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"We give guidance for maximum bolus volumes in key high-risk areas, derived from anatomical and imaging studies."
Injecting dermal fillers in all facial areas carries a risk of intravascular injection and retrograde flow of filler into the ophthalmic artery (OA) and central retinal artery (CRA), potentially causing retinal ischemia leading to visual loss. Cadaveric and radiologic studies have measured the volume of arteries from various facial injection sites to the ocular circulation.
Based on these findings, practitioners should limit the filler volume per bolus (in a single injection or retrograde thread) to well below the capacity of the connecting vessels. This applies to all soft tissue filler materials (hyaluronic acid and others), since the critical volume for occlusion is a mechanical issue of volume in the artery, not the filler type. In a consensus paper that focuses on the prevention of blindness, a maximum bolus amount of 0,1 ml anywhere in the face was advised . However, in several high- and very high-risk anatomic areas of the face, this recommendation is not conservative enough.
Here, we give guidance for maximum bolus volumes in key high-risk areas, derived from anatomical and imaging studies.
The forehead and eyebrow region is supplied by the supratrochlear and supraorbital arteries, which connect to the ophthalmic artery. Studies show these arteries fill with very small volumes. In one study, the mean volume from the forehead area (supratrochlear/ supraorbital) to the ophthalmic circulation was only about 0.04 mL (40 µL) [Woodward et al, 2017].
This means even 0.04 mL of filler entering one of these vessels could reach and block the OA/CRA, causing blindness. Therefore, injections in the forehead or lateral brow should be done with microboluses – on the order of 0.01–0.03 mL per injection, injected slowly while withdrawing the needle or cannula (retrograde technique). Keeping each bolus well below the threshold of 0.03 ml is critical.
For practical reasons, as often the smallest markings on a syringe are at 0.05 ml, we advise using a maximum 0f 0.025 ml per retrograde linear thread or per bolus, which means that every marking on the syringe means two retrograde linear threads or two boluses. By using such tiny aliquots and avoiding high pressure, the goal is to stay far under the vessel’s volume capacity and minimize accidental intravascular injection risk.
The glabella (between the eyebrows, above the nose) is a notorious high-risk zone for ocular complications. The supratrochlear arteries run through this region toward the eye. Research by Woodward et al. measured the volume of a supratrochlear artery from the glabella to the orbital apex, finding an average capacity of ~0.085 mL (85 µL), with a range of 0.04–0.12 mL. A filler bolus with those volumes in the glabellar area could theoretically fill the artery to the eye.
Thus, experts advise using extremely small boluses in the glabella at a time in this area [Woodward et al, 2017].
This is corroborated by other studies showing ~0.04 0.05 mL can block the ophthalmic circulation via glabellar arteries [Kyo-Ho et al, 2023]. In practice, this means multiple tiny injections rather than one large bolus, using minimal pressure. By limiting each deposit to a fraction of the artery’s volume, the injector reduces the chance that an inadvertent intravascular injection would have sufficient volume to reach the retina. Therefore, we advise being conservative and limiting bolus volume to 0.025 per injection in the glabella.
Nonsurgical rhinoplasty (filler in the nose) carries one of the highest risks of filler-induced blindness. The dorsal nasal artery (a branch of the ophthalmic via the angular artery) runs along the nose and can carry filler to the eye. Cadaver injections have shown that the dorsal nasal artery holds only about 0.03–0.04 mL from the nose to the ophthalmic artery. In fact, recent case reviews found that the nose is now the most common site associated with filler blindness (more so than glabella).
For this reason, extreme caution and very small volumes are recommended in nasal injections. Practically, injectors should limit each bolus to ≈0.02 0.03 mL in the dorsum or sidewall of the nose [Kyo-Ho et al, 2023]. Using microdroplet technique (multiple tiny injections) and possibly cannulas can help avoid injecting a large volume into any single arterial location. Even this small amount, if accidentally intra-arterial, is enough to occlude the retinal circulation, so the emphasis is on meticulous technique (slow injection, low pressure, frequent needle repositioning) to prevent intravascular entry at all.
Therefore, especially in the upper nasal area, we advise limiting the amount of filler to a maximum of 0.02 per bolus or retrograde linear thread. Ideally, backfilled insulin syringes are used so that micro boluses of 0.01 mL can precisely be injected.
The temple is supplied by branches of the superficial temporal artery (from the external carotid artery) which connects to the supraorbital artery. There are anastomoses linking the deep temporal arteries to the ophthalmic circulation. Cases of blindness from temple filler are rare but have been reported. A 2025 radiologic study by Sheth et al. identified four potential arterial pathways by which filler in the deep temple area could reach the ophthalmic artery. These pathways are longer and more circuitous than those in the glabella or nose, meaning a larger volume might be required to cause an ocular occlusion.
This lower likelihood does not mean injectors can use big boluses – it simply means the risk, while lower, is still present. Standard guidance for temple augmentation is to inject in a deep, supraperiosteal plane, and to use small aliquots (e.g. 0.05 mL per depot at most) with a needle, or either in the subcutaneous or interfascial plane with a cannula. In light of the anastomoses, it is prudent to stay at or below 0.05 mL per bolus in the temple. Using incremental threading injections rather than a single large bolus will reduce the chance that enough filler could find its way through the collateral route to the OA.
Filler in the tear trough (under-eye hollows) or palpebromalar groove lies in the periorbital region where vessels connect to the ophthalmic artery. The infraorbital artery (branch of the maxillary) and the angular artery (terminal branch of the facial) are of concern here, as they form connections to the ophthalmic system (via the dorsal nasal and ophthalmic arteries). While specific volume measurements for these paths are not always given, we can infer risk from adjacent vessels: for example, the angular/dorsal nasal route holds on the order of 0.03–0.04 mL to reach the eye.
Therefore, injections under the eye should follow a “less is more” principle. Use the smallest effective boluses, roughly 0.02–0.05 mL at a time, in the tear trough region. Often a cannula is used here to stay superficial to the orbital septum and reduce arterial injury. As with other areas, injecting slowly while withdrawing, and staying in the correct tissue plane, is crucial. By limiting each deposit to a tiny volume, the injector adds a safety margin below the critical volume that could occlude ocular vessels.
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