Convergence insufficiency in Chinese high school students

Abstract

Background

The frequency of convergence insufficiency was determined in a sample of Chinese high school students. The associations between the frequency of convergence insufficiency, gender, refractive error and accommodative insufficiency were investigated.

Methods

This was a single‐site, prospective cross‐sectional study. In total, 928 eligible teenagers (mean age 15.9 ± 0.8) from a local high school in Guangzhou, Guangdong Province, China participated in this study. Refraction and binocular vision tests were performed on all eligible participants. The following three signs were used to classify participants: sign 1, exophoria at near at least 4^▵ greater than at far; sign 2, receded near point of convergence (≥ 6-cm break point); and sign 3, insufficient near positive fusional vergence (that is, failing Sheard's criterion or ≤ 15^▵ break point). Diagnostic groups of convergence insufficiency classification were defined as follows: (1) 3‐Sign convergence insufficiency (all three signs present); (2) 2‐Sign convergence insufficiency (sign 1 plus sign 2 or 3); (3) 1‐Sign convergence insufficiency (sign 1 only); and (4) no convergence insufficiency (that is, participants not classified into one of the above groups).

Results

The number and frequency of individuals with 3‐Sign, 2‐Sign, and 1‐Sign convergence insufficiency as well as no convergence insufficiency group were 25 (2.7 per cent), 119 (12.8 per cent), 303 (32.6 per cent) and 481 (51.8 per cent), respectively. Gender (χ² = 36.6, df = 3, p < 0.001), refractive error grouping (χ² = 37.7, df = 9, p < 0.001) and accommodative insufficiency (χ² = 15.4, df = 3, p = 0.002) were all significantly associated with convergence insufficiency. Male gender, hyperopia, or accommodative insufficiency were more likely to be classified with 3‐Sign convergence insufficiency. The frequency of accommodative insufficiency was 9.5 per cent (88 of 928 participants).

Conclusion

Compared to the data from school‐ and clinic‐based populations in the USA and South Africa, the data from this sample of Chinese high school students showed a lower frequency of 3‐Sign convergence insufficiency (2.7 per cent). Convergence insufficiency was associated with refractive error, gender and accommodative insufficiency.

Key words:

• asthenopia
• binocular vision
• Chinese
• convergence insufficiency
• exophoria
• vergence

Yuling Liu and Xiang Chen contributed equally to this work.

Yuling Liu and Xiang Chen contributed equally to this work.

Acknowledgements

The authors thank Guangzhou Business Vocational School for their generous support. We also thank Nancy Lin, who assisted with project co‐ordination, and Jian Zhang, who assisted with data analysis. This work was supported by grants from the Science and Technology Program of Guangdong Province, China (grant number 2013B020400003), and the Science and Technology Program of Guangzhou, China (grant number 15570001). The authors declare that they have no conflicts of interest.

Notes

Yuling Liu and Xiang Chen contributed equally to this work.

Additional information

Funding

Science and Technology Program of Guangdong Province, China

Science and Technology Program of Guangzhou, China