Salivary flow rate, pH, viscosity, and buffering capacity in visually impaired children

The global prevalence of visually impaired children has increased. A limitation or absence of light affects neural stimulation and disturbs circadian rhythms. When the dark phase is longer than the light phase, this limits motor responses, including those of the salivary glands. The aim of this study was to compare salivary flow rate, pH, viscosity, and buffering capacity between visually impaired and visually healthy children. This study was performed on 35 visually impaired children, 7-11 years old, and 35 visually healthy children, 7-12 years old. All participants provided unstimulated saliva and stimulated saliva for 5 minutes in the morning by a spitting method for measurement of salivary flow rate and pH. Salivary viscosity was rated visually at the base of the mouth. Salivary pH and buffering capacity were measured electrometrically using a handheld pH meter. Salivary buffering capacity was measured by titration of stimulated saliva with 0.005 N HCl, and the flow rate was expressed as mL saliva produced/5 min. The stimulated salivary flow rate and buffering capacity were significantly lower in the visually impaired children than in the visually healthy children. Unstimulated salivary flow rate and pH showed no statistically significant differences, but were slightly lower in visually impaired children. Salivary viscosity was not significantly different between the two groups. Visual acuity affects the composition of saliva secretions. Salivary flow rate, pH, and buffering capacity are lower in visually impaired children than in visually healthy children.