The term “peribulbar” provides a literal description of its meaning: “around the eyeball.” In medicine, this term is almost exclusively associated with an anesthetic injection for eye operations. A peribulbar block is a form of regional anesthesia designed to numb the eye and its surrounding structures. This method is frequently used to ensure patient comfort and surgical stability during delicate ophthalmic procedures without inducing unconsciousness.
The Peribulbar Block Procedure
A peribulbar block involves the injection of local anesthetic into the peribulbar space, the area of soft tissue within the eye socket that surrounds the eyeball. The primary objective is to achieve both analgesia (pain relief) and akinesia (a lack of eye movement). This stillness is important for the high-precision nature of ophthalmic surgeries. The anesthetic solution spreads through the fatty tissue of the orbit, bathing the nerves that provide sensation and control muscle movement.
The procedure begins after the skin is cleaned with an antiseptic. A very fine, short needle is used to deliver the anesthetic. The injection is typically made through the skin of the lower eyelid, near the outer corner of the eye, or sometimes through the upper lid. The needle is carefully guided parallel to the floor of the orbit and does not enter the eyeball. Gentle pressure may be applied to the eye afterward to help the solution disperse evenly.
Applications in Ophthalmic Surgery
The peribulbar block is a widely utilized technique for several common types of eye surgery where pain control and eye immobility are beneficial. It is frequently employed for cataract surgery, where the clouded natural lens is removed and replaced with an artificial one. The profound numbness and akinesia provided by the block allow surgeons to perform the intricate steps of this procedure with great precision.
This form of anesthesia is also well-suited for glaucoma surgeries, such as trabeculectomy, which involve creating a new drainage channel for the eye’s internal fluid. Certain retinal procedures, like vitrectomy to treat conditions of the vitreous and retina, can also be performed under a peribulbar block. The block’s ability to prevent sudden eye movements is a significant advantage, contributing to the safety of the operation.
Potential Complications and Side Effects
While generally safe, the peribulbar block carries potential side effects, most of which are minor and temporary. The most common issues arise from the injection itself and include bruising around the eye (periorbital ecchymosis) and swelling of the eyelid. Another frequent occurrence is a subconjunctival hemorrhage, which appears as a bright red spot on the white of the eye but is harmless and resolves on its own.
Rarer, more significant complications can occur, including:
- Retrobulbar hemorrhage, which is bleeding behind the eyeball that can increase pressure within the orbit.
- Perforation of the globe (eyeball) with the needle, an extremely rare instance.
- Nerve damage affecting vision or the muscles that move the eye.
- Unintended injection of anesthetic into the fluid surrounding the optic nerve, which can lead to brainstem anesthesia, causing temporary loss of consciousness and respiratory arrest.
Alternatives to Peribulbar Anesthesia
Several other methods of anesthesia are available for eye surgery. Topical anesthesia, which involves administering numbing eye drops, is the most common method for cataract surgery in the United States. This approach is non-invasive but does not prevent eye movement, requiring significant patient cooperation.
A retrobulbar block is another injection technique, delivering the anesthetic deeper into the orbit, behind the eye and inside the cone formed by the eye muscles. This typically requires a smaller volume of anesthetic but has a higher risk of injuring the optic nerve. A sub-Tenon’s block involves making a small incision in the conjunctiva, the eye’s outer membrane, and using a blunt cannula to deliver anesthetic. This technique avoids a sharp needle, which can be an advantage for patients on blood thinners.