The Functional Change of Accommodation and Convergence in the Mid-Forties by Using Smartphone

Abstract

································································································································································································································Purpose: The present study was aimed to investigate the effect of excessive near work by using a smartphone on subjective symptoms and accommodative and convergent function in their 40s. Methods: A total of 40 subjects(male, 10; female, 30; age, 43±7.2 year) in their 40s who have monocular and binocular visual acuities of 0.8 and 1.0, respectively, were divided into presbyopia group and non-presbyopia group. The subjects were asked to watch a movie on the screen of smartphone for 30 minutes. Their accommodative amplitude and facility, and relative accommodation were measured and compared before and after the use of smartphone. Changes in fusional vergence and near heterophoria by using smartphone were also evaluated. Furthermore, the change of subjective symptoms was surveyed using a questionnaire. Results: The presbyopia in mid-40s reported discomfort in an order of asthenopia, blur and dryness after the use of smartphone. Accommodative function and non-strabismic binocular function were generally decreased. Accommodative functions such as monocular accommodative amplitude, and relative accommodation were significantly decreased after smartphone use, and the change of phoria was observed as a result of decreased convergence and divergence. Negative fusional vergence was also significantly reduced. On the other hand, nonpresbyopia in mid-40s reported discomfort in an order of asthenopia, dryness and blur, and only accommodative amplitude among the accommodative functions was significantly reduced. Significant reduction of negative fusional vergence was also observed. Conclusion: From the results, it was confirmed that the subjective discomfort of mid-40s after smarphone use might be related to whether presbyopia or not. It was due to not only the reduction of accommodative function but also the overall deterioration of visual function including heterophoria and fusional vergence. Therefore, it suggests that the accurate determination of the cause based on the overall visual functional tests such as heterophoria, fusional vergence as well as the decrease of accommodation due to the aging may be necessary when the mid-40s feels discomfortable symptoms by near work.

Ocular and visual discomfort associated with smartphones, tablets and computers: what we do and do not know

“…Accommodation has been shown to be altered with smartphone and tablet use, with decreased amplitude and increased lag . This is similar to what happens with computer use .…”

“…The findings of Kwon et al found a similar reduction in accommodative amplitude, 0.80 D, after viewing a smartphone for 30 minutes . While the implications of an approximately 1.00 D loss of accommodative amplitude may not seem to be clinically relevant for a young person, the reduction after such short‐term use leads to a concern about the effect of longer durations of use …”

“…Although smartphone viewing can induce larger exophoric shifts during device viewing compared to before device use, this may only be applicable for younger‐age adults. A report of an older cohort of adults aged 36–50 years showed no change to esophoria or exophoria with smartphone use for 30 minutes . At this point it appears that any ocular deviation changes induced by short‐term (20 minutes) digital device use will recover to normal levels in a relatively short time.…”

“…Much research into the impact of digital devices on the vergence system has measured the change to negative fusional vergence and positive fusional vergence, but the link between these parameters and ocular and visual discomfort symptoms remains inconclusive. Fusional convergence has been shown to reduce after reading on an iPad and on a liquid crystal display screen at 50 cm for 20 minutes in subjects younger than 30 years but this finding was not replicated with smartphones viewed at 40 cm for 30 minutes in similar aged participants . Negative fusional vergence was reduced in both presbyopes and non‐presbyopes while the change in positive fusional vergence post task was insignificant …”

“…Reduced subjective accommodative amplitude has been shown after digital device use . For example, reduced accommodative amplitude was reported in subjects who read from a computer and iPad for 20 minutes at a viewing distance of 50 cm.…”