OCT 21, 2010
The authors of this short "Research Letter," describe a technique that appears to rapidly identify patients with nonorganic visual field loss. They detail their novel use of kinetic perimetry to demonstrate and document a target visual field consistent with nonorganic visual field constriction.
To perform their repeated III4e isopter method, the authors use a Goldmann kinetic perimeter and present a size III4e stimulus peripherally. They gradually move it toward the center and plot when the patient indicates observation. Later, they present the same stimulus at the previously plotted location and moved toward the center.
The authors report their results using this technique in 18 patients (32 affected eyes) with nonorganic visual field loss, two healthy control subjects (two eyes) and eight control patients (eight eyes) with documented organic visual field loss. More than 90 percent of the nonorganic visual field loss patients recorded the second stimulus well inside the original plotted target field. None of the control patients demonstrated a target pattern.
The authors say use of this technique to demonstrate a target field can rapidly and reliably provide convincing documentation of nonorganic visual field loss, with testing of both eyes using only three isopters during kinetic perimetry taking just 10 to 15 minutes. However, they note that this method cannot be used for subjects whose reported visual fields are so constricted that they only respond at central fixation or whose reported decreased visual acuity precludes visualization of the testing isopter.