The visual field analyzer (automated perimeter) is one of the most important diagnostic instruments in optometric practice. It maps functional peripheral and central vision, detecting losses caused by glaucoma, neurological lesions, retinal disease, and other conditions. Paraoptometric professionals who perform visual field tests are responsible for ensuring reliable results through proper patient preparation, positioning, and instruction—making their role directly critical to diagnostic accuracy.
Preparing for Visual Field Testing
Enter Patient Data
Enter name, date of birth, and any relevant correction (near add, contact lens) into the perimeter software. Confirm the correct eye to be tested first.
Near Correction Lens
For patients over ~40, place the appropriate near correction in the trial lens holder. The correction power depends on the patient's age and the test distance (typically 33 cm for Goldmann; variable for automated perimetry—follow the instrument protocol).
Patch the Fellow Eye
Use an eye patch or occluder to cover the non-test eye. Ensure no pressure is applied to the eye (pressure can temporarily distort vision in the patched eye, affecting the next field).
Explain the Test
Thorough patient instruction before starting dramatically reduces fixation losses and improves reliability. Walk through all key points: fixate center, press button on every flash, don't worry about misses.
Adjust Position
Position the patient comfortably. Chin and forehead should contact their respective rests. The test eye should be at the center of the bowl. Drooping lids may need to be taped for patients with significant ptosis.
Select Protocol
Choose the appropriate test program: 24-2 SITA Standard or Fast for glaucoma monitoring; 30-2 for neurological concerns; FDT or SITA-SWAP for early detection.
Reliability Indices: What They Mean
| Index | Acceptable | Elevated Means | Effect on Field |
|---|
Common Visual Field Defect Patterns
- Arcuate Scotoma — RNFL—superior or inferior bundle — Glaucoma (classic), AION — Arc-shaped defect following the nerve fiber layer distribution; starts near blind spot and arcs to the nasal horizontal midline
- Nasal Step — RNFL—superior or inferior nasal bundle — Early glaucoma — Loss in nasal field that respects the horizontal midline; often an early glaucoma sign
- Altitudinal Defect — Horizontal midline — AION, retinal artery/vein occlusion, glaucoma — Loss in the upper or lower half of the visual field, respecting the horizontal midline
- Bitemporal Hemianopia — Optic chiasm (crossing fibers) — Pituitary tumor/adenoma, craniopharyngioma — Loss of temporal (outer) fields in both eyes; respects vertical midline; classic chiasmal lesion pattern
- Homonymous Hemianopia — Post-chiasmal visual pathway — Stroke, tumor affecting optic tract, radiation, or occipital cortex — Loss of the same side of the visual field in both eyes (e.g., left half of field in both OD and OS) respecting the vertical midline
- Generalized Depression — Diffuse — Cataract (media opacity), pupil abnormalities, fatigue, advanced glaucoma — Overall reduction in sensitivity across the entire field; often artifactual due to media opacity or poor test reliability