Glaucoma is the disturbance in the structure or function of the optic nerve that causes it to atrophy. This usually leads to gradual loss of the visual field over a period of time. The disturbance is usually as a result of increased intraocular pressure although some patients exhibit atrophic changes without having a raised intraocular pressure (Bell). Risk factors for developing glaucoma include a family history of glaucoma, old age and elevated intraocular pressure from any cause (Bell). Previous ocular surgery and ocular or head trauma are also predisposing factors.
Two main types of glaucoma include angle-closure glaucoma and open-angle glaucoma.
In angle closure glaucoma, there is a blockage in the normal drainage canal of aqueous humor which leads to sudden pressure build up in the eye. It usually presents as an emergency.(Aherne)
In open-angle glaucoma, the drainage system for aqueous humor is not impaired. This is usually the chronic form. Mixed mechanism glaucoma therefore is glaucoma that presents with a mixture of the above mechanisms. It has features of both open-angle and acute angle closure glaucoma. This type of glaucoma is not common. (Bell)
Signs and symptoms vary from patient to patient. It is a combination of symptoms of both acute angle closure and open angle glaucoma. Patient may be asymptomatic until the disease is advanced, especially in cases of open-angle glaucoma. Other symptoms include headache, uveitis, eye pain, multicolored halos. There could also be a previous history of ocular disease, like cataracts.(Aherne)
Investigations include direct tonometry in which the intraocular pressure is measured. An examination of the eye through the dilated pupils is required to diagnose glaucoma. Perimetry is also used to determine if there are defects within the fields of vision (Che-yung).
Treatment can either be medical or surgical. Drug classes include alpha-agonists, beta-blockers, carbonic anhydrase inhibitors, miotic agents and prostaglandin analogs. They either reduce the production of aqeous humor or aid its removal. (Che-yung)
Surgical treatments include iridotomy, trabeculoplasty and cyclophotocoagulation and filtering.
Works Cited
Jerald, Bell et al. “Primary Open-Angle Glaucoma”. Medscape Reference. (2012).
Andrew, Aherne et al. “Acute Angle-Closure Glaucoma”. Medscape Reference. (2010).
Clement Che-yung. Glaucoma, “Acute Closure, Chronic Clinical Presentation”. (2010).
