Dark adaptometry and FST test

Introduction

The examination of dark adaptation evaluates the recovery of light sensitivity after exposure to bright light.
It presents several clinical applications:
• the functional evaluation of processes that affect directly the eye (retinitis pigmentosa, ..) Responses can often be obtained with the psychophysical exam of dark adaptation whereas the electroretinogram is extinct,
• when a metabolic process is suspected (vitamin-A deficiency),
• the functional evaluation of subjects working under low luminance conditions,
• the evaluation of subjects who complain of visual difficulties at night.

The FST test (Full Field Stimulus threshold) measures the threshold of light sensitivity with full field stimulations after dark adaptation.
It is used during clinical research studies, for example for retinitis pigmentosa. The use of full field stimulations allows measurements even when fixation is not stable (nystagmus).

Methodology

The program for dark adaptometry starts with a light adaptation phase of typically 5 minutes duration followed by a dark phase.
Tests for false positives are included to evaluate the patient's reliability.
The curve here-by shows a typical result. The ordinate scale is given in dB with a 0 dB level set at 318 cd/m2 (reference of the Goldmann perimeter).

The program for the FST test begins right after dark adaptation and measures the sensitivity threshold to full field light stimulations with a staircase strategy starting from the lowest luminance level.

Specifications

This program is available on several models of the Vision Monitor:
- MonCvONE for clinical research. It includes the FST tests (full field stimulus threshold) as well as tests with several wavelenths and several locations,
- MonPackONE, for standard clinical exams and
- MonCv3, for screening exams.
For detailed specification,refer to the PDF brochure.