Childhood Glaucomas (Congenital Glaucomas)

Oscar V. Beaujon-Balbi

Oscar Beaujon-Rubin

Claudia L. Pabon

Douglas J. Rhee

INTRODUCTION

The World Glaucoma Association defines Childhood Glaucoma as a related intraocular pressure damage to the eye. This definition was adopted as a result of a consensus made in 2013. Developmental glaucomas are a group of conditions characterized by a developmental abnormality of the aqueous outflow system of the eye. This group includes the following:

• Congenital glaucoma, in which the developmental abnormality of the anterior chamber angle is not associated with other ocular or systemic anomalies

• Developmental glaucomas with associated anomalies, in which ocular or systemic anomalies are present

• Secondary glaucomas of childhood, in which other ocular pathologies are the cause of the impairment of the aqueous outflow

Several different systems are used to classify developmental glaucomas. The most common are the Shaffer-Weiss and the Hoskin anatomic classifications. The former divides congenital glaucoma into three major groups:

Primary congenital glaucoma (PCG)
Glaucoma associated with congenital anomalies
Secondary glaucomas of childhood

The latter defines the actual developmental disorder clinically evident at the time of examination and also includes three groups:

• Isolated trabeculodysgenesis with malformation of the trabecular meshwork in the absence of iris or corneal anomalies

• Iridotrabeculodysgenesis that includes angle and iris anomalies

• Corneotrabeculodysgenesis, usually associated with iris anomalies

The identification of anatomic defects can be useful in determining the appropriate therapy and prognostic factors. The world Glaucoma Association, as a result of consensus made in 2013, classifies childhood glaucoma as primary and secondary glaucomas. The latest are subdivided according to whether the condition is present at birth or is acquired after birth. Nonacquired glaucomas are then classified as associated to ocular or systemic signs.

PRIMARY CONGENITAL GLAUCOMA

PCG is the most common form of infantile glaucoma, representing 50% of all cases of congenital glaucoma. It is characterized by a trabecular meshwork anomaly and is not associated with other ocular or systemic diseases. Seventy-five percent of PCG cases occur bilaterally.

Epidemiology

• The incidence is 1 in 5,000 to 10,000 live births. More than 80% of cases present before 1 year of age: 40% at birth, 70% between 1 and 6 months, and 80% before 1 year.

• The disorder is more common in males (70% males, 30% females), and 90% of cases are sporadic, without a family history.

• Although an autosomal-recessive model with variable penetrance has been suggested, it is thought that most of the cases are the result of multifactorial inheritance with nongenetic factors involved (e.g., environmental factors).

Clinical Examination

Initial evaluation is usually done at the office. The child may have at least one of the symptoms as photophobia, tearing, and blepharospasm. Sometimes big eyes or bupthalmos are the main complaint. The physician may evaluate visual acuity according to age, as pupil contraction at light stimulus at birth, light fixation around 3 months of age. Inspection for systemic and facial associations and evaluation at the slit lamp, to evaluate cornea transparency, anterior chamber configuration, iris, and crystalline lens. Intraocular pressure can be measured at the office using the Tono-Pen and recently the use of rebound tonometry, which does not require fluorescein nor topical anesthesic drops (Fig. 11-2).

If posible, an ultrasound evaluation can be performed to determine axial length. If the axial length is higher than expected for age, glaucoma is one potential cause. An evaluation under anesthesia must be performed in children who cannot be fully evaluated in the office. This is often followed by a surgical intervention to treat the glaucoma at the same session (Fig. 11-3).

• The normal horizontal corneal diameter in a full-term newborn is 10 to 10.5 mm. This increases to the adult diameter of approximately 11.5 to 12 mm by 2 years of age. A diameter greater than 12 mm in an infant is highly suggestive of congenital glaucoma.

• Measurements of the cornea are made in the horizontal meridian with calipers. Other findings include corneal cloudiness, tears in the Descemet membrane (Haab striae), deep anterior chamber, intraocular pressure greater than 21 mm Hg, iris stroma hypoplasia, isolated trabeculodysgenesis on gonioscopy, and increased optic nerve cupping. Haab striae may be single or multiple and are characteristically oriented horizontally or concentrically to the limbus (Figs. 11-4 and 11-5).

• Optic nerve evaluation is a very important part of the glaucoma evaluation. Glaucomatous disc changes occur more rapidly in infants and at lower pressures than in older children or adults. Cup-to-disc ratios greater than 0.3 are rare in normal infants and must be considered suspicious for glaucoma. Asymmetry of optic nerve cupping is also suggestive of glaucoma, particularly
differences of greater than 0.2 between the two eyes. The glaucomatous cupping may be oval in configuration but is more often round and central (Fig. 11-6). Reversal of optic nerve cupping has been observed after normalization of intraocular pressure.

• Evaluation of the anterior chamber angle is essential for an accurate diagnosis and treatment. The developmental anomalies can present in two major forms: (1) flat iris insertion, in which the iris inserts directly or anterior to the trabecular meshwork with iris processes that can overcome the scleral spur (Fig. 11-7A) and (2) concave iris insertion, in which the iris is observed behind the trabecular meshwork but is covered with a dense abnormal tissue (Fig. 11-7B). For comparison, a gonioscopic photograph of a normal anterior chamber angle from an infant is also presented (Fig. 11-8).

• Elevation of the intraocular pressure causes rapid enlargement of the globe with progressive enlargement of the cornea in children younger than 3 years. As the cornea enlarges, stretching leads to ruptures in Descemet membrane, epithelial and stromal edema, and corneal clouding. The iris is stretched so that the stroma appears thinned. The scleral canal through which the optic nerve passes also enlarges with elevated intraocular pressure. This results in rapid cupping of the optic nerve, which can quickly reverse if the intraocular pressure is normalized.

This dramatic reversal in cupping is not seen in adult eyes and is probably related to the greater elasticity of the optic nerve head connective tissue in the infant. If the intraocular pressure is not controlled, a buphthalmos can develop (Fig. 11-9; see also Fig. 11-1).

Management

• The treatment of congenital glaucoma is surgical. Medical treatment can be used for a limited time while the surgery is being scheduled.

• Procedures that involve trabecular incisions are the choice in this condition.

Goniotomy requires a clear cornea for visualization of the angle.
Trabeculectomy with an external approach to Schlemm canal does not require corneal transparency.

• The goniotomy is performed using a goniotome and direct gonioscopy lens. Traditionally, a Barkan goniolens is preferred. An incision is made in the dense abnormal tissue at the trabecular meshwork for an extension of 90 to 180 degrees using the goniotome through clear cornea (Figs. 11-10 and 11-11).

• Alternatively, a modified Swan-Jacob lens can be used with a sharp blade, for example, MVR blade, Wheeler knife, or even a 30-gauge needle. The advantage of a flat blade is that it will create less distortion of the corneal wound and allow the wound to be closed more easily (Fig. 11-12).

• For a patient with cloudy or opacified corneas, trabeculotomy is indicated. A scleral flap is made and Schlemm canal must be found to perform the procedure. The trabecular meshwork is broken using a trabeculotome (Fig. 11-13) or by using a suture (usually propylene) through Schlemm canal (Lynch procedure). An alternative to suture trabeculotomy is to use a fiberoptic catheter
(iCath, iScience), which has the advantage of an illuminated tip that identifies the location of the catheter (Fig. 11-14). At present, we perform a surgical technique similar to canaloplasty. We have found it to be effective to perform a scleral flap of 3 × 3 mm at 50% thickness and a second deeper flap of 2 mm extending to the clear cornea. The Sclemm canal is found and viscodilated to pass the illuminated catheter in 360 grades and pulled through to incise the trabecular meshwork all around (Fig. 11-15). The deeper flap is excised and the first flap is tightly closed (Figs. 11-15 and 11-16).

• In cases where Schlemm canal is not found, trabeculectomy is performed. Another choice is the placement of a valved or nonvalved glaucoma-filtering device (Fig. 11-17).

FIGURE 11-1. Unilateral primary congenital glaucoma. This photograph demonstrates a cloudy cornea and buphthalmos.

FIGURE 11-2. Rebound tonometry. A. Rebound tonometry during the induction before general anesthetics. B. Using the rebound tonometer at the office.

FIGURE 11-3. Evaluation under anesthesia. A and B. Measuring corneal diameter with caliper (black arrows identify the tips of the caliper). C. Gonioscopy with a four-mirror lens. D. Gonioscopy with a Transcend Volk Goniolens (TVG) surgical goniolens. E. Optic disc and retina observation using a handheld lens and the operating room (OR) microscope.

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