Anesthesia Considerations for Glaucoma Surgery

Glaucoma surgery is performed to reduce intraocular pressure (IOP) and prevent further optic nerve damage. The most common procedures include trabeculectomy, glaucoma drainage implants, and laser surgeries.

1. Types of Glaucoma & Surgical Indications

1. Open-Angle Glaucoma (Chronic)
• Indication: Failed medical therapy (eye drops, systemic drugs).
• Surgery: Trabeculectomy, Drainage Implants, Minimally Invasive Glaucoma Surgery (MIGS).

2. Angle-Closure Glaucoma (Acute)

• Indication: Emergency surgery if medical treatment fails.
• Surgery: Laser Peripheral Iridotomy, Trabeculectomy, Lens Extraction.

3. Secondary Glaucoma (Post-Trauma, Neovascular, Uveitic)

• Indication: Persistent IOP rise despite treatment.
• Surgery: Drainage Implants, Cyclodestructive Procedures.

2. Preoperative Considerations

A. Patient Factors

• Elderly patients → Common comorbidities (Hypertension, Diabetes, Cardiovascular Disease).
• Medication Review → Many patients are on beta-blocker eye drops (e.g., Timolol), which can cause bradycardia and bronchospasm.
• Anxiety & Hypertension → Can increase IOP → Consider preoperative anxiolysis.

B. Ophthalmic Considerations

• Target: Maintain Low & Stable IOP
• Avoid coughing, straining, or bucking on the tube.
• Avoid excessive IV fluids → Orbital congestion increases IOP.
• Positioning: Head slightly elevated (≥30°) to enhance venous drainage.
• Systemic Anti-Glaucoma Drugs & Their Effects:

3. Anesthetic Techniques

A. Local (Preferred in Most Cases)

• Peribulbar Block – Most commonly used.
• Sub-Tenon’s Block – Safer alternative.
• Retrobulbar Block – Avoided due to risk of optic nerve damage.
• Drugs Used:
• Lignocaine 2% + Bupivacaine 0.5% ± Hyaluronidase for better diffusion.

✅ Advantages of Local Anesthesia:

• IOP Stability
• Minimal systemic side effects
• Faster recovery, outpatient procedure

⚠️ Complications of Regional Blocks:

• Retrobulbar hemorrhage
• Globe perforation
• Brainstem anesthesia (severe respiratory depression if anesthetic spreads via optic nerve sheath).

B. General Anesthesia (Selected Cases)

• Indications:
• Uncooperative patients
• Pediatric glaucoma surgeries
• Significant comorbidities where local block is contraindicated
• Induction:
• Propofol (1.5-2.5 mg/kg IV) (reduces IOP).
• Fentanyl (1-2 mcg/kg IV) (blunts response to laryngoscopy).
• Succinylcholine (if rapid-sequence induction needed) OR Rocuronium (if needed for airway control, but must be fully reversed to prevent cough on extubation).
• Maintenance:
• Sevoflurane or TIVA with Propofol (preferred for stable IOP).
• Avoid N₂O (may cause orbital congestion).
• Airway Management:
• LMA preferred (less coughing & bucking than ETT).
• ETT in pediatric or prolonged cases.

4. Intraoperative Considerations

A. IOP Control

• AVOID factors that increase IOP:
• Hypercapnia → Causes orbital venous congestion.
• Hypoxia → Increases sympathetic activity → Raises IOP.
• Deep suctioning, excessive IV fluids, Trendelenburg position.
• Drugs That Reduce IOP:
• Propofol – Reduces aqueous humor production.
• Mannitol (1 g/kg IV) – Osmotic diuretic to acutely lower IOP.

B. Oculocardiac Reflex (OCR) Risk

• Triggered by extraocular muscle manipulation → Can cause severe bradycardia or asystole.
• Managed by:
• Stopping the stimulus.
• IV Atropine (0.01 mg/kg) if bradycardia persists.

C. Hemodynamic Stability

• Avoid Hypertension:
• Sudden BP surges can cause intraoperative bleeding → Use Labetalol or Esmolol if needed.
• Maintain Normotension:
• Avoid hypotension, which can compromise optic nerve perfusion.

5. Postoperative Considerations

A. Pain Management

• Minimal pain expected unless a drainage implant is placed.
• Paracetamol ± NSAIDs usually sufficient.
• Avoid opioids (may cause nausea, increasing IOP).

B. Postoperative Nausea and Vomiting (PONV)

• Very common due to vagal stimulation.
• Preventive strategy:
• Ondansetron (4-8 mg IV).
• Dexamethasone (4-8 mg IV).
• Minimize opioid use.

C. Vision Recovery & Precautions

• Vision may be temporarily blurred due to corneal edema.
• IOP monitoring postoperatively is essential to detect hypotony or IOP spikes.
• Avoid straining, heavy lifting, bending forward for a few weeks.

 MCQs for Exam Preparation

1. Which of the following drugs can lower intraocular pressure?
   a) Ketamine
   b) Nitrous oxide
   c) Propofol
   d) Succinylcholine
   Answer: c) Propofol
2. Which of the following is NOT a contraindication for regional anesthesia in glaucoma surgery?
   a) Patient anxiety
   b) Severe coagulopathy
   c) Retrobulbar hemorrhage
   d) Pediatric patient
   Answer: a) Patient anxiety
3. Which systemic anti-glaucoma drug can cause bradycardia?
   a) Acetazolamide
   b) Timolol
   c) Brimonidine
   d) Latanoprost
   Answer: b) Timolol
4. What is the most common anesthesia-related complication in glaucoma surgery?
   a) Malignant hyperthermia
   b) Oculocardiac reflex
   c) Postoperative hypertension
   d) Laryngospasm
   Answer: b) Oculocardiac reflex