Convergence insufficiency is a sensory and neuromuscular anomaly of the binocular vision system, characterized by an inability to converge the eyes 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 vergence dysfunction, reversing them.
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: High exophoria at near, reduced accommodative convergence/accommodation ratio, receded near-point of convergence, low fusional vergence ranges and/or facility.
Convergence insufficiency may be treated with convergence exercises prescribed by an orthoptist or vision therapist. Some cases of convergence insufficency are successfully managed by prescription of eyeglasses with therapeutic Prism (optics) and/or lenses.
In 2005, the Convergence Insufficency Treatment Trial (CITT) published two large, randomized clinical studies. The first demonstrated that in-office based vision therapy was more effective than home based treatment for convergency insufficiency in 9 to 18 year old children. The second found similar results for adults 19 to 30 years of age.
A British survey found that less than 1 in 300 patients receiving optometric eye examinations had convergence insufficiency and a Spanish study found that nearly 1 in 100 (0.8%) of symptomatic patients in an optometric clinic had CI. In contrast, studies conducted by the Southern California College of Optometry found that approximately 1 in 8 (13%) of fifth and six grade children examined during visual screenings had the disorder as did nearly 1 in 5 (17.6%) of 8 to 12 year olds receiving examinations at optometry clinics. A recent Romanian study revealed that roughly 3 in 5 (60.4%) of young adult patients complaining of blurred vision at near work suffered from convergence insufficiency.
- ↑ 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.
- ↑ Stidwill D. "Epidemiology of strabismus". Ophthalmic Physiol Opt. 1997 Nov;17(6):536-9. PMID 9666929.
- ↑ Lara F, Cacho P, Garcia A, "Megias R. General binocular disorders: prevalence in a clinic population." Ophthalmic Physiol Opt. 2001 Jan;21(1):70-4. PMID 11220042.
- ↑ Rouse MW, Borsting E, Hyman L, Hussein M, Cotter SA, Flynn M, Scheiman M, Gallaway M, De Land PN. "Frequency of convergence insufficiency among fifth and sixth graders. The Convergence Insufficiency and Reading Study (CIRS) group." Optom Vis Sci. 1999 Sep;76(9):643-9. PMID 10498006.>
- ↑ Rouse MW, Hyman L, Hussein M, Solan H. "Frequency of convergence insufficiency in optometry clinic settings. Convergence Insufficiency and Reading Study (CIRS) Group." Optom Vis Sci. 1998 Feb;75(2):88-96. PMID 9503434.
- ↑ Dragomir M, Trus L, Chirila D, Stingu C. "[Orthoptic treatment efficiency in convergence insufficiency treatment]". Oftalmologia. 2001;53(3):66-9. PMID 11915694.
- College of Optometrists in Vision Development
- New York Times article on convergence insufficiency