About this procedure
Visual-field loss may cause difficulty noticing objects to the side, but many people notice little at an early stage. Clinicians may recommend perimetry even without major symptoms when optic nerve findings or other risk factors warrant functional testing.
Clinical features
Perimetry and OCT measure different things. Perimetry tests functional sensitivity to light, while OCT depicts the structure of retinal or optic nerve tissues. Neither should be interpreted in isolation as a complete diagnosis of glaucoma or a neurological condition.
Important differences and warning signs
During the examination a person looks at a fixed point and signals when a light is noticed. Attention, fatigue, eye position and familiarity with the task affect reliability. A repeat test may be appropriate to distinguish variability from a persistent change.
Assessment and individual care
The ophthalmologist reviews the visual-field map alongside eye pressure, optic nerve findings and previous results. Results help guide monitoring, but a single abnormal plot does not prove a particular disease. The scope of testing and follow-up are decided individually.
Related information: Glaucoma; OCT eye scanning.
Signs and symptoms
- Difficulty detecting objects to one side or bumping into obstacles.
- No clear symptoms despite suspected field changes at examination.
- Need to compare functional vision over time during eye or neurological follow-up.
Diagnosis and tests
Computerised light-detection testing is interpreted with reliability indices and the wider eye examination, sometimes requiring repeated measurements.
Care and treatment approaches
The result informs diagnosis and monitoring, but does not itself provide treatment. Any change to care is decided by the ophthalmologist.
When to seek urgent care
Sudden loss of part of the visual field can indicate an eye or neurological emergency. Do not wait for scheduled perimetry; seek urgent care and call 103 for abrupt visual loss or accompanying neurological deficits.
Frequently asked questions
How is perimetry different from OCT?
Perimetry measures the function of the visual field; OCT shows the anatomical structure of retinal or optic nerve tissues.
Why might the test need repeating?
Fatigue, learning effects and fixation can alter results, so comparison or repetition may help confirm a real change.
Does an abnormal visual-field test automatically mean glaucoma?
No. The ophthalmologist combines results with the optic nerve examination, pressure measurements and other clinical findings.
Information sources
Medical source links used when preparing this article.
Important information
A medical consultation is needed for diagnosis and treatment recommendations.
Self-treatment can be harmful to your health.
