Bell's palsy and the eye: what to do when the eyelid will not close

Bell's palsy announces itself in the mirror before it announces itself anywhere else. One side of the face stops moving the way it used to, the corner of the mouth drops, and the eyelid on that side no longer shuts all the way. That last part, the eye that will not close, is the piece I get involved in, because an eye that stays partly open around the clock is an eye that dries out and can scar.

What is Bell's palsy, and why does it stop the eyelid closing?

Bell's palsy is a sudden weakness of one side of the face caused by a problem with the seventh cranial nerve, the facial nerve, which is the single nerve that drives every muscle you use to smile, frown and blink. It is the most common cause of facial weakness of this kind, and the leading evidence points to a herpes virus reactivating and inflaming the nerve as it passes through a narrow bony canal near the ear. The orbicularis oculi, the ring of muscle that closes the eyelid, is one of the muscles that nerve controls, so when the nerve stops firing properly, that muscle stops closing the lid fully. The medical name for an eyelid that will not close all the way is lagophthalmos, from Greek words meaning hare's eye, because hares are thought to sleep with their eyes open.

Why does the eye need special attention if the face will probably recover?

Most Bell's palsy does improve with time, and I am not the doctor who manages the facial weakness itself. My concern is narrower and more urgent: the cornea, the clear dome at the front of the eye, is designed to stay wet and covered. Every blink spreads a fresh film of tears across it and clears away anything sitting on the surface. Take that mechanism away and the surface starts to dry, particularly along the lower third where evaporation is greatest. Left alone, dryness progresses from a gritty ache to fine pinpoint erosions of the surface layer, then to a genuine defect where a patch of surface cells is missing altogether, and a defect that stays open is vulnerable to infection. Exposure keratopathy, damage from prolonged surface exposure, is a real and vision-threatening complication of Bell's palsy, not a rare footnote, and it can progress while the facial weakness itself is still recovering.

Why is the eye often worse overnight, when I am not even aware of it?

Daytime lagophthalmos is at least something you can notice and manage as it happens. Sleep is the harder problem, because the lid gapes open for hours with nobody watching, and the surface dries in the still air of the bedroom without any blink to interrupt it. People with this pattern wake with a gritty, burning, watering eye that seems to calm down through the day, purely because they are finally blinking and lubricating again. There is also a natural safety mechanism most people rely on without knowing it exists: Bell's phenomenon, the reflex that rolls the eyeball upward and out of view as the lid begins to close, so that even an imperfectly shutting lid still tucks the cornea up behind it. In some people this reflex is weak or absent, and when it is, the same millimetre of lagophthalmos carries noticeably more risk, which is one reason I do not judge severity from the gap alone.

What actually protects the eye while the nerve recovers?

The mainstay is unglamorous and needs doing consistently rather than cleverly. Preservative-free artificial tears through the day keep the surface wet between blinks, and a thicker lubricating ointment at bedtime holds that protection over the many unblinking hours of sleep. At night, taping the eyelid closed, or using a moisture chamber that seals a humid pocket of air over the eye, buys the surface real protection while you are not there to manage it consciously. None of this is specific to Bell's palsy. It is the same lubrication ladder I use for other causes of an eye that will not close properly, including the lid retraction of thyroid eye disease, where the cornea is exposed by a completely different mechanism but needs the same basic protection while the underlying cause is addressed.

When does lubrication stop being enough, and what comes after it?

Drops and tape are a holding strategy, not a cure, and they are meant to buy time while the nerve has a chance to recover on its own, which most facial nerve palsies of this kind do over weeks to months. If the exposure is severe, if the cornea is already showing damage, or if recovery is clearly taking longer than expected, there are further options that add mechanical closure rather than more lubricant. A small weight, gold or platinum, can be implanted in the upper lid so that gravity helps the lid fall closed with each blink attempt, a discreet and often reversible step. A temporary tarsorrhaphy, where a portion of the upper and lower lid margins is stitched together, narrows the opening the tears have to protect and can be undone once the nerve recovers. These interventions are generally reserved for longstanding or severe cases rather than offered to every new diagnosis, and deciding between them is an assessment I make in person, checking corneal sensation, tear film and the strength of that protective Bell's phenomenon reflex together rather than from the size of the gap alone.

Can the same facial nerve weakness cause other eyelid problems, not just a lid that will not close?

Yes, and it is worth knowing the pattern because it looks like the opposite problem. A weak orbicularis muscle no longer holds the lower lid snugly against the eyeball, so over time the lower lid can sag outward and turn away from the eye, a condition called ectropion, which I treat as its own distinct problem when facial nerve weakness is the cause. So a single episode of facial palsy can leave you managing exposure from a lid that will not close and, separately, a lower lid that has drifted outward, and the two are often addressed together once it is clear how much the nerve is going to recover on its own.

When should I actually be seen, rather than just trying artificial tears at home?

New facial weakness on one side deserves prompt medical assessment on its own, partly to confirm it truly is Bell's palsy and not a stroke or another cause of facial nerve damage, which is assessed by how the weakness is distributed and by other findings a doctor checks for. From the eye side specifically, I want to see anyone whose eye is not fully closing within the first few days, because the earlier the lubrication routine starts, the less chance the surface has to be damaged before it is protected. For a fuller look at how I assess an eyelid that will not close for other reasons and what a full oculoplastic work-up covers, my eyelid conditions page sets out the wider picture, and the general principles of protecting a cornea under threat are the same ones I apply across the whole range of eyelid problems that change how the eye looks and functions. There is no fixed timeline for recovery, and I would rather say that plainly than offer a number that does not hold for everyone. Many people with Bell's palsy do regain most or all facial movement over weeks to a few months, and as the orbicularis regains strength, the eyelid gradually closes further with each blink until the lubrication routine can be relaxed. Others recover more slowly or incompletely, and the eye protection regimen simply continues for as long as the gap does. What I track at each review is not a calendar date but three practical measures: how far the lid actually closes on gentle attempted blink, whether Bell's phenomenon is rolling the eye up to help cover the cornea, and what the surface looks like under the microscope with a dye that stains any dry or damaged patch. Those three findings, taken together, tell me whether the current routine of drops, ointment and taping is holding the situation steady or whether it is time to talk about a weight or a temporary tarsorrhaphy instead of waiting longer. The same staged thinking, protect first, reassess on the tissue rather than the calendar, only add surgery once conservative measures are clearly not enough, is one I also use once someone is past the acute period and now managing a dry, gritty eye as a longer term issue, which overlaps with what I cover in dry eye that persists once an eyelid problem has otherwise settled.