Age effects on frequency doubling perimetry testing in drive.

Abstract

Ageing produces a series of changes that affect the entire organism. Effect on vision include a loss of visual acuity (VA) and contrast sensitivity (CS) and an increased sensitivity towards glare. Recent studies have shown that the contrast threshold varies in young subjects at a rate of 0.10 dB/per decade of age. The visual field can be measured using several methods. Herein, we used an instrument based on frequency doubling (FDT) technology. There are two main visual afferent pathways, magno and parvo. Cells of hte parvo pathway, or P cells, are responsible for analyzing details and colour. These cells have small receptive fields and axons, and they elicit a linear response. The magno, or M cell, system deals with motion; M cells have large axons and receptive fields and they respond to all stimuli. The precision required for the tasl of driving means that these two systems need to function in a coordinated manner, although M cells, since they detect motion, participate most in controlling the size and sensitivity of the visual field. The FDT instrument uses stimuli that are only detected by de M (nonlinear) cells, since P (linear) cells are unaffected by large, moving, colourless stimuli.