Glaucoma surgery: MIGS, trabeculectomy, and others

Glaucoma surgery: MIGS, trabeculectomy, and others

Anesthesia type	MAC
Airway	Noninvasive O2
Lines and access	PIV
Monitors	Standard, 5 lead ECG
Primary anesthetic considerations
Preoperative
Intraoperative	Oculocardiac reflex
Postoperative
Article quality
Editor rating	Unrated
User likes	0

Open-angle glaucoma (OAG) is the most common form of glaucoma and is characterized by a gradual increase in intraocular pressure (IOP) due to the slow blockage of the drainage canals in the eye. Management includes medications, laser therapies, and surgical procedures including minimally invasive glaucoma surgery (MIGS). MIGS aims to lower IOP with less risk and faster recovery than traditional surgeries.

Overview

Indications

Failure of medical and laser therapy to adequately control IOP or continued progression of optic nerve or visual field damage despite maximal tolerated non-surgical treatment.

Surgical procedure

1. Laser therapies
   • Laser Trabeculoplasty: This procedure uses a laser to improve the drainage of fluid through the trabecular meshwork
   • Selective Laser Trabeculoplasty (SLT): A more recent and less invasive option that targets specific cells in the trabecular meshwork and can be repeated if necessary
2. Surgical procedures
   • Trabeculectomy: creates a new drainage pathway to reduce IOP by removing a part of the trabecular meshwork and sclera
   • Tube Shunt Surgery: Involves placing a small tube (shunt) in the eye to assist with the drainage of aqueous humor
3. MIGS
   • iStent: A tiny device that creates a new drain for fluid
   • Hydrus Microstent: A small stent implanted in the drainage canal to help fluid drain better
   • Kahook Dual Blade: A technique that removes tissue in the trabecular meshwork to facilitate drainage

Preoperative management

Patient evaluation

System	Considerations
Airway
Neurologic
Cardiovascular
Pulmonary
Gastrointestinal
Hematologic
Renal
Endocrine
Other

Regional and neuraxial techniques

Regional blocks are briefly painful and stimulating. Consider remifentanil (0.25-1mcg/kg), alfentanil (5-7mcg/kg), or propofol bolus (30-50mg) prior to block. Prepare to treat apnea or drop in BP.

1. Peribulbar block: injecting a local anesthetic into the space surrounding the eye (the peribulbar space). Provides a dense block of the sensory nerves supplying the eye and can also induce temporary paralysis of the ocular muscles. Risks include potential injury to the optic nerve, hemorrhage, or globe perforation
2. Retrobulbar block: local anesthetic injected behind the eyeball (retrobulbar space) to block the optic nerve and other sensory nerves. Provides profound anesthesia for the eye. Can also produce akinesia (paralysis of eye movement). Higher risk block including potential injury to the optic nerve, hemorrhage, globe perforation, or systemic toxicity
3. Subtenon block: anesthetic injected into the subtenon space, which is located just outside the sclera (the white part of the eye but under the Tenon's capsule). Allows anesthetic to diffuse around the eye. Lower risk of complications compared to the above blocks. Will have preservation of eye movement which may be suboptimal for surgical conditions.

Intraoperative management

Monitoring and access

• Standard ASA monitors
• 5 Lead EKG
• 1 Peripheral IV

Induction and airway management

• Most commonly use nasal cannula for O2 supplementation, but LMA for select patient populations
• Benzodiazapenes (ex. midazolam) and opioids (ex. fentanyl) are commonly administered throughout the case as needed for patient comfort
• Consider use of precedex as an adjunct throughout case given its sedative effects and ability to lower the IOP

Positioning

• supine

Maintenance and surgical considerations

• Short cases ranging between 30 - 90 min depending on complexity and technique
• Oculocardiac reflex, caused by traction on extraocular muscles, can result in rapid decrease in heart rate and blood pressure
  • Stop surgical manipulation, give atropine/glycopyrrolate

Postoperative management

Disposition

• Short post-op monitoring
• Usually home same day

Pain management

• Tylenol
• +/- Ketorolac

Potential complications

• hemorrhage
• infection
• cataract formation
• corneal edema
• ocular hypotony (IOP iatrogenically too low)

Procedure variants

	Variant 1	Variant 2
Unique considerations
Indications
Position
Surgical time
EBL
Postoperative disposition
Pain management
Potential complications