1. The EARL-LIGHT
A New Tool for Improving Microscopic
Diagnosis in the Field in Developing Countries
2. In most developing countries:
The biologic diagnosis of many infectious diseases (including the two
major killers, malaria and tuberculosis) relies on microscopic examination
of stained specimens.
However, this examination is often hindered by the lack of a reliable light
source to illuminate the specimens.
• Microscopes which depend on a light bulb are unusable during power
failures.
• Microscopes equipped with a mirror that reflects ambient daylight are
unusable at night, during cloudy days, or when far from a well-lighted
window.
This problem can now be overcome with a versatile illuminator (the EARL-
Light*) initially developed by the US Centers for Disease Control and
Prevention (Atlanta, USA).
*EARL: External, Autonomous, Repositionable, Lightweight
3. Figure 1
Figure 2
A battery pack (A) powers a light-emitting diode (C); a
flexible stem (B) allows the microscopist to direct the light
beam towards a microscope mirror (as in Fig 1), or to shine
directly into a microscope condenser (as in Fig 2).
A
A
B B
C
C
The EARL-Light
4. Flexible
metal stem
(33 cm; 13”)
allows
variable
positioning
of the light
beam
White light-emitting
diode: produces an
intense, cool bluish
white light (thus no
filter required and
no heat produced)
Cover
(removed to
show
batteries)
Three flashlight (D) batteries provide
power for 1,250 hours (one year of work, at
4 hours a day, 6 days per week)
Rotating knob
functions as switch
and intensity
control
The EARL-Light
-670 gm (1.5 lb)
-13 X 13 X 4 cm (5.1 X 5.1 X 1.6”)
5. Using the EARL-Light under field conditions
(Democratic Republic of Congo)
Malaria parasites
Tuberculosis bacilli
Two major killers in the
developing world, seen
through microscopes using
illumination provided by the
EARL-Light.
