Biomedical subjects

P C Acosta

Publications and source records attributed to P C Acosta.

5 recordsLinked to original sources

PubMed1981

A screening method for chiasmal visual-field defects.

A strategy that selectively explores the vertical fixational meridian of the visual field was as sensitive as conventional quantitative Goldmann perimetry in detecting chiasmal hemianopic field defects, although it required only one quarter of the usual testing time. A trained but "masked" perimetrist, applying this abbreviated method to the examination of 28 eyes with hemianopic defects, 17 eyes with nerve-fiber defects, and 14 normal eyes, detected 100% of the hemianopias when using the Goldmann perimeter, 92% when using the conventional tangent screen, and 87% when using the projection tangent screen. False-positive diagnoses of hemianopic defects were 16%, 11%, and 14% on the respective instruments. While this strategy did not define the field defects fully, it accurately identified the features of diagnostic importance. By its efficiency, this approach may encourage greater use of visual fields as a determinant in managing the conditions of patients with unexplained visual loss.

Hemianopsia↗

PubMed1981

Confrontation visual field techniques in the detection of anterior visual pathway lesions.

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.

Hemianopsia↗

PubMed1981

Diagnostic strategies in the management of unexplained visual loss. A cost-benefit analysis.

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.

Cerebral Angiography↗

PubMed1980

An evaluation of the accuracy of community-based perimetry.

We assessed the accuracy of five office-based perimetric technicians in the examination of 14 patients with prechiasmal and chiasmal defects unknown to them. A pre-test followed by two days of instruction and supervised practice; the technicians were then retested on the same patients (post-test). An independent evaluator scored their results. The identification of any field defect rose significantly (P = .039) from 69% in the pre-test to 95% in the post-test. The identification of the hemianopic configuration of a defect rose from 45% in the pre-test to 84% in the post-test (P = .11); initial identification of nasal steps was 77%, falling to 67% in the post-test. Adequate definition of extent, depth, and slope of defects was rare (5%) on the pre-test, but rose significantly (P = .032) to 57% on the post-test. The monitored patient examinations were essential for correcting recurrent flaws in technique. This study shows that such teaching efforts, including emphasis on identifying hemianopic defects, are necessary to raise visual field examination to the level of a consistently reliable diagnostic determinant.

Evaluation Studies as Topic↗

PubMedDate not supplied

An algorithm for visual fields.

The authors present an algorithm, or sequential strategy, for the performance and interpretation of visual fields. Based on the principle that particular areas of the visual field are relatively vulnerable and that particular defect configurations are relatively more diagnostic, the strategy proposes certain "core maneuvers" for all initial examinations, followed by selective exploration of the vertical meridian "rectangle" and central "keyhole." This constitutes the "qualitative" portion of perimetry and combines threshold kinetic and suprathreshold static techniques. If time and patience permit, qualitative perimetry is followed by quantiative definition of defect size, depth and slope, using the requisite number of stimuli. This approach may be adapted to all visual field instruments. The interpretation of the field defects is based on assessing their localizing features.

Eye Diseases↗