The essential factors of the app include the following: the mechanics and kinetics of intravitreous gas or air tamponading after PPV; the semirigid property of the eyeball; Boyles law (pressure × volume=constant); the relationship between atmospheric pressure and altitude; and the ratio of the expanded volume of intravitreous gas or air to that of the anterior chamber. As proposed by Lincoff and Aronowitz, the eyeball has 3 compensation mechanisms to accommodate the expansion of intravitreous gas or air: choroidal compression, scleral expansion, and accelerated aqueous outflow. These mechanisms are significant for us to have an in-depth understanding of elevated IOP induced by decreases in atmospheric pressure.
Unlike previously reported mathematical models, we developed our app based on the assumption that the patient with intravitreous gas or air would be travelling immediately from one place to another. Therefore, the abovementioned compensation mechanisms were not incorporated into the app design. Another reason for developing this app was to provide a readily available electronic tool for both surgeons and patients to calculate a preliminary estimation of the risk. Therefore, it was decided to develop the app based on a simplified and feasible principle. We contributed our best efforts to making the app suitable for both surgeons and patients to achieve more friendly interactions and higher interobserver agreement.