Bell’s phenomenon is a corneal protective reflex in which the eyeball deviates upward and outward during forced eyelid closure. Inverse Bell’s phenomenon refers to a paradoxical deviation of the eyeball downward and inward during eyelid closure (reflexive globe hypotonia).
Gupta et al. (1965) reported the prevalence of inverse Bell’s phenomenon in the normal population as 2% 1). Bell’s phenomenon varies within the population; about 10% of normal individuals show some deviation from the standard Bell’s phenomenon, and about 8% have a congenital downward response. It is seen across a wide age range from children to adults, with the youngest recorded case being a 6-year-old who underwent levator resection for congenital ptosis.
About 8% of the normal population has a congenital inverse Bell’s phenomenon (downward response during eyelid closure). When limited to postoperative inverse Bell’s phenomenon, the prevalence is about 2% 1). It can also occur after ptosis surgery or in association with various ocular diseases.
Bell’s phenomenon itself has few specific subjective symptoms. Possible associated symptoms include the following:
The main findings confirmed by the physician are as follows.
In late-onset cases after trauma, reverse Bell phenomenon with central peaking of the upper eyelid has been reported 6 months after injury 1).
Blepharoptosis repair (levator palpebrae superioris shortening) is the most common cause, accounting for the majority of reported cases 1). Other causes involve various diseases and conditions.
Postoperative / Iatrogenic
Levator palpebrae superioris shortening: Most common cause. It occurs frequently after congenital ptosis surgery, reoperation for residual ptosis, and repeated surgeries.
Frontalis suspension: Also reported after frontalis sling surgery.
Postoperative monocular elevation deficiency and hypotropia: Can occur after eye muscle surgery.
Systemic and Ocular Local Diseases
Peripheral facial nerve palsy: May be accompanied by lagophthalmos due to eyelid closure dysfunction. Ectropion of the lower eyelid is common.
Tabes dorsalis: Reported as a case associated with systemic neurological disease.
Thyroid eye disease: Can occur with orbital inflammation and proptosis.
Conjunctival scarring and cicatricial entropion of the eyelid: Involves changes in eyelid morphology.
Salzmann nodular corneal degeneration: May be observed when there are superior nodules.
The overall prevalence of postoperative reverse Bell phenomenon is 2% (reported in 1965)1). The risk increases with greater shortening of the levator palpebrae superioris muscle; in cases of massive shortening of 18–28 mm, reverse Bell phenomenon occurred in 2 of 32 patients (approximately 6%)1). About 17% of patients with reverse Bell phenomenon have concurrent ocular surface abnormalities such as inferior keratitis, decreased tear production, and conjunctivochalasis.
Levator palpebrae superioris shortening surgery involves manipulation of the soft tissues around the superior rectus muscle during the procedure. Postoperative tissue edema and inflammation are thought to cause transient dysfunction of the superior rectus muscle, leading to reverse Bell phenomenon. It often resolves spontaneously as edema and inflammation subside.
The diagnosis of reverse Bell phenomenon is usually clinical.
Examination technique: The examiner lifts the patient’s upper eyelid with a finger while instructing them to close their eyes, and observes whether the eyeball rotates downward. It is also confirmed that gaze movements in all directions are normal.
Importance of preoperative evaluation: Assessing whether a reverse Bell phenomenon existed before surgery is essential for differentiating it from postoperative complications. Obtain a detailed history of the patient’s past surgeries.
The presence or absence of Bell’s phenomenon is used to differentiate supranuclear monocular elevation deficit (where Bell’s phenomenon is present) from peripheral disorders. When the inferior oblique (IO) and superior rectus (SR) fibers running along the lateral side of the peripheral oculomotor nerve are selectively damaged, Bell’s phenomenon on the affected side is absent.
Differential diagnosis: Differentiate from progressive external ophthalmoplegia, oculomotor nerve palsy, etc.
MRI examination is recommended if the following criteria are met.
| Indication criteria | Details |
|---|---|
| Age | Under 50 years |
| History | History of malignant tumor |
| Neurological findings | Complication of cranial nerve III, IV, VI palsy |
| Fundus findings | Optic disc edema |
| Course | No significant improvement after 3 months |
Other tests such as electrodiagnostic testing to determine the level of oculomotor nerve damage and electronystagmography may also be considered.
There is no established treatment or medication for the inverse Bell phenomenon.
Spontaneous resolution is the typical course, and in the majority of postoperative cases, it disappears naturally within days to months. All 10 previously reported cases recovered to a normal Bell phenomenon within 1 to 4 weeks1). Spontaneous resolution at 3 weeks postoperatively has been shown to correlate with a decrease in tissue edema and inflammation.
Symptomatic treatment until resolution is as follows:
Below are the recovery periods for previously reported postoperative cases.
| Literature | Surgical procedure | Recovery period |
|---|---|---|
| Betharia & Kalra (1985) | Levator resection | 12 days |
| Betharia & Sharma (2006) | Levator resection | 1 week |
| Na & Yang (2009) | Levator resection | 2–4 weeks |
| Goel et al. (2017) | Levator shortening | 2–3 weeks |
| Pandey et al. (2019) | Frontalis suspension | 2 weeks |
(Adapted from Liakopoulos et al. 2021, Table 11))
Surgical management of post-traumatic cases: In one case of delayed inverse Bell’s phenomenon after trauma reported by Liakopoulos et al. (2021), the inverse Bell’s phenomenon normalized 3 months after surgical correction of lagophthalmos (reconstructive blepharoplasty with full-thickness skin graft)1).
There is no established drug therapy, and it usually resolves spontaneously in postoperative cases. Until it disappears, sufficient use of lubricating eye drops and regular ophthalmological observation are necessary to prevent exposure keratitis. If corneal damage is present, active corneal protection measures are required.
Several theories have been proposed regarding the mechanism of the inverse Bell phenomenon.
The peripheral oculomotor nerve runs from the brainstem in separate fascicles according to the target extraocular muscles. When the laterally running fibers to the inferior oblique (IO) and superior rectus (SR) are selectively damaged, Bell’s phenomenon on the affected side is absent. In supranuclear monocular elevation deficit, Bell’s phenomenon is preserved, so the presence or absence of Bell’s phenomenon helps estimate the site of the lesion.
During normal eyelid closure, the eye moves upward (Bell’s phenomenon) via the trigeminal-oculomotor projection. In reverse Bell’s phenomenon, this reflex is reversed by some mechanism, causing the eye to deviate downward and inward due to the action of the superior oblique and inferior rectus muscles. Several mechanisms have been proposed, such as postoperative edema or abnormal connections between the trochlear nucleus and the facial nerve nucleus, but a single clear mechanism has not been established.
Liakopoulos et al. (2021) reported a case of delayed inverse Bell’s phenomenon after trauma in a 6-year-old girl1). Normal Bell’s phenomenon was observed 10 days after trauma to the left upper eyelid and eyebrow (traffic accident), but inverse Bell’s phenomenon appeared 6 months after injury. This is a previously unreported case of delayed onset after trauma. The inverse Bell’s phenomenon normalized 3 months after reconstructive blepharoplasty (full-thickness skin graft) for lagophthalmos. The authors noted that the patient also had contralateral trochlear nerve palsy, suggesting that increased depressor equivalence innervation via brain plasticity in children may have been involved. They also stated that the disappearance of inverse Bell’s phenomenon after surgical correction of lagophthalmos supports the theory of abnormal communication between the fourth and seventh cranial nerve nuclei1).
