Indoor Time, Near Work Associated with Reduced Acuity

Teenage girl reading book at desk in class. Students are learning in high school. They are wearing uniforms.
Researchers consider the factors behind the prevalence of reduced uncorrected distance visual acuity in children throughout China.

With myopia affecting between 80% and 90% of teenagers in East Asia, researchers in China are saying the country’s visual health is in a “critical state.”

“The high prevalence of reduced uncorrected distance visual acuity (UCDVA) warns us about the deteriorating ocular health of children and adolescents and urges us to take appropriate measures,” according to the researchers. 

The BMC Ophthalmology report analyzed UCDVA in Chinese school-aged children and suggests that its prevalence may be related to the routine near work that’s part of the Chinese education system. Long study hours, a sedentary lifestyle with not much time spent outdoors and limited exposure to sunlight greatly increases the chance of developing myopia, the investigators explained.

To investigate the prevalence of reduced UCDVA in school-aged children, the study evaluated students from 236 schools in all 6 districts of Changsha, Hunan, China. In total, 250,980 primary, middle and high school students were included in the study, covering 12 grade levels. 

The authors defined vision lower than than 0.00 logMAR as reduced UCDVA, which was further divided into 3 groups according to the severity: mild (0.000 to 0.175), moderate (0.200 to 0.400), and severe (greater than 0.425).

A questionnaire with the following questions was also completed by faculty members from each school.

  • Is the school a key school or non-key school? (In China, key schools are distinguished by their strong academic reputation and state-supported resources). 
  • Are eye exercises carried out at the school? 
  • Are there any physical education classes at the school? How often? 

The study  found out that “the overall prevalence of reduced UCDVA was 51.8% (95% CI 51.6–52.0%) in 6 districts of Changsha, and 3496(1.39%) students manifested severe unilateral visual impairment in both distance and near VA with the other eye’s VA being normal.”

There was a statistically significant difference in the prevalence between districts (P <.05).  The list below shares the 6 districts followed by prevalence and 95% CI. 

  • Furong: 59.9%, 57.9–61.8%
  • Tianxin: 62.3%, 60.5–64.0%
  • Wangcheng: 47.8%, 46.8–48.8%
  • Kaifu: 58.5%, 58.0–58.9%
  • Yuhua: 47.0%, 46.7–47.4%
  • Yuelu: 52.6%, 52.3–52.9%

Also, the authors identified a statistically significant difference in the prevalence between grades (P <.05). As children progressed through school, prevalence increased steadily from primary grade levels to high school. For example, for primary grade 6, prevalence was 52.4% (95% CI 51.7–52.9%); secondary grade 3, prevalence was 72.4% (95% CI 71.3–73.5%); and for high school grade 6, prevalence was 80.9% (95% CI 78.4–83.3%). 

Because, the study claims, current eye care services are insufficient, there are worldwide efforts to establish other methods for eye care, such as telemedicine and artificial intelligence. 

The authors of the study seek to conceive a “cloud platform to collect visual data and analyze the prevalence of reduced UCDVA in screening programs, optimize resource management and promote work efficiency,” which can align with other international developments around technology and more sufficient eye care. 

“The cloud platform includes a data logging system and a primary system. The students, guardians and school faculties are all allowed to log in with specified permission. We upload visual data after ocular examination and gather data for an overview. The data can be archived and downloaded whenever it is needed,” according to the researchers. 

This platform would allow eye care providers to offer appropriate refractive prescriptions and suggestions, and there would be more useful data to inform care. 

“If clients establish individual visual data files from childhood to adulthood, we are able to monitor their visual development over a long period of time.”


Liao M, Cai Z, Khan M. Prevalence of reduced visual acuity among school-aged children and adolescents in 6 districts of Changsha city: a population-based survey. BMC Ophthalmology. Published online August 26, 2020. Accessed September 30, 2020. doi: 10.1186/s12886-020-01619-2