gonioscopy

DEFINITION of gonioscopy

Gonioscopy is a specialized ophthalmic examination technique in which a gonioscope (a goniolens coupled with a slit-lamp biomicroscope) is placed on the anesthetized cornea to neutralize the total internal reflection that normally prevents direct visualization of the anterior chamber angle. The procedure allows the clinician to assess the trabecular meshwork, Schlemm’s canal, the iris insertion, the ciliary body band, and the scleral spur. It is the gold standard for classifying glaucoma as open-angle vs. angle-closure, grading the angle using systems such as the Shaffer, Spaeth, or Van Herick grading scales, identifying angle pathology (recession, neovascularization, pigment dispersion, synechiae), and guiding surgical planning (e.g., trabeculectomy, goniotomy, iStent placement).

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ETYMOLOGY of gonioscopy

greek gonio- Greek gōnia (γωνία); Angle, corner -scopy Greek skopein (σκοπεῖν); To examine, to look

Literally: “examination of the angle.”

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RELATED TERMS

• Goniolens / Gonioscope — the contact lens used (e.g., Goldmann 3-mirror, Zeiss 4-mirror, Sussman, Koeppe)
• Trabecular meshwork — primary drainage structure visualized
• Iridocorneal angle — the anatomic target
• Synechiae (peripheral anterior) — PAS; adhesions closing the angle, identified on gonioscopy
• Angle recession — traumatic tearing of the ciliary body; a key gonioscopic finding
• Neovascularization of the angle (NVA) — rubeosis iridis extending to the angle
• Shaffer grading system — grades angle width 0-4
• Goniotomy — surgical procedure guided by gonioscopy
• Trabeculoplasty (SLT/ALT) — laser procedures targeting the trabecular meshwork

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CODING AND NUANCE

CPT CODE

Code	Description
92020	Gonioscopy (separate procedure)

⚠️ Note: 92020 is billable per session, not per eye. It is often bundled into a comprehensive ophthalmologic exam (92004/92014) when performed the same day by the same provider, so check for bundling edits (NCCI).

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RELEVANT ICD-10-CM DIAGNOSIS CODES

(Common indications for gonioscopy — full codes as applicable)

Glaucoma — Open Angle

Code	Description
H40.10X0	Unspecified open-angle glaucoma, stage unspecified
H40.10X1	Unspecified open-angle glaucoma, mild stage
H40.10X2	Unspecified open-angle glaucoma, moderate stage
H40.10X3	Unspecified open-angle glaucoma, severe stage

Glaucoma — Angle Closure

Code	Description
H40.211	Acute angle-closure glaucoma, right eye
H40.213	Acute angle-closure glaucoma, bilateral
H40.231	Intermittent angle-closure glaucoma, right eye
H40.233	Intermittent angle-closure glaucoma, bilateral

Primary Angle Closure (without glaucoma damage)

Code	Description
H40.061	Primary angle closure without glaucoma damage, right eye

Anterior Chamber Angle Pathology

Code	Description
H21.211	Degeneration of chamber angle, right eye
H21.212	Degeneration of chamber angle, left eye
H21.213	Degeneration of chamber angle, bilateral
H21.219	Degeneration of chamber angle, unspecified eye
H21.551	Recession of chamber angle, right eye
H21.552	Recession of chamber angle, left eye
H21.553	Recession of chamber angle, bilateral
H21.559	Recession of chamber angle, unspecified eye

💡 Coding tip: For glaucoma codes in the H40.1x family, the 7th character represents the stage (0=unspecified, 1=mild, 2=moderate, 3=severe, 4=indeterminate), and the “X” is a placeholder used to hold the 6th character position when no 6th character is defined — making them effectively 7 characters total (e.g., H40.10X0). Always confirm stage documentation supports the character selected.

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DERIVATIONS of gonioscopy

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Query functionality

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Med roots Appendix A Prefixes Appendix B Combining Forms Appendix C Suffixes Appendix D Suffix forms