Papadopoulos M, Cable N, Rahi J, Khaw PT; BIG Eye Study Investigators. The British Infantile and Childhood Glaucoma (BIG) Eye Study. Invest Ophthalmol Vis Sci. 2007;48(9):4100–4106.
Yeung HH, Walton DS. Clinical classification of childhood glaucomas. Arch Ophthalmol. 2010; 128(6):680–684.
Primary Childhood Glaucoma
Primary Congenital Glaucoma
PCG is also called congenital or infantile glaucoma. The incidence of PCG varies in different populations, ranging from 1 in 2500 to 1 in 68,000. PCG results in blindness in 2%–15% of cases. Visual acuity remains worse than 20/50 in at least 50% of cases. PCG is bilateral in about two-thirds of patients and occurs more frequently in males (who account for 65% of cases) than in females.
Although diagnosis is made at birth in only 25% of affected infants, disease onset occurs within the first year of life in more than 80% of cases. Neonatal-onset and late-recognized PCG are associated with guarded prognoses.
Pathophysiology
The basic pathologic defect is increased resistance to aqueous outflow due to abnormal development of anterior chamber angle tissue, which is derived from neural crest cells. The anomaly occurs late in embryologic development.
Clinical manifestations and diagnosis
PCG usually presents in the neonatal or infantile period. Epiphora, photophobia, and blepharospasm constitute the classic clinical triad of PCG. Eye redness may be present. Other signs include clouding and enlargement of the cornea (Fig 22-1).
Figure 22-1 Primary congenital glaucoma, right eye. The cornea is enlarged. (Courtesy of Gregg T. Lueder, MD.)
Corneal edema results from elevated intraocular pressure (IOP) and may be gradual or sudden in onset. Corneal edema is often the presenting sign in infants younger than 3 months and is responsible for the clinical triad. Microcystic edema initially involves the corneal epithelium but later extends to the stroma, often accompanied by 1 or more curvilinear breaks in Descemet membrane (Haab striae). Although edema may resolve with IOP reduction, the split in Descemet membrane persists as paired curved lines. Significant corneal scarring and persistent opacification may require penetrating keratoplasty.
Corneal enlargement occurs with gradual stretching of the cornea as a result of elevated IOP. In newborns, the normal horizontal corneal diameter is 9.5–10.5 mm; a diameter greater than 11.5 mm suggests glaucoma. By age 1 year, the normal corneal diameter is 10.0–11.5 mm; a diameter greater than 12.5 mm suggests abnormality. Glaucoma should be suspected in any child with a corneal diameter greater than 13.0 mm.
The signs and symptoms of PCG can occur in infants with other forms of glaucoma as well. Nonglaucomatous conditions may also cause some of the signs and symptoms seen in PCG (Table 22-2).
Table 22-2
Diagnostic examination A full ophthalmic examination of every child suspected of having glaucoma is imperative, despite the challenges. Both office examination and examination under general anesthesia are usually required. Although it is helpful in following disease progression in older children, visual field testing is rarely reliable in children younger than 6–8 years. Vision is usually poorer in the affected eye in unilateral cases and may be poor in both eyes when glaucoma is bilateral. Fixation and following behavior and the presence of nystagmus should be noted. Refraction measurement, when possible, often reveals myopia and astigmatism from eye enlargement and corneal irregularity.
CORNEAL INSPECTION The cornea should be examined for size, clarity, and Haab striae. A difference in corneal diameter of the eyes as small as 0.5 mm may be significant. Haab striae are best seen against the red reflex after pupil dilation (Fig 22-2).
Figure 22-2 A, Breaks in Descemet membrane (Haab striae), right eye. B, Retroillumination, same eye.
TONOMETRY If the child is struggling during measurement of IOP, pressure readings may be falsely elevated. IOP is unpredictably altered (usually lowered) when systemic sedatives or anesthetics are administered. A useful technique is to have a parent bottle-feed the hungry infant at the time of pressure measurement. The Tono-Pen (Reichert Ophthalmic Instruments, Depew, NY), Icare (Icare Finland Oy, Helsinki, Finland), and Perkins (Haag-Streit USA, Mason, OH) tonometers are most commonly used for infants and young children. Goldmann applanation readings are preferred when a child is old enough to cooperate.
The normal mean IOP in infants and young children is lower than in adults: between 10 and 12 mm Hg in newborns and approximately 14 mm Hg by age 7–8 years. In PCG, IOP commonly ranges between 30 and 40 mm Hg, and it is usually greater than 20 mm Hg even under anesthesia. Asymmetric IOP readings in a quiet or anesthetized child should raise suspicion of glaucoma.
MEASUREMENT OF CENTRAL CORNEAL THICKNESS Portable ultrasonic pachymeters may be used to measure central corneal thickness (CCT), which is typically higher in infants with glaucoma. The CCT affects the IOP measurement, but current evidence is inadequate to quantify these effects. See also Chapter 15.
Freedman SF. Central corneal thickness in children—does it help or hinder our evaluation of eyes at risk for glaucoma? J AAPOS. 2008;12(1):1–2.
ANTERIOR SEGMENT EXAMINATION A portable slit lamp allows detailed inspection of the anterior segment. An abnormally deep anterior chamber and hypoplasia of the peripheral iris stroma are common findings in PCG.
Gonioscopy provides important information regarding the mechanism of glaucoma. It is best performed with the use of a goniolens and a portable slit lamp or loupes. The anterior chamber angle of a normal infant’s eye (Fig 22-3A) differs from that of an adult in the following ways:
The trabecular meshwork is more lightly pigmented. The Schwalbe line is often less distinct.
The uveal meshwork is translucent, so the junction between the scleral spur and the ciliary body band is often not well seen.
Figure 22-3 A, The anterior chamber angle of a normal infant’s eye, as seen by direct gonioscopy with a Koeppe lens. B, Typical appearance of the anterior chamber angle of an infant with congenital glaucoma. (Courtesy of Ken K. Nischal, MD.)
In PCG, the iris often shows an insertion more anterior than that in a normal infant, and the translucence of the uveal meshwork is altered, making the ciliary body band, trabecular meshwork, and scleral spur indistinct. The scalloped border of the iris pigment epithelium is often unusually prominent, especially when peripheral iris stromal hypoplasia is present (Fig 22-3B).