JMIR Publications

ABSTRACT

Background:

Pars plana vitrectomy (PPV) with intravitreous tamponade of gas/air has been widely used by vitreoretinal surgeons to achieve anatomic success after surgery for a large series of vitreoretinal diseases. It is roughly estimated that one hundred thousand patients per year undergo PPV all over the world, and about 60% of them were subsequently tamponaded with gas/air. According to Boyle’s Law (P1V1=P2V2), patients with intravitreous remnant of gas/air will be under high risk of intraocular pressure (IOP) elevation and subsequent vision loss due to the expanded intravitreous gas/air, when have postoperative travelling to another place with significantly higher altitude. In our clinical work, we always explain to patients why postoperative travel is potentially risky. Emergency of elevated IOP caused by postoperative travelling would sometimes occur to the surgeons, which was anecdotally reported. However, there has been few disease education or reference tool for both the surgeons and patients to have better communication. It is difficult and complex to have a preliminary risk estimation when postoperative traveling to another place of higher altitude is planned.

Objective:

To introduce and evaluate a smartphone app developed by the surgeons (the authors) for preliminary risk estimation of volume expansion and IOP elevation in patients with intravitreous gas/air when travel to another place of higher altitude.

Methods:

The app was developed under iOS and Android operating systems. Boyle’s Law (P1V1=P2V2) was the theoretical basis of the app. Intravitreous gas/air volume and altitude values acted as independent factors to deduce the risk report. Consecutive patients underwent vitrectomy and with intravitreous remnant of gas/air were recruited. The surgeons judged the vertical height of fluid/gas interface through the dilated pupil; the patients were instructed to judge it according to his/her visual field when looking straight ahead and line it out on a chart included in the app. Finally, all the patients were required to fill in a Likert scale with two main items, in order to evaluate the participants’ using experience and attitudes towards the app.

Results:

Fifty patients were included (male/female=30/20). All patients could independently operate the app to complete the test. The median heights of the fluid/gas interface independently judged by the surgeon and patients were 40% (range, 10–75%) and 41% (range, 9–78%), respectively (P = .63). The median altitude of the participants’ destinations was 150.0 m (range, 0–3490 m). The Bland-Altman analysis revealed good agreement between the surgeons’ and patients’ judgements (bias of −0.3%), with 95% limits of agreement, of −5.8% to 5.3%. The Likert scale revealed a generally positive attitude from the patients towards the app.

Conclusions:

The app is reliable for patients to have preliminary risk estimation of intravitreous gas/air volume expansion and IOP elevation if traveling to another place of higher altitude is planned. The surgeons could also use it as a platform for better disease communication.