3.2 Confrontation Fields & Automated Perimetry in Retina

Confrontation Fields and Automated Perimetry

Visual-field testing asks what locations can be detected while fixation is maintained. Retina technicians need a reproducible technique and an understanding of artifacts, but should not turn an automated printout into an independent diagnosis.

Confrontation screening

Test one eye at a time with appropriate distance correction when needed. Sit at approximately eye level, ask the patient to look at the examiner's open eye or nose, and compare responses in corresponding areas of the examiner's own field. Depending on protocol, use finger counting, finger movement, or a small red target. Sample all quadrants and the horizontal and vertical meridians. Monitor fixation and repeat surprising responses.

Confrontation can reveal a dense hemianopia, quadrantanopia, altitudinal loss, or large central defect, but it is insensitive to subtle loss. Record the target, distance, eye, correction, fixation quality, and pattern observed. An abnormal screen usually calls for clinician review and, when ordered, formal perimetry.

Automated static perimetry

The perimeter presents stimuli against a controlled background and adjusts intensity to estimate differential light sensitivity in decibels. Common central programs include 10-2, 24-2, 24-2C, and 30-2. Grid names describe sampling patterns, not diagnoses. The ordered program, stimulus size, strategy, correction, pupil, and tested eye all matter.

Before testing, explain fixation, the response button, normal pauses, and why the patient should respond only when a stimulus is seen. Position the patient comfortably, enter the correct birth date and lens, patch the fellow eye, avoid lens-rim obstruction, and monitor gaze and fatigue. Trial lenses must be close enough to reduce rim artifact without touching lashes.

Reliability and artifacts

Fixation losses, false positives, false negatives, gaze tracking, response time, and technician observations help judge quality. No single percentage is a universal accept-or-reject rule across all devices, algorithms, diseases, and patients. A high false-positive pattern can create implausibly high sensitivities and an abnormally bright field; false negatives may rise in genuine advanced disease or fatigue. Lens rims, ptosis, small pupils, defocus, cataract, poor fixation, and learning effects can mimic loss.

Review raw thresholds, total deviation, pattern deviation when available, grayscale, probability plots, and repeatability. Pattern deviation adjusts for generalized depression, but it can also mislead in diffuse or advanced loss. The clinician interprets the complete study.

Choosing the grid

A 10-2 grid densely samples the central field and can support evaluation of macular disease. Wider patterns sample more eccentric retina and are often needed for peripheral, pericentral, or neurologic questions. Do not choose a grid solely from race or ethnicity; disease pattern and the clinician's order control.

Hydroxychloroquine screening update

The AAO's 2025 revision recommends spectral-domain OCT plus wide-pattern fundus autofluorescence as the primary objective screening tools. Automated fields and multifocal electroretinography are secondary or confirmatory tests. When fields are used, testing should be capable of assessing both parafoveal and pericentral patterns; a combined pattern such as 24-2C or appropriately selected central and wider grids may be used. A single noisy field must not trigger a medication decision. Repeat questionable acquisition and compare it with OCT, FAF, prior fields, and clinician assessment.

Technician workflow

1. Verify the order, eye, program, correction, and patient factors.
2. Explain and demonstrate the task without coaching toward a desired response.
3. Monitor fixation, lids, lens position, and fatigue.
4. Save the complete report and note deviations or interruptions.
5. Repeat only according to protocol or clinician direction.
6. Route urgent or unexpected findings promptly without independently diagnosing them.

Perimetry is most useful when technique is reproducible and serial tests are comparable.

Quality control and escalation

For confrontation testing, position the patient at the protocol distance, align eye level, occlude the non-tested eye without pressure, and compare the patient's field with the examiner's field. Present targets from nonseeing to seeing areas in more than one quadrant and vary timing so the patient cannot anticipate. Poor fixation, ptosis, spectacle rims, fatigue, hearing difficulty, or an examiner field defect can create a false abnormality.

Automated perimetry requires correct patient and eye, current near correction when specified, trial-lens position, pupil information, fixation setup, and the ordered strategy. Watch for lens-rim artifact, head drift, trigger-happy responses, sleepiness, and loss of fixation. Reliability indices and grayscale appearance support quality review but do not independently prove disease. Save the complete report and route unexpected defects, unreliable studies, or symptoms to the clinician. Repeat testing only when authorized; a technician does not delete an unfavorable field or substitute another strategy to make the printout look normal.