Glaucoma is a group of eye disorders characterized by progressive damage to the optic nerve. This nerve transmits visual information from the eye to the brain, and its deterioration leads to irreversible vision loss. Glaucoma definitively affects side vision, as the damage typically targets the nerve fibers responsible for peripheral vision first. This silent process often begins without noticeable symptoms, making the disease a significant cause of preventable blindness worldwide.
The Mechanism of Vision Loss in Glaucoma
Vision loss occurs when the axons of the retinal ganglion cells, which form the optic nerve, are damaged and die off. This damage is strongly linked to elevated intraocular pressure (IOP), the fluid pressure inside the eye.
The eye constantly produces aqueous humor, a clear fluid, which is normally balanced by a specialized drainage system. If the drainage angle becomes blocked, the aqueous humor cannot exit quickly enough, causing high pressure. This sustained pressure mechanically stresses the optic nerve head, leading to the gradual loss of nerve fibers and corresponding blind spots in the visual field.
The Progression of Peripheral Vision Loss
Glaucoma’s effect on vision is insidious because initial damage occurs at the edges of the visual field. This creates small, isolated blind spots, known as scotomas, in the outer periphery that patients usually miss. The brain often compensates for these gaps by filling in the missing information, masking the early stages of the disease.
The pattern of nerve fiber loss makes peripheral vision more vulnerable than central vision. As the disease advances, these peripheral scotomas merge and spread inward, gradually constricting the visual field. This progression eventually leads to “tunnel vision,” where the patient retains only a small, clear area of central sight. The preservation of central vision until later stages emphasizes the importance of regular screening for early detection.
Detecting Early Glaucoma Damage
Since patients rarely notice the early loss of side vision, specialized diagnostic tools are necessary to detect damage before it becomes severe. The visual field test, or perimetry, is the primary functional assessment used to map the extent and pattern of peripheral vision loss. During perimetry, a patient signals when they see a tiny flash of light across their visual field, allowing the doctor to chart blind spots.
To complement this functional testing, other tools assess the physical state of the eye. Tonometry measures the intraocular pressure, assessing fluid dynamics within the eye. Optical Coherence Tomography (OCT) is a non-invasive imaging technology that provides a cross-sectional view of the retina. OCT allows the clinician to measure the thickness of the retinal nerve fiber layer, which thins as optic nerve damage progresses.
Managing Glaucoma to Preserve Sight
The goal of glaucoma management is to lower the intraocular pressure to a target level that prevents further optic nerve damage. Current treatments cannot restore peripheral vision that has already been lost, so adherence to a treatment plan is paramount for preserving remaining sight.
The initial and most common treatment involves prescription eye drops. These topical medications work by either decreasing the production of aqueous humor or improving its outflow.
If drops are insufficient, laser procedures offer another pathway to reduce pressure. Selective Laser Trabeculoplasty (SLT) can enhance the natural drainage tissue’s function. For advanced or uncontrolled cases, surgical options like trabeculectomy or minimally invasive glaucoma surgery (MIGS) are performed to create a new drainage channel for the eye’s fluid.