Static vergence and accommodation: population norms and orthoptics effects

Hung, George K.; Ciuffreda, Kenneth J.; Semmlow, John L.

doi:10.1007/bf00229128

Cited by 42 publications

(29 citation statements)

References 11 publications

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“…17 The near point of convergence (NPC) measures the closest point to which one can maintain convergence while focusing on an object before diplopia occurs. 18 Previously, we reported that frontal soccer headings immediately increased (worsened) NPC compared with baseline, with NPC impairment persisting for 24 hours after heading. 19 The near point of convergence immediately after and 24 hours after heading were higher than in control individuals.…”

Section: Invited Commentarymentioning

confidence: 97%

Association of Football Subconcussive Head Impacts With Ocular Near Point of Convergence

et al. 2016

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IMPORTANCE An increased understanding of the relationship between subconcussive head impacts and near point of convergence (NPC) ocular-motor function may be useful in delineating traumatic brain injury.OBJECTIVE To investigate whether repetitive subconcussive head impacts during preseason football practice cause changes in NPC. DESIGN, SETTING, AND PARTICIPANTSThis prospective, observational study of 29 National Collegiate Athletic Association Division I football players included baseline and preseason practices (1 noncontact and 4 contact), and postseason follow-up and outcome measures were obtained for each time. An accelerometer-embedded mouthguard measured head impact kinematics. Based on the sum of head impacts from all 5 practices, players were categorized into lower (n = 7) or higher (n = 22) impact groups.EXPOSURES Players participated in regular practices, and all head impacts greater than 10g from the 5 practices were recorded using the i1Biometerics Vector mouthguard (i1 Biometrics Inc). MAIN OUTCOMES AND MEASURES Near point of convergence measures and symptom scores.RESULTS A total of 1193 head impacts were recorded from 5 training camp practices in the 29 collegiate football players; 22 were categorized into the higher-impact group and 7 into the lower-impact group. There were significant differences in head impact kinematics between lower-and higher-impact groups (number of impacts, 6 vs 41 [lower impact minus higher impact = 35; 95% CI, 21-51; P < .001]; linear acceleration, 99g vs 1112g [lower impact minus higher impact= 1013; 95% CI, 621 -1578; P < .001]; angular acceleration, 7589 radian/s 2 vs 65 016 radian/s 2 [lower impact minus higher impact= 57 427; 95% CI , 31 123-80 498; P < .001], respectively). The trajectory and cumulative burden of subconcussive impacts on NPC differed by group (F for group × linear trend 1, 238 = 12.14, P < .001 and F for group × quadratic trend 1, 238 = 12.97, P < .001). In the higher-impact group, there was a linear increase in NPC over time (B for linear trend, unstandardized coefficient [SE]: 0.76 [0.12], P < .001) that plateaued and resolved by postseason follow-up (B for quadratic trend [SE]: −0.06 [0.008], P < .001). In the lower-impact group, there was no change in NPC over time. Group differences were first observed after the first contact practice and remained until the final full-gear practice. No group differences were observed postseason follow-up. There were no differences in symptom scores between groups over time. CONCLUSIONS AND RELEVANCEAlthough asymptomatic, these data suggest that repetitive subconcussive head impacts were associated with changes in NPC. The increase in NPC highlights the vulnerability and slow recovery of the ocular-motor system following subconcussive head impacts. Changes in NPC may become a useful clinical tool in deciphering brain injury severity.

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Section: Invited Commentarymentioning

confidence: 97%

Association of Football Subconcussive Head Impacts With Ocular Near Point of Convergence

et al. 2016

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“…From the current models, this improved ability of the vergence system to adapt following fusional vergence training is predicted to modify the cross-link ratios. Although a few studies showed the possibility of the change in the ratios (Flom, 1959;Manas, 1958;Hung et al, 1986), a recent study did not show a significant alteration with training (Brautaset & Jennings., 2006).…”

Section: Normalizing Vergence Adaptation With Positive Fusional Vergementioning

confidence: 99%

Effect of Vergence Adaptation and Positive Fusional Vergence Training on Oculomotor Parameters

Thiagarajan

Lakshminarayanan²,

Bobier³

2010

Optometry and Vision Science

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“…1 MA represent the reciprocal of the distance in meters to which the eyes are converged (Fincham & Walton, 1957). Some of these studies are confounded by the effect of age, which causes a decrease in accommodation function, leading to an increase in the response AC/A Ciuffreda, Rosenfield, & Chen, 1997;Fincham & Walton, 1957;Hung, Cuiffreda, & Semmlow, 1986;Rosenfield, Ciuffreda, & Chen, 1995) and decrease in the response CA/C ratio Rosenfield, Ciuffreda, & Chen, 1995;Wick & Currie, 1991). In addition, some studies have small subject numbers (Alpern, 1962;Morgan, 1968;Ogle, Martens, & Dyer, 1967;, and none have quantified the stimulus and response ratios for both AC/A and CA/C within the same population.…”

Section: Introductionmentioning

confidence: 96%

“…The accommodation loop was opened using a difference of Gaussian target and the authors suggested this method could be employed to measure the stimulus CA/C in clinical practice . Other studies have examined only the response CA/C ratio Hung, Cuiffreda, & Semmlow, 1986;Rosenfield, Ciuffreda, & Chen, 1995) and further work is required to establish the characteristics of the relationship between stimulus and response CA/C ratio in a larger sample.…”

Section: Introductionmentioning

confidence: 97%

“…The response CA/C ratio provides the most accurate measure of this cross-link interaction as the responses of both the accommodation and vergence systems are observed directly . Of the studies which have examined either the stimulus or the response CA/C ratio in adult populations Hung, Cuiffreda, & Semmlow, 1986;Rosenfield, Ciuffreda, & Chen, 1995;Wick & Currie, 1991), only one has compared stimulus and response ratios . Tsuetaki and Schor (1987) reported good agreement between the stimulus and response CA/C in a small sample of 6 subjects.…”

Section: Introductionmentioning

confidence: 98%

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Quantifying interactions between accommodation and vergence in a binocularly normal population

et al. 2014

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Stimulation of the accommodation system results in a response in the vergence system via accommodative vergence cross-link interactions, and stimulation of the vergence system results in an accommodation response via vergence accommodation cross-link interactions. Cross-link interactions are necessary in order to ensure simultaneous responses in the accommodation and vergence systems. The crosslink interactions are represented most comprehensively by the response AC/A (accommodative vergence) and CA/C (vergence accommodation) ratios, although the stimulus AC/A ratio is measured clinically, and the stimulus CA/C ratio is seldom measured in clinical practice. The present study aims to quantify both stimulus and response AC/A and CA/C ratios in a binocularly normal population, and determine the relationship between them. 25 Subjects (mean ± SD age 21.0 ± 1.9 years) were recruited from the university population. A significant linear relationship was found between the stimulus and response ratios, for both AC/A (r² = 0.96, p < 0.001) and CA/C ratios (r² = 0.40, p < 0.05). Good agreement was found between the stimulus and response AC/A ratios (95% CI -0.06 to 0.24 MA/D). Stimulus and response CA/C ratios are linearly related. Stimulus CA/C ratios were higher than response ratios at low values, and lower than response ratios at high values (95% CI -0.46 to 0.42 D/MA). Agreement between stimulus and response CA/C ratios is poorer than that found for AC/A ratios due to increased variability in vergence responses when viewing the Gaussian blurred target. This study has shown that more work is needed to refine the methodology of CA/C ratio measurement.

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Static vergence and accommodation: population norms and orthoptics effects

Cited by 42 publications

References 11 publications

Association of Football Subconcussive Head Impacts With Ocular Near Point of Convergence

Association of Football Subconcussive Head Impacts With Ocular Near Point of Convergence

Effect of Vergence Adaptation and Positive Fusional Vergence Training on Oculomotor Parameters

Quantifying interactions between accommodation and vergence in a binocularly normal population

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