Many athletic endeavors require excellent vision. Baseball players, for example, likely benefit from good visual acuity when batting because they must monitor the direction of the rotation of seams on the pitched ball.^1,2 As expected, professional baseball players have been found to have excellent Snellen visual acuity.³ The extent of peripheral vision is also likely to be correlated with athletic performance. For instance, a football quarterback must scan the field to find an open receiver or to avoid an oncoming rusher.

Generally, contact lenses are thought to be superior to spectacles for sports, although one significant benefit of spectacles over contact lenses is that spectacles specifically designed for eye protection (that is, those that meet the American Society for Testing and Materials [ASTM] performance standards) can reduce injuries from projectiles.⁴ Practical reasons why contact lenses may be better than spectacles are for sports include problems with fitting spectacles in a helmet, slippage of the spectacles, and accumulation of debris on the spectacles. And, when comparing vision in contact lenses and spectacles, while some studies demonstrate better contrast sensitivity with contact lenses, other studies have reported the opposite or have shown no difference in contrast sensitivity between the two modalities.^5-22

There are, however, clear advantages of contact lenses over spectacles. Spectacle lenses manifest prismatic deviations, while contact lenses generally do not.²³ These spectacle deviations increase as gaze is directed more peripherally. In addition, the prismatic distortion associated with spectacles can affect a person’s ability to point at single targets in the dark.²⁴ Individuals could reduce the influence of those distortions by moving the head in the direction of the pointing targets.

Spectacle lenses also may manifest significant chromatic aberrations. While the peripheral visual effects of chromatic aberrations are probably not significant in contact lens wear, these aberrations can disrupt vision in spectacle wearers.²⁵

A final potential visual advantage of contact lenses over spectacles is the field of view. For myopic individuals, spectacles provide a larger field of view for a stationary eye compared to contact lenses because the prismatic effect of the negatively-powered spectacle lenses brings more of the periphery into view.²⁵ However, the spectacle frame can create a physical barrier to peripheral vision. Thus, the peripheral field of view in spectacles is, to an extent, dependent on the size and temple configuration of the spectacle frame.²⁶

Given that there appear to be advantages to contact lenses over spectacles for sports, it is reasonable to ask whether a direct comparison between contact lenses and spectacles in sports-related or hand-eye coordination activities has been performed.

To our knowledge, there are two previous studies related to this matter. Schnider et al²⁷ investigated differences in performance on a battery of visual tests while participants wore their spectacles or contact lenses. There were no statistically significant differences in performance between contact lenses and spectacles on any of the tests utilized. However, the investigators concluded that contact lens wear provided “psychological advantages” over spectacle wear.²⁷

Gallaway et al²⁶ measured the static visual field of individuals without spectacles or while wearing seven different individual pairs of protective spectacles. In addition, these investigators compared performance on a task requiring peripheral target detection and target pointing while participants wore the various spectacle frames. The investigators demonstrated that while the visual field was reduced with the spectacles, such reductions did not affect pointing performance. The authors speculated that a more demanding visuomotor task may have revealed differences in performance between the viewing conditions with and without spectacles.

Given the paucity of data comparing performance on peripheral visuomotor tasks with spectacle and contact lens wear, we decided to investigate the issue further by comparing hand-eye coordination in a rapid pointing task while participants wore spectacles and while these same participants wore contact lenses.

METHODS

The Ohio State University Biomedical Institutional Review Board approved all of the recruitment and experimental procedures utilized in this study. Participants were recruited through an e-mail sent to the faculty, staff, and students of an optometric teaching institution and by word-of-mouth. All participants gave written informed consent prior to participation. Data were collected from 31 male and female participants ranging in age from 22 to 37 years. Participants were required to have visual acuity of 20/20 in each eye in both spectacles and contact lenses, to wear both spectacles and contact lenses habitually, and to have stereoacuity of at least 30 seconds.

The task in this study was performed on an AcuVision 1000 (International AcuVision Systems, Inc.), a touch-sensitive board that was mounted on a wall.²⁸ The illuminated AcuVision 1000 targets are circles about 3cm in diameter that appear within outlined squares. There are more than 1,000 squares demarcated on the AcuVision 1000 board, but only 120 of these squares contain a circle used as a target. The targets are illuminated one at a time. The AcuVision 1000 presents the targets over an area of approximately 105º horizontally and about 82º vertically.

In this experiment, the maximum time between targets was 0.80 seconds (speed setting 8). This time value represents the maximum elapsed time, because the next target was illuminated as soon as the participant struck a target. The target was actually illuminated for 0.56 seconds. If the participant successfully depressed the target in that time, this was counted as a “correct” response. If the target was depressed during the remaining 30% of the allotted time, the response was counted as “late.”

Detailed Study Procedures After the experiment was explained to participants and written informed consent was obtained, the entry criteria were assessed. Next, the participants put on a headband to which an inertial tracker was attached (Intersense InertiaCube 3, Thales Visionix, Inc.).

Participants began the study viewing through the refractive modality in which they arrived. Fifteen participants began in their habitual contact lenses, and 16 participants began in their spectacles. Participants were instructed to place the left hand on the left vertical edge of the board and the right hand on the right vertical edge. They then stepped back from the AcuVision 1000 until their fingertips could just reach the board. They were then instructed to keep their feet in that position.

After these preliminary procedures, the AcuVision 1000 trials began. The overhead lights were on during the study. Participants completed three consecutive trials with the AcuVision 1000. Participants were not instructed on how to move the eyes and the head in performing the task. Some participants asked whether they were permitted to turn the head, and an affirmative response was given. Participants were told to complete the test as rapidly and as accurately as possible using both hands, and they were informed that late responses would be recorded as “late” or “missed.” Participants were also informed that the AcuVision 1000 beeps when the response is “correct” or “late,” while no sound is made for a “missed” target.

The first of the AcuVision 1000 trials was a practice trial. Next, the participant performed a 120-target trial while wearing the refractive correction in which they arrived. After this trial, the participant switched to the other refraction correction, and visual acuity and stereoacuity were once again measured. Participants then performed another 120-target trial.

Following completion of the AcuVision 1000 trials for all participants, permission was granted from the Ohio State University Biomedical Institutional Review Board to obtain participants’ contact lens prescriptions. Prescriptions were successfully obtained from 30 of the 31 participants.

RESULTS

The time required to complete the task and the number of correct, late, and missed responses for each participant in both conditions were collected from the AcuVision 1000. Table 1 shows these values.

The mean difference in time to completion between the contact lens wearing conditions was 1.50 ± 1.87 seconds. That is, on average, the task required 1.5 seconds longer to complete with spectacles. This mean difference was statistically significant (paired t-test, 30df, p < 0.001).

The total correct, late, and missed responses for the contact lens and spectacle conditions were also compared (Figure 1). The mean difference in correct responses was 5.32 ± 7.60, demonstrating that, on average, the number of correct responses was greater for the contact lens condition. This difference was also statistically significant (paired t-test, 30df, p = 0.001). The mean difference in late responses was 0.16 ± 8.08. This difference was not statistically significant (paired t-test, 30df, p = 0.91). The mean difference in missed responses was 5.16 ± 7.46, demonstrating that, on average, more targets were missed in the spectacle condition. This difference was statistically significant (paired t-test, 30df, p = 0.001).

While there were statistically significant differences in time to completion, correct responses, and missed responses between the contact lens and spectacle conditions, determining the clinical significance of these differences is more complex. Clinical significance suggests that differences in performance between contact lenses and spectacles on devices such as the AcuVision 1000 will correlate with differences in on-field performance between these refractive modalities.

There is some evidence that performance on devices similar to the AcuVision 1000 is correlated with performance on the field.^29,30 What is not known is the size of the decrement that must be measured on eye-hand coordination devices to reflect a decrease in on-field performance. The number of correct responses in the current study was, on average, about 12% less in the spectacle condition compared to the contact lens condition. We may expect such a difference to be associated with a significant reduction in performance with spectacles compared to contact lenses on the field, but further studies will be required to prove this supposition.

It was thought that any differences in eye-hand coordination between contact lenses and spectacles may be most obvious for peripheral targets compared to central targets. Because the AcuVision 1000 provides the number of correct, late, and missed responses in six quadrants on the AcuVision 1000 board, these values were compared for contact lens wear and for spectacle wear for the two central quadrants (40 targets: 35º horizontal and 82º vertical) and for the four peripheral quadrants (80 targets: 70º horizontal and 82º vertical).

In comparing the correct, late, and missed responses for the central quadrants, there were no significant differences (p > 0.05) between contact lens wear and spectacle lens wear for any parameter (Figure 2). However, for the peripheral quadrants, there was a significant difference between both the number of correct responses for the contact lens condition compared to the spectacle condition (mean difference = 3.42 ± 5.45) (paired t-test, 30df, p = 0.001) and between the number of misses for the contact lens and spectacle conditions (mean difference = 4.10 ± 6.12) (Figure 3). Thus, statistically significant differences in performance between contact lens and spectacle wear occurred only for the peripheral quadrants; the number correct was significantly greater for contact lenses, and the number of misses was significantly greater for spectacles.

We might expect that if optical aberrations or prismatic effects negatively impact hand-eye coordination with spectacle wear, then these effects would increase with refractive error. The mean spherical equivalent (SE) refractive error for the 30 participants from whom these data were collected (right eye) was –3.59D ± 2.07D, and the range was 0.50D to –9.13D. Linear regression was used to test for linear relationships between the SE refractive error and differences in various parameters (time to completion, total correct, total late, total missed, correct central, late central, missed central, correct peripheral, late peripheral, missed peripheral) between contact lenses and spectacles. The p-value associated with these regression equations was insignificant in all cases (p > 0.05).

Finally, the standard deviation of horizontal head rotation was compared for the contact lens and spectacle conditions. A paired t-test comparing these standard deviations showed that the results of the two conditions were not significantly different (p = 0.42).

DISCUSSION

While it may be expected that contact lenses provide advantages over spectacles for sports, specific studies demonstrating or quantifying these advantages are rare.^26,27 Here we compared contact lens and spectacle performance on a rapid pointing task that requires peripheral search and accurate target localization.

Performance was better in contact lenses than in spectacles for total correct responses, total missed responses, and time to complete the task (Table 1). To our knowledge, this is the first study to demonstrate and quantify the advantage of contact lenses over spectacles for hand-eye coordination tasks. The differences were significant only in the periphery, suggesting that peripheral optics are factors in producing these results. However, the lack of a correlation between the differences in performance and the refractive error suggests that neither optical aberrations nor prismatic effects were primary causes of these differences.

This leads to the idea that the reduced field of view of spectacles resulting from the spectacle frame could have resulted in differences in performance between spectacles and contact lenses. However, this conclusion is complicated by the fact that the angular dimensions of the Acuvision 1000 board are such that the entire visual field over which the pointing targets were presented was probably visible when participants looked straight ahead.

It seems likely that the head was moved toward the targets in both the spectacle and contact lens conditions, and this may explain how the relative field of view of spectacles and contact lenses resulted in these findings.³¹ By moving the head in the direction of the target, portions of the AcuVision 1000 board that were not initially outside of the field of view become more peripheral and potentially leave the field of view in spectacles. To test this hypothesis, it will be necessary to monitor eye and head movements and relate these movements to the location and appearance of the targets.

SUMMARY

To our knowledge, this is the first study to demonstrate benefits of contact lens wear over spectacle wear on a peripheral detection and target localization task. Perhaps the combination of the large visual angles over which targets were presented and the rapid pointing responses required of the task were necessary to uncover these differences. These data suggest that contact lenses are advantageous for sports-related activities that require rapid scanning. CLS

This study was supported by The Ohio State University College of Optometry. This work formed the basis of Brennen Yaquinto’s 2018 Master of Science thesis. These data were presented at the 2018 American Academy of Optometry annual meeting.

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