Influence of spectral distribution on accommodation—vergence and reading performance

Shiva Ram Male, Rishi Bhardwaj, Chiranjib Majumder


Background: To assess the influence of different spectral energy distribution on accommodation, vergence and reading performance.
Methods: A Randomized experimental study was conducted after getting the approval of the Ethical Committee of University of Hyderabad. Forty participants with an age group of 18–21 years was integrated, out of which 50% was male and 50% was female. Subjects with emmetropia and no history of ocular pathology were included in the study. Near point of accommodation (NPA) & near point of convergence (NPC) was measured with the help of royal air force (RAF) ruler followed by near visual task of a readability passage.
Results: A statistically significant result was obtained when reading rate, reading speed and NPC was compared among different spectral distribution of light (P<0.001) except NPA (P=0.43). Post hoc analysis showed a significant difference (P<0.001) when tungsten was compared with fluorescent light (FLOU), compact fluorescent light (CFL), and light emitting diode (LED) for reading rate, reading speed and NPC. But there is no noteworthy difference exist when fluorescent was compared with CFL for reading rate (P=0.530) & reading speed (P=0.595). Similarly, LED also showed no considerable difference when compared with CFL (P=0.682) and fluorescent (P=0.490) for NPC. When NPA was assessed within the group LED showed insignificant difference with CFL (P=0.205) and fluorescent (P=0.275) similar like fluorescent and tungsten (P=0.482).
Conclusions: This study concluded that reading performance (reading rate and reading speed) and NPC has a significance change if we use inappropriate lighting during visual tasks. It will cause visual fatigue and strain after sustained near work. In addition, tungsten spectral energy influences the convergence which can also show an impact on reading and near visual tasks because of its brightness and miosis. Prolonged reading and working under this lighting can cause convergence disorders and visual fatigue.