Glaucoma is a group of slow progressive eye diseases that is defined as an optic neuropathy. Although there are up to eight types described, the two main types are:
open-angle
closed angle glaucoma (interchangeably referred to as angle-closure or narrow-angle)
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Epidemiology
Glaucoma is one of the leading causes of vision loss and blindness in the world. Of the population affected by glaucoma, approximately 10% have resulted in blindness1.
Open-angle is the more common type of glaucoma among white and black populations, whereas closed angle is more common among Asian populations 2.
Risk factors
The following are risk factors for glaucoma:
age: increasing age
race: approximately black populations are three times more likely to have open-angle glaucoma
diabetes
hypertension
elevated intraocular pressure: More closely associated with open-angle glaucoma
family history
female: more commonly associated with closed angle glaucoma
Clinical presentation
Glaucoma can have a varied acute presentation. The presence of sudden onset symptoms is typically suggestive of closed angle glaucoma as result of a rapid increase in intraocular pressure.
Common symptoms of closed angle include:
decreased vision
halos
headache
severe eye pain
nausea and vomiting
red eye/conjunctival redness
Open-angle glaucoma is typically insidious, with patients largely asymptomatic until late in the disease. Many are identified during routine eye examinations or as an incidental finding during workup of another eye condition.
Pathology
The pathology of open-angle glaucoma is not fully understood. Preliminary evidence suggests that there is neural axonal loss leading to neuropathy with open angle glaucoma. It is important to note that a large population of patients with open angle glaucoma will not have the characteristic "elevated intraocular pressure" 3.
Closed-angle glaucoma is further subdivided into primary angle, chronic angle, and secondary angle closure. The main pathogenesis involves an increase in intraocular pressure from the lack of aqueous humor drainage.
Radiographic features
MRI
There is evolving literature regarding the use of MRI in the setting of glaucoma 4. The following may be features of glaucoma detected by MRI:
decreased optic nerve diameter and thinning
optic chiasm atrophy and loss of height (due to axonal density loss)
Treatment and prognosis
Closed-angle glaucoma requires prompt treatment with subsequent referral to ophthalmology for consideration of surgical therapy, i.e. trabeculetomy or mechanical shunts.
Open-angle glaucoma is treated with topical prostaglandin therapy, topical beta-blockers, or other agent such as topical carbonic anhydrase inhibitors. Surgical therapy is typically considered in the setting of severe visual loss at baseline or failed medical therapy. First line surgical therapy involves a trabeculetomy (creation of an alternative route by which of aqueous humor can filtrate from). Failing this, mechanical shunts or "valves" can be considered in the setting of advanced disease or underlying conditions such as corneal transplants, whereby there is increased risk of failure from the more conventional surgical approach.
Complications
Left untreated, glaucoma can lead vision loss and subsequent blindness.
Differential diagnosis
Most cases of glaucoma will be unremarkable on MRI. In advanced cases, an increase in axial diameter of the ocular globe and optic nerve atrophy may be identified.
The clinical differentials depend on the presentation and may include:
keratitis
acute conjunctivitis
corneal ulcer
episcleritis or scleritis
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