Gonioscopy

Synonym/Acronym

N/A

Rationale

To detect abnormalities in the structure of the anterior chamber of the eye such as in glaucoma.

Patient Preparation

There are no food, fluid, activity, or medication restrictions unless by medical direction.

Normal Findings

Normal appearance of anterior chamber structures and wide, unblocked, normal angle.

Critical Findings and Potential Interventions ⬆ ⬇

Overview ⬆ ⬇

(Study type: Sensory (ocular); related body system: Nervous system.)

Gonioscopy is a technique used for examination of the anterior chamber structures of the eye (i.e., the trabecular meshwork and the anatomical relationship of the trabecular meshwork to the iris). The trabecular meshwork is the drainage system of the eye, and gonioscopy is performed to determine if the drainage angle is damaged, blocked, or clogged. Gonioscopy in combination with biomicroscopy is considered to be the most thorough basis to confirm a diagnosis of glaucoma and to differentiate between open-angle and angle-closure glaucoma. The angle structures of the anterior chamber are normally not visible because light entering the eye through the cornea is reflected back into the anterior chamber. Placement of a special contact lens (goniolens) over the cornea allows reflected light to pass back through the cornea and onto a reflective mirror in the contact lens. It is in this way that the angle structures can be visualized.

There are two types of gonioscopy: indirect and direct. The more commonly used indirect technique employs a mirrored goniolens and biomicroscope. Direct gonioscopy is performed with a gonioscope containing a dome-shaped contact lens known as a gonioprism. The gonioprism eliminates internally reflected light, allowing direct visualization of the angle. Interpretation of visual examination is usually documented in a colored hand-drawn diagram. Scheie classification is used to standardize definition of angles based on appearance by gonioscopy. Shaffer classification is based on the angular width of the angle recess.

Indications ⬆ ⬇

Assess degenerative conditions of the anterior chamber.
Assess for hyperpigmentation.
Assess peripheral anterior synechiae (PAS).
Assess for the presence of glaucoma (confirmation of normal structures and estimation of angle width).
Assess for the presence of uveitis.
Evaluate growth or tumor in the angle.
Evaluate post-trauma evaluation for angle recession.
Investigate conditions affecting the ciliary body.
Investigate suspected neovascularization of the angle.

Interfering Factors ⬆ ⬇

Potential Medical Diagnosis: Clinical Significance of Results ⬆ ⬇

Scheie Classification Based on Visible Angle Structures
Classification		Appearance
Wide open		All angle structures seen
Grade I narrow		Difficult to see over the iris root
Grade II narrow		Ciliary band obscured
Grade III narrow		Posterior trabeculae hazy
Grade IV narrow		Only Schwalbe line visible

Shaffer Classification Based on Angle Width
Classification		Appearance
Wide open (20°–45°)		Closure improbable
Moderately narrow (10°–20°)		Closure possible
Extremely narrow (less than 10°)		Closure possible
Partially/totally closed		Closure present

Abnormal Findings Related to

Corneal endothelial disorders (Fuchs endothelial dystrophy, iridocorneal endothelial syndrome)
Glaucoma
Lens disorders (cataract, displaced lens)
Malignant ocular tumor in angle
Neovascularization in angle
Ocular hemorrhage
PAS
Schwartz syndrome
Trauma
Tumors
Uveitis

Nursing Implications ⬆

Before the Study: Planning and Implementation

Teaching the Patient What to Expect

Review the procedure with the patient.
Discuss that this procedure takes about 5 min to complete and can assist in evaluating the eye for disease.
Explain that no pain will be experienced during the test. Some discomfort may be experienced after the test when the numbness wears off from anesthetic drops administered prior to the test.

Procedural Information

Positioning for this procedure is to be comfortably seated.
The ordered mydriatic is administered to each eye if dilation is to be performed. Remind the patient that the dilating effects of ordered mydriatic drops may last up to 4 to 6 hr. Advise there may be a brief stinging sensation when the drop is put in the eye, but no discomfort will be experienced during the examination.
Topical anesthetic drops are instilled in each eye and allowed time to take effect. The patient is asked to place their chin on a chin rest and gently press the forehead against the support bar. The ophthalmologist or optometrist places a lens on the eye while a narrow beam of light is focused on the eye.
The patient is advised when to open the eyes wide and look at the desired target.
Once the examination is completed, the patient is advised to gently rinse the face, especially eyelids and corners of the eye, to remove any crystallized residue of the dilation drops. Gentle rinsing and drying by dabbing without rubbing is crucial to avoid causing a corneal abrasion. Rinsing helps decrease the time the eyes remain dilated by removing residue that otherwise would be washed back into the eye when the patient blinks.

Potential Nursing Actions

Investigate health concerns related to known or suspected vision loss or changes in visual acuity, including type and cause, use of glasses or contact lenses, eye conditions with treatment regimens, and eye surgery.
Ensure removal of contact lenses or glasses and explain the importance of keeping the eyes open for the test.

After the Study: Implementation & Evaluation Potential Nursing Actions

Treatment Considerations

Provide information on glaucoma treatment and information regarding the clinical implications of the test results.
Review implications of abnormal test results on the patient’s lifestyle, such as impaired activity or anticipated loss of driving privileges due to loss of visual acuity.

Clinical Judgement

Consider how to address fears related to vision loss associated with glaucoma.

Follow-Up Evaluation and Desired Outcomes

Acknowledges that glaucoma is a leading cause of blindness in the United States. Agrees to seek additional information from the American Academy of Ophthalmology (www.aao.org), American Optometric Association (www.aoa.org/optometrists), National Eye Institute (https://nei.nih.gov/health/glaucoma), and All About Vision (www.allaboutvision .com/conditions/glaucoma.htm).