The eye maintains healthy pressure through a balance between production and drainage of aqueous humor, a clear fluid inside the eye. This fluid drains through a structure called the iridocorneal angle (drainage angle). In dogs with abnormal or narrowed drainage angles, fluid outflow becomes restricted, increasing the risk of elevated eye pressure and glaucoma.
Gonioscopy is performed to visually examine this drainage angle using a special magnifying lens called a gonioscope. During the procedure, a veterinarian or veterinary ophthalmologist places a contact lens on the surface of the eye after applying a local anesthetic. This allows direct visualization of the internal drainage structures and helps assess whether the angle is normal, narrowed, or abnormal.
The test is especially important in breeds predisposed to Primary Angle-Closure Glaucoma (PACG) or Primary Open Angle Glaucoma (POAG), where structural abnormalities of the drainage system may be present before any clinical symptoms appear.
Clinical signs of glaucoma risk may not be visible during early stages. However, dogs that eventually develop glaucoma may show symptoms such as eye redness, excessive tearing, squinting, cloudiness of the cornea, enlarged eyes (buphthalmos), and vision loss. Because damage from glaucoma is irreversible, early detection of abnormal drainage angles is critical.
The Gonioscopy (PLA) Test is typically performed by a veterinary ophthalmologist and provides a direct assessment of the eye’s anatomical risk factors. It is often part of a comprehensive eye examination along with intraocular pressure measurement (tonometry) and slit-lamp biomicroscopy.
Results are generally reported as:
- Normal Angle: The drainage angle appears open and functional, with low risk of primary glaucoma.
- Mild Abnormality: Slight narrowing or structural variation is present, indicating increased risk and need for monitoring.
- Moderate Abnormality: Significant narrowing of the drainage angle, associated with higher glaucoma risk.
- Severe Abnormality (High Risk): Marked angle closure or malformation, strongly predisposing the dog to primary glaucoma.
Gonioscopy is highly valuable for breeders, veterinarians, and dog owners. For breeders, it helps identify dogs with healthy eye anatomy and reduce the risk of passing on structural predisposition to glaucoma in future generations. For at-risk breeds, routine screening is often recommended before breeding decisions are made.
For dog owners, early detection of abnormal drainage angles allows proactive monitoring and preventive care. While gonioscopy does not treat disease, it helps guide long-term eye health management. Dogs identified as high risk should undergo regular ophthalmic check-ups to monitor intraocular pressure and detect early signs of glaucoma.
The Gonioscopy (PLA) Eye Screening Test is a valuable diagnostic tool that supports early identification of glaucoma risk, improves breeding decisions, and helps protect long-term vision health in dogs.
