Juvenile Open Angle Glaucoma

Juvenile open angle glaucoma (JOAG) is primary open angle glaucoma with onset between about 3 years and 40 years of age, with high intraocular pressure, open angles, and no buphthalmos or other ocular anomaly.

• Autosomal dominant inheritance in many cases, with high penetrance; MYOC (myocilin) gene mutations in about 10 percent of cases (commoner in familial juvenile cases), and others (OPTN, WDR36).
• Typically high pressure (often over 30 to 40 mmHg), strong family history, and high myopia in many patients.
• Pathology: developmental trabecular dysgenesis (Schlemm canal and meshwork abnormality), aggregated myocilin in the meshwork.
• Aggressive disease with early vision loss if untreated; relatively asymptomatic, so it is often detected late.

• Frequently asymptomatic; may notice blurred distance vision from progressive myopia, visual field loss; fluctuating intraocular pressure rise after steroids.
• Intraocular pressure often 30 to 50 mmHg, normal corneal diameter and clarity, deep chamber, myopia.
• Gonioscopy: open angle, sometimes with immature features (high iris insertion, prominent iris processes, a flat iris insertion), absent pigment.
• Optic disc: large cup, rim thinning, notching; visual field loss (arcuate, then tunnel) with preserved central acuity until late.
• Family history of early glaucoma or blindness.

• Tonometry (diurnal variation), pachymetry, gonioscopy to exclude secondary causes (angle recession, uveitis, steroid response, pigment dispersion) and developmental syndromes (Axenfeld-Rieger, aniridia).
• Dilated optic disc evaluation with photography, optical coherence tomography, visual field testing (child cooperation from about 7 years).
• Genetic testing for MYOC and family screening of first degree relatives (examination of siblings and parents; predictive testing in at risk family members, ideally from the age of 10).
• Cycloplegic refraction.

• Early and aggressive control, with a target pressure in the low teens (below 15 mmHg), because of long life expectancy.
• Medical therapy first, though often inadequate in severe disease: prostaglandin analogue at night (latanoprost 0.005 percent), timolol 0.5 percent twice daily, dorzolamide 2 percent three times daily (caution in young children), and brimonidine 0.2 percent (avoid below 6 years).
• Laser trabeculoplasty is less effective in young patients and is not generally recommended.
• Surgery is usually needed early: trabeculotomy or goniotomy (effective in juvenile disease with an immature angle, especially in patients under 30 years), trabeculectomy with mitomycin C 0.2 to 0.4 mg/mL, or glaucoma drainage devices; cyclophotocoagulation for refractory cases.
• Treat myopia with spectacles and contact lenses.
• Lifelong follow up with pressure measured every 3 to 6 months, disc imaging and visual field testing every 6 months initially; genetic counselling (50 percent risk of transmission in autosomal dominant disease) and screening of relatives.
• Avoid steroid exposure, which can cause marked pressure rises in carriers of myocilin variants.