There are two methods of using the ophthalmoscope. The =indirect= and
the =direct= methods. One is more useful at one time and the other at
another time. By the indirect method we view the whole field of the
fundus more readily but less in detail. With the ophthalmoscope before
his eye the examiner’s face is twelve to fifteen inches from that of
the patient. When the “=red reflex=” of the eye is seen a plus 13 or 16
D lens is interposed near the patient’s eye. This magnifies the field.
The image is inverted. As a rule it is best seen with a +4 D lens in
the aperture of the ophthalmoscope.
This method is especially more satisfactory in high degrees of myopia
and astigmatism. The =optic disc= is the objective point. One may see
a retinal vessel first; this should be followed to its emergence from
the disc. From this point view all parts of the fundus by having the
patient look in different directions. This is better by the indirect
method than for the examiner to vary his position.
The direct method of ophthalmoscopy is better for detail work and in
all cases except high degrees of myopia and astigmatism. It is also
better in determining errors of refraction. The patient looks straight
across the room. For a beginner it may be essential to dilate the
pupil, hence the schematic eye as suggested.
If the examiner has a refractive error, he should wear his own glasses
or correct by throwing in front of his eye proper lenses in the
ophthalmoscope. Face the patient and sit on the side of the eye to be
examined. Use left eye to examine the patient’s left eye and right eye
for the patient’s right. Examiner and patient keep both eyes open. The
examiner may not be able to suppress the image of his other eye and may
have to close it part of the time. Catch the “red reflex” some 15 to 18
inches away and move close to the patient’s eye. The “red reflex” color
varies with the error of refraction, the transparency of the media, the
degree of pigmentation and the size of the pupil. A blood clot will
make it redder, some exudates will make it gray or yellow.
The examiner may approach as close as half an inch from the eye to be
examined. Find the optic disc and examine all points of the fundus from
it. Rotate in glasses to correct the patient’s refractive error if he
has any. The strongest plus glass with which the fine retinal vessels
can be clearly seen will represent the =hyperopia= of the eye. This
is true only if the examiner’s accommodation is at rest. The weakest
minus glass with which the fine retinal vessels can be clearly seen
represents the =myopia=.
=A Normal Fundus.=—The color of the fundus is due to the blood vessels
of the retina and choroid and the connective tissue of the choroid and
sclera. Variation is due to the pigment. In the albino it is light
pink. In the negro it is dark reddish. There are all gradations between
the two.
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