INTRODUCTION: The present study aimed to evaluate the effect of estimated individual vitreous volume (VV) on intraocular pressure (IOP) spikes after intravitreal anti-vascular endothelial growth factor injections (IVIs). METHODS: VVs of eyes were calculated using an axial length (AL)-based formula AL3 × (π/6) × 0.76 + 0.012 × (AL - 24), and study eyes were divided into four groups according to their VVs
<
4.5 cm3 (Group 1, n = 52), 4.5-5.0 cm3 (Group 2, n = 60), 5.0-5.50 cm3 (Group 3, n = 60), and >
5.50 cm3 (Group 4, n = 35). IOP measurements were taken Pre-IVI, immediately after (Post-IVI-0), 5 min (Post-IVI-5), 15 min (Post-IVI-15), and 30 min after the IVI. RESULTS: A significant IOP change was found between the five-time points in all groups (p <
0.001 for all). Regarding the same time point measurement comparison between the groups, only a statistically significant change was found in the Post-IVI-0 point (p = 0.001). In a post hoc analysis, Group 1, Group 2, and Group 3 had significantly higher IOP values when compared to Group 4 (p <
0.05 for all). Patients treated with prefilled ranibizumab syringes exhibited lower IOP increases than vial-prepared aflibercept injection at the Post-IVI-0 time point (p = 0.042). CONCLUSIONS: A similar increase in IOP was observed in eyes with low and intermediate volumes, but the increase was less pronounced in those with high volumes after the IVI. Prefilled syringe form showed a lower IOP increase tendency in comparison with vial-prepared forms of the molecules.