The players were literally off the charts

Thursday, May 13th, 2021

Louis J. Rosenbaum had been the team ophthalmologist for the Phoenix Cardinals football team, but in 1992, David Epstein explains (in The Sports Gene), he was brought in to work with the Los Angeles Dodgers baseball team, and he met with an unexpected problem:

The players were literally off the charts.


The trouble was that Rosenbaum used commercially available Landolt ring charts, which tested visual acuity down to 20/15. Nearly every player maxed out the test.

Landolt Ring Chart

When Tommy Lasorda asked him to predict which minor leaguer would thrive in the major league, he didn’t have the players’ baseball statistics, but he did have the vision testing data from his other tests:

He chose a minor league first baseman with outstanding scores. The player was Eric Karros, a mere sixth-round pick in the 1988 draft. By ’92, though, Karros was starting at first base for the Dodgers and won the National League Rookie of the Year award. It was his first of thirteen full seasons as a major leaguer.

The following spring, Rosenbaum returned to Dodgertown with a custom-made visual acuity test that went down to 20/8. Given the size and shape of particular photoreceptor cells, or cones, in the eye, 20/8 is around the theoretical limit of human visual acuity.


This time, the player whose vision tests stood out to Rosenbaum was Mike Piazza, a lightly regarded catcher.

Piazza had been picked by the Dodgers five years earlier in the sixty-second round of the draft, the 1,390th player taken overall, and only because Piazza’s father was a childhood friend of Lasorda’s. Nonetheless, Piazza would make good on Rosenbaum’s prediction. He won the National League Rookie of the Year in 1993 and went on to become the greatest hitting catcher in baseball history.

Over four years of testing, and 387 minor and major league players, Rosenbaum and his team found an average visual acuity around 20/13.


Major league position players had an average right eye visual acuity of 20/11 and an average left eye visual acuity of 20/12. In the test of fine depth perception, 58 percent of the baseball players scored “superior,” compared with 18 percent of a control population. In tests of contrast sensitivity, the pro players scored better than collegiate baseball players had in previous research, and collegiate players scored better than young people in the general population.

In each eye test, pro baseball players were better than nonathletes, and major league players were better than minor league players.

“Half the guys on the Dodgers’ major league roster were 20/10 uncorrected,” Rosenbaum says.


In the Indian study, out of 9,411 tested eyes, one single eye had 20/10 vision. In the Beijing Eye Study, only 22 out of 4,438 eyes tested at 20/17 or better.


Seventeen- and eighteen-year-olds in a Swedish study had average visual acuity around 20/16.

Ted Williams, the last man to hit .400 over a major league season, used to insist that he only saw ducks on the horizon before his hunting partners because he was “intent on seeing them.” Perhaps. But Williams’s 20/10 vision, discovered during his World War II pilot’s exam, probably didn’t hurt either.

About 2 percent of the players in the Dodgers organization dipped below 20/9, flirting with the theoretical limit of the human eye.


When Laby and Kirschen studied U.S. Olympians from the 2008 Beijing Games, they found that the softball team had an average visual acuity of 20/11, outstanding depth perception, and better contrast sensitivity than athletes from any other sport.

Olympic archers also had exceptional visual acuity — they scored similarly to the Dodgers — but not particularly good depth perception. That makes sense, Laby says, because the target is far away, but it’s also flat.

Fencers, who must make rapid use of tiny, close-range variations in distance, scored very well on depth perception.

Athletes who track flying objects at a distance — softball players and to a lesser extent soccer and volleyball players — scored well on contrast sensitivity, which is “probably set at a certain ability you’re born with,” Laby says.


In a study of catching skill among Belgian college students, some of whom had normal depth perception and others who had weak depth perception, there was little difference in catching ability at low ball speeds. But at high speeds, there was a tremendous difference in catching skill.


A clever follow-up study by an international team of scientists recruited a group of young women, all with normal visual acuity but some who had poor depth perception and others with good depth perception. Each woman had a catching pretest — in which she had to snag tennis balls shot out of a machine — followed by more than 1,400 practice catches over two weeks, and then a posttest. The women with good depth perception improved rapidly during the training, while the women with poor depth perception didn’t improve at all.


Conversely, a 2009 Emory medical school study suggested that children with poor depth perception start self-selecting out of Little League baseball and softball by age ten.


  1. Lucklucky says:

    I feel that when I am in nature my vision gets better due to stimuli and the fact that I vary the observation distance often.

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