Intravitreal injections are frequently administered to patients with wet macular degeneration, retinal vein occlusion or diabetic eye disease. During the injection procedure, povidone-iodine drops are used to disinfect the ocular surface, which reduces the risk of post-injection infection in the eye (endophthalmitis – which is very rare but can cause significant visual loss if it occurs). Many patients experience mild discomfort following the injection which usually lasts less than one day; this is due to the irritant effect of iodine rather than allergy.
True allergy to topical povidone-iodine is very rare, and this study analysed records of over 60,000 injections. Patients in whom iodine was avoided on account of a purported iodine allergy unfortunately experienced a much higher rate of post-injection infection. The study was not able to perform a direct comparison of infection rates due to its design, but some 12% of those with infections had not received the iodine preparation, which is likely to be far higher than the proportion of total injections performed without iodine preparation.
It remains the case therefore that despite the frequent irritation it causes, povidone-iodine remains the recommended preparation agent during intravitreal injection therapy.