Abstract
Purpose :
Convergence insufficiency is the most common binocular vision disorder but there is not much data available on its frequency in adults. We performed a prospective cross-sectional study to determine the prevalence of convergence insufficiency in a group of metro drivers in Madrid, Spain.
Methods :
A randomly selected group of metro drivers participated in the study. We examined a total of 274 workers from May to December 2021. The age of participants was between 27 and 65 years (mean age 43.65 ± 8.19). 94.16% were males and 5.84% females. The inclusion criteria was drivers of the Company Metro de Madrid, and the exclusion criteria was having any kind of ocular or systemic pathology that could interfere with ocular function. 8 subjects were excluded for having strabismus (2.92%). Clinical evaluation: visual acuity, subjective refraction and binocular vision tests were performed, including near and far cover test (CT), near point of convergence (NPC) and Base Out (BO) vergences, measured with prism bar. We defined Convergence Insufficiency (CI) as having: 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. We also used a second definition of CI using the same criteria for the cutt-off point of vergence and phoria difference, but using the criterion of PPC ≥ 6 cm.
Results :
The prevalence of CI was 1.9%. There was a 16.7% of subject with a receded NPC (≥ 10 cm), of which 1.9% had a NPC≥ 20 cm. BO vergences ≤15Δ was found in 33.1% of subjects. Difference between near and far foria ≥ 4 Δ was found in 20.2% of subjects. 36.5% of all subjects didn't have any of the signs. 47.1% had just one sign, 14.4% had two signs and 1.9% had the three signs. Median of near and far cover test was orto phoria. Median NPC was 4.00 cm [0.8,8], and median BO first break or blur point was 16Δ [10,25]. Only NPC was found to be significantly different between age groups (Kruskal-Wallis, p=0.025). The under 40 group had the lowest NPC: median 3.00 cm [0.25,6]. Using the second definition of CI, the prevalence we found was 4.6%.
Conclusions :
Even in adults whose work is not related to near activities, there is a percentage of subjects who have convergence insufficiency. 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 abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.