Anyanee Norranitchaiyakul, MD¹

Background: Intravitreal injection is the most commonly performed procedure in outpatient retina clinics. However, the optimal injection site for intravitreal injection has not been determined.

Objective: To identify the least painful intravitreal injection site.

Materials and Methods: Prospective, randomized, six-armed clinical trial. One hundred ninety-two patients who were treated with intravitreal injection were randomized into 6 groups according to the injection site: superonasal (SN), superior (S), superotemporal (ST ), inferotemporal (IT), inferior (I), and inferonasal (IN). The pain score (visual analog scale), anxiety score (visual analog scale), visual experience during injection, and baseline demographic data were recorded.

Results: The overall median (interquartile range, IQR) pain score across all groups was 2 (2). By injection site, the median pain scores were SN 3 (3), S 2 (2), ST 2 (2), IT 2 (2), I 2 (2), and IN 1 (2). The lowest pain scores were observed in the IN group, whereas the highest were in the SN group. Statistically significant differences were observed between the IN and S sites (p=0.021) and between the IN and SN sites (p<0.001), at a significance level of 0.05. Further analysis comparing the upper and lower halves of the eye showed significantly higher pain scores in the upper half (p<0.001). Pain scores were positively correlated with anxiety scores, with a low correlation observed (Spearman’s rank correlation coefficient of 0.399, p<0.01). The three most common visual experiences during injection were water flow (47.6%), bright light (32.5%), and shadow of the needle object (12.6%).

Conclusion: The site of injection that gave the minimum pain score and anxiety score was IN. The pain and anxiety scores seem to be less when the injection was performed in the inferior half of the eye.

Received 28 January 2025 | Revised 10 April 2026 | Accepted 24 April 2026

J Med Assoc Thai 2026;109(8):639-46

DOI: 10.35755/jmedassocthai.2026.8.02130