Causes, Types, and Why Early Detection Matters
Glaucoma is not just one disease but a group of conditions that share a common feature: progressive damage to the optic nerve at the point where it exits the eye. This damage occurs in a characteristic pattern and results in a gradual loss of side vision, often before central vision is affected.
For a long time, glaucoma was believed to be caused solely by high eye pressure. Today, we know that while other factors can also contribute, elevated eye pressure remains the most important risk factor. When the optic nerve becomes damaged, vision loss begins at the periphery and moves inward, which is why early detection is so critical.
The Main Types of Glaucoma
The classification of glaucoma is based on the appearance of the drainage angle, which is examined during gonioscopy. Broadly, glaucoma can be divided into open-angle and angle-closure types.
Primary Open-Angle Glaucoma (POAG)
In this form, the drainage angle appears normal and open, but the outflow of aqueous humour is reduced. This leads to a slow, painless rise in eye pressure over months or years. Because symptoms are minimal or absent in the early stages, patients are often unaware of the damage until significant vision loss has already occurred.
Primary Angle-Closure Glaucoma (PACG)
In this type, the drainage angle becomes narrow or completely blocked, causing a sudden increase in eye pressure. An acute attack of angle closure is a medical emergency and can cause severe eye pain, blurred vision, and coloured halos around lights. Without prompt treatment, permanent loss of vision can occur within hours.
Other forms of glaucoma include congenital glaucoma, which is present at or around birth, and secondary glaucoma, which arises as a complication of other eye diseases, injuries, or surgeries. Both congenital and secondary types can be open-angle or angle-closure in nature.
Glaucoma can occur at any age, though its form and cause may differ between age groups. What remains constant is the importance of early detection, regular check-ups, and timely management. The earlier glaucoma is found, the greater the chance of preserving good vision for life.