Convergence Insufficiency Clinical Presentation

Updated: Jul 25, 2018
  • Author: Eric R Eggenberger, DO, MS, FAAN; Chief Editor: Hampton Roy, Sr, MD  more...
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Presentation

History

Individual patients with convergence insufficiency may report a wide range of symptoms, including blur, motion of the visual target, eye strain, headache during near work, or diplopia. Difficulty reading or attending to near work is reported, either in isolation or accompanied by further descriptors. A standardized questionnaire, the Convergence Insufficiency Symptom Survey, was established for research purposes but may be helpful in identifying symptoms, although it lacks specificity as a screening tool. [8, 9, 10] Particularly in children, it may also be helpful to confirm symptoms with a range of activities rather than just required reading. [11]

Patients with convergence insufficiency often present as teenagers or in early adulthood, reporting gradually worsening eyestrain, blurred vision after brief periods of reading, and, sometimes, diplopia with near work. It is not unusual for the patient to squint or close one eye while reading to relieve blurring or diplopia. Few, if any, symptoms are present at distance fixation. Symptoms are aggravated by illness, sedative-hypnotic medications, lack of sleep, anxiety, and prolonged near work. [12]

The symptoms of convergence insufficiency are directly associated with reading or other near work visual demands. Many patients with objectively measured convergence insufficiency may not report symptoms. The clinician should inquire about any avoidance behavior in patients who are asymptomatic despite clinical findings consistent with convergence insufficiency. [13, 14] The most common symptoms associated with convergence insufficiency include asthenopia (eyestrain) and headache during near work, diplopia, blurred vision, and perceived moving of print while reading. [15]

Asthenopia (eyestrain)

These symptoms were clearly described by von Graefe as early as 1855. Typically, such symptoms occur after short periods of reading or other close work. This most frequently occurs because of the sustained increased effort required to increase fusional convergence.

Diplopia

The diplopia that manifests in patients with convergence insufficiency may present as two separate or overlapping images (a "ghost" image). Some patients describe blurry rather than double vision, but they may be able to identify that symptoms resolve with closure of either eye. These nondiplopic binocular symptoms are easily diagnosed in the symptomatic patient by checking monocular eye closure, which alleviates binocular symptoms.

Some patients with convergence insufficiency do not have symptoms of diplopia despite an obvious exodeviation at near. This may result from suppression of the nonfixating eye.

Blurred vision

Efforts to increase convergence through stimulation of accommodative convergence to eliminate diplopia can sometimes cause blur by simultaneously producing refractive error via over-accommodation.

Moving of print while reading

A sense of letters moving while reading may result from unstable binocular alignment relative to the near vision convergence demand. This usually occurs when the patient is unable to maintain sufficient fusional convergence to establish and maintain binocular vision, with visual attention alternating between competing eyes.

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Physical

The cardinal signs of convergence insufficiency include an increased near point of convergence, decreased fusional convergence amplitude, and exodeviation greater at near.

Near point of convergence is tested by bringing a fixation target toward the patient and observing for the loss of binocular fixation. When the patient reports diplopia or loses binocular fixation, this is the near point of convergence. Norms for the near point of convergence increase during childhood, and various distances have been suggested as cutoffs for normal values. However, the 6-cm measure used by the Convergence Insufficiency Treatment Trial seems reasonable given limited normative data. [3, 16, 17] The authors of this article find the near point of convergence to be the least objective of the testing methodologies used for vergence dysfunction, as it is extremely effort dependent.

Positive fusional convergence amplitude is measured by placing increasing power of base-out prism in front of either of the patient’s eyes while they focus on a distant target. The maximum prism at which either the patient is observed to lose binocular fixation or reports diplopia is the positive fusional vergence amplitude. Healthy patients have prism diopter convergence amplitude of more than 15. Sheard’s criteria state that healthy individuals should have a convergence amplitude twice the magnitude of near phoria measured at 40 cm. [4, 3]

Ocular alignment tested via alternate cover reveals an exophoria at near that is ≥4 prism diopters greater than at distance.

Patients may demonstrate reduced stereoacuity at near.

Monocular near visual acuity should also be evaluated.

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Causes

Convergence insufficiency is often seen in healthy children or aging patients. It has been proposed that the introduction of plus lenses for presbyopia may reduce accommodative stimuli for convergence; however, this was not shown in a population-based cohort. [6] Mild traumatic brain injury may be associated with subsequent convergence insufficiency. [18] More than 40% of patients with sports-related concussion demonstrated an abnormal near point of convergence. [19] Neurodegenerative diseases, including Parkinson disease and progressive supranuclear palsy, also cause convergence insufficiency. In Parkinson disease, decreased convergence amplitudes have been demonstrated early in the disease course. [20] Improvement of convergence with levodopa treatment has been reported. [21] Centrally acting medications also contribute to vergence dysfunction. [4]

While isolated impairment of convergence due to discrete brainstem lesions is rare, it has been reported. It can also occur with lesions of the medial longitudinal fasciculus causing internuclear ophthalmoplegia or with the dorsal midbrain syndrome, although convergence excess is more common in this scenario, and additional features are uniformly present on exam, assisting in the diagnosis. [4]

Patients with uncorrected hyperopia in excess of +5.00 diopters (D) may generate little or no accommodative effort at near.

Patients with mild-to-moderate myopia do not need to stimulate accommodation to see clearly at the usual near working distance in their uncorrected state. This lack of accommodative effort may result in decreased accommodative convergence.

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