MEASURING USABLE VISUAL FIELD AND SCOTOMAS

Visual field testing determines the extent and distribution of the patient's sensitivity to light.

Macular perimetry should be performed using flashing lights (patients fixate on a central spot and indicate when they can see flashing lights).

The preferred instrument used for macular perimetry should monitor fixation very carefully (for example, the scanning laser ophthalmoscope, SLO, even though its cost prohibits widespread use).

A hybrid technique is favored for those patients with age-related macular degeneration (AMD) whose fixation is less stable. This technique involves a single stimulus intensity for all test locations, like kinetic perimetry, but the target is presented at specific retinal locations (visual field locations) as in static perimetry.This technique detects small scotomas and determines the extent of the macular scotoma at a single isopter.

Amsler grid testing, although easy to use, has been shown to be insensitive to detecting the existence of scotomas and inaccurate at determining the extent of macular scotomas, because the lines on the grid often appear straight and complete even when there is a scotoma present.

Patients with visual loss may report photopsias or formed hallucinations.