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: 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, a little amount of 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]
Risk Factors
Juvenile-onset open-angle glaucoma has many risk factors such as:
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]
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 may present include an enlarged eye, blurred vision, eye pain, decreased visual acuity, signs of 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 of juvenile open-angle glaucoma should include the measurement of IOP and assessment of visual acuity, the optic disc, and the anterior chamber angle.
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 was performed on 23 patients, 83% of patients of juvenile glaucoma require filtration surgery (trabeculectomy).[9]
Medical therapy of juvenile open-angle glaucoma includes β blockers, topical carbonic anhydrase inhibitor, prostaglandin analogs, α-adrenergic agonists. If no contraindications such as asthma exist, β-blockers are often the first-line therapy of juvenile open-angle glaucoma. Topical carbonic anhydrase inhibitors are less effective than β blockers, but they are useful as alternatives when β blockers are contraindicated. Prostaglandins are more effective in adult glaucoma than childhood glaucoma. α-adrenergic agonists have potential systemic side effects, which request close observation when used in young infants.[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 intraocular pressure IOP control without medications during three years postoperation.[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 IOPs. However, there is a high 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] A 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 was no loss of light perception.[25] In a prospective study of 52 eyes with juvenile glaucoma, the Molteno implant resulted in intraocular pressure IOP control less than 21 mmHg.[26] Although there are reports showed the 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 decreases intraocular pressure IOP. Selective laser trabeculoplasty (SLT) induces less coagulative damage and structural change than older laser trabeculoplasty techniques. SLT does not typically provide the same IOP lower 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]
Other conditions can also be mistaken for juvenile open-angle glaucoma juvenile open-angle glaucoma as they may present similarly such as:
Prognosis of the visual field for juvenile open-angle glaucoma patients is rarely because most patients are too young to be examined. In a Japanese study of 47 eyes, 21 eyes (45%) had normal visual fields, whereas 13 eyes (28%) were at an advanced stage, most of which were ascribable to a delay in disease diagnosis.[20]
If glaucoma remains untreated, visual impairment and blindness may develop. It is not uncommon for the diagnosis of glaucoma to delay since it may be asymptomatic until an advanced stage.[5][28]
Other complications depend on the type of surgery performed. They include:
Although juvenile open-angle glaucoma is an uncommon condition, patients should receive education about this condition. Since those 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.
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 patients' 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.[29][30] [Level 5]
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