How to measure intraocular pressure (IOP) in a person with blepharospasm?

Measuring IOP in Blepharospasm

In patients with blepharospasm, use rebound tonometry (iCare) or ocular response analyzer as first-line methods, as these devices do not require topical anesthesia and minimize patient discomfort during involuntary eyelid spasms. 1

Optimal Tonometry Methods for Blepharospasm

First-Line Techniques (No Anesthesia Required)

• Rebound tonometry is the preferred method because it requires no topical anesthesia, uses rapid probe contact (0.05 seconds), and can be performed quickly between spasms 1
• The device fires a magnetized plastic-tipped probe against the cornea at 0.25 m/sec and analyzes deceleration rate to calculate IOP, requiring 6 measurements for accuracy 1
• Ocular response analyzer is an excellent alternative as it uses a collimated air pulse without requiring topical anesthesia, measures corneal biomechanical properties, and calculates "corneal-compensated" IOP 1

Second-Line Techniques (Anesthesia Required)

If rebound tonometry or ocular response analyzer are unavailable, consider these alternatives that require topical anesthesia 2:

• Pneumotonometer uses a 5-mm fenestrated silicone tip that conforms to the cornea, generates 40 readings per second, and may be easier to apply during brief periods between spasms 1
• Dynamic contour tonometer (Pascal) requires 6 seconds of stable contact and calculates IOP independent of corneal properties, but may be challenging with active spasms 1
• Goldmann applanation tonometry is the gold standard for normal corneas but requires sustained patient cooperation and topical anesthesia, making it difficult in active blepharospasm 3, 2

Clinical Considerations Specific to Blepharospasm

Timing of Measurement

• Measure IOP after botulinum toxin A (BTX-A) treatment when possible, as eyelid pressure and IOP are significantly reduced following injection 4
• Eyelid pressure in blepharospasm patients (35.3 mmHg upper, 37.8 mmHg lower) is significantly higher than normal controls (31.0 mmHg upper, 29.9 mmHg lower), which can artificially elevate IOP readings 4
• After BTX-A treatment, eyelid pressure decreases to near-normal levels (29.9 mmHg upper, 32.8 mmHg lower), and IOP decreases from 15.1 mmHg to 14.5 mmHg 4

Important Pitfalls

• Avoid measuring during active spasm, as forceful eyelid closure can transiently elevate IOP and produce falsely high readings 4
• Lower eyelid pressure correlates significantly with IOP (P = 0.0435), so measurements taken during involuntary lid closure may overestimate true baseline IOP 4
• Blepharospasm itself is not a risk factor for glaucoma development, so elevated IOP readings during spasms should not trigger unnecessary glaucoma treatment 5

Practical Algorithm

1. First attempt: Use rebound tonometry (iCare) or ocular response analyzer—no anesthesia needed, rapid measurement possible between spasms 1, 3
2. If unavailable: Apply topical anesthesia 2 and use pneumotonometer for quick measurements with conforming tip 1
3. If measurements inconsistent: Consider scheduling measurement after BTX-A treatment when spasms are controlled 4
4. Maintain consistency: Use the same device for serial measurements, as switching between tonometry methods introduces variability that can mask true IOP changes 3