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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.

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.

Figure 590-1.

A 3-month-old girl with bilateral congenital glaucoma associated with corneal enlargement, cloudiness (note iris details are difficult to visualize), and photophobia.

Table 590-1. Causes of Corneal Opacification in Childhood

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 mm is considered small....

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