Continuing Education Activity

Juvenile open-angle glaucoma is an uncommon and more severe form of primary open-angle glaucoma. It occurs as a result of abnormal development of trabecular meshwork. It is manageable medically or surgically. This activity discusses the etiology and the pathophysiology of the Ashman phenomenon and highlights the role of the interprofessional team in evaluating and treating patients with this condition.

Objectives:

• Review the etiology for developing juvenile open-angle glaucoma.
• Outline the typical presentation of a patient with juvenile open-angle glaucoma.
• Identify the most common complications associated with juvenile open-angle glaucoma.
• Summarize the importance of improving communication and care coordination amongst the interprofessional team to enhance the delivery of care for patients with juvenile open-angle glaucoma.

Introduction

Glaucoma is a neurodegenerative disorder characterized by the progressive degeneration of the optic disc and visual field loss, for which intraocular pressure (IOP) is the chief modifiable risk factor. Glaucoma is the most common etiology of irreversible blindness. It affects more than 2 million individuals in the United States and 67 million individuals worldwide.

Glaucoma has two main subtypes: open-angle glaucoma and angle-closure glaucoma. Juvenile open-angle glaucoma (JOAG) is an uncommon form of primary open-angle glaucoma, with earlier onset (3 to 40 years of age), higher IOP, and more severe visual field loss compared with adult-onset primary open-angle glaucoma (POAG).

Many studies report that this form of glaucoma typically demonstrates an autosomal dominant inheritance pattern. The myocilin (MYOC) gene is identified abundantly through linkage analysis in the trabecular meshwork (TM) of the affected patients.[1][2][3][4][5][6][7] 

Anatomy of the Eye

The eye can subdivide into two parts: anterior and posterior. The anterior part is located in front of the lens and divides into anterior and posterior chambers. In the posterior chamber, the ciliary body of the eye produces a fluid called aqueous humor. This fluid flows from the posterior chamber into the anterior chamber through the pupil and exits the eye via two pathways: the trabecular and uveoscleral pathways. The majority of aqueous humor outflow flows through the trabecular meshwork (TM) and the canal of Schlemm (SC), which are parts of the trabecular pathway. In the uveoscleral pathway, aqueous humor passes into the supraciliary and suprachoroidal spaces through the ciliary muscle. Finally, both routes drain the aqueous humor into the venous circulation.[8]

Etiology

Juvenile open-angle glaucoma often occurs as a result of abnormal development of trabecular meshwork.[5][7] Therefore, drainage of aqueous humor may not be adequate, leading to increased intraocular pressure and damage to the optic nerve.[8]

Juvenile-onset open-angle glaucoma has many risk factors such as:

• Male sex: in a study of 125 eyes with JOAG, 64% were male.[5]
• Myopia: Researchers found 87% of JOAG individuals to be myopic in a study of 23 affected patients.[9]
• Severe elevation of intraocular pressure IOP: it is a typical feature of juvenile-onset primary open-angle glaucoma. Generally, intraocular pressures range over 40 mmHg.[10]
• African ancestry[2]
• MYOC mutation[4]

Epidemiology

The prevalence of juvenile open-angle glaucoma is 0.38 per 100,000, ages ranging between 4 and 20 years.[5] Based on a study from the Dallas Glaucoma Registry, which comprised 376 eyes of 239 childhood glaucoma patients, 4% of patients had juvenile open-angle glaucoma.[11]

Pathophysiology

The pathophysiology of glaucoma remains incompletely understood.[12] However, it appears that the elevated intraocular pressure IOP in juvenile-onset primary open-angle glaucoma patients is due to goniodysgenesis, a failure of anterior chamber development, which includes an immature trabecular meshwork and thickened trabecular beams. Developmental abnormalities of the anterior chamber angle are less apparent with older subjects. Later age presentation of glaucoma may have less severe abnormalities of the trabecular meshwork and tends to involve only one eye.[6]

History and Physical

Juvenile open-angle glaucoma and adult-onset primary open-angle glaucoma have similar findings. A significant number of individuals with juvenile open-angle glaucoma are asymptomatic. Symptoms that may present include an enlarged eye, blurred vision, eye pain, decreased visual acuity, tearing, blinking, and glare. A family history of glaucoma should be taken in addition to other histories to rule out secondary glaucoma.[5][13]

Evaluation

Evaluation of juvenile open-angle glaucoma should include the measurement of IOP and assessment of visual acuity, the optic disc, and the anterior chamber angle.

• Intraocular pressure: Goldmann Applanation Tonometry is the gold-standard method used to obtain an accurate IOP.[14]
• Optic disc: optic discs of juvenile open-angle glaucoma tend to be more extensive than adult-onset primary open-angle glaucoma discs.[15]
• Pachymetry: This is used to measure the thickness of the eye's cornea and is recommended as a part of the pre-operative evaluation of juvenile open-angle glaucoma. Thinner corneas are a risk factor for JOAG.[16]
• Anterior chamber angle: Will typically appear normal on gonioscopy in patients with juvenile open-angle glaucoma. However, dysgenesis of the angle may be present with severe elevation of intraocular pressure.[17]

Treatment / Management

Treatment for juvenile open-angle glaucoma aims to stop further degeneration of the optic nerve by decreasing the IOP. Imaging of the optic nerve is often necessary to assess disease progression. Frequently, the IOP in juvenile open-angle glaucoma tends to be resistant to medical therapy, and surgical treatment is often needed.[18]

Medical Therapy

The first-line treatment of juvenile open-angle glaucoma is medical therapy, followed by surgery if medical therapy fails. Often medical therapy is applied as a bridge to surgical intervention. According to one study performed on 23 patients, 83% of patients with juvenile glaucoma require filtration surgery (trabeculectomy).[9]

Medical therapy for juvenile open-angle glaucoma includes β blockers, topical carbonic anhydrase inhibitors, prostaglandin analogs, and α-adrenergic agonists. If no contraindications such as asthma exist, β-blockers are often the first-line therapy for juvenile open-angle glaucoma. Topical carbonic anhydrase inhibitors are less effective than β blockers, but they are useful as additional therapy or as alternatives when β blockers are contraindicated. Prostaglandins are more effective in adult glaucoma than childhood glaucoma. The α-adrenergic agonists can be effective but have potential systemic side effects, which request close observation when used in young patients.[19] 

Surgery

Surgical therapy has multiple options, such as trabeculectomy, drainage implants, angle procedures (goniotomy, trabeculotomy), and cycloablative procedures.[20]

For juvenile open-angle glaucoma, trabeculectomy is the backbone of surgical therapy, which has a good outcome. In an Indian study that included 60 eyes of 41 patients, 50 to 87% of cases have reported IOP control without medications for three years after the operation.[21][22][23] Mitomycin C (MMC) or other types of antifibrotics have been used to prevent fibrosis during operation. The addition of mitomycin C (MMC) to trabeculectomy has resulted in lower intraocular pressures. However, there is a higher risk of developing hypotony maculopathy and bleb-related infection.[23]

Glaucoma drainage implants (GDIs) are an alternative surgical option for JOAG; they include many types of implants such as the Ahmed glaucoma valve, Baerveldt implant, and Molteno implant. Glaucoma drainage implants (GDIs) are preferable in the case of conjunctival scarring that prevents trabeculectomy.[24] One retrospective study showed that the Ahmed glaucoma valve has a 100% success rate at one year when used for pediatric glaucoma. The final intraocular pressure IOP was between 6-18 mmHg, and there were no patients that lost vision completely.[25] In a prospective study of 52 eyes with juvenile glaucoma, the Molteno implant resulted in intraocular pressure (IOP) of less than 21 mmHg.[26] Although there are reports showing successful angle procedures in juvenile open-angle glaucoma, they are usually used in congenital glaucoma management instead.[16] 

Laser

Laser trabeculoplasty is an alternative option to treat glaucoma. It works to lower intraocular pressure IOP. Selective laser trabeculoplasty (SLT) is one of the modalities of laser trabeculoplasty, which uses a Q-switched, frequency-doubled Nd:YAG (532 nm) laser. It enhances aqueous outflow through the trabecular meshwork to decrease IOP. SLT induces less coagulative damage and structural change than older laser trabeculoplasty techniques. SLT does not typically provide the same IOP lowering effect as surgical therapy, and due to goniodysgenesis in juvenile open-angle glaucoma, it often is not as effective as other forms of primary open-angle glaucoma.[27]

Differential Diagnosis

Other conditions can also be mistaken for juvenile open-angle glaucoma juvenile open-angle glaucoma as they may present similarly such as:

• Congenital glaucoma
• Steroid-induced glaucoma
• Traumatic glaucoma
• Inflammatory glaucoma
• Other forms of primary open-angle glaucoma

Prognosis

The prognosis for juvenile open-angle glaucoma patients is generally favorable if diagnosed and treated early in the disease course. In a Japanese study of 47 eyes with juvenile glaucoma, 21 eyes (45%) had normal visual fields, whereas 13 eyes (28%) were at an advanced stage, most of which were ascribed to a delay in disease diagnosis.[20] Even if the patient needs a trabeculectomy, the patient's IOP can be decreased and visual field loss halted.[28]

Complications

If glaucoma remains untreated, visual impairment and blindness may develop. It is not uncommon for the diagnosis of glaucoma to be delayed since it may be asymptomatic until an advanced stage.[5][29]

Other complications depend on the type of surgery performed. They include:

• Eye redness or pain
• Irritation of the cornea
• Persistent high intraocular pressure
• Hypotony
• Choroidal effusions
• Suprachoroidal hemorrhages
• Infection
• Cataract development or progression

Deterrence and Patient Education

Although juvenile open-angle glaucoma is uncommon, patients and parents should receive education about this condition. Since these patients are at an increased risk of developing visual impairment and blindness, they should understand the nature of the disease and its symptoms. Early diagnosis and treatment increase the chance of preserving vision and preventing permanent visual field loss.

Enhancing Healthcare Team Outcomes

Patients with juvenile open-angle glaucoma may initially present to the emergency department physician, primary care provider, or other medical providers. Good communication between health care providers is necessary to improve the patient's vision outcomes. These patients should receive a referral to an ophthalmologist for definitive diagnosis and treatment planning. The prognosis depends on the time of diagnosis and the treatment received. Practice patterns should be developed and followed so that this disease can be recognized early, preventing irreversible loss of vision.[30][31] [Level 5]