The disruption of the seventh cranial nerve, known as 7th nerve palsy or facial nerve palsy, results in the loss of movement on one side of the face. While this condition causes a noticeable facial droop, the most serious consequence is the impact on the eye’s ability to protect itself. Because the nerve that controls facial expression is affected, the mechanisms that keep the eye healthy—blinking and complete closure—become compromised. Effectively managing the ocular effects of 7th nerve palsy is paramount to preserving vision and maintaining the integrity of the eye’s surface.
How Facial Nerve Damage Affects Eye Closure
The fundamental problem for the eye in 7th nerve palsy lies in the paralysis of the orbicularis oculi muscle, which is directly innervated by the facial nerve (CN VII). This muscle is responsible for closing the eyelids, controlling both the gentle blink and the forceful squeeze. Without the proper signal, the muscle cannot contract effectively, leading to an inability to fully meet the upper and lower eyelids, a condition known as paralytic lagophthalmos.
The impairment also significantly reduces the natural blink reflex. Blinking is necessary to spread the tear film evenly across the cornea and clear debris. When blinking is diminished, the eye’s surface is no longer regularly lubricated, resulting in an exposed environment.
Immediate Ocular Health Risks
The inability to achieve complete eyelid closure and the loss of the natural blink exposes the eye’s surface to desiccation. This exposure causes the tear film, which normally protects the eye, to evaporate at an accelerated rate. The resulting dryness directly injures the superficial layer of the eye, a condition often called exposure keratopathy.
Exposure keratopathy can begin as mild damage but can quickly progress. Persistent drying can lead to a corneal abrasion. If left unprotected, this damaged area is highly susceptible to bacterial or fungal invasion, potentially developing into a corneal ulcer. These complications pose a direct threat to vision and, in severe cases, can result in permanent loss of sight.
Essential Non-Surgical Eye Management
Immediate and consistent conservative care is the first line of defense to prevent damage from exposure. Frequent application of lubricating eye drops, often called artificial tears, is necessary throughout the day to supplement the eye’s diminished natural moisture. These drops should ideally be preservative-free, given the high frequency of use required.
For overnight protection, a thicker lubricating ointment is recommended. This ointment provides a viscous barrier against dryness, but it must be applied immediately before sleep as it will blur vision. Eyelid taping is also effective, using specialized medical tape to hold the upper eyelid down for complete closure. Furthermore, wearing moisture chamber glasses or goggles helps create a humid microclimate around the eye, reducing tear evaporation.
Long-Term and Surgical Eye Solutions
When conservative management proves insufficient or the nerve damage is expected to be permanent, surgical interventions are considered to restore eyelid function. A common and highly effective procedure involves inserting a small, custom-weighted implant—typically platinum or gold—into the upper eyelid. This weight uses gravity to assist the paralyzed upper lid in closing the eye, offering passive protection.
Another option is tarsorrhaphy, a procedure where the outer portions of the upper and lower eyelids are temporarily or permanently stitched together. This physically narrows the eye opening, reliably minimizing desiccation by reducing the exposed surface area. For more dynamic control, a specialized device like an eyelid or palpebral spring can be implanted to provide a mechanical closing force to the upper lid.
In cases where the paralysis is chronic, nerve transfer or nerve graft procedures may be performed. These procedures reroute a healthy nerve to the facial muscles, aiming to restore muscle tone and movement for long-term eye protection.