Funduscopically controlled scotometry.

Abstract

The following is a brief summary of the results in our ten groups of cases. The positive features of laser scotometry are emphasized. The normal response is well defined: there are no uncertain blind spot margins. The peripheral field is probably extended beyond 60 degrees nasally and superiorly. The size and shape of the small central scotomas associated with macular holes are easily defined and correlated directly with the visible edge of the hole. This result is distinct from the intact subjective response with cystoid maculopathy and surface wrinkling retinopathy. Plotting the margins of peripheral abnormalities such as retinal detachments, retinoschisis, and lattice degeneration is easily done. Schisis is distinguished by an absolute scotoma. This scotometry is facilitated by a larger "normal" field with the laser instrument. Lattice degeneration causes a field defect. A branch retinal artery occlusion shows a slightly jagged border, difficult to detect by standard methods. A cotton-wool spot does not show a total nerve-fiber-bundle defect. Small absolute scotomas are correlated with degenerative changes within nevi. Degenerative changes over small melanomas--ie, the orange spots--also produce absolute field defects. "Bear track" lesions have a normal field, whereas dense black isolated lesions are associated with absolute scotomas. In macular degeneration the bright laser test object is usually visible to the patient within detachments of neuroepithelium, detachments of the pigment epithelium, and over recent subretinal neovascularization. Response is absent over sharply-defined zones of pigment atrophy and over late subretinal fibrovascular mounds. In contrast to the degenerative cases, a selection of hereditary cases showed no direct correlation between the zone of pigment atrophy and the zone of absolute scotoma. The scotoma was much larger than the atrophic region, extending to the edge of the cream-colored subretinal spots. The laser target method sharply defines the absolute scotoma associated with papilledema. It also detects a slit-like nerve-fiber-bundle defect, suggesting progressive damage. Small, but possibly not the earliest, scotomas associated with glaucoma can be detected with laser scotometry. In some cases they are detected when the Goldmann perimetric field is normal. Late residual visual fields are easily defined, since fixation can be directly monitored. The vertical border of hemianopic defects can be defined within one degree of accuracy.

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