Welch Allyn 18200 Manual Del Usuario página 7

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F) Rotate the control sleeve until the streak is horizontal
and move the streak vertically. The reflex will appear as in
Figures 4 or 5.
No oblique astigmatism
G) If the streak and the reflex move in the same direction with
no lens in the refractive apparatus, the refraction is one of
these:
1. Hyperopia;
2. Emmetropia;
3. Myopia of less than 1.50 diopters.
If the reflex moves in the opposite direction, the error is myopia
greater than 1.50 diopters.
3. Determining Refractive Error By Neutralization
Before starting, make sure the eye not being refracted has some
"against" motion using the plano mirror effect. This will blur vision
to prevent accommodation. If "with" or neutral motion is noticed
initially, place about a +1.00 sphere before the eye once neutral
motion is seen.
A) Neutralizing with spheres only:
1. Change sphere in the minus direction until the reflexes in
all axes have "with" motion.
2. Adjust in the plus direction until the reflex fills the pupil
in one meridian and all motion has stopped. This will be
one of the principal meridians if astigmatism is present.
That meridian is then said to be neutralized.
Figure 4 Figure 5
Oblique astigmatism
5