Importance of Visual Field
Visual Field
When we focus on a small object, we can see its details accurately because its image falls on the macula (central spot) of our eye. However, if we pay attention, even while keeping our eyes fixed on the object, we can also perceive a broader area around it—on the right, left, above, and below the object—but not with the same clarity. This broader area of vision is called the visual field.
The visual field allows us to be aware of our surroundings while focusing on a specific object. This ability not only enhances the efficiency of our visual system but also gives us better control over our environment.
If your doctor has recommended a visual field test, it typically indicates concerns about your optic nerve. This concern could stem from either ocular or neurological issues. The most common causes include increased intraocular pressure (leading to glaucoma), space-occupying lesions along the optic nerve path, increased cerebrospinal fluid pressure, or optic nerve inflammation.
Types of Visual Field Tests:
The test is conducted using a machine called a perimeter or hemisphere, where light points flash on a white screen. There are two main types of tests:
Kinetic Perimetry: In this method, light spots move within the hemisphere, and the observer has to identify them.
Static Perimetry: In this method, the position of the light spots remains fixed, and the observer presses a button when they detect the spot.
The most commonly used visual field analysis system is the Humphrey Automated Visual Field Analyzer, which uses central test patterns (24-degree or 30-degree visual field) for assessment.