Studies of Vision in Cricket-A Narrative Review.

Vision is thought to play a substantial role in hitting and fielding in cricket. An understanding of which visual skills contribute during cricket play could inform future clinical training trials. This paper reviews what has been reported thus far regarding the relationship of visual skills to cricket performance and reviews the results of clinical trials in which the impact of visual skills training on cricket performance has been addressed. Fundamental or low-level visual skills, with the exception of color vision and perhaps near stereopsis and dynamic visual acuity, are similar between cricket players and the general population. Simple reaction time has been found to be shorter in cricket players in some but not all studies. While there is mixed or no evidence that the aforementioned visual skills are superior in cricket players compared to non-players, comparisons of eye and head movements and gaze tracking have revealed consistent differences between elite cricket batters and sub-elite batters. Future training studies could examine whether teaching sub-elite batters to emulate the gaze tracking patterns of elite batters is beneficial for batting. Lastly, clinical trials in which visual skills of cricket players have been trained have in many cases resulted in positive effects on visual skills, or judgments required in cricket, or cricket play. However, clinical trials with larger and more diverse groups of participants and correlations to on-field metrics and on-field performance (i.e., domain-specific assessments) are necessary before conclusions can be drawn regarding the efficacy of vision training.

Topical Review: Methodological Variables in Clinical and Laboratory Measurements of Fixation Disparity.

SIGNIFICANCE: Fixation disparity is a small vergence error that does not disrupt fusion. Fixation disparity measures correlate with binocular symptoms. This article covers methodological differences between clinical fixation disparity measurement devices, findings when objective and subjective fixation disparities are compared, and the potential impact of binocular capture on fixation disparity measurements. Fixation disparity is a small vergence error that occurs in nonstrabismic individuals and does not disrupt fusion. This article reviews clinical fixation disparity variables and their clinical diagnostic value. Clinical devices that are used to measure these variables are described, as are studies in which the output from these devices has been compared. Methodological differences between the devices such as the location of the fusional stimulus, the rate at which judgments of dichoptic alignment are made, and the strength of the accommodative stimulus are all considered. In addition, the article covers theories of the neural origins of fixation disparity and control system models incorporating fixation disparity. Studies in which objective fixation disparities (oculomotor portion of fixation disparity assessed with an eye tracker) and subjective fixation disparities (sensory portion of fixation disparity assessed psychophysically with dichoptic Nonius lines) have been compared are also examined, and consideration is given to why some investigators find differences in these measures, whereas other investigators do not. The conclusion thus far is that there are likely complex interactions between vergence adaptation, accommodation, and the location of the fusional stimulus that lead to differences in objective and subjective fixation disparity measures. Finally, capture of the visual direction of monocular stimuli by adjacent fusional stimuli and the implications for fixation disparity measures are considered.

Functional magnetic resonance imaging activation for different vergence eye movement subtypes.

INTRODUCTION: Maddox suggested that there were four convergence subtypes, each driven by a different stimulus. The purpose of this study was to assess the neural correlates for accommodative convergence, proximal convergence (convergence stimulus provided), disparity convergence and voluntary convergence (no specific convergence stimulus provided) using functional magnetic resonance imaging (fMRI). METHODS: Ten subjects (mean age = 24.4 years) with normal binocular vision participated. The blood oxygenation level-dependent (BOLD) signals of the brain from fMRI scans were measured when subjects made vergence eye movements while: (1) alternately viewing letters monocularly where one eye viewed through a -2.00 D lens, (2) alternately viewing Difference of Gaussian targets monocularly at distance and near, (3) viewing random dot stereograms with increasing disparity and (4) voluntarily converging the eyes with binocular viewing. RESULTS: The accommodative convergence paradigm resulted in activation on the right side in the right fusiform cortex and the right middle occipital cortex. The proximal convergence stimulus mainly activated areas in the right occipital lobe. The disparity stimulus activated areas in the left occipital cortex and the left frontal cortex. Finally, the voluntary convergence paradigm resulted in activation primarily in the occipital lobe and mostly bilaterally. CONCLUSION: The accommodative, proximal, disparity and voluntary convergence paradigms resulted in activation in unique areas in the brain with functional MRI. Activation was found in more areas in the proximal and voluntary conditions compared with the accommodative and disparity conditions.

Normative Performance Profiles of College Aged Esport Athletes in a Pilot Study.

Aims: This study aimed to holistically assess the physical and cognitive attributes of esport athletes. Methods and Results: Forty-six adults between 18 and 32 years old with experience playing videogames were enrolled in this study. Participants completed assessments in five areas: demographics, self-report questionnaires, cognitive performance, physical performance, and gaming performance. Participants self-reported Overwatch ranking and physical activity participation (Pediatric Physical Activity Measure), and grip strength was measured with a handheld dynamometer. Seven domains of physical, mental, and social health and well-being were measured with the Patient Reported Outcomes Measurement Information System (PROMIS-29). The List Sorting Working Memory Test and Picture Sequence Memory Test from the National Institutes of Health (NIH) Toolbox Cognition Batteries were used to measure cognitive performance. Finally, esports performance was measured using a series of tasks through Alienware Academy and AIM Booster to record accuracy, reaction time, and targets hit. Participants were separated into high and low ranking groups for comparisons. This sample of esport athletes was similar to the general population for grip strength, each of the PROMIS-29 metrics, the List Sorting Working Memory Test, and the Picture Sequence Memory Test. Reaction time was the variable with the only significant difference between ranking groups. Conclusion: This study represents a primary investigation of esport athletes using a holistic approach. By incorporating physical and cognitive components, the most important factors to esport athletes' health and performance can be better understood and applied.

Arousal/Stress Effects of "Overwatch" eSports Game Competition in Collegiate Gamers.

ABSTRACT: Kraemer, WJ, Caldwell, LK, Post, EM, Beeler, MK, Emerson, A, Volek, JS, Maresh, CM, Fogt, JS, Fogt, N, Häkkinen, K, Newton, RU, Lopez, P, Sanchez, BN, and Onate, JA. Arousal/stress effects of "Overwatch" eSports game competition in collegiate gamers. J Strength Cond Res 36(10): 2671-2675, 2022-To date, no physical response data are available for one of the most popular eSport games, Overwatch . The purpose of this investigation was to describe the stress signaling associated with competitive Overwatch play and to understand how acute hormonal responses may affect performance. Thirty-two male college-aged gamers (age: 21.3 ± 2.7 years; estimated time played per week: 18 ± 15 hours) completed the study. Subjects were randomly assigned to a 6-player team to compete in a tournament-style match. Salivary measures of cortisol and testosterone were collected immediately before (PRE) and after (POST) the first-round game, with the heart rate recorded continuously during the match. The mean characteristics were calculated for each variable and comparisons made by the skill level. Significance was defined as p ≤ 0.05. There were no differences in measures of salivary cortisol. A differential response pattern was observed by the skill level for testosterone. The low skill group displayed a significant increase in testosterone with game play (mean ± SD , testosterone PRE: 418.3 ± 89.5 pmol·L -1 , POST: 527.6 ± 132.4 pmol·L -1 , p < 0.001), whereas no change was observed in the high skill group. There were no differences in heart rate characteristics between skill groups. Overall, the average heart rate was 107.2 ± 17.8 bpm with an average max heart rate of 133.3 ± 19.1 bpm. This study provides unique physiological evidence that a sedentary Overwatch match modulates endocrine and cardiovascular responses, with the skill level emerging as a potential modulator.

Coincidence Anticipation Timing Responses with Head Tracking and Eye Tracking.

BACKGROUND: Head tracking movements are common in interceptive tasks. The benefits of these movements are unclear. The purpose of this study was to compare coincidence anticipation timing (CAT) responses for a simulated approaching object when the eyes were used in tracking the object and when the head was used in tracking the object.METHODS: A total of 29 subjects participated. A Bassin Anticipation Timer consisting of a track of sequentially illuminated lights was used to simulate an approaching object at velocities of 223 cm · s-1 to 894 cm · s-1. Each velocity was used 10 times under 2 conditions. In one condition, subjects were told to turn the eyes with the stimulus. In the other condition, subjects viewed the stimulus through apertures and were told to turn the head with the stimulus. Subjects pushed a button to coincide with illumination of the final light on the track.RESULTS: Signed CAT errors, unsigned CAT errors, and variable CAT errors were compared between the head movement (HM) and eye movement (EM) conditions. No significant differences were noted for the signed errors (mean signed error at 894 cm · s-1; 10.3 ± 75.4 ms (HM), -16.1 ± 51.0 ms (EM). However, the unsigned and variable errors were significantly larger at some stimulus velocities in the head movement condition [mean unsigned error at 894 cm · s-1: 82.6.0 ± 45.9 ms (HM), 59.0 ± 22.4 ms (EM); mean variable error at 894 cm · s-1; 78.0 ± 37.8 ms (HM), 49.2 ± 17.1ms (EM)].DISCUSSION: Head movement did not result in improved CAT performance compared to eye movements. Further work will be required to determine whether these results are generalizable to situations where head tracking is required but apertures are not worn.Ross E, Kinney M, Fogt N. Coincidence anticipation timing responses with head tracking and eye tracking. Aerosp Med Hum Perform. 2022; 93(2):79-88.

Driving performance and road sign identification by multifocal contact lens wearers in a driving simulator.

PURPOSE: The purpose of this study was to compare sign identification distances and driving performance metrics in presbyopic participants while wearing multifocal contact lenses (MFCL) and while wearing progressive addition lens (PAL) spectacles. METHODS: 19 presbyopic participants completed PAL spectacle assessments and contact lens fitting and follow up visits before driving assessments began. These assessments occurred in a simulator equipped with a full-sized sedan on a motion platform and a 260 degree screen. Participants completed the driving task with PAL and with MFCL. Participants followed a lead car and identified signs at various distances from the road. For the two wearing conditions, comparisons of the distance along the road at which signs were identified were made using repeated measures ANOVA. Paired t-tests were used to compare driving performance for the two conditions. RESULTS: There was no statistical difference in sign identification distance between PAL and MFLC for signs 32.0 m from the road side of the road (182 ± 46 m for MFCL; 205 ± 45 m for PAL; P = 0.07) or 51.4 m from the side of the road (204 ± 43 m for MFCL; 216 ± 36 m for PAL; P = 0.3). Only signs 70.2 m from the roadside showed a significant difference (207 ± 42 m with MFCL; 232 ± 39 m with PAL; P = 0.01), All distances were greater than those required to safely stop a vehicle. There were no significant differences in the driving performance metrics between the refractive corrections. CONCLUSION: Driving performance metrics were similar for MFCL and PAL spectacles. Sign identification distances with both eyewear types were well within the distances required for safe vehicle stopping.

Estimations of the Passing Height of Approaching Objects.

SIGNIFICANCE: Limited optical cues associated with ball flight were inadequate to estimate the vertical passing distance of approaching balls. These results suggest that these optical cues either must be integrated with contextual and kinematic cues or must be of larger amplitude to contribute to estimates of vertical passing distance. PURPOSE: To intercept or avoid approaching objects, individuals must estimate both when and where the object will arrive. The purpose of this experiment was to determine whether individuals could estimate the vertical passing height of a ball approaching at different linear speeds when vertical angular retinal image velocity and cues for time to contact were minimized. METHODS: Twenty participants stood 40 feet from a pitching machine that projected tennis balls toward observers at six random speeds from 56 to 80 mph. The flight of the balls was stopped after 9 feet. The actual passing height ranged from about 35 (lowest speed) to 136 cm (highest speed). Observers indicated the height at which they expected the balls to arrive. Overall, the height estimates increased as ball speed increased (means, 121 ± 13 cm [lowest speed] and 131 ± 10 cm [highest speed]). However, only at the higher speeds were the absolute height estimates close to the actual height of the ball. At the higher ball speeds, estimates for participants with some experience in baseball or softball were more accurate (86.4% correct at the highest speed) than estimates for participants with no experience. CONCLUSIONS: Overall, estimates of vertical passing distance were inaccurate particularly at the lower speeds. Underestimates of vertical drop at lower speeds may have resulted from overestimates of ball speeds. At short exposure durations, optical cues associated with ball flight were inadequate for predictions of vertical passing distance at all speeds for the no-experience group and at lower speeds for the experienced group.

Visual performance with multifocal contact lenses and progressive addition spectacles.

PURPOSE: As presbyopia occurs, new visual demands create a need for clear vision at multiple distances. Many spectacle wearers adapt into progressive addition lenses (PAL) in order to see clearly at distance, intermediate, and near. A multifocal contact lens provides the ability to see at these same distances without the prismatic effects of a spectacle lens or the peripheral obstruction of a spectacle frame. No studies have been done to date comparing the effect of these types of presbyopic vision correction on a variety of tests of visual performance representative of everyday tasks. METHODS: A battery of visual performance tasks were completed by subjects while wearing their habitual PAL spectacles. These subjects were then fit with a multifocal contact lens and wore lenses for 2 weeks or more before completing the tasks again. These functional vision tests included assessments of coincidence anticipation timing, peripheral search and hand-eye coordination, and dynamic visual acuity. Following functional vision testing, subjects completed a preference survey comparing both types of refractive correction while performing common activities of daily living. RESULTS: Performance on the majority of the tests of visual performance were equivalent (P < 0.05) when comparing PAL spectacles and multifocal contact lenses. Survey results demonstrated a preference for multifocal contact lenses overall. CONCLUSION: PAL spectacles are widely prescribed for presbyopic patients. The findings of this study suggest that in addition to providing excellent vision, multifocal contact lenses provide functional vision performance equal to PAL spectacle wear and patients may prefer them over PAL spectacles.

Review: Head and Eye Movements and Gaze Tracking in Baseball Batting.

SIGNIFICANCE: After a 30-year gap, several studies on head and eye movements and gaze tracking in baseball batting have been performed in the last decade. These baseball studies may lead to training protocols for batting. Here we review these studies and compare the tracking behaviors with those in other sports.Baseball batters are often instructed to "keep your eye on the ball." Until recently, the evidence regarding whether batters follow this instruction and if there are benefits to following this instruction was limited. Baseball batting studies demonstrate that batters tend to move the head more than the eyes in the direction of the ball at least until a saccade occurs. Foveal gaze tracking is often maintained on the ball through the early portion of the pitch, so it can be said that baseball batters do keep the eyes on the ball. While batters place gaze at or near the point of bat-ball contact, the way this is accomplished varies. In some studies, foveal gaze tracking continues late in the pitch trajectory, whereas in other studies, anticipatory saccades occur. The relative advantages of these discrepant gaze strategies on perceptual processing and motor planning speed and accuracy are discussed, and other variables that may influence anticipatory saccades including the predictability of the pitch and the level of batter expertise are described. Further studies involving larger groups with different levels of expertise under game conditions are required to determine which gaze tracking strategies are most beneficial for baseball batting.

Visual and Ocular Characteristics of eSports Participants.

SIGNIFICANCE: The popularity of competitive video game play is growing rapidly. Little is known about the ocular characteristics of esports participants. Refractive error and binocular measures in young adult gamers were similar to population norms. However, tear breakup time was lower, and accommodative lag was higher. PURPOSE: In a recent report, very young video game players were found to have greater levels of refractive error and heterophoria and reduced stereopsis. The purpose of this study was to assess the visual and ocular characteristics of a group of recreational esports athletes to determine if the findings in young children were similar to findings in a group of young adult video game players. METHODS: Vision tests were performed on 36 college students during a video game combine event. Testing included high- and low-contrast visual acuity, autorefraction at distance and at 33 cm, stereoacuity, near heterophoria, and tear breakup time. Participants also indicated their level or rank in the game Overwatch. RESULTS: Fifteen participants were myopic, and 21 did not wear vision correction. The mean local stereopsis was 31.9 seconds. The mean of the esophoric value was 3.2 prism diopters, and the mean of the exophoric value was 5.7 prism diopters. The mean lag of accommodation was 0.81 D. The mean tear breakup time was 5.8 seconds. Average hours of play did not differ between those who wore vision correction and those who did not. There were no significant relationships between the hours of play and the ocular findings. CONCLUSIONS: The prevalence of refractive error and the mean heterophoria were similar to population norms, and the mean stereoacuity was normal. However, accommodative lag was slightly higher, and the tear breakup time was lower than expected. Differences in these latter values were also noted between high- and low-level Overwatch players.

Comparison of nanoemulsion and non-emollient artificial tears on tear lipid layer thickness and symptoms / Comparación del efecto de las gotas oftálmicas de nanoemulsión vs no emolientes en el grosor de la capa lipídica lagrimal y los síntomas

PURPOSE: Dry eye disease (DED) is often managed with over-the-counter eye drops. This study evaluated the diurnal effects of a single drop of two ocular lubricants (nanoemulsion vs. non-emollient) on tear film lipid layer thickness (LLT) and symptoms of ocular dryness. Subjects were also assessed after 1 month of nanoemulsion eye drop use. METHODS: Part 1 was a cross-over comparison of a nanoemulsion and a non-emollient eye drop. LLT and dry eye symptoms were measured at baseline and at 15min, 1 h, 2 h, 4 h and 6 h after instillation of each drop. Part 2 was a 1-month observational study assessing LLT and symptoms after 30-day use of the nanoemulsion drop four times daily (qid). RESULTS: Total of 20 subjects completed the study (mean age = 45.6 ± 7.9, 15 female). Part 1 found a significant increase in average LLT 15min after nanoemulsion drop instillation in the overall and inferior third of the tear film for subjects with baseline LLT values < 50 nm. Average LLT values did not increase after use of the non-emollient. Symptoms of dryness improved up to 6h following instillation of both drops. Part 2 results found that using the nanoemulsion eye drop for 1 month improved symptoms reported on symptom surveys. CONCLUSION: Nanoemulsion eye drop use increased average LLT in subjects with low baseline levels. Statistically and clinically significant improvement in symptoms were found on symptom surveys after qid-use (four times a day) of the nanoemulsion drop. Results suggest that a nanoemulsion eye drop can benefit subjects with dry eye symptoms

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Comparison of nanoemulsion and non-emollient artificial tears on tear lipid layer thickness and symptoms.

PURPOSE: Dry eye disease (DED) is often managed with over-the-counter eye drops. This study evaluated the diurnal effects of a single drop of two ocular lubricants (nanoemulsion vs. non-emollient) on tear film lipid layer thickness (LLT) and symptoms of ocular dryness. Subjects were also assessed after 1 month of nanoemulsion eye drop use. METHODS: Part 1 was a cross-over comparison of a nanoemulsion and a non-emollient eye drop. LLT and dry eye symptoms were measured at baseline and at 15min, 1h, 2h, 4h and 6h after instillation of each drop. Part 2 was a 1-month observational study assessing LLT and symptoms after 30-day use of the nanoemulsion drop four times daily (qid). RESULTS: Total of 20 subjects completed the study (mean age=45.6±7.9, 15 female). Part 1 found a significant increase in average LLT 15min after nanoemulsion drop instillation in the overall and inferior third of the tear film for subjects with baseline LLT values <50nm. Average LLT values did not increase after use of the non-emollient. Symptoms of dryness improved up to 6h following instillation of both drops. Part 2 results found that using the nanoemulsion eye drop for 1 month improved symptoms reported on symptom surveys. CONCLUSION: Nanoemulsion eye drop use increased average LLT in subjects with low baseline levels. Statistically and clinically significant improvement in symptoms were found on symptom surveys after qid-use (four times a day) of the nanoemulsion drop. Results suggest that a nanoemulsion eye drop can benefit subjects with dry eye symptoms.

Vertical head and eye movements in baseball batting.

PURPOSE: The purpose of this paper is to describe a method utilized to measure vertical head and eye movements and gaze positions of baseball batters and to report the initial findings generated with this method. METHOD: Two former collegiate baseball players participated. Subjects batted balls from a pitching machine. RESULTS: Responses were similar for the two subjects. The head demonstrated a small upward rotation followed by a downward rotation. The eye was rotated opposite to the head throughout portions of the swing while gaze was directed below the ball (more for one subject than the other) for much of the pitch trajectory. DISCUSSION: These data align with previous assertions that in baseball batting, players attempt to keep pitched balls in a constant egocentric direction.

Comparisons of proximal vergence measures.

BACKGROUND: Proximal vergence is defined as a vergence eye movement subtype driven by an "awareness of nearness". The purpose of this experiment was to compare values of proximal vergence calculated with and without measures of accommodation to assess the clinical utility of each measurement method. METHODS: Thirteen participants between the ages of 22 and 37 (mean = 28.5 ± 4.5 years) were enrolled. The distance and near heterophoria were measured using the Modified Thorington technique. The near heterophoria was measured under three randomized viewing conditions (no lenses, +1.00D lenses, +2.50D lenses). Refractive error was measured with an autorefractor. Proximal vergence was calculated as the difference in calculated (far-near) and gradient (+1.00) stimulus AC/A ratios (stimulus AC/A differencing method), the difference in calculated and gradient response AC/A ratios (response AC/A differencing method), and the change in vergence from distance to near with the +2.50D lenses (uncorrected +2.50D method). This latter value was also corrected for any active accommodation with +2.50D lenses (corrected +2.50D method). RESULTS: The mean proximal vergence values (Δ) were 7.82 ± 5.98 (stimulus AC/A differencing method), 8.29 ± 3.30 (response AC/A differencing method), 6.23 ± 3.52 (uncorrected +2.50D method), and 5.13 ± 2.98 (corrected +2.50D method). The only comparison that showed both a significant correlation (p<0.05) and a non-significant difference from the paired t-test (p>0.05) was that between the stimulus AC/A differencing method and the uncorrected +2.50D method. CONCLUSIONS: When response accommodation was accounted for, differences occurred in the mean proximal values obtained with the various methods. The means of the methods most likely to be used clinically (stimulus AC/A differencing method and uncorrected +2.50D method) were similar, although some individuals demonstrated significant differences between these methods.

Changes in Tear Lipid Layer Thickness and Symptoms Following the Use of Artificial Tears with and Without Omega-3 Fatty Acids: A Randomized, Double-Masked, Crossover Study.

PURPOSE: To determine if an eye drop containing omega-3 fatty acids (Refresh Optive MEGA-3®, Allergan plc, Dublin, Ireland) increases the lipid layer thickness (LLT) of the tear film versus a non-emollient eye drop (Refresh Optive, Allergan plc). METHODS: Patients (≥30 years) with baseline LLT ≤75 nm completed the Current Symptoms Survey (CSS - a visual analog survey of dry eye symptoms), and LLT was measured pre- and post-instillation (15 and 60 mins) of their randomly assigned treatment. After washout, patients were tested with the other treatment. Primary endpoint: change in LLT from baseline. Secondary endpoint: CSS results. RESULTS: Of 21 patients enrolled, 19 completed the study. With the omega-3-containing eye drop, the mean (standard deviation) LLT increase from baseline at 15 mins was statistically significant in the overall field (8.8 [11.5] nm; P<0.001), and in each individual zone (superior, central, and inferior). At 1 hr, the LLT change from baseline was statistically significant overall (4.4 [9.7] nm; P<0.02) and in the inferior and central zones. With the aqueous eye drop, LLT change from baseline was only significant at 15 mins in the inferior field. The CSS analysis revealed a ≥8.68-unit decrease in mean average dryness score from baseline at 15 and 60 mins post-instillation of the lipid-based treatment (P≤0.03). CONCLUSION: The eye drop containing omega-3 fatty acids increased LLT at 15 mins, maintaining it at 1 hr post-instillation. Dryness symptoms also improved and maintained improved levels 1 hr after instillation, indicating that the product may benefit symptomatic patients with evaporative dry eye.

A Pilot Study of Horizontal Head and Eye Rotations in Baseball Batting.

PURPOSE: The purpose of the study was to measure and compare horizontal head and eye tracking movements as baseball batters "took" pitches and swung at baseball pitches. METHODS: Two former college baseball players were tested in two conditions. A pitching machine was used to project tennis balls toward the subjects. In the first condition, subjects acted as if they were taking (i.e., not swinging) the pitches. In the second condition, subjects attempted to bat the pitched balls. Head movements were measured with an inertial sensor; eye movements were measured with a video eye tracker. RESULTS: For each condition, the relationship between the horizontal head and eye rotations was similar for the two subjects, as were the overall head-, eye-, and gaze-tracking strategies. In the "take" condition, head movements in the direction of the ball were larger than eye movements for much of the pitch trajectory. Large eye movements occurred only late in the pitch trajectory. Gaze was directed near the ball until approximately 150 milliseconds before the ball arrived at the batter, at which time gaze was directed ahead of the ball to a location near that occupied when the ball crosses the plate. In the "swing" condition, head movements in the direction of the ball were larger than eye movements throughout the pitch trajectory. Gaze was directed near the ball until approximately 50 to 60 milliseconds prior to pitch arrival at the batter. DISCUSSION: Horizontal head rotations were larger than horizontal eye rotations in both the "take" and "swing" conditions. Gaze was directed ahead of the ball late in the pitch trajectory in the "take" condition, whereas gaze was directed near the ball throughout much of the pitch trajectory in the "swing" condition.

A review of proximal inputs to the near response.

Maddox proposed that the perceived nearness of a target could influence the ocular vergence response. Proximal inputs have been used to refer to all static and dynamic cues to depth other than disparity and blur. In this paper, we review a number of studies in which proximal influences have been assessed. While general agreement exists that proximal contributions are significant when blur and disparity cues are absent (open-loop conditions), there are conflicting reports on the role of proximal vergence and accommodation under closed-loop conditions.

Evaluation of single pixel step sizes in visual acuity assessment.

PURPOSE: Adaptive thresholding procedures (e.g., ZEST) benefit from testing near the current estimate of threshold. Therefore, small increments may improve precision of these techniques. We evaluated the validity of visual acuity assessment when letters are not constrained to a multiple of 5 pixels high. METHODS: Snellen letters were presented over a ±5 pixel range spanning the final threshold estimate. Sizes that were a multiple of 5 pixels (e.g., 20 and 25) were presented 160 times, and other sizes were presented 40 times. This resulted in 320 letter presentations at multiples of 5 and at non-multiples of 5. Post hoc ZEST procedures were used to compute acuity threshold estimates based on testing at those two sets of sizes. Two subjects participated: subject 1 for the right and left eyes and subject 2 in two sessions with binocular viewing. Psychometric functions were fit to the data and were used to model simulated observers. Simulations were run for each data set, and the number of presentations at each size matched the number presented to the subject. Ninety percent limits for proportion correct at each letter size were determined from the simulation data, and these limits were used as criteria for identifying outliers in the subject's data. RESULTS: No significant difference in acuity thresholds were found when letters were rendered in multiples of 5 pixel heights vs. letters without this constraint. Empirical data fell within the bounds defined by simulations, with no idiosyncratic results found for either set of letter sizes. CONCLUSIONS: Letter sizes that do not conform to a multiple of 5 pixel letter height yield valid acuity scores. This facilitates adaptive psychometric procedures for acuity testing, such as ZEST and QUEST, in which letter sizes are selected to be as close to the current estimate of threshold size as possible.