The effect of smartphone and conventional near activity on near reflexes and binocularity

Purpose: The widespread use of smartphones may have a similar or different effect on ocular functions compared to conventional activities such as reading book. In this study, it is aimed to reveal the possible effects of smartphones on accommodation, convergence and binocularity. Method: In the third decade of life, 50 adults with appropriate ocular functions, primarily accommodative convergence/ accommodation ratio (AK/A) , amplitude of accommodation (AA), near point of convergence (NPC), presence of heterophoria, binocularity, positive and negative relative accommodation(PRA&NRA), amplitude of convergence and divergence (PFV&NFV) were formed as control group. The same volunteers were asked to read a book for 30 minutes at a fixed illuminated room and a fixed position at a distance of 40 cm, and the measurements were repeated as a book reading group. In another session, the same volunteers were asked to watch a movie from a single phone under the same conditions for 30 minutes and the measurements were repeated and recorded as a telephone activity group. Book reading group, telephone group and control group results were compared with each other. Results: reading and smartphone near activities significantly decreased AK/A, AA for both right and left eyes and near PFV values (p <0.001, p <0.01, p <0.01 and p = 0.018) . There was no statistically significant difference between the two activities. The value of the NPC and severity of the exophoria were significantly increased with both activities (p <0.001). There was no statistically significant difference between the two activities. For NRA and the distance NFV values, no statistically significant difference was observed between the control group and the book reading activity, whereas after the smartphone activity NRA&NFV decreased significantly compared to the control group (p <0.001 and p = 0.011). Conclusions: Nowadays, near digital activity has replaced the conventional near activities like reading book. Smartphone near activity decreased NFV& NRA and 69 increased the severity of exophoria in our study. Considering that our study reflects a small part of the near activity of daily life in terms of smartphone use, we think that we should inform our patients about the possible adverse effects of smartphone usage, such as transforming phoria into manifest squint. Key words: Smartphone, Near Vision Complex, Fusional Vergence, Binocularity, Digital Eye Fatigue.