Stimulus Parameters for Goldmann Kinetic Perimetry in Nonorganic Visual Loss

Abstract

Objective: To investigate the influence of the stimulus parameters on perimetry at various distances and draw conclusions for the clinical exploration of nonorganic visual loss. Methods: Visual field testing using Goldmann kinetic perimetry was performed on 15 healthy volunteers. The I/1e isopter at 33 cm was compared to the I/1e, II/1e and I/2e isopters at 66 cm. The 0/1e isopter at 33 cm was compared to the 0/1e, I/1e and 0/2e isopters at 66 cm. Results: Doubling the examination distance without adjusting the stimulus parameters resulted in significant perimetric visual field constriction. Doubling the stimulus diameter resulted in perimetric visual field expansion by a factor of 2.26 and 3.32 for I/1e and 0/1e, respectively. Increasing stimulus luminance by a factor of 3.17 caused expansion by a factor of 2.15 and 2.32 for I/1e and 0/1e, respectively. Conclusions: To avoid falsely diagnosing visual field constriction, stimulus parameters need to be adjusted when visual field testing is performed at double distance. Increasing stimulus luminance was more appropriate than augmenting stimulus size.

Functional vision loss

“…The examiner should not use regular letters because they reverse with the mirror, so Landolt Cs or tumbling Es are preferred. It is also necessary to enlarge the optotype stimulus when increasing the testing distance [24].…”