sample size. Players had an average age of 28.5 years (range 21 to 40 years) and average MLB experience of 6.7 years (median 7 years) at the time of surgery. (Table 1.)

 

The sample included 21 right-handed hitters (47.7%), 19 left-handed hitters (43.2%), and four switch hitters (9.1%). The included players had an average total career WAR of 24.31 (range –1.5 to 88.3) and average seasonal WAR of 1.43 (range –0.35 to 5.35).

For each offensive metric, the mean value across all qualified player seasons are plotted in Figure 1 (below).

 

Most batting metrics followed a similar trend across the four seasons, where the mean drops in the season prior to LASIK before rebounding back towards the baseline for the two seasons after LASIK. In comparison of paired seasonal statistics to the baseline season (two seasons before LASIK), the only statistically significant difference in offensive performance metrics came when comparing the season immediately preceding LASIK to baseline. The metrics that showed a statistically significant decrease from the baseline season to the season immediately preceding LASIK were BA(p=0.015), WAR(p=0.002), wRC+(p=0.032), wRAA(p=0.021). Others also decreased in the season preceding LASIK, but the differences were not statistically significant. These included SLG(p=0.052), OPS(p=0.057), OBA(p=0.118), BB/K(p 0.77), and wOBA(p=0.081). BB%(p 0.191) and K%(p=0.532) increased slightly before LASIK, but the changes were not statistically significant.

Other than the two seasons prior to LASIK, there were no statistically significant differences when comparing performance across consecutive seasons for the cohort, including the seasons before and after LASIK. From the season preceding LASIK to the season after the procedure, players experienced an average change of +0.004 in BA (p=0.437), –0.006 in BB% (p=0.175), 0.000 in K% (p=0.895), –0.003 in OBA (p=0.659), –0.005 in BB/K (p=0.893), +0.008 in SLG (p=0.554), +0.006 in OPS (p=0.761), +0.541 in WAR (p=0.155), +0.976 in wRC+(p=0.833), +3.946 in wRAA (p=0.833), and -0.001 in wOBA (p=0.912). Similarly, on average, no statistically significant changes were noted from the first season after LASIK to the second season after LASIK. These findings are summarized in Table 2.

 

Table 2. Seasonal comparisons

 

When grouping players based upon performance changes over time, common trends appeared before and after LASIK. Sixty-three percent of players experienced a decrease in BA, 68% a decrease in SLG, 65% a decrease in OPS, 70% a decrease in WAR, 70% a decrease in wRC+, 63% a decrease in wRAA, 47% a decrease in BB% and K%, 65% a decrease in OBA, 50% a decrease in BB/K, and 65% a decrease in wOBA from their second season prior to LASIK compared to the season immediately before the procedure. (Figure 2). On the other hand, from the season preceding LASIK to the season after LASIK, 61% percent of players experienced an increase in BA, 56% an increase in SLG, 49% an increase in OPS, 54% an increase in WAR, 49% an increase in wRC+, 59% an increase in wRAA, 47% an increase in BB%, 50% an increase in K%, 44% an increase in OBA, 46% an increase in BB/K, and 51% an increase in wOBA.

 

DISCUSSION

The purpose of this study was to identify the impact of LASIK on MLB player batting performance. Despite multiple reports in the lay news media, there is no evidence in the medical literature supporting a clinically significant and sustained performance benefit after LASIK. This study demonstrates that MLB players have a statistically significant reduction in traditional and sabermetric offensive metric performance, including BA, WAR, wRC+, and wRAA, in the season immediately preceding LASIK compared to the second season before the procedure. Prior to LASIK surgery, on average, player BA decreased by 14 points (p=0.015), WAR decreased by 0.993 (p 0.002), wRC+ decreased by 9.525 (p=0.021), and wRAA decreased by 5.633 (p=0.032). OPS, SLG, OBA, and wOBA also decreased in the season prior to having LASIK compared to the prior season, however, the reductions were not statistically significant.

Our finding that batting performance can decrease prior to LASIK suggests that players may turn to the procedure after a season with poor performance in an attempt to improve future outcomes. A blog post examining the effect of LASIK on hitting performance postulated that players opted for LASIK in response to disappointing seasons, but did not conduct statistical analysis on the data.10 It makes logical sense that a player’s decision to undergo a vision-altering procedure would coincide with a disappointing performance in the previous year. In a data-driven sport like MLB, a season of poor performance could lead to reduced playing time and salary prospects, so players are highly motivated to address any potential weaknesses. In our study, the key statistics of BA, WAR, wRC+, and wRAA showed statistically significant drops in the season prior to LASIK. Overall, SLG, OPS, OBA, and wOBA did not show statistically significant drops in the season prior to LASIK, but followed a similar trend to the above statistics when comparing the second season prior to LASIK to the final season preceding LASIK. This conclusion is an important addition to the literature as it provides context around professional baseball players’ performance-influenced decision to pursue refractive surgery.

Our findings regarding post-LASIK improvements to batting statistics are more ambiguous. The only previously published paper about the effects of LASIK on professional athlete performance found no increase in performance when examining traditional hitting statistics for 12 MLB players.11 Our larger dataset examining advanced hitting statistics also showed no statistically significant changes in hitting performance after LASIK. A mild, albeit not statistically significant, improvement in most statistics was seen after the surgery. Additionally, most players improved their BA, SLG, OPS, WAR, wRC+, wRAA, and wOBA in the season after LASIK.

When examining these statistics across a four-season period, player metrics appeared to rebound to near-baseline levels from the pre-LASIK season drop in production. In our study, the mean age of players prior to LASIK was 28.5. Prior literature on player performance and aging has shown that most players begin to see declining performance after their peak near 27 to 29 years old.12 With the cohorts’ average age within their prime performance years, statistical regression to the mean following a poor season is common in a sport like baseball and the improvements players showed may have occurred even without LASIK.13 Many complex factors—including batting strategy evolution, age-related performance, and league-wide pitching strategy changes—influence batter performance in different ways each year. Therefore, no certain conclusions on LASIK’s ability to improve batter performance can be made.

Further, our inconclusive findings are highlighted by unexpected changes in the plate discipline statistics BB%, K%, OBA and BB/K before and after LASIK. For example, the average strikeout rate for players who had LASIK remained unchanged at 17.9% both seasons before surgery and remained nearly identical at 18% and 17.2% during the first and second seasons, respectively, post-LASIK. Further, average walk rates among this cohort remained nearly constant between 9.3% and 10% pre- and post-LASIK. Given statistically significant decreases observed for BA, WAR, wRC+, and wRAA amongst this cohort, it is surprising that average strikeout rates, walk rates, and walk-to-strikeout ratio values for this cohort remained relatively unchanged before and after LASIK. Strikeout, walk, and BB/K values have been shown to correlate with other hitting skills, including plate discipline and contact ability, that require elite visual function.14 Resultantly, the lack of statistically significant change for hitters’ walk, strikeout, BB/K ratio, and OBA before and after LASIK surgery indicates that further research is required that utilizes modern contact quality and swing decision data to evaluate if LASIK surgery significantly influences hitters’ plate discipline & contact ability.

There are several limitations to this work. First, our collection process of players who have had LASIK likely results in an incomplete list. We relied on public data and many of our statistical findings may have been limited by sample size. This methodology also introduces reporting bias, including but not limited to biasing towards players with better LASIK results being willing to disclose their procedure. However, if mostly players with good outcomes were included, this would skew the results toward a more likely positive result post-LASIK, whereas our study found no significant improvement in batting performance following LASIK.

Further, to our knowledge, this is the best available information, as there is no known public database that collects this information for professional baseball players. Secondly, our study may not have been adequately powered to detect the statistical significance of the small improvements seen after LASIK. While there is reason to believe LASIK helps players rebound after a poor season to perform in line with their previously normal trend, the degree of inter-season and inter-player variability in professional baseball makes this difficult to prove. Thirdly, players self-select to undergo LASIK surgery and our collection process was unable to determine each player’s motivation, nor determine the magnitude of refractive correction from the procedure. Both factors would provide an interesting variable by which players could be segmented to better delineate the impact of LASIK.

For players who previously did not wear refractive correction and obtained the procedure to improve vision (i.e., those not wearing corrective lenses), one would anticipate improved performance. However, for those who already had excellent corrected vision with contacts or glasses and elected to undergo LASIK for other factors (i.e., not wanting to wear glasses during games, contact lens intolerance), the expected performance benefit may be less significant. As a result, our results may be diluted by the different treatment effects. Finally, given that all data were retrospectively collected and without a matched control group, we cannot account for confounding factors such as aging, injuries, position changes, trades, and any number of external variables that may have influenced these results. Despite these limitations, we feel that our findings add to the literature about the impact of LASIK on MLB player performance as the most extensive and inclusive study thus far.

Our study demonstrated that professional baseball players have a significant drop in batting performance in the season prior to LASIK, likely motivating some to seek surgery. While performance improved on average after LASIK, the change was not statistically significant. Nevertheless, many athletes and refractive surgery practices promote performance benefits from LASIK surgery. Further evaluation with a larger sample size and in a controlled format may provide enough statistical power to prove a benefit as well as address the motivation for the procedure as a unique variable. Based on the findings from our study, ophthalmologists and athletes should have an individualized informed discussion regarding the potential risks and benefits of refractive surgery and have tempered expectations for the magnitude of performance benefit from the procedure. 

M.P. GEISS is an aspiring ophthalmologist and a 2024 MPA Graduate from the Maxwell School of Citizenship and Public Affairs with a BA in Physics from Syracuse University. He has published research on topics including glaucoma biophysics, water quality, and geographic barriers to eyecare, and currently helps lead glaucoma surgery clinical outcomes research at SUNY Upstate’s Department of Ophthalmology, funded by the American Academy of Ophthalmology and the Research to Prevent Blindness foundation. A former pitcher for SU, MP presented about Syracuse University’s rich baseball history at the 2022 National Baseball Hall of Fame’s Symposium on Baseball and American Culture.

DAVID PORTNEY is an ophthalmology resident at the University of Michigan’s Kellogg Eye Center in Ann Arbor, Michigan. He has published research on topics across the spectrum of ophthalmology, including the surgical costs, telemedicine, resident education, and more. He is an avid sports fan, rooting for the University of Michigan and Detroit sports teams.

 

Acknowledgments

The authors would like to thank our six collaborators for this interdisciplinary project that brought together ophthalmologists, an orthopedic surgeon, an aspiring ophthalmologist, and an aspiring MLB team data scientist. Special thanks to Dr. Christopher Hood MD, medical director of the University of Michigan’s Kellogg Eye Center Cornea, Cataract, and Refractive Surgery Clinic, Dr. Daniel Portney MD, a 2024–25 hand and upper extremity orthopedic surgery fellow at Brown University’s Warren Alpert Medical School’s Department of Orthopedics, and Dr. Ravi Parikh MD, a vitreoretinal specialist at Manhattan Retina and Eye Consultants and Clinical Associate Professor at New York University Grossman School of Medicine’s Department of Ophthalmology, for their support developing the project idea and reviewing manuscript drafts. In addition, thank you to Dr. Michael J Geiss III MD, a cornea and external disease specialist at Eye Associates of Central New York who serves as co-medical director of ConnectLife Eye and Tissue Bank, an Accreditation Board member and site inspector for the Eye Bank Association of America, and a clinical assistant professor of ophthalmology at SUNY Upstate Medical University, and Dr. Tina S. Taggart, a comprehensive ophthalmologist at Eye Associates of Central New York and clinical assistant professor of ophthalmology at SUNY Upstate Medical University, for their support and helpful discussions to shape this analysis. Finally, thank you to Andrew LaRock, a third-year sports analytics student at Syracuse University’s Falk College, for helping scrape, clean, and analyze plate discipline data from FanGraphs.

 

Notes

1. Refractive Surgery Council, “5 Reasons Competitive Athletes Choose LASIK,” https://americanrefractivesurgerycouncil.org/5-reasons-competitive-athletes-choose-lasik/, accessed April 20, 2024.

2. Kevin Armstrong, “How Lasik Steadied Two Mets Behind the Plate,” New York Times, March 9, 2019. https://www.nytimes.com/2019/03/09/sports/mets-lasik-eye-surgery.html, accessed April 21, 2024; Jesse Dougherty, “The secret to Chris Paul’s hot shooting start: Lasik eye surgery,” Los Angeles Times, November 16, 2016. https://www.latimes.com/sports/clippers/la-sp-chris-paul-lasik-20161116-story.html, accessed April 21, 2024.“Athletes in a variety of sports are singing the praises of LASIK, a surgical procedure on the eye that negates the need for glasses or contact lenses,” Chicago Tribune, May 11, 2000. https://www.chicagotribune.com/news/ct-xpm-2000-05-11-0005110202-story.html, accessed April 22, 2024.

3. Daniel Laby, Josh Davidson, Louis Rosenbaum, Christopher Strasser, Michael Mellman, Arthur Rosenbaum, David Kirschen, “The visual function of professional baseball players,” American Journal of Ophthalmology 122, no. 4 (October 1996): 476–85.

4.  Matthew Namee, “New Eyes, Better Bats?” The Hardball Times, April 25, 2004, https://tht.fangraphs.com/new-eyes-better-bats, accessed April 21, 2021.

5.  David Klemish, Benjamin Ramger, Kelly Vittetoe, Jerome Reiter, Surya Tokdar, Lawrence Appelbaum, “Visual abilities distinguish pitchers from hitters in professional baseball,” Journal of Sports Science 36, no. 2 (2018): 171–79; Daniel Laby, David Kirschen, Usha Govindarajulu, Paul DeLand,. “The Effect of Visual Function on the Batting Performance of Professional Baseball Players,” Nature Scientific Reports 9, no. 1 (2019): 1–11; Jordan Muraskin, Jason Sherwin, Paul Sajda, “Knowing when not to swing: EEG evidence that enhanced perception-action coupling underlies baseball batter expertise,” NeuroImage 12, no. 123 (2015): 1–10.

6.  Jason Muraskin, Jason Sherwin, Gregory Lieberman, Javier Garcia, Timothy Verstynen, Jean Vettel, Paul Sajda, “Fusing multiple neuroimaging modalities to assess group differences in perception-action coupling,” Proceedings to the Institute of Electrical and Electronics Engineers 105, no. 1 (2017): 83–100.

7.  Daniel Laby, David Kirschen, Paul DeLand, “The effect of laser refractive surgery on the on-field performance of professional baseball players,” Optometry 76, no. 11 (2005): 647–52.

8.  Neil Weinberg, “The Beginner’s Guide to Plate Discipline,” FanGraphs, April 27, 2015. https://library.fangraphs.com/the-beginners-guide-to-plate-discipline/, accessed November 6, 2023:

9.  We chose 130 at the threshold as it is the minimum number of at-bats to qualify for a rookie (first) season. “What is a Rookie Eligibility,” MLB.com. http://m.mlb.com/glossary/rules/rookie-eligibility, accessed April 21, 2024:.

10. Jeff Sullivan, “On The Benefits Of LASIK Surgery: A Quick Analysis,” Lookout Landing, March 19, 2010. https://www.lookoutlanding.com/2010/3/19/1381852/on-the-benefits-of-lasik-surgery-a, accessed April 21, 2024.

11. Daniel Laby, Josh Davidson, Louis Rosenbaum, Christopher Strasser, Michael Mellman, Arthur Rosenbaum, David Kirschen, “The visual function of professional baseball players,” American Journal of Ophthalmology 122, no. 4 (October 1996): 476–85.

12. Richard Schulz, Donald Musa, James Staszewski, Robert Siegler. “The relationship between age and major league baseball performance: Implications for development,” Psychology Aging 9, no. 2 (1994): 274–86; John Bradbury. “Peak athletic performance and ageing: Evidence from baseball.” Journal of Sports Science 27, no. 6 (2009): 599–610.

13. Timothy Schall, Gary Smith. “Do Baseball Players Regress Toward the Mean?” American Statistician 54, no. 4 (2000): 231–35.

14. Kyle Burris, Kelly Vittetoe, Benjamin Ramger, Sunith Suresh, Surya Tokdar, Jerome Reiter, Gregory Appelbaum, “Sensorimotor abilities predict on-field performance in professional baseball,” Nature Scientific Reports 8, no. 1 (2018): 116.