|Classification and external resources|
Convergence insufficiency or Convergence Disorder is a sensory and neuromuscular anomaly of the binocular vision system, characterized by a reduced ability of the eyes to turn towards each other, or sustain convergence.
The symptoms and signs associated with convergence insufficiency are related to prolonged, visually demanding, near-centered tasks. They may include, but are not limited to, diplopia (double vision), asthenopia (eye strain), transient blurred vision, difficulty sustaining near-visual function, abnormal fatigue, headache, and abnormal postural adaptation, among others. Note that some Internet resources confuse convergence and divergence dysfunction, reversing them.
In studies that used standardized definitions of Convergence insufficiency, investigators have reported a prevalence of 4.2% to 6% in school and clinic settings. The standard definition of Convergence insufficiency is exophoria greater at near than at distance, a receded near point of convergence, and reduced convergence amplitudes at near.
Diagnosis of convergence insufficiency is made by an eye care professional skilled in binocular vision dysfunctions to rule out any organic disease. Convergence insufficiency characterized by one or more of the following diagnostic findings: Patient symptoms, High exophoria at near, reduced accommodative convergence/accommodation ratio, receded near point of convergence, low fusional vergence ranges and/or facility. Some patients with convergence insufficiency have concurrent accommodative insufficiency—accommodative amplitudes should therefore also be measured in symptomatic patients.
Convergence insufficiency may be treated with convergence exercises prescribed by an eyecare specialist trained in orthoptics or binocular vision anomalies. Some cases of convergence insufficiency are successfully managed by prescription of eyeglasses, sometimes with therapeutic prisms.
Pencil push-ups therapy is performed at home. Patient brings a pencil slowly to within 2–3 cm of the eye just above the nose about 15 minutes per day 5 times per week. Patients should record the closest distance that they could maintain fusion (keep the pencil from going double as long as possible) after each 5 minutes of therapy. Computer software may be used at home or in an orthoptists office to treat convergence insufficiency. A weekly 60-minute in-office therapy visit may be prescribed. This is generally accompanied with additional in home therapy.
In 2005, the Convergence Insufficiency Treatment Trial (CITT) published two randomized clinical studies. The first, published in Archives of Ophthalmology demonstrated that computer exercises when combined with office based vision therapy/orthoptics were more effective than "pencil pushups" or computer exercises alone for convergency insufficiency in 9 to 18 year old children. The second found similar results for adults 19 to 30 years of age. In a bibliographic review of 2010, the CITT confirmed their view that office-based accommodative/vergence therapy is the most effective treatment of convergence insufficiency, and that substituting it in entirety or in part with other eye training approaches such as home-based therapy may offer advantages in cost but not in outcome. A later study of 2012 confirmed that orthoptic exercises led to longstanding improvements of the asthenopic symptoms of convergence sufficiency both in adults and in children.
Surgical correction options are also available, but the decision to proceed with surgery should be made with caution as convergence insufficiency generally does not improve with surgery. Bilateral medial rectus resection is the preferred type of surgery. However, the patient should be warned about the possibility of uncrossed diplopia at distance fixation after surgery. This typically resolves within 1–3 months postoperatively. The exophoria at near often recurs after several years, although most patients remain asymptomatic.
- Negative relative accommodation
- Positive relative accommodation
- Vision therapy
- Convergence Insufficiency Treatment Trial (CITT) Study, Group (2008 Jan-Feb). "The convergence insufficiency treatment trial: design, methods, and baseline data.". Ophthalmic epidemiology 15 (1): 24–36. PMID 18300086.
- Scheiman M, Mitchell GL, Cotter S, Cooper J, Kulp M, Rouse M, Borsting E, London R, Wensveen J; Convergence Insufficiency Treatment Trial Study Group. "A randomized clinical trial of treatments for convergence insufficiency in children." Arch Ophthalmol. 2005 Jan;123(1):14-24. PMID 15642806.
- Scheiman M, Mitchell GL, Cotter S, Kulp MT, Cooper J, Rouse M, Borsting E, London R, Wensveen J. "A randomized clinical trial of vision therapy/orthoptics versus pencil pushups for the treatment of convergence insufficiency in young adults." Optom Vis Sci. 2005 Jul;82(7):583-95. PMID 16044063.
- "Treatment of Convergence Insufficiency in Childhood: A Current Perspective". Optom Vis Sci. 86 (5). May 2009. pp. 420–428. doi:10.1097/OPX.0b013e31819fa712. PMCID:PMC2821445, NIHMSID:NIHMS153855
- Matti Westman; M. Johanna Liinamaa (May 2012). "Relief of asthenopic symptoms with orthoptic exercises in convergence insufficiency is achieved in both adults and children". Journal of Optometry 5 (2). pp. 62–67. doi:10.1016/j.optom.2012.03.002.
- P. Thiagarajan (Jul 2010). "Effect of vergence adaptation and positive fusional vergence training on oculomotor parameters". Optom Vis Sci. 7 (87). pp. 487–493. doi:10.1097/OPX.0b013e3181e19ec2. PMID 20473234.
- K.M. Daum (July 1986). "Negative vergence training in humans". Am J Optom Physiol Opt. 7 (63). pp. 487–496. PMID 3740204.
- Mitchell Scheiman; Bruce Wick (2008). Clinical Management of Binocular Vision: Heterophoric, Accommodative, and Eye Movement Disorders. Lippincott Williams & Wilkins. p. 165. ISBN 978-0-7817-7784-1.
- International Orthoptic Association
- New York Times article on convergence insufficiency
- Vision Disorder Responds Best to Office-Based Therapy Combined with Home-Based Computer Therapy peer-reviewed article from MedPage Today