Tonometry

Tonometry refers to measurement of intraocular pressure (IOP), a key parameter in glaucoma management, used to screen, diagnose, and monitor treatment.

Modern tonometers estimate IOP via applanation, indentation, or non-contact methods; readings can be affected by corneal thickness, curvature, and hydration.

Goldmann applanation tonometry, the gold standard, flattens a fixed corneal area with a prism under a slit lamp; fluorescein is used to improve accuracy.

Non-contact tonometry uses an air puff to applanate the cornea without touching it; quick but less precise and influenced by corneal properties.

Rebound tonometry uses a short, spring-loaded probe that bounces off the cornea; suitable for children and busy clinics.

Indentation tonometry (Schiötz) predates applanation; largely replaced by more accurate methods but remains of historical interest.

Normal IOP ranges roughly 10–21 mmHg; diurnal variation and central corneal thickness affect readings; values must be interpreted in context.

Advantages and limitations vary by method; risks are minimal for most techniques, with infection or corneal injury possible in contact tonometry.