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A. J. Toole, G. L. Mitchell, M. T. Kulp, M. J. Earley, CITT-Study Group; Discriminating Asymptomatic from Symptomatic Subjects Following Treatment for Convergence Insufficiency. Invest. Ophthalmol. Vis. Sci. 2008;49(13):1123.
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We evaluated the ability of near point of convergence (NPC), positive fusional vergence (PFV), amplitude of accommodation (AA), accommodative facility (AF), and a Sheard’s criterion variable (PFV/near phoria) to detect symptomatic status following 12 weeks of real or placebo treatment for symptomatic convergence insufficiency (CI).
The Convergence Insufficiency Treatment Trial (CITT) is a multi-center, randomized, placebo controlled, clinical trial designed to evaluate the effectiveness of pencil push-ups, computer vergence/accommodative therapy with pencil push-ups, office-based vergence/accommodative therapy, and office-based placebo therapy as treatments for symptomatic CI. Children (n=218) 9 to 17 years with symptomatic CI (exophoria at least 4Δ greater at near than distance, receded NPC ≥ 6cm, and PFV < 15Δ or failed Sheard’s Criterion) completed 12 weeks of randomly-assigned treatment. Symptoms were assessed with the CI Symptom Survey with a score of < 16 considered asymptomatic. Discriminative ability of single measures was determined based on the area under the receiver operating characteristic curve (AUC). Cut points were determined based on maximizing the sum of sensitivity (Sen) for detection of symptomatic patients who failed the criterion and specificity (Spec) for detection of asymptomatic patients who passed the criterion. Positive predictive value (PPV: % of subjects who failed who were symptomatic) and negative predictive value (NPV: % of subjects who passed who were asymptomatic) were also determined.
Statistically significantly greater than chance AUCs were found for NPC, PFV, AF, and a modified Sheard’s criterion, but not for AA (0.54).
Following treatment for CI, a high PPV was found for failure of any one of the criteria for NPC, PFV and AF; thus failing a single criterion suggests that a patient will remain symptomatic. However, sensitivity and NPV for individual criteria were low due to false negatives indicating that passing an individual criterion is insufficient evidence to suggest that a patient will be asymptomatic.
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