Subjective Visual Floaters after Intravitreal Injection and Effect of the Inverse Tapping Technique

Purpose: To analyze the incidence of vitreous floaters after intravitreal antivascular endothelial growth factor injection and the effectiveness of the inverse tapping technique, which involves tapping the syringe with the needle downwards to prevent the entry of air bubbles during injection.Methods: The study enrolled patients undergoing their first intravitreal injection for exudative age-related macular degeneration or diabetic macular edema. The patients were divided into two groups: those who received an injection after inverse tapping (IT group) and controls who received the injection without tapping. Patients who consented to the study were randomly assigned to the IT group and the control group through block randomization. One week after injection, a questionnaire was used to assess the presence of vitreous floaters; those who reported them were examined via optical coherence tomography and wide fundus photography.Results: Of the 39 patients in the IT group, two (5.1%) reported floaters 1 week after injection. By contrast, eight (20.5%) of the 39 controls reported them, with a significant difference (p = 0.042). Patients with floaters were significantly younger. Posterior vitreous detachment, as evaluated by pre-injection optical coherence tomography, was observed in 10.0% of those with floaters and 76.5% of those without them.Conclusions: The occurrence of vitreous floaters after intravitreal injection is related to age and the presence of posterior vitreous detachment. The use of the inverse tapping technique may help reduce these after intravitreal injection.