AIM: To compare intraocular pressure (IOP) measured via the trans palpebral IOP (tpIOP) method using a Diaton or with a Goldman applanation tonometer (GAT) and study the determinants of IOP difference in eyes undergoing transepithelial photorefractive keratectomy (TPRK) for myopia. METHODS: This cross-sectional validation study was held in 2020 in an eye hospital in Saudi Arabia. IOP was measured by Diaton and GAT before treatment, after one week, and one month of TPRK. It is considered if IOP difference by Diaton and GAT was less than ±2 mm Hg acceptable. The IOP difference was tested if correlated to spherical equivalent (SE), central corneal thickness (CCT), age, gender, or tpIOP. RESULTS: Totolly 200 myopic eyes of 100 patients were included in the study. The mean difference of IOP measured by two methods before TPRK, 1wk, and 1mo after TPRK were 0.790, -0.790, and -0.920 mm Hg, respectively (P<0.001). Diaton could measure IOP effectively 89.5% eyes before TPRK and 82% and 84% at 1wk and 1mo after TPTK, respectively. At week 1, IOP differences were significantly correlated to baseline CCT (P=0.02) and tpIOP at week 1 (P<0.001). One month after TPRK, only tpIOP was significantly correlated to the difference in IOP (P<0.001). CONCLUSION: Diaton is a good screening tool for IOP before TPRK. It helps in monitoring IOP after surgery. Although more practical, it is less efficient than GAT. In eyes with high myopia and low tpIOP before surgery, IOP post-TPRK by Diaton and GAT could differ.