Glaucoma is defined as a condition of increased eye pressure which may result in optic nerve damage, causing irreversible vision loss. However glaucoma can develop even if the eye pressure is normal.
Types of Glaucoma- Glaucoma have mainly two types- Open angle Glaucoma and Angle closure Glaucoma. Here angle refers to drainage angle which is inside the eye and is responsible for control of drainage of Aqueous humor. This fluid called aqueous humor is produced by eyes continuously and any blockage in its drainage can raise the Intraocular pressure (IOP).
- Open angle Glaucoma (Wide angle Glaucoma): Also called Primary chronic open angle Glaucoma (COAG), is the commonest type with maximum incidences. It gradually develops and is usually painless. Symptoms are not present initially. It starts with loss of peripheral vision which is usually not noticed by the patient till more sight is lost. This is due to improper eye drainage. Usually asymptomatic till condition progresses significantly. Gradually the visual field is lost.
- Angle closure Glaucoma (Narrow angle Glaucoma): More common in Asian countries. Due to narrow drainage & physical blockage, this can lead to sudden increase in eye pressure and may lead to acute or chronic Glaucoma. It can raise the eye pressure suddenly and can cause emergency situation. It can cause sudden and severe eye pain, redness, headache, nausea, vomiting, seeing halos around the eyes. Such conditions needs prompt medical attention or vision may be permanently affected.
- Low tension or Normal tension Glaucoma: Also there could be Glaucoma with optic nerve damage & peripheral vision loss without raised intra ocular pressure. Compromised blood flow to the eyes is believed to be responsible.
- Congenital Glaucoma: This type is usually inherited and is present at birth itself. There is inborn defect in angle of eye (drainage area). This condition is quite rare.
Secondary Glaucoma: Here, Glaucoma is secondary to some disease condition like diabetic retinopathy, eye trauma, eye infection, tumour, eye surgery, cataract etc. Following are the most common forms of secondary glaucoma:
- Neo vascular Glaucoma: Uncommon type, mostly seen in Diabetic retinopathy or uncontrolled hypertension cases, where due to restricted blood supply, many new blood channels open which blocks the drainage of aqueous humor; leading to Glaucoma.
- Toxic Glaucoma: There is excessive and sudden rise of intraocular pressure. Exact cause behind this is not known.
- Absolute Glaucoma: Most severe and the end result of all types of Glaucoma, where there is no vision, papillary light reflex, or response. There is severe eye pain with stony appearance.
- Pigmentary Glaucoma: Pigment of iris breaks down to cause blockage, affecting drainage.
- Exfoliative Glaucoma: This is due to flaky material deposit at drainage angle resulting in less drainage and raised IOP.