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Non-contact tonometry

Eye Care estimated about CNY 50-120

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Description

A non-invasive method of measuring intraocular pressure using a puff of air to applanate the cornea, without direct contact with the eye, commonly used in routine eye examinations.

Main Uses

Non-contact tonometry (NCT) is primarily used for rapid, non-invasive screening of intraocular pressure in routine eye exams, glaucoma risk assessment, pre- and post-operative monitoring (e.g., cataract or refractive surgery), large-scale population screenings, and pediatric or anxious patients who cannot tolerate contact methods. It serves as an initial triage tool but is not a standalone diagnostic test for glaucoma — abnormal results require confirmation with Goldmann applanation tonometry and comprehensive optic nerve/visual field evaluation.

Normal Range

Typical intraocular pressure (IOP) measured by non-contact tonometry (NCT) ranges from 10 to 21 mmHg in healthy adults. Values between 12–20 mmHg are most common; readings <10 mmHg or >21 mmHg warrant further evaluation. Note: NCT may slightly overestimate IOP compared to Goldmann applanation tonometry (GAT), especially at extremes, and results can vary with corneal thickness, tear film stability, and patient cooperation.

Low Values - Possible Causes

Hypotony (IOP <6 mmHg) may result from: 1) Post-surgical complications (e.g., bleb leak after trabeculectomy or wound leak after cataract surgery), 2) Chronic uveitis with ciliary body suppression, 3) Retinal detachment causing reduced aqueous production, 4) Severe ocular trauma with cyclodialysis cleft, 5) Advanced glaucoma drainage device overfiltration.

High Values - Possible Causes

Elevated IOP (>21 mmHg) on NCT may indicate: 1) Primary open-angle glaucoma (POAG), 2) Ocular hypertension (OHT) — elevated IOP without optic nerve damage, 3) Angle-closure glaucoma (acute or chronic), 4) Secondary glaucomas (e.g., pigmentary, pseudoexfoliative, steroid-induced), 5) Corneal edema or thickened cornea (corneal hysteresis artifact leading to falsely high NCT readings).

non-contact tonometry intraocular pressure test glaucoma screening test eye pressure measurement eye exam

estimated about CNY 50-120