Viewing distance and character size in the use of smartphone in presbyopic and non-presbyopic individuals.

Grasso P.A., Gurioli M., Boccardo L.
  Giovedì 15/09   10:00 - 12:30   Aula I   VI - Fisica applicata, acceleratori e beni culturali   Presentazione
The use of handheld devices has seen a tremendous growth in recent years to the point that users spend four hours a day looking at their smartphone. It is then become increasingly relevant to identify visual habits in using smartphones across the lifespan. In the present observational study, we measured viewing distance and character size in a group of non-presbyopic (NP; $n = 157$) and presbyopic (P; $n = 60$) while participants read a simple text message. We found that NP individuals use shorter viewing distance ({33.4 ${cm}$) as compared to P ({39.6 ${cm}$) which results in a statistically significant higher accommodative demand (NP: $3.16 {D}$; P: $2.6 {D}$). Also, the average character size differed between NP ({1.6 ${mm}$) and P ({1.83 ${mm}$) but did not the corresponding angular size (NP: $0.53 {LogMar}$; P: $0.5 {LogMar}$). Our data reveal that NP and P individuals have different visual habits when using a digital device. While NP reach the desired reading acuity by reducing viewing distance, P increase character size. The increased accommodative demand in the NP group may potentially induce a larger lag of accommodation and greater fatigue which should be considered when determining the best near correction.