gonioscopy

Examination of the angle of the anterior chamber of the eye with a gonioscope or with a contact prism lens.

Examination of the angle of the anterior chamber of the eye with a gonioscope or with a contact prism lens.

Observation of the angle of the anterior chamber of the eye with a gonioscope. When the angle is wide open all structures are visible (cornea, Schwalbe's line, trabecular meshwork, scleral spur, ciliary body); when the angle is closed only the cornea is seen. The width of the angle can be described according to either Shaffer classification (grade 4, wide open (35º-45º): grade 3, moderately open (25º-34º); grade 2, moderately narrow (20º); grade 1, very narrow (10º); grade 0, closed (0º), or Spaeth classification, which categorizes the angle estimated in degrees, as well as the location of the iris insertion and iris curvature. See Shaffer and Schwartz van Herick method.
direct gonioscopy Observation of the virtual, erect image of the angle of the anterior chamber as formed by a gonioscopic lens (e.g. Koeppe lens). The image can be viewed with a handheld magnification system with the patient in a supine position.
indentation gonioscopy Gonioscopy performed when the angle of the anterior chamber is closed in order to determine whether the closure is appositional or synechial. It is usually done with the four-mirror Zeiss lens by pressing the lens against the cornea forcing the aqueous into the peripheral part of the angle and pushing the iris posteriorly: If the angle is closed by apposition between the iris and cornea (appositional closure) the angle will open. If the angle is closed by adhesion between the iris and cornea (synechial closure) it will remain closed.
indirect gonioscopy Observation of the real, inverted image of the angle of the anterior chamber as formed by a gonioscopic lens, such as the Goldmann or Zeiss lens. The image is viewed through a biomicroscope. This is the most commonly used gonioscopic method.

Table G2 Structures of the angle of the anterior chamber as seen by gonioscopy in an individual in whom the angle is open and none of the structures is obscured by the iris
structure (anterior to posterior)		anatomy/physiology		normal appearance
Schwalbe's line		posterior termination of Descemet's membrane		not always discernible off-white ridge; pigment may collect on it
trabecular meshwork		site of aqueous flow; covers internal part of Schlemm's canal		variable degree of pigmentation
scleral spur		strip of scleral tissue		thin white line
ciliary body band		anterior face of ciliary body in the angle recess		pigmented seen more easily if iris is moved backward