Glaucoma Grand Rounds

Trabeculum Trouble Complicates This Boy’s Treatment

J. James Thimons, O.D.

A 9-year-old African-American male with elevated intraocular pressures and increased optic nerve head changes was referred to us for consultation. His prior medical and ocular history was unremarkable. His family ocular history included an uncle who developed vision loss secondary to glaucoma. The patient had been a full-term pregnancy with no notable illness, and the delivery was unremarkable.

Physical Examination

Physical examination of the patient revealed a well-developed 9-year-old boy with normal body symmetry and symmetrical facial development. Size of the globe and cornea were within normal limits, and he showed good motor coordination. Visual acuity with correction was 20/20 O.U. External examination revealed pupils to be 5/4, 3+, and positive Marcus Gunn O.D. Extraocular muscle assessment, confrontation fields and slit lamp exam were normal. The cornea showed no evidence of increased nerve visibility, and the diameter of the cornea was approximately 12.5mm horizontally.

Anterior chambers were deep and quiet, and the lenses were clear bilaterally. Applanation tensions at the initial visit were 26mm Hg O.D., 23mm Hg O.S. at 5 p.m.

Dilated fundus exam showed significant optic nerve head cupping with cup-to-disc ratio in the right eye approximately 0.8-0.85. There was also an erosion of the superior margin of the disc and a decrease in the nerve fiber layer intensity in the superior zone. The left eye showed approximately 0.75-0.8 cup-to-disc ratio with a healthy neuroretinal rim. Nerve fiber layer in the left eye displayed no significant defects.

Visual field testing showed a loss of sensitivity inferior to fixation in the right eye. The left eye’s visual field was normal. Gonioscopy demonstrated open angles. The trabeculum showed incomplete development; the meshwork was poorly differentiated and had a satin-like sheen, as opposed to the usual textured appearance.

We asked the patient to return in two weeks for an early morning IOP reading. At that 8:30 a.m. visit, the IOPs were 30mm Hg O.D. and 26mm Hg O.S.

Discussion

This patient presents with a unique variation of glaucoma that is best classified as juvenile. In cases such as this, anatomical abnormalities are common, and patients frequently show changes such as maldevelopment of the trabecular meshwork, mis-insertion of the iris roots or changes in the structure of the corneal endothelial system.

In this case, the most likely diagnosis is trabecular dysgenesis, in which the trabeculum fails to differentiate itself completely in utero and therefore has a compromised outflow at a very early age. Treatment of patients such as this individual can be complex; the likelihood of success diminishes over time.

Determining a goal pressure is difficult, especially with the risk factors presented. In this case, the patient has a family history of glaucoma and is African-American. The ophthalmic concerns are the persistent elevation of intraocular pressure, the increased optic nerve head cupping and the visual field abnormality. This patient also has shown optic nerve head damage at a relatively modest elevation of IOP in the mid- to high-20s. All these factors contributed to our initial goal of 40% IOP reduction to begin the therapeutic process.

Selecting an anti-glaucoma agent is also complex. The newer glaucoma therapies are not clinically approved for children, and in many instances there is no profile for the risk of long-term complications. For this reason, a beta-blocker is a reasonable initial therapeutic intervention. Beta-blockers have a long history in ophthalmic management of glaucoma, and there is significant literature on their use in children. The indications, contraindications and clinical side effects are well established.

Because of these factors, I chose to initiate medical therapy with Betoptic S (betaxolol suspension), a selective beta-blocker, 1 drop bid O.U. Betaxolol is unique among beta-blockers because it is cardiac-selective and has demonstrated a low risk of pulmonary complications. Additionally, the drug has had some initial indications as a potential neuroprotective agent, probably due to its calcium-channel blocking ability and a decrease in peripheral resistance to blood flow to the optic nerve.

In three weeks the patient returned for follow-up consultation, and at 10 a.m. his IOPs were 17mm Hg O.D. and 15mm Hg O.S. This met the goal pressure, and we sent the patient to the referring clinician for a 3-month follow-up evaluation. We also recommended a repeat of the visual field at that time to closely monitor the potential for progressive disease.

In most cases of pediatric glaucoma, patients who present with early elevations of IOP show progressive optic nerve head change even with the very best medical management.

Additionally, these patients can certainly show rapid increases in pressure over time as the trabecular meshwork becomes overloaded and fails to provide adequate aqueous outflow. Because of this, these patients can undergo significant early disease and progress to surgical intervention in response to inadequate medical control.

Due to the relative instability of this disease and its progressive nature, the primary eye care provider and the surgeon must work diligently together to monitor the individual patient regularly and to look for trends in IOP levels as well as optic nerve head changes. This will allow the doctors to redirect their clinical therapy intelligently.

top

Return to September 2000 Highlights


	\| \| \| \| \| \|