The Tonopen (144) has recently become available for use in a wide variety of primary care settings. It is easy to use, reasonably accurate, and can be a very useful screening device in children and even infants. Any degree of forced eyelid closure renders the results invalid, but asymmetric values in particular can be very helpful in planning subsequent referrals and diagnostic interventions. The Tonopen can be utilized in children as young as 4 years of age during office examinations, and in infants who are sleeping (145) or actively bottle-feeding. Lastly, the direct ophthalmoscope can be used to assess the degree of optic nerve cupping and reproduced for the chart. Once referral has been made to the ophthalmic specialist, a much more detailed examination can be undertaken, usually under general anesthesia, including IOP determination, corneal diameter measurement, biomicroscopy of the anterior segment, gonioscopy (examination of the anterior chamber angle), funduscopy (including disc examination), and cycloplegic refraction. Ultrasonic biometric determination of axial length is obtained for the serial determination of ocular growth and glaucoma pressure control.

144

145

144, 145 Tonopen and its use in a sleeping child.

Differential diagnosis of pediatric glaucoma

The signs of glaucoma in children are shared by a multitude of other eye diseases, most of which occur much more commonly. Table 12 includes some of the ocular and systemic conditions involved with, and complicated by, pediatric glaucoma. Tearing is most commonly associated with nasolacrimal duct obstruction in children. Corneal enlargement can occur in the absence of glaucoma, but is uncommon and should warrant early referral to a specialist. Corneal opacification (146, 147) can occur in several ocular and systemic conditions. Storage diseases, corneal dystrophies, and anterior segment inflammation all warrant careful investigation and may require prolonged ocular and/or systemic treatment, even in the absence of glaucoma. Nevertheless, it is always important to exclude glaucoma in the presence of these signs or symptoms even when a nonglaucomatous cause is initially suspected.

146

147

146, 147 Bilateral corneal clouding in congenital hereditary endothelial dystrophy (CHED).IOP was normal.Patient’s older sister had similar corneal appearance with moderate visual compromise.Corneal transplantation was not required.

Primary infantile glaucoma

ETIOLOGY

Primary infantile glaucoma is the most common pediatric glaucoma, occurring in approximately 1 in 10,000 live births. Most cases (65–80%) are bilateral, but unilateral cases occur. Gender predilection has not been consistently described. About one-fourth of cases are diagnosed at birth, but more than 80% have onset of disease within the first year of life. Most cases of primary infantile glaucoma are sporadic without known family history, but about 10% of cases are familial, usually inherited as an AR trait. The primary defect consists of an isolated maldevelopment of the anterior chamber. The insertion of the iris can be observed to be higher than in unaffected children. The trabecular meshwork is less permeable to the passage of aqueous humor (148).

DIAGNOSIS

Disease severity can be variable, making early detection difficult in mild cases. Progressive corneal enlargement can occur with corneal edema caused by breaks in Descemet’s membrane (149) during the first year of life. Corneal enlargement over 13 mm in the first year of life is unusual and should arouse suspicion for the presence of increased intraocular pressure. Asymmetric corneal enlargement occurs in unilateral glaucoma and is surprisingly obvious even when as little as 1 mm of difference in horizontal diameter is noted (150).

148 Gonioscopic appearance of the angle deformity present in primary infantile glaucoma. Goniotomy was required for IOP control.

150 Asymmetric corneal enlargement in congenital glaucoma.Patient was referred by a family physician because of apparent drooping of the right upper eyelid.She responded well to goniotomy in the left eye and now has 20/30 vision with correction 12 years later. Right eye has remained normal without

IOP elevation.Current refraction is OD plano, OS + 2.00 + 2.25 × 160.

149 Haab’s striae.Horizontal rupture of Descemet’s membrane generally persists following normalization of IOP and is a major cause of astigmatism and amblyopia in children with congenital glaucoma.

150

MANAGEMENT/TREATMENT

Surgical intervention is the definitive treatment for primary infantile glaucoma. Angle surgery (goniotomy or trabeculotomy) is successful in lowering pressure in the majority of cases, but is less effective in cases presenting at birth or if diagnosis (and treatment) are delayed until after 2 years of age. Topical medication is generally less effective and can be difficult to administer chronically. Other surgical modalities including filtration, cycloablation, and glaucoma Seton implantation are used in cases refractory to angle surgery with variable success in lowering pressure.

PROGNOSIS

The ultimate visual outcome in children with primary infantile glaucoma depends upon the amount of damage to the optic nerve and the cornea as well the presence of any associated amblyopia. Structural changes in the cornea (scarring or astigmatism) or the development of significant levels of myopia lead to the development of amblyopia in many children with glaucoma. It is important to remember that the most common cause of poor vision in these children is secondary to amblyopia rather than optic nerve damage due to uncontrolled IOP.

Juvenile open-angle glaucoma

ETIOLOGY AND DIAGNOSIS

Juvenile open-angle glaucoma is a rare, bilateral and acquired form of pediatric glaucoma characterized by marked IOP elevation typically beginning late in the first decade of life. The etiology of juvenile glaucoma is similar to that of primary infantile glaucoma. The anterior chamber shows a similar high insertion of the iris.

Loss of central vision and/or visual field loss often brings the patient in for initial examination. The typical signs and symptoms of primary infantile glaucoma are not present in most cases.

MANAGEMENT/TREATMENT AND PROGNOSIS

Treatment is difficult. Many cases do not respond to medical management and will require surgery. Unlike primary infantile glaucoma, angle surgery tends not to be effective. Alternative pathways for the outflow of aqueous fluid are often needed.

Because of the lack of signs and symptoms early in the disease, most children present late when significant optic nerve damage has already occurred. Therefore, the prognosis tends to be poorer in these patients.