C h a p t e r
7
|
The Head and Neck
225
examples of abnormalities
Anatomy and Physiology andTechniques of Examination
Cornea and Lens.
With oblique lighting, inspect the cornea of each eye
for opacities and note any opacities in the lens that may be visible through
the pupil.
Iris.
At the same time, inspect each iris. The markings should be clearly
defined. With your light shining directly from the temporal side, look for a
crescentic shadow on the medial side of the iris. Because the iris is normally
fairly flat and forms a relatively open angle with the cornea, this lighting
casts no shadow.
See Table 7-9, Opacities of the
Cornea and Lens, p. 268.
Occasionally the iris bows abnor-
mally far forward, forming a very
narrow angle with the cornea. The
light then casts a crescentic shadow.
This narrow angle increases the risk
for acute narrow-angle glaucoma—a
sudden increase in intraocular pres-
sure when drainage of the aqueous
humor is blocked.
In open-angle glaucoma, the com-
mon form of glaucoma, the normal
spatial relation between iris and
cornea is preserved and the iris is
fully lit.
Miosis refers to constriction of the
pupils, mydriasis to dilation.
Light
Light
Pupils.
Inspect the
size, shape,
and
symmetry
of the pupils. If the pupils
are large (
>
5 mm), small (
<
3 mm), or unequal, measure them. Use a card
with black circles of varying sizes to measure pupillary size.
1 2 3 4 5
6
7 mm
Simple
anisocoria,
or a difference in pupillary size of 0.04 mm or greater, is
visible in approximately 35% of healthy people. If pupillary reactions are
normal, anisocoria is considered benign.
41
Test the
pupillary reaction to light.
Ask the patient to look into the distance,
and shine a bright light obliquely into each pupil in turn. Both the distant
gaze and the oblique lighting help to prevent a near reaction. Look for:
●●
The
direct reaction
(pupillary constriction in the same eye)
●●
The
consensual reaction
(pupillary constriction in the opposite eye)
Compare benign anisocoria with
Horner’s syndrome, oculomotor
nerve paralysis, and tonic pupil. See
Table 7-10, Pupillary Abnormalities,
p. 269.
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