A thorough, accurate clinical evaluation is essential for diagnosis, classification and treatment of pediatric glaucoma, which may be primary or secondary. Primary congenital glaucoma (PCG) occurs in about 1 in 10,000 births, representing 50 to 70 percent of congenital glaucoma cases and 22 percent of all pediatric glaucomas. Examination of a pediatric patient can be challenging, especially for certain glaucoma-specific exam elements or when the patient is uncooperative or unwilling. This article discusses the most important exam elements for glaucoma diagnosis and management.
Tonometry: Intraocular Pressure
Intraocular pressure (IOP) is the key exam element in the diagnosis, classification and treatment of pediatric glaucoma. Optimal IOP measurements are obtained in the office because IOP is usually lowered by most anesthetic agents and sedatives.1,2 Normal IOP in infants ranges from 10 to 15 mmHg under anesthesia.2 If an exam under anesthesia (EUA) is needed, IOP should be measured as soon as possible after anesthesia is induced.2 In contrast, other medications, such as ketamine and succinylcholine, may raise IOP.1,2 Since crying and screaming also elevate IOP, measurements should ideally be taken in the office when the baby is not crying or is distracted. Although chloral hydrate does not appear to affect IOP in either normal or glaucomatous eyes,1,3 this is not a convenient method for repeat office exams.
A variety of methods can be used for office IOP measurement. Parents can be told not to feed the baby for two hours prior to the appointment, at which time the patient is fed. While the baby is drinking from a bottle, IOP can often easily be measured. In children who are older but still under four to five years of age, the portable Perkins applanation tonometer (Haag-Streit USA, Inc.) is a dynamic method that allows the examiner to know the child's IOP between cries or when not squeezing. A lid speculum is not recommended because it often upsets both parents and patients. Plus, by manually holding the eyelids open, the examiner can assess when the patient is not squeezing and when IOP measurement is most accurate. Slit-lamp Goldmann applanation tonometry is still the gold standard; so when the patient is a few years old and certainly by age four or five, attempts should be made to check the IOP at the slit lamp. Other authors have also used the Tono-Pen XL (Medtronic Solan) for infants and young children.1,4,5
Central Corneal Thickness
Since the importance of central corneal thickness (CCT) measurement was emphasized by the Ocular Hypertension Treatment Study (OHTS) in 2001, CCT measurement has become an integral part of the glaucoma exam.6 Thicker central corneas are associated with artifactually higher IOP readings. CCT measurements can be obtained with a portable device, such as the Pachmate DGH55 (DGH Technology, Inc.).
In adults, mean normal CCT has been reported as 537 μm (with a range from 427 to 620 μm).7 In normal children, CCT does not vary significantly with age (Table 1). Although CCT appears to be similar in normal children and those with PCG, thicker CCT has been noted in various disease states, such as aphakic glaucoma, Sturge-Weber syndrome, aniridia and microcornea (Table 2).