The accuracy of a variety of finger and color confrontation tests in identifying chiasmal and optic nerve visual field defects was assessed in patients whose field defects had been established beforehand by a conventional achromatic kinetic technique on the Goldmann perimeter. Kinetic and static finger confrontation methods identified an average of 42% of the 28 chiasmal hemianopic defects. False negatives included eyes with hemianopias complete to the largest (V4e) Goldmann isopter. False positives (average, 15%) occurred in eyes containing nerve fiber bundle defects with borders that fell near the vertical fixational meridian. Kinetic and static color confrontation techniques were 78.6% sensitive to hemianopias. Accuracy did not differ significantly whether the red target was presented kinetically or statically against the tangent screen, projected on the Autoplot screen, or held in the examiner's hand without attention to background. False positives (average, 23%) were slightly greater than with finger confrontation methods and occurred not only in eyes with nerve fiber bundle defects but also in eyes with no defects in reference visual fields. Finger confrontation identified 11% or fewer of optic nerve field defects, while some color techniques detected as many as 31 1/3%. There were no false positives.
In the investigation of visual loss from anterior visual pathway disease, it is imperative to differentiate the infrequent compressive from the much more common noncompressive lesions. To determine how relatively low-cost, risk-free, but error-prone visual field examination (VF) and high-cost, risk-prone, but accurate CT Scan (CT) and cerebral angiography (Angio) can be cost-effectively utilized to solve this diagnostic problem, the authors have developed a decision making model for the analysis of three management strategies. The visual field examination precedes and determines the use of neuroradiologic studies in Strategy A (VF-CT-Angio), whereas it follows the neuroradiologic studies in Strategies B (CT-VF-Angio) and C (CT-Angio-VF). The visual field-determined strategy (A) proved most cost-effective, based upon an estimated 6% or lower relative prevalence of chiasmal compressive lesions, a negligible risk in delaying their diagnosis, and a sensitive method of visual field examination. At a visual field sensitivity to chiasmal defects of 84% and a specificity of 88%, Strategy A annually saves $4 million over Strategy B and $27 million over Strategy C. At lower levels of perimetric accuracy, Strategy B is the most cost-effective approach. Strategy C is never cost-effective.
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