Although the 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.
Primary congenital glaucoma usually presents in the neonatal period or within the first 2 years of life (infantile PCG), but it can present or be recognized after 2 years of age (late-onset or late-diagnosed PCG). Epiphora, photophobia, and blepharospasm constitute the classic clinical triad of PCG. A red eye may be present. Other signs include clouding and enlargement of the cornea (Fig 22-2).
Corneal edema results from elevated 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 into the stroma, often accompanied by one or more curvilinear breaks in Descemet membrane (Haab striae) (Fig 22-3). Although the edema may resolve with IOP reduction, the split in Descemet membrane persists. 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.
Figure 22-2 Primary congenital glaucoma, right eye. The cornea is enlarged.
(Courtesy of Gregg T. Lueder, MD.)
A, Breaks in Descemet membrane (Haab striae), right eye. B, Retroillumination, same eye.
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).
A full ophthalmologic 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 visual field testing is helpful in following disease progression in older children, results of these tests are 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, when possible, often reveals myopia and astigmatism from eye enlargement and corneal irregularity.
The cornea should be examined for size, clarity, and Haab striae. In newborns, the normal horizontal diameter of the cornea 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. A difference as small as 0.5 mm between the 2 eyes may be significant. Haab striae are best seen against the red reflex after pupil dilation (see Fig 22-3B).
Table 22-2 Differential Diagnosis of Signs in Primary Congenital Glaucoma
Central corneal thickness
Portable ultrasonic pachymeters may be used to measure central corneal thickness (CCT), which is typically higher in infants with glaucoma. CCT affects the IOP measurement, but current evidence is inadequate to quantify these effects. See also Chapter 15.
If the child is struggling during measurement of IOP, pressure readings may be falsely elevated. Examination under sedation or anesthesia may be necessary in children for accurate assessment, but IOP can also be unpredictably altered (usually lowered) with anesthetics and sedation. A useful technique to avoid these issues is to have the parent bottle-feed the infant during pressure measurement. In infants and young children, the most commonly used tonometers are Icare (Icare Finland Oy, Helsinki, Finland), Tono-Pen (Reichert Technologies, Depew, NY), and Perkins (Haag-Streit USA, Mason, OH). 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 that 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 with the patient under anesthesia. Asymmetric IOP readings in a quiet or anesthetized child should raise suspicion of glaucoma.
A portable slit lamp enables detailed examination 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 about the mechanism of glaucoma. A direct (Koeppe-type) goniolens is preferred for examining children. The anterior chamber angle of a normal infant eye (Fig 22-4A) differs from that of an adult’s eye 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.
In an eye with PCG, the iris often shows a more anterior insertion compared with the insertion in a normal infant eye, and the translucence of the uveal meshwork is altered, making the ciliary body band, trabecular meshwork, and scleral spur indistinct (Fig 22-4B). The scalloped border of the iris pigment epithelium is often unusually prominent, especially when peripheral iris stromal hypoplasia is present.
In PCG, the optic nerve, when visible, usually shows increased cupping. Generalized enlargement of the optic cup in very young patients with glaucoma has been attributed to stretching of the optic canal and backward bowing of the lamina cribrosa. In most eyes with PCG, the cup–disc ratio exceeds 0.3, whereas in most normal newborn eyes, the cup–disc ratio is less than 0.3. Cup–disc asymmetry greater than 0.2 between the 2 eyes is also suggestive of glaucoma. In young children, optic nerve cupping may be reversible if IOP is lowered (Fig 22-5). Whenever possible, photographs should be taken of the optic disc for comparison during later examinations.
A, The anterior chamber angle of a normal infant eye, as seen by direct gonioscopy with a Koeppe lens. B, Typical appearance of the anterior chamber angle of an infant with primary congenital glaucoma. Note the scalloped appearance of the peripheral iris. The anterior iris insertion obscures the scleral spur.
(Courtesy of Ken K. Nischal, MD.)
Figure 22-5 Optic nerve changes after treatment of congenital glaucoma. A, Preoperative enlarged optic disc cup. B, Reduction in disc cupping after intraocular pressure is reduced by goniotomy.
(Reproduced from Mochizuki H, Lesley AG, Brandt JD. Shrinkage of the scleral canal during cupping reversal in children. Ophthalmology. 2011;118(10):2009.)
Serial measurement of axial length is useful for monitoring disease progression in infant eyes. Excessive axial length in an eye, especially compared with the fellow eye, may indicate inadequate IOP control.
Optical coherence tomography
Newer methods of optic nerve and retinal nerve fiber analysis, such as optical coherence tomography (OCT), are being used as objective tools for follow-up of children with elevated IOP and glaucoma. Macular thickness, retinal nerve fiber layer thickness, and optic nerve topography have been shown to vary with race, axial length, and age in children, but normative data are becoming available, which should further increase the usefulness of OCT in the assessment of pediatric glaucoma.
El-Dairi MA, Asrani SG, Enyedi LB, Freedman SF. Optical coherence tomography in the eyes of normal children. Arch Ophthalmol. 2009;127(1):50–58.
Prakalapakorn SG, Freedman SF, Lokhnygina Y, et al. Longitudinal reproducibility of optical coherence tomography measurements in children. J AAPOS. 2012;16(6):523–528.
Untreated PCG almost always progresses to blindness. The cornea irreversibly opacifies and may vascularize. It may continue to enlarge through the first 2–3 years of life, reaching a diameter of up to 17 mm. As the entire eye enlarges, pseudoproptosis and an “ox eye” appearance (buphthalmos) may result. Scleral thinning and myopic fundus changes may occur, and spontaneous lens dislocation can result. Optic nerve damage progresses, leading to complete blindness. However, rare cases of spontaneous resolution have been reported.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.