On the Accommodative Convergence and the Proximal Convergence

Ogle, Kenneth N.; Martens, Theodore G.

doi:10.1001/archopht.1957.00930050714011

Cited by 47 publications

(21 citation statements)

References 12 publications

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“…We considered the AC/A ratio to be normal using the gradient method at either distance or near if it was between 2.5:1 and 6:1. 3,4,8 Finally, the AC/A ratio was determined using the heterophoria method by dividing the difference between the distance and near deviations (obtained after monocular occlusion) by 3 and adding the result to the interpupillary distance (IPD) measured in centimeters. To simplify measurements, in most cases we assumed an IPD of 5 cm for children younger than 5 years, 5.5 cm for children between 5 and 10 years, and 6 cm for patients older than 10 years.…”

Section: Methodsmentioning

confidence: 99%

“…It has previously been reported that the AC/A ratio for most individuals is not identical if calculated both by the gradient and heterophoria methods; this is consistent with the aforementioned assumptions. 3 In addition, a near measurement with +3.00-D lenses was also obtained prior to monocular occlusion for most patients. However, for reasons outlined below, we feel this measurement is of no meaningful clinical utility; we obtained it mainly for investigational reasons.…”

Section: Methodsmentioning

confidence: 99%

“…Proximal convergence has been defined as the mechanism that describes the difference between an AC/A ratio determined by the gradient method and by the heterophoria method. 3,14 Consequently, saying that the distance/near difference is owing to proximal convergence is an incomplete statement because it does not explain the mechanism at work. With accommodation controlled during testing, it should not be a function of accommodative convergence.…”

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confidence: 99%

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Distance/Near Differences in Intermittent Exotropia

Kushner¹

1998

Arch Ophthalmol

136

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Background: Burian's classification of exotropia based on the difference between the distance deviation and near deviation (distance/near differences)leaves some questions unanswered. Controversy exists concerning whether the divergence excess pattern is caused by an excess of divergence or by excessive accommodative convergence. Much of the literature on this subject has been confusing because investigators did not eliminate tenacious proximal fusion as an artifact in calculating the ratio of accommodative convergence to accommodation (AC/A ratio). Previously, one of us (B.J.K.) proposed a classification system that respected this artifact and subdivided the classification system proposed by Burian.Methods: A total of 202 consecutive patients with an exotropia underwent a series of measurements to determine the respective role of accommodative convergence and tenacious proximal fusion as a cause for their distance/near differences. In addition, the value obtained by a rapid prism adaptation test as a possible substitute for 1 hour of monocular occlusion was studied.Results: In 98 patients, the initial distance deviation exceeded the near deviation. In 10 patients, the distance/ near differences were caused by a high AC/A ratio, which

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

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Distance/Near Differences in Intermittent Exotropia

Kushner¹

1998

Arch Ophthalmol

136

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“…For this purpose, the subject's phoria was again measured with the target at 33.33 cm, followed by a second measure taken with the addition of a +2.0-0 lens over the preferred eye. The ACIA ratio was calculated by dividing the change in phoria by the difference in lens power (Ogle & Martens, 1957).…”

Section: Experiments 2 Methodsmentioning

confidence: 99%

Distance adaptation depends upon plasticity in the oculomotor control system

Ebenholtz

Fisher

1982

Perception & Psychophysics

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Maintaining binocular fixation on a target at 20 cm in the absence of secondary cues to distance produced changes in apparent distance and lateral phoria. Positive lenses of 0, .5, 2.0, 3.5, and 5.0 spherical diopters (SD) were used to manipulate the level of accommodative convergence in force during the period of maintained fixation. An inverse relationship was found between the stimulus to accommodation and the magnitude of the induced esophoria, the phoria being linearly related to an increase in apparent distance. The distance aftereffect obtained in the condition with the lowest net accommodative stimulus (Le., 0 D) equaled that typically produced by base-out prism adaptation with full secondary cues to distance available. In a second experi· ment, subjects walked through a well·lit hallway while viewing through a pair of 5 A base-out prisms. It was shown that increasing the stimulus to accommodation by adding negative lenses of 0, 1.5, 3.5, and 5.5 SD reduced the adaptive change in apparent distance, as well as the change in phoria produced by the conventional base-out prism adaptation paradigm. It was concluded that a change in the resting tonus of the disparity vergence system underlies such adaptation, rather than recalibration of the oculomotor cues to distance. Monocular exposure data indicated that a small change in the tonus control for the accommodative system may be present as well.

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“…The response of the lens to disparity stimulation is termed vergence accommodation, while vergence movement produced by blur is called accommodative vergence. Finally, a proximal component driven by a subjective awareness of target distance has been demonstrated under certain stimulus conditions (Ittelson & Ames, 1950;Ogle & Martens, 1957), and has been loosely approximated by a response-stimulus ratio similar to the Ac/As ratio (Ogle & Martens, 1957).…”

Section: Introductionmentioning

confidence: 99%