Canthotomy (also called lateral canthotomy and canthotomy with cantholysis) is a surgical procedure where the lateral

canthus The canthus (: canthi, palpebral commissures) is either corner of the eye where the upper and lower eyelids meet. More specifically, the inner and outer canthi are, respectively, the medial and lateral ends/angles of the palpebral fissure. The ...

, or corner, of the

eye An eye is a sensory organ that allows an organism to perceive visual information. It detects light and converts it into electro-chemical impulses in neurons (neurones). It is part of an organism's visual system. In higher organisms, the ey ...

is cut to relieve the

fluid pressure In physics, a fluid is a liquid, gas, or other material that may continuously move and deform (''flow'') under an applied shear stress, or external force. They have zero shear modulus, or, in simpler terms, are substances which cannot r ...

inside or behind the eye, known as

intraocular pressure Intraocular pressure (IOP) is the fluid pressure inside the eye. Tonometry is the method eye care professionals use to determine this. IOP is an important aspect in the evaluation of patients at risk of glaucoma. Most tonometers are calibrated t ...

(IOC). The procedure is typically done in emergency situations when the intraocular pressure becomes too high, which can damage the

optic nerve In neuroanatomy, the optic nerve, also known as the second cranial nerve, cranial nerve II, or simply CN II, is a paired cranial nerve that transmits visual system, visual information from the retina to the brain. In humans, the optic nerve i ...

and lead to blindness if left untreated. The most common cause of elevated intraocular pressure is orbital

compartment syndrome Compartment syndrome is a serious medical condition in which increased pressure within a Fascial compartment, body compartment compromises blood flow and tissue function, potentially leading to permanent damage if not promptly treated. There are ...

(OCS) caused by trauma, retrobulbar hemorrhage, infections, tumors, or prolonged

hypoxemia Hypoxemia (also spelled hypoxaemia) is an abnormally low level of oxygen in the blood. More specifically, it is oxygen deficiency in arterial blood. Hypoxemia is usually caused by pulmonary disease. Sometimes the concentration of oxygen in the ...

. Absolute contraindications to canthotomy include globe rupture. Complications include bleeding, infections, cosmetic deformities, and functional impairment of eyelids. Lateral canthotomy further specifies that the lateral canthus is being cut. Canthotomy with cantholysis includes cutting the lateral palpebral ligament, also known as the canthal tendon.

History

The first case of orbital compartment syndrome causing monocular blindness was published in 1950 due to a complication of a zygomatic fracture repair. In 1953, the first surgical orbital decompression was performed. Two incisions below and above the external canthus were made and surgical drains were put in place. In 1990, the first lateral canthotomy procedure as presently performed was completed. In 1994, lateral canthotomy was first published in a review of procedures that emergency physicians can perform. Today, a canthotomy is almost always performed with cantholysis of the inferior canthal tendon as this provides the best decompression of intraocular pressure.

Indications

A canthotomy is often used as a last resort to decompress orbital compartment syndrome. Orbital compartment syndrome can be caused by trauma, infections, tumors, retrobulbar hemorrhage, or prolonged hypoxemia. Orbital compartment syndrome can be recognized by elevated intraocular pressure, globe compressibility, afferent pupillary defect, proptosis, decreased visual acuity, and decreased extraocular muscle movements. Studies in animals have demonstrated irreversible vision loss within 90 to 120 minutes, further indicating the emergent nature of this procedure. In an unconscious patient who is unable to comply with a physical exam, an intraocular pressure greater than 40 indicates emergent canthotomy.

Contraindications

The foremost absolute contraindication to canthotomy is globe rupture, sometimes referred to as an open globe injury. Globe rupture can be recognized by these symptoms or physical exam features: * Irregular-shaped

pupil The pupil is a hole located in the center of the iris of the eye that allows light to strike the retina.Cassin, B. and Solomon, S. (1990) ''Dictionary of Eye Terminology''. Gainesville, Florida: Triad Publishing Company. It appears black becau ...

or iris *

Subconjunctival hemorrhage Subconjunctival bleeding, also known as subconjunctival hemorrhage or subconjunctival haemorrhage, is bleeding from a small blood vessel over the whites of the eye. It results in a red spot in the white of the eye. There is generally little to n ...

* Enophthalmos * Conjunctival or scleral tear Due to the emergent nature of this procedure and the possibility of restoring or preventing vision loss, globe rupture is the only absolute contraindication.

Complications

Due to portions of the procedure having poor visualization of anatomical structures, and the overall rarity and difficulty of the procedure,

iatrogenic Iatrogenesis is the causation of a disease, a harmful complication, or other ill effect by any medical activity, including diagnosis, intervention, error, or negligence." Iatrogenic", ''Merriam-Webster.com'', Merriam-Webster, Inc., accessed 27 ...

globe injury is an immediate complication that can occur. Other complications include infections, bleeding, cosmetic deformities, and functional impairment of eyelids.

Alternatives

Due to the infrequency and difficulty of canthotomy, emergency medicine physicians defer more than 50 percent of canthotomies to a consulting physician, which in turn can increase time to treatment. In an effort to decrease difficulty and improve patient outcomes, vertical lid split or paracanthal "one-snip" procedures have been studied. This is performed by making a full-thickness vertical incision a few millimeters medial from the lateral canthus in both the upper and lower eyelids.

History

Indications

Contraindications

Complications

Alternatives

References

Further reading