Visual Field Testing Flashcards

A patient undergoing Humphrey Visual Field testing shows a pattern of decreased sensitivity in a wedge-shaped defect that widens as it extends from the blind spot toward the nasal periphery, respecting the horizontal meridian. Which condition is MOST consistent with this pattern?

Answer: Glaucomatous arcuate nerve fiber bundle defect

An arcuate (Bjerrum) scotoma in glaucoma follows the arcuate nerve fiber bundles that sweep around the macula, originating at the optic nerve and arching toward the nasal raphe. The defect respects the horizontal meridian nasally and can extend from the blind spot in a wedge/arcuate shape. Pituitary adenomas cause bitemporal hemianopia; branch retinal artery occlusions cause dense altitudinal defects corresponding to retinal territory; occipital lesions cause congruous contralateral homonymous hemianopias.

During a 30-2 SITA Standard test, the mean deviation (MD) is -4.2 dB and the pattern standard deviation (PSD) is 6.8 dB. The glaucoma hemifield test (GHT) reads 'Outside Normal Limits.' Which interpretation is MOST accurate?

Answer: Localized defect superimposed on diffuse loss, suspicious for glaucoma

A high PSD (6.8 dB) relative to the MD (-4.2 dB) indicates the field loss is NOT uniformly depressed — there is significant point-to-point variability, meaning a localized defect exists within otherwise relatively preserved areas. This pattern, combined with GHT 'Outside Normal Limits,' is highly suspicious for glaucomatous focal nerve fiber bundle loss. Pure diffuse depression from media opacity or refractive error produces a high MD but a LOW PSD (uniform loss, no localized component). A macular scotoma would show central suppression with a different spatial pattern.

A technician notes that a patient's fixation losses on Humphrey perimetry are 8/14 (57%). The false positive rate is 2% and false negative rate is 5%. How should this field be interpreted?

Answer: Unreliable field due to fixation losses alone, but the pattern may still suggest a real defect if consistent with prior fields

Fixation losses >20% are considered unreliable by standard criteria. However, fixation losses can be spuriously elevated if the blind spot is not properly mapped (the Heijl-Krakau method projects stimuli to the presumed blind spot location, but patient head tilt or poor initial fixation setup causes false 'losses'). An experienced technician should note that despite high fixation losses, if the false positive and false negative rates are acceptable and the pattern is consistent with prior reliable fields, the result may still have clinical value. The field should be flagged as unreliable but not automatically discarded — clinical correlation and repeat testing are warranted.

Which visual field strategy uses a Bayesian approach to estimate threshold, presenting fewer stimuli by starting from a prior probability distribution derived from a database of normal and glaucomatous fields?

Answer: SITA Standard

SITA (Swedish Interactive Thresholding Algorithm) Standard uses a Bayesian approach incorporating prior probability distributions of both normal and glaucomatous visual fields to estimate threshold at each test location. It continuously updates its estimate based on patient responses, allowing fewer stimulus presentations than Full Threshold while maintaining comparable accuracy. SITA Fast uses the same Bayesian framework but with less stringent stopping criteria, reducing test time further at some cost to precision. Fastpac is an older strategy (not Bayesian) that reduces stimulus presentations by using larger step sizes. Full Threshold uses a staircase approach without a Bayesian prior.

A patient with known multiple sclerosis undergoes visual field testing. The result shows a unilateral, dense central scotoma in the right eye with a normal left eye field. The right eye visual acuity is 20/200. Which finding on visual field testing would MOST help distinguish optic neuritis from a macular lesion as the cause?

Answer: A cecocentral scotoma pattern extending from the blind spot to fixation

A cecocentral scotoma — a defect connecting the blind spot to the central fixation area — is characteristic of optic nerve disease affecting the papillomacular bundle, as seen in optic neuritis, toxic/nutritional optic neuropathies, and Leber's hereditary optic neuropathy. Macular disease typically causes a pure central scotoma without the connection to the blind spot. While an RAPD supports optic nerve disease, it doesn't differentiate the scotoma pattern. A preserved temporal crescent indicates intact far peripheral nasal retina and would not differentiate these conditions. A vertical step at the midline is characteristic of chiasmal or post-chiasmal lesions.

When performing Goldmann kinetic perimetry, a technician uses the III4e isopter and the I2e isopter to map a patient's visual field. The III4e isopter is found only 10° from fixation in all meridians, while the I2e cannot be detected. What is the MOST likely explanation for this severely constricted field?

Answer: Retinitis pigmentosa with classic tubular visual field

Retinitis pigmentosa classically produces a 'tubular' or 'gun barrel' field — severe mid-peripheral and peripheral constriction with relative preservation of a small central island. The I2e (small, dim stimulus) often cannot be detected in advanced RP because the peripheral retinal degeneration is severe, while the III4e (larger, brighter) may still map a tiny central island. End-stage glaucoma can also produce tubular fields but typically spares some temporal island. Functional loss characteristically produces spiral fields (the isopter spirals inward on repeated testing) or inconsistent fields not reproducible with kinetic technique. Bilateral occipital damage would produce bilateral homonymous field loss.