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The anterior segment of the eye consists of the cornea, the anterior
chamber, the iris, the pupil, and the lens, which anatomically divides
the anterior segment of the eye from its posterior segment. The
posterior segment includes the vitreous gel, the retina, the optic
nerve, and the choroid. This is a useful clinical division, because
many diseases of the eye predominantly affect the anterior or posterior
segment and are usefully differentiated from conditions (eg, endophthalmitis)
that affect the whole eye. Casual inspection of the eye (the globe)
is inevitably an assessment of the anterior segment structures and
offers very little information about the internal, more posterior
ocular structures. A checklist of anterior segment findings that
may be recognized by the pediatrician would include cornea size
and transparency; iris color (eg, heterochromia); pupil size, shape,
position, and reaction to light; lens clarity (eg, cataract) and
position (eg, dislocation/subluxation); and signs of elevated
eye pressure.
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Transparency of the cornea can be judged by how well the iris
can be visualized and by noting the appearance of the normally black
pupil. Comparing the patient’s cornea with those of a sibling
or parent can be helpful. A cloudy cornea (Fig. 590-1) is always a significant clinical
observation and has many pathological causes (Table
590-1). Corneal transparency is essential for normal vision,
and its loss is an important cause of childhood blindness. Corneal
opacification or change in the cornea’s size are essential
signs of both systemic and ocular disease. Some corneal conditions
that cause cloudiness are best treated promptly, such as glaucoma
and corneal keratitis (inflammation or infection of the cornea).
Glaucoma in young children causes corneal cloudiness and enlargement
(Fig. 590-1), as well as optic neuropathy,
potentially associated with permanent vision loss.
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The corneas are normally transparent and equal in diameter. Rapid
growth occurs in infancy, reaching adult size of 10 to 13 mm in
horizontal diameter by 12 to 81 months of life. A cornea with a
diameter greater than 13 mm is considered enlarged, and a diameter
less than 10 ...