Why Does My Eye Sting So Much From the Betadine Prep Before an Injection?
The Iodine Prep and the Sting at a Glance
A stinging, gritty eye for a few hours is the usual story. A worsening eye is not. Call your eye doctor and ask for a same day slot if you notice any of these in the days after a shot:
- Severe eye pain, or pain that grows instead of easing.
- Loss of vision, or sight that keeps fading.
- An eye that is red and painful together.
- Thick discharge, or lids stuck shut in the morning.
- New floaters in a shower, or new flashing lights.
The label for these injections warns that an infection inside the eye (clinical: endophthalmitis) can follow a shot, and asks that you report such symptoms without delay.1 That is rare. A same day call is what keeps it small.
The sting is the antiseptic, not the needle. Pain after a topical iodine prep is often caused by the ocular surface being exposed to it, and that is felt most with the stronger 5 to 10 percent strengths.2 The solution is deliberately left in contact with the surface of your eye, not just dabbed on the skin around it. So a strong burning feeling is a common reaction rather than a sign of harm.
Betadine is a brand of povidone-iodine, an antiseptic used to clean skin and the surface of the eye before a procedure. The ophthalmic version is a 5 percent solution, and its label covers prepping the lids, brow and cheek and irrigating the surface of the eye, meaning the cornea, the conjunctiva and the pockets behind the lids.3 It is the brown liquid you see swabbed around your eye and dripped onto it before the injection.
This page explains why the prep stings, what the sting does and does not mean, and which comfort measures have been studied. It cannot tell you whether your own discomfort is normal, change your clinic's protocol, or decide whether a different antiseptic suits you. Those are conversations with the team giving your injections. Use the questions at the end to open them.
Why an Antiseptic Is Used Before Every Injection
The needle passes through the surface of the eye, so what is sitting on that surface matters. An expert panel reviewing ten years of injection literature emphasised the continued importance of applying povidone-iodine to the intended injection site and avoiding eyelid contact with the needle.4 The target is an infection inside the eye, which is uncommon but serious.
Not every step around an injection has survived scrutiny; this one has. The same expert panel found a lack of evidence for routinely giving antibiotic drops before, during or after the injection, while keeping the iodine prep in place.4 That is worth knowing if you have been told the drops matter more than the prep. The uncomfortable step is the one the evidence has kept, and the comfortable one is what fell away.
Knowing the size of the risk makes the trade easier to accept. A meta-analysis counted 197 infections inside the eye after 350,535 injections, about 6 in every 10,000.5 Those figures come from an era in which the prep was standard, so they describe the risk with the antiseptic already in place. That is the number the few minutes of stinging is set against.
How the Prep Is Applied at Your Appointment
Your clinic will have its own choreography, and the broad shape is consistent. The label describes saturating applicators for the lashes and lid margins, prepping the lids, brow and cheek in expanding circles, and then irrigating the surface of the eye itself.3 Numbing drops or gel are usually given around this sequence. Ask your clinic where in that order your anaesthetic goes, because the answer differs between units.
Contact time is the part most people feel. The label describes leaving the solution in contact for two minutes before it is flushed away.3 In practice, reported exposure times vary internationally from a minimum of about 30 seconds up to 3 minutes.2 If two minutes feels endless, saying so is reasonable. Your clinic can tell you what it uses and why.
The prep is not meant to be left sitting on your eye. After the two minutes of contact, the label calls for sterile saline in a bulb syringe to flush the residual solution from the cornea, the conjunctiva and the pockets behind the lids.3 A thorough flush is one of the few comfort steps written into the instructions themselves. It is a fair thing to ask about if your eye feels loaded with solution when you leave.
The Stinging and the Other Effects on the Eye Surface
The feeling is irritation of the surface tissue, not injury inside the eye. The label records that local sensitivity has been shown by some individuals to this solution.3 The stronger solutions are the ones most associated with surface pain.2 People often describe tearing, redness and a gritty feeling alongside the sting.
The anaesthetic numbs a small area for the needle, for a short window. The antiseptic, by contrast, is irrigated across the cornea, the conjunctiva and the pockets behind the lids, and left in contact for two minutes.3 That mismatch is why many people describe the injection as a brief pressure and the prep as the memorable part. It is not a sign that your anaesthetic failed, though it is worth telling your clinic if the numbing seems to be wearing off too early.
Repeat exposure has a measurable effect on the eye surface, and it is modest rather than dramatic. In 90 people having repeated injections, 11 of 90 injected eyes scored in the symptomatic range on a dry eye questionnaire against 4 of 90 untreated fellow eyes, and surface staining was slightly but significantly worse in the injected eye.6 A fellow-eye comparison like that is a fair way to separate the prep from ordinary ageing.
The lid margins are prepped too, and the oil glands sit in that margin. In 45 people having repeated injections compared with 28 people who were not, gland loss on both lids and dry eye symptom scores were higher in the injection group, and tear film stability was lower.7 That study could not separate the iodine from the antibiotic drops also used, so treat it as a reason to mention dry eye rather than as a verdict on the prep alone.
Who Should Not Have the Iodine Prep
There is one, and it is narrow. The label says not to use the solution in individuals known to be sensitive to iodine or to other components of the product.3 That means a documented reaction to this preparation or something in it, not a vague worry. If you have ever reacted to a brown antiseptic used on skin before surgery, that is exactly the history your injecting team needs to hear.
One precaution is worth raising if it applies to you. The label advises caution in patients with thyroid disorders because of the possibility of iodine absorption.3 A precaution is not a ban; it is a prompt for your doctor to think it through. Tell the team about thyroid disease, and about any thyroid scan or treatment involving iodine that you have coming up, so they can decide rather than assume.
This one causes a lot of unnecessary worry at check-in. A review of the topic states that no true allergy or anaphylaxis to iodine itself has been reported, that seafood allergy is not a specific risk factor for reactions to iodine-containing contrast agents, and that in the rare systemic reactions to povidone-iodine the reaction is directed at the povidone rather than the iodine.8 Still report the allergy. Let your team decide what it means for you.
Bring specifics rather than labels. Say what happened, to which product, how soon afterwards, and what was done about it. Mention any rash under a dressing, any reaction to a surgical skin prep, thyroid disease, and dry eye you already had before injections started. The one thing the label itself rules out is use in someone known to be sensitive to iodine or the product's other components.3
What Can Actually Be Done About the Sting
This is the first thing to ask about, because it is already in the instructions. The label calls for a sterile saline flush of the cornea, conjunctiva and lid pockets after the two-minute contact time.3 Clinics differ in how generously they do it. Ask whether yours can rinse more thoroughly, and follow your own unit's aftercare sheet on what you may put in the eye at home rather than improvising.
Going into an injection with an already dry surface makes the prep harder to tolerate. In one randomised trial, plugging the tear drainage did not reduce post-injection symptoms across the whole group; only a subgroup with moderate to severe symptoms plus objective signs of dry eye reported better comfort.9 A subgroup result in one trial is a lead to discuss, not proof. Ask whether your dry eye is being treated as its own problem.
Some units use a diluted solution with a longer contact time. In one hospital review of 7,360 injections, no infection occurred in the eyes prepped with the 2.5 percent solution and 3 occurred with the 5 percent solution, a difference that did not reach statistical significance; the authors also noted that patients switched from the weaker to the stronger solution reported more surface irritation, although the study did not formally measure that.2 That is a single centre looking backwards, so treat it as a question to raise, not a settled answer.
Chlorhexidine is the main alternative, and the comparison has now been pooled. Across five studies and 230,656 injections prepped with chlorhexidine, infection occurred about once in every 3,937 injections, close to the rate of about once in every 3,906 with the iodine prep, with no significant difference in relative risk; the authors describe chlorhexidine as an emerging alternative causing less ocular irritation.10 Whether your clinic stocks it is a practical question worth asking.
Risks, Trade-offs and a Realistic Outlook
The honest framing is a trade, not a wrong step you can simply remove. Infection inside the eye occurred after about 6 in every 10,000 injections in pooled data.5 Expert guidance emphasises keeping the iodine prep in the routine.4 That is why comfort is managed around the prep rather than by removing it, and why the useful conversation is about how it is done rather than whether it happens.
A gentler antiseptic changes the surface experience, not the rest of the visit. The needle, the pressure feeling, the floaters afterwards and the red patch on the white of the eye all belong to the injection itself. The alternative antiseptic performed similarly to the iodine prep for infection rates in pooled data.10 So the realistic gain is comfort, and that is still worth asking for over a long course.
Most people settle into the routine, and the measured surface effects build slowly rather than suddenly. In a fellow-eye comparison, the injected eye showed slightly worse dry eye symptoms and surface staining than the untreated eye.6 That is the pattern the studies describe: a drier surface over a long course. Raise it early rather than enduring it, because dry eye is treatable on its own terms.
When to Call Your Eye Team
Certain patterns should not wait for the next scheduled appointment. The injection label asks that symptoms suggesting an infection inside the eye or a detached retina be reported without delay, and notes that eye pressure can rise within 60 minutes of an injection.1 Worsening pain with falling vision is the combination clinics most want to hear about. Ringing and being reassured is the cheapest outcome available to you.
Stinging that fades over the hours after your visit is the usual account. If your eye is still raw days later, or if each injection leaves it sorer than the last, that is a reason to call rather than to wait. Repeated exposure is linked to more dry eye symptoms and more surface staining in the injected eye.6 A surface problem can be treated once someone looks at it.
Save the non-urgent items for the appointment and write them down beforehand. Useful ones include the strength and contact time your clinic uses, whether the rinse can be more thorough, whether a gentler antiseptic is stocked, and whether your dry eye needs treatment of its own. Reported contact times vary internationally from about 30 seconds to 3 minutes.2
Questions People Ask About the Betadine Prep
Because the two touch different things. The anaesthetic numbs a small area for the needle, while the antiseptic covers the whole front of the eye and is left there. Surface pain after a topical iodine prep is frequently caused by that exposure, especially with the stronger solutions.2 Many people find the needle itself is a second of pressure. If the ranking surprises you, it is a common experience rather than a sign something went wrong.
You can ask, and the answer will depend on your clinic's protocol. Reported exposure times range internationally from a minimum of about 30 seconds to 3 minutes, and one single-centre review found no significant difference in infection between the 2.5 percent and 5 percent strengths.2 That evidence is not strong enough to demand a change with, but it is enough to make the conversation reasonable rather than awkward.
Almost certainly not. Stinging is surface irritation, which nearly everyone feels to some degree. An allergic reaction looks different: a spreading rash, swelling, itching, or trouble breathing. A review of this topic states that no true allergy or anaphylaxis to iodine itself has been reported, and that in the rare systemic reactions to povidone-iodine the reaction is directed at the povidone.8 Report anything beyond stinging so your team can look at it properly.
The measured effects are on the surface and are modest. Injected eyes showed slightly worse dry eye symptoms and surface staining than untreated fellow eyes in one comparison of 90 patients.6 The label also states the solution is for external use only and is never injected into the eye.3 So the concern to raise is a drier, grittier eye over a long course, and that is treatable on its own.
Ask your own clinic first, because units differ on what may go into the eye and how soon. Lubricating drops are a common suggestion for surface dryness. The measure tested in a randomised trial here, plugging the tear drainage, did not help the group overall; the improvement seen in a subgroup was limited to people with moderate to severe symptoms plus objective signs of dry eye.9 That points to treating existing dry eye rather than adding a routine for everyone, so say if your eyes were dry before injections started.
More Questions About Alternatives, Aftercare and Sticking With Treatment
No, and availability is the practical limit rather than the evidence. A pooled analysis of five studies and 230,656 chlorhexidine-prepped injections found an infection rate close to that of the iodine prep, with no significant difference in relative risk, and described it as an emerging alternative with less ocular irritation.10 Some units have switched and some have not. Asking costs nothing and tells you where yours stands.
Follow your clinic's aftercare sheet rather than improvising, since rinsing at home can introduce exactly what the prep was there to remove. The flush that matters is the sterile saline one the label calls for at the end of the prep.3 If your eye still feels coated when you leave, say so before you go rather than working on it at home.
Because the risk being managed is small at every single visit and adds up across a course. In a pooled analysis of 43 published reports, infection inside the eye followed 197 of 350,535 injections, about 6 in every 10,000.5 Expert guidance keeps the iodine step while dropping routine antibiotic drops.4 A run of comfortable visits is the expected pattern, not evidence that the step is unnecessary.
Say that out loud to your retina team, because it is a treatable problem rather than something you have to put up with. There are real options to discuss: a more thorough rinse, treating existing dry eye, a different concentration, or a different antiseptic where it is stocked. The alternative antiseptic showed a similar infection rate to the iodine prep in pooled data.10 Skipping treatment is a much bigger decision than changing a prep, so raise the prep instead of dropping the appointment.
Take these to your next appointment and write the answers down.
- What strength of the iodine prep does this clinic use, and for how long?
- Can the saline rinse at the end be more thorough for me?
- Where in the sequence does my numbing drop or gel go?
- Do you stock a gentler antiseptic, and would I be suitable for it?
- Is my dry eye being treated as a problem in its own right?
- What reaction history would make you change my prep?
- Who do I call after hours if the eye becomes painful or my vision drops?
- US Food and Drug Administration prescribing information via DailyMed (2024). EYLEA (aflibercept) injection prescribing information, revised 10/2024.
- Journal of Ophthalmology (Ajlan et al.) (2025). Topical Povidone Iodine 2.5% Versus 5% for Endophthalmitis Prophylaxis During Intravitreal Injections.
- US Food and Drug Administration prescribing information via DailyMed (2022). BETADINE 5% Sterile Ophthalmic Prep Solution (povidone-iodine ophthalmic solution) prescribing information.
- Retina (PMID 25489719) (2014). Intravitreal injection technique and monitoring: updated guidelines of an expert panel.
- Ophthalmic Surgery, Lasers & Imaging Retina (PMID 24635156) (2014). Meta-analysis of infectious endophthalmitis after intravitreal injection of anti-vascular endothelial growth factor agents.
- Cutaneous and Ocular Toxicology (PMID 28166657) (2017). Ocular surface effects of repeated application of povidone iodine in patients receiving frequent intravitreal injections.
- Eye & Contact Lens (PMID 34570021) (2021). Effect of repeated topical povidone-iodine and antibiotic applications on meibomian glands and ocular surface parameters in patients with repeated intravitreal injections.
- Australian Prescriber (Katelaris CH, Smith WB), 2009;32:125-8 (2009). 'Iodine allergy' label is misleading.
- Eye (London) (PMID 33746207) (2022). The effect of punctal plugs in reducing ocular surface irritation after povidone-iodine preparation of intravitreal injection: a randomized trial.
- Survey of Ophthalmology (PMID 39922542) (2025). Chlorhexidine for ocular antisepsis before intravitreal injection: a systematic review and meta-analysis.