Ningxia University

Chinese children are some of the most short-sighted in the world, but only one in five children in poor areas who needs glasses has them. Our team has already shown in other trials that giving children free glasses leads to better grades and that free glasses have a bigger impact on grades than factors like parents' education level and the amount of money a family has. The effect on grades from glasses is greater than from other health services in school, like giving vitamins. Only about one in three children in rural China goes on to a regular, non-vocational high school. The investigators would like to show the Chinese government strong evidence of what glasses can do to help children continue their education, in order to help convince the government to carry out national programs to provide free glasses for children who need them.
Study Plan: The investigators will choose 111 middle schools at random in Liaoning, northern China, and all children in Year 1 at each school will go at random into one of two groups: either a group getting free glasses, with support from teachers to push them to wear the glasses ("Intervention") or a group getting just glasses prescriptions ("Control.") The main study outcome will be the proportion of children going on to academic (as opposed to vocational) high school, and the study is powered to detect a 10% difference in this figure between groups.The study will also assess whether children wear their glasses at school and how often they use blackboards (which disadvantage short-sighted children) vs textbooks to learn from. These other outcomes will help us to better understand the causal pathway between vision and high school attendance. We will also study the total cost of providing glasses and the teacher support to wear them per additional student attending academic high school, as well as student mental health outcomes. We will also collect data on the progression of nearsightedness. The hypothesis of this study is that providing glasses will increase academic high school attendance.

The goal of this multicenter cross-sectional study is to investigate the prevalence of peri-implantitis in China. The main questions it aims to answer are:
What is the prevalence of peri-implantitis in China
What are the risk indicators of peri-implantitis in China
Participants will be invited to a free-of-charge clinical and radiographic examination of conventional dental implants present for over 5 years.