Adult convergence insufficiency prevalence is likely between 1.9% and 4.6%, depending on the definition used for convergence insufficiency, according to research presented at the Association for Research in Vision and Ophthalmology (ARVO) 2023 Annual Meeting, held in New Orleans from April 23 to April 27, 2023. According to researchers, the study suggests convergence insufficiency is not necessarily an age-related condition.
Researchers conducted a prospective cross-sectional study to determine the prevalence of adult convergence insufficiency by evaluating a cohort of metro drivers in Madrid, Spain. They randomly selected a group of metro drivers and evaluated a total of 274 workers (mean age, 43.65 years; age range, 27-65 years; 94.16% men, 5.84% women) between May and December 2021. The study excluded individuals with any kind of ocular or systemic pathology that could interfere with ocular function. A total of 8 participants were excluded for having strabismus (2.92%).
All adult convergence insufficiency participants underwent clinical evaluations that included visual acuity exams, subjective refraction, and binocular vision tests — including near and far cover test (CT), near point of convergence (NPC) and base out (BO) vergences, measured with prism bar.
The researchers relied on 2 different definitions of convergence insufficiency. In the first definition, convergence insufficiency was defined by a BO break or blur point ≤15Δ or failing Sheard’s criterion; break point of NPC ≥10 cm; and difference between near and far foria ≥4Δ. In the second definition, they defined convergence insufficiency using the same criteria for the cut-off point of vergence and phoria difference, but using the criterion of posterior parietal cortex ≥6 cm.
The researchers report that the prevalence of adult convergence insufficiency was 1.9%, using the first definition. A total of 16.7% of participants had receded NPC (≥10 cm), of which 1.9% had an NPC ≥20 cm. The researchers found a BO vergence of ≤15Δ in 33.1% of participants. In 20.2% of participants, the research team found a difference between near and far foria ≥4Δ.
According to the report, 36.5% of all participants did not have any of the signs, 47.1% had just 1 sign, 14.4% had 2 signs and 1.9% had the 3 signs. The median of near and far cover test was orto phoria, the median NPC was 4.00 cm (0.8,8), and the median BO first break or blur point was 16Δ (10,25).
The researchers report that only NPC was significantly different between age groups (Kruskal-Wallis, P =.025). The under 40 group had the lowest NPC: median 3.00 cm (0.25,6), the report shows.
When using the second definition, adult convergence insufficiency prevalence was 4.6%.
“Even in adults whose work is not related to near activities, there is a percentage of subjects who have convergence insufficiency,” according to the researchers. “Using the second definition of CI, the percentage we found was similar to that found in other studies conducted in children and adolescents. CI does not appear to be age-related.”
This research was limited by the overrepresentation of men in the study sample.
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