Three acceptable targets can be used to measure the breakpoint, including 1) an accommodative target, 2) a penlight, and 3) a penlight with red/green glasses. ![]() A normative value for this measurement is approximately 5 cm break from the nasal bridge. This number is generally recorded in cm and is labeled as the "break" point. The magnitude is measured when the patient subjectively reports diplopia or when the examiner objectively observes an eye drift outwards. NPC measures the magnitude of convergence by following a target in towards the nose. Exophoria describes temporally deviated ocular alignment, whereas esophoria describes nasally deviated alignment. Phorias, the natural ocular alignment, are best measured by performing an alternating cover test and neutralizing eye movements to determine the magnitude. Symptomatic according to the Convergence Insufficiency Symptom Survey (CISS) The contributions of fusional and accommodative vergences were found to be untrainable. Accommodative convergence, the final component, describes the coupling relationship between stimulated convergence and the response to ensure clarity by the accommodative system.įor CI, treatment options are tailored towards improving the tonic and proximal vergence components through procedural therapies, as they are adaptable with exercises. Fusional, or disparity vergence, is the third component and utilizes feedback from retinal image disparity to maintain ocular alignment accurately through small eye movements. Upon the completion of binocular shifts from proximal vergence, fusional vergence takes over to maintain vergence. Proximal vergence results in binocular fixation composed of large gaze shifts and comprises the majority of binocular shifts in fixation. Phorias are elicited in monocular viewing since, under binocular viewing, the other vergence components compensate for a difference in vergence demand.Īnother component is proximal vergence, which refers to vergence stimulated by a perceived distance or depth. A phoria manifests during a disruption of binocular vision, such as monocular viewing, and is an error of binocular alignment. The physiological position determined by tonic vergence often differs from the fusional vergence demand, and this difference is what constitutes an individual's phoria. Tonic vergence describes the angle of vergence in the absence of a stimulus. ![]() These components, often described as Maddox components of vergence, include tonic, proximal, fusional, and accommodative vergences. In patients with convergence insufficiency, the etiology is presumed to be an innervational difference in these components that results in the limited capacity to converge with near demands. ![]() Vergence implies the movement of both eyes in conjunction with one another. Vergence eye movements (either convergence or divergence) are a summation of components in response to a stimulus.
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