Apertures And Filters - Welch Allyn PanOptic 118 Series Directions For Use Manual

Apertures and Filters

There is a wide range of practical apertures and filters to select from:
small spot, large spot, micro spot, slit aperture, red-free filter, cobalt
blue filter (optional), and half-moon aperture (optional).
1. Small Aperture: Provides easy view of the fundus
through an undilated pupil. Always start the examination
with this aperture and proceed to micro aperture if pupil is
particularly small and/or sensitive to light. This position is
the "Home" position on the aperture dial and is denoted
by the green marking.
2. Large Aperture: Standard aperture for dilated pupil
examination of the eye.
3. Micro Spot Aperture: Allows easy entry in very small,
undilated pupils.
4. Slit Aperture (Models 11810, 11820 only): Helpful in
determining various elevations of lesions, particularly
tumors and edematous discs.
5. Red-Free Filter (Model 11810, 11820 only): This filter
excludes red rays from the examination field: this is
superior to ordinary light in viewing slight alterations in
vessels, minute retinal hemorrhages, ill-defined exudates and
obscure changes in the macula. The nerve fibers become visible
and the observer may note the disappearance of such fibers, as in
optic nerve atrophy. The background appears gray, the disc
appears white, the macula appears yellow, the fundus reflex is
intense and the vessels appear almost black. This filter is also
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