Gonioscopy

Landmarks (darkly pigmented iris)

1. Schwalbe's line: Fine, irregular shiny line (sometimes pigmented) at the termination of Descemet’s membrane

2. Anterior trabecular meshwork (ATM): Non-pigmented homogenous zone below Schwalbe’s line

3. Posterior trabecular meshwork (PTM): Slightly more mottled, variably pigmented (none to heavy).

4. Scleral spur (SS): Homogenous, dense white and somewhat shiny band

5. Ciliary body band (CBB): Dull pink, brown or grey band

Landmarks (lightly pigmented iris)

1. Schwalbe's line: Fine, irregular shiny line (sometimes pigmented) at the termination of Descemet’s membrane. This may be difficult to identify, particularly in patients with light-coloured irides.

2. Anterior trabecular meshwork (ATM): Non-pigmented homogenous zone below Schwalbe’s line

3. Posterior trabecular meshwork (PTM): In patients with light-coloured irises the PTM typically appears mottled with variable amounts of pigmentation.

4. Scleral spur (SS): Homogenous, dense white and somewhat shiny band

5. Ciliary body band (CBB): Dull pink, brown or grey band

Anatomical features of the angle

This anterior OCT image shows the key anatomical features of the anterior chamber angle.

Aqueous drains from the eye via Schlemm's canal. The trabecular meshwork is a tissue that covers the entrance to Schlemm's canal and its primary function is to filter the aqueous leaving the eye.

Apposition or contact between the iris and cornea causes a mechanical blockage of Schlemm's canal, reducing or preventing drainage of aqueous from the eye and leading to increased intraocular pressure.

The deeper the structures identified on gonioscopy, the more wide open the angle is. If no structures are visible, this may be an indication that the angle is closed, or that the iris profile is impairing the clinician's view of the angle structures.

More information on angle closure spectrum disease is available using the link at the bottom of this page.

Examples of different angles on gonisocopy

The blue arrows in each image point to the deepest structure visible.

1. In this gonioscopy photograph, there are no angle structures visible. Following this, lens tilt or indentation would be indicated to assess for iridotrabecular contact. These techniques will be discussed later.

2. In this image, the angle is open to the posterior trabecular meshwork (PTM), marked by the blue arrow. The PTM can be difficult to detect particularly in light coloured irides; however looking for a band of slightly mottled pigmentation will help in locating the PTM.

3. Gonioscopy shows the deepest structure visible to be the scleral spur, most visible inferiorly in this photograph and marked by the blue arrows. The scleral spur presents as a white, somewhat shiny band between the ciliary body and pigmented trabecular meshwork.

4. The angle is wide open to the ciliary body body (CBB) which is marked by the blue arrow in this image. The CBB appears as a brown band of pigmentation.

Corresponding angles as imaged by anterior OCT

These anterior OCT images correspond to the gonioscopy photographs shown previously. The position of Schlemm's canal is marked in each image. The Schlemm's canal is located between the trabecular meshwork and scleral spur. It is not easily visible on gonioscopy unless there is blood within the canal.

In image 1, it can be seen that this canal appears to be blocked by the iris anatomy. In images 2-4 this canal is not obstructed.

Gonioscopy photo taken in primary gaze (1) and with lens tilt (2) - left eye

On primary gaze, there are no visible structures seen on gonioscopy.

However, with lens tilt, the posterior trabecular meshwork becomes visible.

Indentation gonioscopy

To conduct indentation gonioscopy, the practitioner should apply direct pressure to the eye using a non-flanged (or small diameter) contact goniolens until stress lines (identified by the white arrows) appear.

In this patient, the pigmented trabecular meshwork is visible in primary gaze (image 1). With indentation gonioscopy (image 2), the angle opens up to the ciliary body band (blue arrow).

This procedure is best performed with some, but not an excessive amount, of fluid to minimise corneal staining

Gonioscopy of the inferior angle (1) and anterior OCT line scan of the right eye (2)

In this gonioscopy photo, you can see the deeply pigmented trabecular meshwork, and a broad band of iridocorneal adhesion, indicative of peripheral anterior synechiae (PAS).

Given the focal nature and otherwise open angles, it is likely this presentation of PAS is related to previous inflammation/ trauma (e.g. uveitis) rather than primary angle closure.

Anterior OCT through the PAS shows peripheral iris adhesion to the posterior cornea.

Gonioscopy photo (left eye, inferior angle)

You can appreciate the focal area of peripheral anterior synechiae. Please note the narrow angles in this photograph, with only edge of PTM visible indicating the likely cause of PAS is narrow angles.

Gonioscopy photos (right eye)

These photos show multiple areas of iridocorneal adhesion in a patient with history of previous intraocular surgery and inflammation

Anterior OCT (1 - right eye, 2- left eye)

These OCT images were taken from the same patient with a history of previous intraocular surgery and inflammation. The areas of PAS are shown by the blue arrows.

Gonioscopy photo (left eye, inferior angle)

The area of angle recession is identified by the blue arrow.

Gonioscopy photo (left inferior angle)

The area of angle recession is identified by the blue arrow.

Gonioscopy photo (right inferior angle)

The area of angle recession is identified by the blue arrow.

Gonioscopy photo (left, inferior angle)

The blood in Schlemm's canal appears as a red line

Anterior eye photo (1) and gonioscopy photo (2) - patient 1

Gonioscopy photo showing angle neovascularisation

Examples of angles with increased pigmentation due to pseudoexfoliation syndrome

PXF is associated with increased pigmentation of the angle as seen on gonioscopy. This pigmentation is often patchy and is most notable in the inferior angle. Shuba et al (2007) confirmed a positive correlation between pigmentation and intraocular pressure (IOP) in PXF.

These images are taken from 3 different patients and Sampaolesi's line is identified by the blue arrows.

Examples of angles with increased pigmentation due to pigment dispersion syndrome

PDS is associated with a heavy and homogenous pigmentation of the trabecular meshwork. The amount of pigment varies over time, initially increasing in its 'active' phase and then later decreasing in the "burnt out" phase. Use the link provided at the bottom of this page to read more about PDS.

The three examples here illustrate the dense pigmentation associated with this condition. Comparison with the images from PXF shows that the angle pigmentation in PDS is denser and more homogenous. Sampaolesi's line is marked by the blue arrows.

Gonioscopy photo (1), Anterior OCT (2) and Ultrasound biomicroscopy (3) - right eye

On gonioscopy a focal elevation of the iris is observed which partially narrows the angle in this quadrant.

OCT confirms elevation of the iris in this location, however the internal characteristics of the iris lesion is unknown as signal transmission is blocked by iris pigment epithelium.

Ultrasound biomicroscopy (UBM) shows a focal, round lesion with a thin, hyperechoic wall with hypoechoic internal content, confirming the diagnosis of iridociliary cyst.

Case 1: Gonioscopy photo (1), Ultrasound biomicroscopy (2) and Anterior OCT (3)

This iris naevus can be viewed on gonioscopy as an area of hyperpigmentation (1). Anterior OCT (3) shows the lesion to be elevated, however the pigmentation is blocking the OCT signal so no additional information about the internal composition of the lesion is available with this technique. Ultrasound biomicroscopy (2) penetrates deeper into the tissue, showing the lesion to be uniformly hyperechoic and thus, solid in nature.

Case 2: Gonioscopy photo (left eye)

Elevated iris naevus invading the nasal anterior chamber angle in the left eye.

Case 3: Gonioscopy photo (left eye)

Elevated iris naevus in the inferior angle of the left eye.

Typical iris configuration

Plateau Iris Configuration

This OCT image shows the anteriorly-bowing iris configuration termed "plateau iris".

Goniophotos without (1) and with (2) lens tilt

With lens tilt (or redirecting patients’ gaze) more structures are visible in a plateau iris configuration.

Anterior OCT and Pentacam anterior chamber depth (left eye)

OCT of the anterior segment shows a steep peripheral iris with a flat iris plane and anteriorly positioned lens

Pentacam indicates a shallow anterior chamber depth

Posteriorly bowed iris (concave iris)

This image was taken from a young child. Note the concave nature of the iris plane.

Anterior OCT showing posterior bowing of the iris

This image was taken from a 57 year old male. Also noted was heavy pigmentation on gonioscopy, iris transillumination defects and a faint Kruckenberg's spindle. This clinical presentation is consistent with a diagnosis of pigment dispersion syndrome (PDS).